Journal articles: 'Hagfish'

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Lim, J. L., and T. M. Winegard. "Diverse anguilliform swimming kinematics in Pacific hagfish (Eptatretus stoutii) and Atlantic hagfish (Myxine glutinosa)." Canadian Journal of Zoology 93, no. 3 (March 2015): 213–23. http://dx.doi.org/10.1139/cjz-2014-0260.

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Anguilliform mode swimmers pass waves of lateral bending down their elongate bodies to propel forward. Hagfishes (Myxinidae) are classified as anguilliform swimmers, but their unique habits and reduced morphology—including a flexible body lacking a vertebral column—have the potential to translate into unique swimming behaviour within this broad classification. Their roles as active scavengers and hunters can require considerable bouts of swimming, yet quantitative data on hagfish locomotion are limited. Here, we aim to provide a more complete mechanistic understanding of hagfish swimming by quantifying whole-body kinematics of steady swimming in Pacific hagfish (Eptatretus stoutii (Lockington, 1878)) and Atlantic hagfish (Myxine glutinosa L., 1758), species from the two main lineages of Myxinidae. We analyzed high-speed video of hagfishes swimming at voluntary swim speeds and found that both species swim using high-amplitude undulatory waves. Swim speed is generally frequency-modulated, but patterns in wave speed, wavelength, and amplitude along the body and across swim speeds are variable, implying versatile mechanisms for the control of swim speed in these highly flexible fishes. We propose mechanistic explanations for this kinematic variability and compare hagfish with other elongate swimmers, demonstrating that the hagfish’s rich locomotory repertoire adds variety to the already diverse set of locomotory kinematics found in anguilliform swimmers.

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Boggett, Sarah, Jean-Luc Stiles, Adam P. Summers, and Douglas S. Fudge. "Flaccid skin protects hagfishes from shark bites." Journal of The Royal Society Interface 14, no. 137 (December 2017): 20170765. http://dx.doi.org/10.1098/rsif.2017.0765.

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Hagfishes defend themselves from fish predators by releasing large volumes of gill-clogging slime when they are attacked. Slime release is not anticipatory, but is only released after an attack has been initiated, raising the question of how hagfishes survive the initial attack, especially from biting predators such as sharks. We tested two hypotheses that could explain how hagfishes avoid damage from shark bites: puncture-resistant skin, and a loose and flaccid body design that makes it difficult for teeth to penetrate body musculature and viscera. Based on data from skin puncture tests from 22 fish species, we found that hagfish skin is not remarkably puncture resistant. Simulated shark bites on hagfish and their closest living relatives, lamprey, as well as whole animal inflation tests, revealed that the loose attachment of hagfish skin to the rest of the body and the substantial ‘slack volume' in the subcutaneous sinus protect hagfish musculature and viscera from penetrating teeth. While recent work has found evidence that the capacious subcutaneous sinus in hagfishes is important for behaviours such as knot-tying and burrowing, our work demonstrates that it also plays a role in predator defence.

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Sundin, L., M. Axelsson, S. Nilsson, W. Davison, and M. Forster. "EVIDENCE OF REGULATORY MECHANISMS FOR THE DISTRIBUTION OF BLOOD BETWEEN THE ARTERIAL AND THE VENOUS COMPARTMENTS IN THE HAGFISH GILL POUCH." Journal of Experimental Biology 190, no. 1 (May 1, 1994): 281–86. http://dx.doi.org/10.1242/jeb.190.1.281.

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Of the extant vertebrate animals, the hagfishes are generally considered to be the group which diverged first from the ancestral vertebrate lineage, although molecular sequence analysis has recently suggested that they form a monophyletic group with lampreys (Stock and Whitt, 1992). The circulatory system of hagfishes has features that have been described as 'primitive' (Burggren et al. 1985), but their gills are effective gas exchangers. The gills are contained within discrete muscular pouches, and the anatomy of the blood system and ventilatory ducts has an ideal countercurrent arrangement (Mallatt and Paulsen, 1986; Elger, 1987). Reite (1969) first reported effects of catecholamines and other drugs on the branchial vasculature of hagfish. Recent studies of both perfused gills in situ and of blood flow in vivo have suggested that blood flow through the gills of hagfish is under tonic control by catecholamines (Axelsson et al. 1990; Forster et al. 1992). In teleosts, several studies have shown that adrenergic control mechanisms are involved in the distribution of blood between the arterio-arterial and the arterio-venous pathways of the gill vasculature (see Nilsson, 1983). Anatomical and ultrastructural studies have demonstrated the existence of similar pathways in hagfish (Cole, 1925; Mallatt and Paulsen, 1986; Elger, 1987). The experiments reported here demonstrate that, in the hagfish gill pouch, both adrenaline and isoprenaline can increase the proportion of fluid leaving via the efferent arterial route, at the expense of the venous outflow. Hagfish (Eptatretus cirrhatus Forster) were collected off Motunau, North Canterbury, New Zealand, and held in seawater aquaria until used. The masses of the 11 animals used in these experiments ranged from 680 to 1720 g with a mean of 1140±110 g (s.e.m.). Animals were anaesthetized in a 0.4 % solution of benzocaine in sea water. The hagfish were opened ventrally to expose the gills and their blood supply. Individual gill pouches were prepared for perfusion studies.

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Miyashita, Tetsuto. "A Paleozoic stem hagfish Myxinikela siroka — revised anatomy and implications for evolution of the living jawless vertebrate lineages." Canadian Journal of Zoology 98, no. 12 (December 2020): 850–65. http://dx.doi.org/10.1139/cjz-2020-0046.

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Hagfishes and lampreys comprise cyclostomes, the earliest branching and sole surviving clade of the once diverse assemblage of jawless crown-group vertebrates. Lacking mineralized skeletons, both of the crown cyclostome lineages have notoriously poor fossil record. Particularly in the hagfish total group, †Myxinikela siroka Bardack, 1991 from the Late Carboniferous estuarine system of Illinois (USA) represents the only definitive stem taxon. Previously known from a single specimen, Myxinikela has been reconstructed as a short-bodied form with pigmented eyes but otherwise difficult to distinguish from the living counterpart. With a new, second specimen of Myxinikela reported here, I reevaluate the soft tissue anatomy and formulate diagnosis for the taxon. Myxinikela has a number of general features of cyclostomes, including cartilaginous branchial baskets, separation between the esophageal and the branchial passages, and a well-differentiated midline finfold. In effect, these features give more lamprey-like appearance to this stem hagfish than previously assumed. Myxinikela still has many traits that set modern hagfishes apart from other vertebrates (e.g., nasohypophyseal aperture, large velar cavity, and cardinal heart) and some intermediate conditions of modern hagfishes (e.g., incipient posterior displacement of branchial region). Thus, Myxinikela provides an important calibration point with which to date origins of these characters.

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Edwards, Susan L., Justin Arnold, Salvatore D. Blair, Margaret Pray, Rachel Bradley, Olivia Erikson, and Patrick J. Walsh. "Ammonia excretion in the Atlantic hagfish (Myxine glutinosa) and responses of an Rhc glycoprotein." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 308, no. 9 (May 1, 2015): R769—R778. http://dx.doi.org/10.1152/ajpregu.00355.2014.

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Hagfishes, the most ancient of the extant craniates, demonstrate a high tolerance for a number of unfavorable environmental conditions, including elevated ammonia. Proposed mechanisms of ammonia excretion in aquatic organisms include vesicular NH4+ transport and release by exocytosis in marine crabs, and passive NH3 diffusion, active NH4+ transport, and paracellular leakage of NH3 or NH4+ across the gills of fishes. Recently, an emerging paradigm suggests that Rhesus glycoproteins play a vital role in ammonia transport in both aquatic invertebrates and vertebrates. This study has identified an Rh glycoprotein ortholog from the gills of Atlantic hagfish. The hagfish Rhcg shares a 56–60% amino acid identity to other vertebrate Rhcg cDNAs. Sequence information was used to produce an anti-hagfish Rhcg (hRhcg) antibody. We have used hRhcg to localize protein expression to epithelial cells of the gill and the skin. In addition, we have quantified hRhcg expression following exposure to elevated plasma ammonia levels. Animals exposed to a 3 mmol/kg NH4Cl load resulted in significantly elevated plasma ammonia concentrations compared with controls for up to 4 h postinjection. This correlated with net ammonia excretion rates that were also significantly elevated for up to 4 h postinjection. Rhcg mRNA expression in both the gill and skin was significantly elevated by 15 min and 1 h, respectively, and hRhcg protein expression in gills was significantly elevated at 2, 4, and 8 h postinjection. These results demonstrate a potential role for Rhcg in the excretion of ammonia in the Atlantic hagfish.

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6

Gorbman, Aubrey. "Hagfish Development." Zoological Science 14, no. 3 (June 1997): 375–90. http://dx.doi.org/10.2108/zsj.14.375.

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Fago, Angela, Laura Giangiacomo, Rossana D'Avino, Vito Carratore, Mario Romano, Alberto Boffi, and Emilia Chiancone. "Hagfish Hemoglobins." Journal of Biological Chemistry 276, no. 29 (April 9, 2001): 27415–23. http://dx.doi.org/10.1074/jbc.m100759200.

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Clifford, Alexander M., Alyssa M. Weinrauch, Susan L. Edwards, Michael P. Wilkie, and Greg G. Goss. "Flexible ammonia handling strategies using both cutaneous and branchial epithelia in the highly ammonia-tolerant Pacific hagfish." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 313, no. 2 (August 1, 2017): R78—R90. http://dx.doi.org/10.1152/ajpregu.00351.2016.

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Hagfish consume carrion, potentially exposing them to hypoxia, hypercapnia, and high environmental ammonia (HEA). We investigated branchial and cutaneous ammonia handling strategies by which Pacific hagfish ( Eptatretus stoutii) tolerate and recover from high ammonia loading. Hagfish were exposed to HEA (20 mmol/l) for 48 h to elevate plasma total ammonia (TAmm) levels before placement into divided chambers for a 4-h recovery period in ammonia-free seawater where ammonia excretion ( JAmm) was measured independently in the anterior and posterior compartments. Localized HEA exposures were also conducted by subjecting hagfish to HEA in either the anterior or posterior compartments. During recovery, HEA-exposed animals increased JAmm in both compartments, with the posterior compartment comprising ~20% of the total JAmm compared with ~11% in non-HEA-exposed fish. Plasma TAmm increased substantially when whole hagfish and the posterior regions were exposed to HEA. Alternatively, plasma TAmm did not elevate after anterior localized HEA exposure. JAmm was concentration dependent (0.05–5 mmol/l) across excised skin patches at up to eightfold greater rates than in skin sections that were excised from HEA-exposed hagfish. Skin excised from more posterior regions displayed greater JAmm than those from more anterior regions. Immunohistochemistry with hagfish-specific anti-rhesus glycoprotein type c (α-hRhcg; ammonia transporter) antibody was characterized by staining on the basal aspect of hagfish epidermis while Western blotting demonstrated greater expression of Rhcg in more posterior skin sections. We conclude that cutaneous Rhcg proteins are involved in cutaneous ammonia excretion by Pacific hagfish and that this mechanism could be particularly important during feeding.

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9

Miyashita, Tetsuto, Michael I. Coates, Robert Farrar, Peter Larson, Phillip L. Manning, Roy A. Wogelius, Nicholas P. Edwards, et al. "Hagfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny." Proceedings of the National Academy of Sciences 116, no. 6 (January 22, 2019): 2146–51. http://dx.doi.org/10.1073/pnas.1814794116.

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Hagfish depart so much from other fishes anatomically that they were sometimes considered not fully vertebrate. They may represent: (i) an anatomically primitive outgroup of vertebrates (the morphology-based craniate hypothesis); or (ii) an anatomically degenerate vertebrate lineage sister to lampreys (the molecular-based cyclostome hypothesis). This systematic conundrum has become a prominent case of conflict between morphology- and molecular-based phylogenies. To date, the fossil record has offered few insights to this long-branch problem or the evolutionary history of hagfish in general, because unequivocal fossil members of the group are unknown. Here, we report an unequivocal fossil hagfish from the early Late Cretaceous of Lebanon. The soft tissue anatomy includes key attributes of living hagfish: cartilages of barbels, postcranial position of branchial apparatus, and chemical traces of slime glands. This indicates that the suite of characters unique to living hagfish appeared well before Cretaceous times. This new hagfish prompted a reevaluation of morphological characters for interrelationships among jawless vertebrates. By addressing nonindependence of characters, our phylogenetic analyses recovered hagfish and lampreys in a clade of cyclostomes (congruent with the cyclostome hypothesis) using only morphological data. This new phylogeny places the fossil taxon within the hagfish crown group, and resolved other putative fossil cyclostomes to the stem of either hagfish or lamprey crown groups. These results potentially resolve the morphological–molecular conflict at the base of the Vertebrata. Thus, assessment of character nonindependence may help reconcile morphological and molecular inferences for other major discords in animal phylogeny.

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10

Schultz, Aaron G., Samuel C. Guffey, Alexander M. Clifford, and Greg G. Goss. "Phosphate absorption across multiple epithelia in the Pacific hagfish (Eptatretus stoutii)." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 307, no. 6 (September 15, 2014): R643—R652. http://dx.doi.org/10.1152/ajpregu.00443.2013.

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Inorganic phosphate (Pi) is an essential nutrient for all organisms, but in seawater, Pi is a limiting nutrient. This study investigated the primary mechanisms of Pi uptake in Pacific hagfish ( Eptatretus stoutii) using ex vivo physiological and molecular techniques. Hagfish were observed to have the capacity to absorb Pi from the environment into at least three epithelial surfaces: the intestine, skin, and gill. Pi uptake in all tissues was concentration dependent, and saturable Pi transport was observed in the skin and gill at <2.0 mmol/l Pi. Gill and intestinal Pi uptake was sodium dependent, but Pi uptake into the skin increased under low sodium conditions. Gill Pi transport exhibited an apparent affinity constant ∼0.23–0.6 mmol/l Pi. A complete sequence of a type II sodium phosphate cotransporter (Slc34a) was obtained from the hagfish gill. Phylogenetic analysis of the hagfish Slc34a transporter indicates that it is earlier diverging than, and/or ancestral to, the other identified vertebrate Slc34a transporters (Slc34a1, Slc34a2, and Slc34a3). With the use of RT-PCR, the hagfish Slc34a transcript was detected in the intestine, skin, gill, and kidney, suggesting that this may be the transporter involved in Pi uptake into multiple epithelia in the hagfish. This is the first measurement of Pi uptake across the gill or skin of any vertebrate animal and first sodium phosphate cotransporter identified in hagfish.

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Osugi, Tomohiro, Katsuhisa Uchida, Masumi Nozaki, and Kazuyoshi Tsutsui. "Characterization of Novel RFamide Peptides in the Central Nervous System of the Brown Hagfish: Isolation, Localization, and Functional Analysis." Endocrinology 152, no. 11 (August 23, 2011): 4252–64. http://dx.doi.org/10.1210/en.2011-1375.

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RFamide (RFa) peptides play various important roles in the central nervous system in both invertebrates and vertebrates. However, there is no evidence of the existence of any RFamide peptide in the brain of hagfish, one of the oldest lineages of vertebrates. In this study, we sought to identify novel RFamide peptides from the brains of hagfish (Paramyxine atami). We identified four novel RFamide peptides, which had the C-terminal Pro-Gln-Arg-Phe-NH2 structure. cDNA cloning revealed that the identified RFamide peptides are encoded in two types of cDNA. Molecular phylogenetic analysis of the two precursors indicated that the hagfish RFamide peptides belong to the PQRFamide peptide group that includes mammalian neuropeptide FF and AF. Based on immunohistochemistry and in situ hybridization, hagfish PQRFamide peptide precursor mRNA and its translated peptides were localized in the infundibular nucleus of the hypothalamus. Immunoreactive fibers were terminated on blood vessels in the infundibular nucleus. Dense immunoreactive fibers were also observed in other brain regions. We further showed that one of the hagfish PQRFamide peptides significantly stimulated the expression of gonadotropin-β mRNA in the cultured hagfish pituitary. These results indicate that the control mechanism of gonadotropin expression by a hypothalamic neuropeptide evolved in the agnathan brain. This is the first evidence describing the identification of RFamide peptides in the hagfish brain. This is also the first report showing the regulation of gonadotropin expression by a homolog of neuropeptide FF that belongs to the PQRFamide peptide group in any vertebrate.

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Young, J. D., Y. Syn, C. M. Tse, A. Davies, and S. A. Baldwin. "FUNCTIONAL AND MOLECULAR CHARACTERISTICS OF A PRIMITIVE VERTEBRATE GLUCOSE TRANSPORTER: STUDIES OF GLUCOSE TRANSPORT BY ERYTHROCYTES FROM THE PACIFIC HAGFISH (EPTATRETUS STOUTI)." Journal of Experimental Biology 186, no. 1 (January 1, 1994): 23–41. http://dx.doi.org/10.1242/jeb.186.1.23.

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The characteristics of glucose transport were investigated in erythrocytes of a primitive vertebrate, the Pacific hagfish (Eptatretus stouti) Lockington. Transport of glucose by intact hagfish erythrocytes and by phospholipid vesicles reconstituted with n-octylglucoside extract of hagfish erythrocyte membranes was rapid and mediated by a saturable stereospecific mechanism sensitive to inhibition by cytochalasin B. Covalent photoaffinity labelling experiments with [3H]cytochalasin B identified the hagfish glucose transporter on SDS/polyacrylamide gels as a protein with an apparent average Mr of 55 000. Amino acid sequence homology between the hagfish and human erythrocyte glucose transporters (GLUT 1) was investigated in immunoblotting experiments using a panel of 12 different antipeptide antisera and affinity-purified antibodies raised against cytoplasmic extramembranous regions of the human transporter, and with an antibody to the intact purified human protein. The latter antibody labelled a component in the membrane with the same apparent Mr as cytochalasin B. Two affinity-purified antipeptide antibodies, corresponding to residues 240–255 and 450–467 of the human erythrocyte transporter, also labelled a component in the membrane with this relative molecular mass, demonstrating localised sequence similarity between the polypeptides of the two species within the central cytoplasmic loop and within the cytoplasmic C-terminal region. Glucose transport by hagfish erythrocytes was not coupled to the movement of protons.

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Riegel, JA. "Analysis of fluid dynamics in perfused glomeruli of the hagfish eptatretus stouti (Lockington)." Journal of Experimental Biology 201, no. 22 (November 1, 1998): 3097–104. http://dx.doi.org/10.1242/jeb.201.22.3097.

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The capillary tuft of glomeruli of the hagfish mesonephros contains both 'low'-pressure and 'high'-pressure glomerular vessels (LPGVs and HPGVs). The existence of the HPGV raised the possibility that pressure filtration could occur in the hagfish kidney when the blood pressure was sufficiently high. Therefore, measurements of glomerular capillary pressure were made in HPGVs and LPGVs whilst single glomeruli were perfused with hagfish Ringer's solution that contained the colloid Ficoll 70. Calculations of the effective colloid osmotic pressure in perfused capillaries were made; these showed that hydrostatic pressures within the HPGV were inadequate to effect pressure filtration except at high rates of perfusion. However, high rates of perfusion provoked perfusion pressures that exceeded the highest values measured in the renal blood supply of lightly anaesthetised hagfish. It was concluded that some process other than pressure filtration must account for formation of the primary urine by hagfish glomeruli. The proportion of the perfusate that became urine, the single glomerulus filtration fraction (SGFF), bore a strong positive relationship to the vascular resistance of perfused glomeruli. Both the SGFF and the vascular resistance were inversely related to the rate of perfusion except when that rate was very high. From these two observations it was concluded that at least two flow pathways exist in hagfish glomeruli: one that has a high vascular resistance and that contributes to the elaboration of the urine, and one that has a low vascular resistance and does not contribute to urine formation. The possible anatomical location of the various flow pathways through hagfish glomeruli and how they may function are discussed.

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Jensen, Frank B. "Comparative Analysis of Autoxidation of Haemoglobin." Journal of Experimental Biology 204, no. 11 (June 1, 2001): 2029–33. http://dx.doi.org/10.1242/jeb.204.11.2029.

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SUMMARY Autoxidation of oxyhaemoglobin (oxyHb) to methaemoglobin was measured at different temperatures in haemoglobin solutions from Atlantic hagfish, river lamprey, common carp, yellowfin tuna and pig. The aims were to evaluate the impact of the absent distal histidine in hagfish haemoglobin, the importance of oxyHb being either monomeric (hagfish and lamprey) or tetrameric (carp, tuna and pig) and to gain information on the temperature-sensitivity of autoxidation. The rate of autoxidation was lower in hagfish than in carp, yellowfin tuna and lamprey haemoglobins at any given temperature. Substitution of the distal histidine residue (His E7) with glutamine in hagfish haemoglobin was therefore not associated with an accelerated autoxidation, as might be expected on the basis of the normal protective role of His E7. Glutamine may have similar qualities to histidine and be involved in the low susceptibility to autoxidation. The low oxidation rate of hagfish haemoglobin, together with an oxidation rate of lamprey haemoglobin that did not differ from that of carp and yellowfin tuna haemoglobins, also revealed that autoxidation was not accelerated in the monomeric oxyhaemoglobins. Pig haemoglobin was oxidised more slowly than fish haemoglobins, demonstrating that fish haemoglobins are more sensitive to autoxidation than mammalian haemoglobins. The rate of autoxidation of hagfish haemoglobin was, however, only significantly greater than that of pig haemoglobin at high temperatures. Autoxidation was accelerated by rising temperature in all haemoglobins. Arrhenius plots of carp and yellowfin tuna haemoglobin revealed a break at 25°C, reflecting a lower temperature-sensitivity between 5 and 25°C than between 25 and 40°C.

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Chaudhary, Gaurav, Randy H. Ewoldt, and Jean-Luc Thiffeault. "Unravelling hagfish slime." Journal of The Royal Society Interface 16, no. 150 (January 2019): 20180710. http://dx.doi.org/10.1098/rsif.2018.0710.

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Hagfish slime is a unique predator defence material containing a network of long fibrous threads each ∼10 cm in length. Hagfish release the threads in a condensed coiled state known as skeins (∼100 µm), which must unravel within a fraction of a second to thwart a predator attack. Here we consider the hypothesis that viscous hydrodynamics can be responsible for this rapid unravelling, as opposed to chemical reaction kinetics alone. Our main conclusion is that, under reasonable physiological conditions, unravelling due to viscous drag can occur within a few hundred milliseconds, and is accelerated if the skein is pinned at a surface such as the mouth of a predator. We model a single skein unspooling as the fibre peels away due to viscous drag. We capture essential features by considering simplified cases of physiologically relevant flows and one-dimensional scenarios where the fibre is aligned with streamlines in either uniform or uniaxial extensional flow. The peeling resistance is modelled with a power-law dependence on peeling velocity. A dimensionless ratio of viscous drag to peeling resistance appears in the dynamical equations and determines the unraveling time scale. Our modelling approach is general and can be refined with future experimental measurements of peel strength for skein unravelling. It provides key insights into the unravelling process, offers potential answers to lingering questions about slime formation from threads and mucous vesicles, and will aid the growing interest in engineering similar bioinspired material systems.

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McDONALD, D. G., V. CAVDEK, L. CALVERT, and C. L. MLLLIGAN. "Acid-Base Regulation in the Atlantic Hagfish Myxine Glutinosa." Journal of Experimental Biology 161, no. 1 (November 1, 1991): 201–15. http://dx.doi.org/10.1242/jeb.161.1.201.

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Blood acid-base status and net transfers of acidic equivalents to the external environment were studied in hagfish, Myxine glutinosa, infused with ammonium sulphate (4mequivkg−1 NH4+) or with sulphuric acid (3mequiv kg−1 H+). Hagfish extracellular fluids (ECF) play a greater role in acid-base regulation than in teleosts. This is because hagfish have a much larger blood volume relative to teleosts, despite a relatively low blood buffering capacity. Consequently, infusion of ammonium sulphate produced only half of the acidosis produced in marine teleosts in comparable studies, and hagfish readily tolerated a threefold greater direct H+ load. Furthermore, the H+ load was largely retained and buffered in the extracellular space. Despite smaller acid-base disturbances, rates of net H+ excretion to the external environment were, nonetheless, comparable to those of marine teleosts, and net acid excretion persisted until blood acid-base disturbances were corrected. We conclude that the gills of the hagfish are at least as competent for acid-base regulation as those of marine teleosts. The nature of the H+ excretion mechanism is discussed.

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Mallatt, Jon, David M. Conley, and Richard L. Ridgway. "Why do hagfish have gill "chloride cells" when they need not regulate plasma NaCl concentration?" Canadian Journal of Zoology 65, no. 8 (August 1, 1987): 1956–65. http://dx.doi.org/10.1139/z87-298.

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Two enzymes implicated in branchial ion transport, Na+-K+-ATPase and carbonic anhydrase, were localized in gill ionocytes ("chloride cells") of the Pacific hagfish, Eptatretus stouti, by light microscopic histochemical techniques. In hagfish, ouabain-sensitive Na+-K+-ATPase activity was confined to apical halves of ionocytes, where most of the cytoplasmic tubular system is located. In marine teleosts, Na+-K+-ATPase was noted in chloride cells and erythrocytes. Acetazolamide and potassium cyanate sensitive carbonic anhydrase activity occurred throughout the cytoplasm and nucleus of hagfish ionocytes. Biochemical assay of hagfish gill homogenates for Na+-K+-ATPase yielded a specific activity of 3.1 μmol Pi∙mg protein−1∙h−1 at 37 °C. This resembles values we obtained for freshwater fish (Carassius auratus: 3.3 μmol Pi∙mg protein−1∙h−1; Tilapia shirana: 3.7 μmol Pi∙mg protein−1∙h−1), and is less than values we obtained for marine teleosts (Pomacentrus spp.: 13 μmol Pi∙mg protein−1∙h−1; Gillichthys mirabilis: 6.7 μmol Pi∙mg protein−1∙h−1). Hagfish resemble freshwater teleosts in many other gill features related to ion transport. The presence of carbonic anhydrase in gill ionocytes of hagfish supports the proposal that these cells function in acid–base regulation, i.e., that they exchange H+ for Na+ and [Formula: see text] for Cl−.

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Suzuki, M., K. Kubokawa, H. Nagasawa, and A. Urano. "Sequence analysis of vasotocin cDNAs of the lamprey, Lampetra japonica, and the hagfish, Eptatretus burgeri: evolution of cyclostome vasotocin precursors." Journal of Molecular Endocrinology 14, no. 1 (February 1995): 67–77. http://dx.doi.org/10.1677/jme.0.0140067.

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ABSTRACT We determined the nucleotide sequences of cDNAs encoding precursors of vasotocin (VT) from two cyclostomes, the lamprey Lampetra japonica and the hagfish Eptatretus burgeri, for estimation of their phylogenetic relationships. Although only 47% similarity was found between the VT cDNAs, the predicted VT precursors of the lamprey and the hagfish were both composed of a signal peptide, VT, Gly-Lys-Arg and a neurophysin, as has been shown for precursors of vasopressin (VP) family hormones, including VP, VT and molluscan conopressin. The central region of the lamprey neurophysin was very similar to those of previously characterized gnathostome neurophysins. Conspicuously, all the positions of 14 Cys residues were conserved in the lamprey neurophysin. The C-terminal region did not have a distinctive Leu-rich core segment, which is always found in the glycopeptide (copeptin) moiety of VP precursors. In contrast, the hagfish neurophysin showed at least two insertions and one deletion in the conserved central region including 14 Cys residues, but contained a potential N-linked glycosylation site and had a high proportion of Leu residues in the C-terminal region, like the neurophysin of another hagfish, Eptatretus stouti. The evolutionary relationships of the precursors of VP family hormones among the lamprey, hagfish, gnathostomes and a mollusc were estimated by a maximum likelihood method. The phylogenetic tree with the highest bootstrap probability showed that the lamprey VT precursor is more closely related to the gnathostome VT and VP precursors than to the hagfish VT precursors.

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Dong, Emily M., and W. Ted Allison. "Vertebrate features revealed in the rudimentary eye of the Pacific hagfish ( Eptatretus stoutii )." Proceedings of the Royal Society B: Biological Sciences 288, no. 1942 (January 13, 2021): 20202187. http://dx.doi.org/10.1098/rspb.2020.2187.

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Hagfish eyes are markedly basic compared to the eyes of other vertebrates, lacking a pigmented epithelium, a lens and a retinal architecture built of three cell layers: the photoreceptors, interneurons and ganglion cells. Concomitant with hagfish belonging to the earliest-branching vertebrate group (the jawless Agnathans), this lack of derived characters has prompted competing interpretations that hagfish eyes represent either a transitional form in the early evolution of vertebrate vision, or a regression from a previously elaborate organ. Here, we show the hagfish retina is not extensively degenerating during its ontogeny, but instead grows throughout life via a recognizable PAX6 + ciliary marginal zone. The retina has a distinct layer of photoreceptor cells that appear to homogeneously express a single opsin of the RH1 rod opsin class. The epithelium that encompasses these photoreceptors is striking because it lacks the melanin pigment that is universally associated with animal vision; notwithstanding, we suggest this epithelium is a homologue of gnathosome retinal pigment epithelium (RPE) based on its robust expression of RPE65 and its engulfment of photoreceptor outer segments. We infer that the hagfish retina is not entirely rudimentary in its wiring, despite lacking a morphologically distinct layer of interneurons: multiple populations of cells exist in the hagfish inner retina and subsets of these express markers of vertebrate retinal interneurons. Overall, these data clarify Agnathan retinal homologies, reveal characters that now appear to be ubiquitous across the eyes of vertebrates, and refine interpretations of early vertebrate visual system evolution.

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Jensen, F. B. "Haemoglobin H+ equilibria in lamprey (Lampetra fluviatilis) and hagfish (Myxine glutinosa)." Journal of Experimental Biology 202, no. 14 (July 15, 1999): 1963–68. http://dx.doi.org/10.1242/jeb.202.14.1963.

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Agnathans, comprising lamprey and hagfish species, have been reported to be practically devoid of HCO3-/Cl- exchange across the red blood cell membrane. This suggests that the capacity of their haemoglobin (Hb) to remove H+ is essential for obtaining a high CO2-carrying capacity in the blood. Hydrogen ion titrations were performed on oxygenated and deoxygenated composite Hbs from river lamprey and from Atlantic hagfish at 15 degrees C and an ionic strength of 0.1 (0.1 mol l-1 KCl). Lamprey Hb was characterised by very low buffer values when the degree of oxygenation was constant, whereas the fixed-acid Haldane effect was large (uptake of approximately 0.9 H+ per monomer upon deoxygenation). Hagfish Hb, in contrast, had large buffer values and a moderate fixed-acid Haldane effect. In deoxygenated Hb, the low buffer values in lamprey correlated with the presence of only 1–1.5 titratable ‘neutral’ groups (normally histidines and α -amino groups) per monomer, whereas there were 4–5 titratable ‘neutral’ groups per monomer in hagfish. The large differences in Hb/H+ equilibria between the two species reflect the early evolutionary divergence between lampreys and hagfish. With respect to CO2 transport, the special Hb/H+ equilibria and the high red blood cell pH in lamprey ensure a high concentration of free HCO3- inside the red cells in venous blood, which compensates for the absence of a shift of HCO3- to the plasma. The Hb/H+ equilibria in hagfish are less effective in ensuring a high CO2-carrying capacity given the virtual absence of a red blood cell HCO3-/Cl- exchange, and other adaptations may be involved.

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Davies, Sarah, Ali Griffiths, and T. E. Reimchen. "Pacific Hagfish, Eptatretus stoutii, Spotted Ratfish, Hydrolagus colliei, and Scavenger Activity on Tethered Carrion in Subtidal Benthic Communities off Western Vancouver Island." Canadian Field-Naturalist 120, no. 3 (July 1, 2006): 363. http://dx.doi.org/10.22621/cfn.v120i3.329.

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The influence of pelagic carrion food falls on marine benthic scavenging communities was investigated at two depths (10 m, 50 m) in Barkley Sound, west Vancouver Island, British Columbia from 12 May to 4 June, 2003. A remotely operated vehicle (ROV) equipped with video cameras was used to monitor anchored carrion (15 kg pig leg) during daylight and darkness. The videos were subsequently analyzed for species diversity, abundance and the intensity of scavenging. At 10 m, Redrock Crab (Cancer productus) and Kelp Greenling (Hexagrammos decagrammus) dominated, while at 50 m, Spot Shrimp (Pandalus platyceros), Spotted Ratfish (Hydrolagus colliei) and Pacific Hagfish (Eptatretus stoutii) were the dominant species, most of which were nocturnal. Hagfish were the major consumers of the carrion and after 23 days, no soft tissues remained at 50 m while 40% remained at 10 m. Within 24 hours of the carrion deployment, two of eleven ratfish succumbed, probably due to the direct clogging effects of hagfish mucus on the respiratory apparatus of the ratfish. These field observations are consistent with laboratory results suggesting high efficacy of hagfish mucus in competitive interactions.

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Glover, Chris N., Carol Bucking, and Chris M. Wood. "Adaptations to in situ feeding: novel nutrient acquisition pathways in an ancient vertebrate." Proceedings of the Royal Society B: Biological Sciences 278, no. 1721 (March 2, 2011): 3096–101. http://dx.doi.org/10.1098/rspb.2010.2784.

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During feeding, hagfish may immerse themselves in the body cavities of decaying carcasses, encountering high levels of dissolved organic nutrients. We hypothesized that this feeding environment might promote nutrient acquisition by the branchial and epidermal epithelia. The potential for Pacific hagfish, Eptatretus stoutii , to absorb amino acids from the environment across the skin and gill was thus investigated. l -alanine and glycine were absorbed via specific transport pathways across both gill and skin surfaces, the first such documentation of direct organic nutrient acquisition in a vertebrate animal. Uptake occurred via distinct mechanisms with respect to concentration dependence, sodium dependence and effects of putative transport inhibitors across each epithelium. Significant differences in the absorbed amino acid distribution between the skin of juveniles and adults were noted. The ability to absorb dissolved organic matter across the skin and gill may be an adaptation to a scavenging lifestyle, allowing hagfish to maximize sporadic opportunities for organic nutrient acquisition. From an evolutionary perspective, hagfish represent a transitory state between the generalized nutrient absorption pathways of aquatic invertebrates and the more specialized digestive systems of aquatic vertebrates.

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Hearle, John. "Of wool and hagfish." Physics World 23, no. 11 (November 2010): 22. http://dx.doi.org/10.1088/2058-7058/23/11/31.

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Amador, Molly H. B. "Hagfish pump some iron." Journal of Experimental Biology 220, no. 2 (January 15, 2017): 136.1–136. http://dx.doi.org/10.1242/jeb.147421.

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Herzig, Shoshana J., William C. Aird, Brijen J. Shah, Michael McKernan, and Mark L. Zeidel. "From Hagfish to Humans." Academic Medicine 87, no. 3 (March 2012): 372–77. http://dx.doi.org/10.1097/acm.0b013e3182444c1b.

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Hardisty, M. W., I. C. Potter, and R. W. Hilliard. "Physiological adaptations of the living agnathans." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 80, no. 3-4 (1989): 241–54. http://dx.doi.org/10.1017/s0263593300028686.

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ABSTRACTThe modes of life and environments of the extant agnathans (cyclostomes) are discussed in relation to their adaptations to temperature, light, oxygen and salinity. As their antitropical distribution indicates, both hagfishes and lampreys are cold water groups. Since hagfishes live in deeper waters than lampreys, they are not exposed to the marked seasonal changes in temperature and light which influence major events in the lamprey life cycle. Both groups tend to be nocturnally active, either burrowing during daylight as in the case of larval lampreys (ammocoetes) and most hagfishes, or showing cryptic behaviour as in the case of adult lampreys. Olfaction plays a major part in the location of prey, presumably aided in adult lampreys by their eyes and sensitive electrosensory system. Rates of standard oxygen consumption, ventilatory frequency and heart rate of adult lampreys increase at night. Standard oxygen consumption is relatively low in ammocoetes (as it also is in hagfishes) but increases markedly during metamorphosis into the adult lamprey. Ammocoetes and hagfishes, and to a lesser extent adult lampreys, are resistant to reduced environmental oxygen tensions. Differences in the oxygen dissociation curves of ammocoetes, adult lampreys and hagfishes can be related to differences in the characteristics of their monomeric haemoglobins and their environments and modes of life. The extraordinary tolerance of the hagfish heart to hypoxia is a reflection of a robust capacity for glycolysis, an LDH isozyme geared towards anaerobic functioning and a low work output. The hagfishes, which are restricted to marine waters, are osmoconformers. The osmolality of their blood, which is almost wholly attributable to inorganic ions, is virtually identical to that of full strength sea water (c. 1000 mOsmkg−1). By contrast, the osmolality of the blood of larval and adult lampreys when in fresh water is only 205-260 mOsm kg−1, i.e. about one quarter to one fifth of those of hagfish, and these rise only to 240-270 mOsm kg−1 in the adults of anadromous lampreys in sea water. The regulation of ions by adult lampreys is achieved by mechanisms similar to those adopted by teleosts. The implications of the contrasting ionic and osmotic physiology of the two living groups of agnathans are discussed in relation to their possible environmental history and against the background of their Carboniferous fossil representatives.

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Russell, Michael J., Nancy J. Pelaez, C. Subah Packer, Malcom E. Forster, and Kenneth R. Olson. "Intracellular and extracellular calcium utilization during hypoxic vasoconstriction of cyclostome aortas." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 281, no. 5 (November 1, 2001): R1506—R1513. http://dx.doi.org/10.1152/ajpregu.2001.281.5.r1506.

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Hypoxic vasoconstriction (HV) is an intrinsic response of mammalian pulmonary and cyclostome aortic vascular smooth muscle. The present study examined the utilization of calcium during HV in dorsal aortas (DA) from sea lamprey and New Zealand hagfish. HV was temporally correlated with increased free cytosolic calcium (Ca[Formula: see text]) in lamprey DA. Extracellular calcium (Ca[Formula: see text]) did not contribute significantly to HV in lamprey DA, but it accounted for 38.1 ± 5.3% of HV in hagfish DA. Treatment of lamprey DA with ionomycin, ryanodine, or caffeine added to thapsigargin-reduced HV, whereas HV was augmented by BAY K 8644. Methoxyverapamil (D600) in zero Ca[Formula: see text] did not affect HV in lamprey DA, nor did it prevent further constriction when Ca[Formula: see text] was restored during hypoxia in hagfish DA. Removal of extracellular sodium (Na[Formula: see text]) caused a constriction in both species. Lamprey DA relaxed to prehypoxic tension following return to normoxia in zero Na[Formula: see text], whereas relaxation was inhibited in hagfish DA. Relaxation following HV was inhibited in lamprey DA when Na[Formula: see text] and Ca[Formula: see text] were removed. These results show that HV is correlated with [Ca2+]c in lamprey DA and that Na+/Ca2+ exchange is used during HV in hagfish but not lamprey DA. Multiple receptor types appear to mediate stored intracellular calcium release in lamprey DA, and L-type calcium channels do not contribute significantly to constriction in either cyclostome.

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Riegel, J. A. "The absence of an arterial pressure effect on filtration by perfused glomeruli of the hagfish, Eptatretus stouti (Lockington)." Journal of Experimental Biology 126, no. 1 (November 1, 1986): 361–74. http://dx.doi.org/10.1242/jeb.126.1.361.

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Single renal corpuscles of hagfish were perfused with a Ringer solution containing Ficoll 70 to simulate the colloid osmotic pressure of hagfish plasma. Simultaneous measurements were made of single glomerulus filtration rate (SGFR), perfusion pressure and the pressure in a vessel of the renal vasculature. The results confirm that SGFR is independent of pressure in the glomerular capillaries (PGC). The results also suggest that flow through glomeruli and SGFR are closely linked. Studies of the pressures in glomerular capillaries during periods when the perfusion rate was varied indicate that PGC reflects the area of the active capillaries and the rate of perfusion. Therefore, in the hagfish, PGC appears to be an effect of factors that cause glomerular filtration, not the main cause of that process.

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Toop, T., J. A. Donald, and D. H. Evans. "Natriuretic peptide receptors in the kidney and the ventral and dorsal aortae of the Atlantic hagfish Myxine glutinosa (Agnatha)." Journal of Experimental Biology 198, no. 9 (September 1, 1995): 1875–82. http://dx.doi.org/10.1242/jeb.198.9.1875.

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The character of natriuretic peptide receptors (NPRs) in the kidney and aortae of the Atlantic hagfish Myxine glutinosa was determined and compared with that of NPRs in hagfish gills. The relationship of hagfish kidney and aortic NPRs with NPRs from higher vertebrates was also examined. Iodinated atrial and C-type natriuretic peptides (NPs) (125I-ANP, 125I-CNP) were used in tissue section autoradiography, competition studies and guanylate cyclase (GC) assays. Rat atrial and porcine C-type NPs (rANP, pCNP) and rat des[Gln18, Ser19, Gly20, Leu21 Gly22]ANP-(4-23)-NH2 (C-ANF, which binds to the mammalian and teleost 'clearance' receptor, NPR-C), were used as competing ligands. 125I-ANP binding sites were observed on both aortae and on the glomeruli, neck segments and archinephric ducts of the kidney. 4.0 nmol l-1 rANP competed for 50% of 125I-ANP glomerular sites. 125I-CNP did not visibly bind to any of the tissues, but 300 nmol l-1 pCNP competed for 50% of 125I-ANP glomerular sites. C-ANF failed to compete for 125I-ANP sites. rANP and pCNP stimulated cyclic GMP production in kidney membrane preparations, but C-ANF did not, demonstrating that the hagfish kidney NPR is GC-linked. This study suggests that a predominant population of ANP-like receptors, similar to the mammalian NPR-A, exists in the myxinoid aortae and kidney tissue. However, no detectable population of a receptor that binds all NPs, such as is present in the hagfish gill, nor an NPR similar to the NPR-C of higher vertebrates was discovered.

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Tait, L. W., C. W. C. Simpson, Y. Takei, and M. E. Forster. "Hagfish natriuretic peptide changes urine flow rates and vascular tensions in a hagfish." Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology 150, no. 1 (July 2009): 45–49. http://dx.doi.org/10.1016/j.cbpc.2009.02.006.

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31

FINCHAM, DARON A., MICHAEL W. WOLOWYK, and JAMES D. YOUNG. "Characterisation of Amino Acid Transport in Red Blood Cells of a Primitive vertebrate, the Pacific Hagfish (Eptatretus Stouti)." Journal of Experimental Biology 154, no. 1 (November 1, 1990): 355–70. http://dx.doi.org/10.1242/jeb.154.1.355.

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Intracellular amino acid levels and the characteristics of amino acid transport were investigated in red blood cells of a primitive vertebrate, the Pacific hagfish (Eptatretus stouti Lockington). In contrast to red cells from euryhaline teleosts and elasmobranchs, which contain high concentrations of β-amino acids, those from hagfish exhibited an intracellular amino acid pool (approx. lOOmmoll−1cell water) composed almost entirely of conventional aαamino acids. Red cell:plasma distribution ratios for individual amino acids ranged from 219, 203 and 173 for alanine, αaminonbutyrate and proline, respectively, to 11 and 13 for lysine and arginine. Corresponding distribution ratios for Na+, K+ and Cl− were 0.043, 21 and 0.32, respectively. The cellular uptake of amino acids, with the exception of Lproline and glycine, was Na+-independent. Compared with mammalian and avian red cells, those from hagfish exhibited 104-fold higher rates of L-alanine transport. Uptake of this amino acid from the extracellular medium was concentrative, but occurred as a 1:1 exchange with intracellular amino acids. The L-alanine transport mechanism was identified as an asc-type system on the basis of its Na+ independence and selectivity for neutral amino acids of intermediate size. A volume-sensitive amino acid channel, which is found in both euryhaline teleosts and in elasmobranchs, is absent from hagfish red cells.

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32

Feng, Jun, Kiichiro Yano, Rita Monahan-Earley, Ellen S. Morgan, Ann M. Dvorak, Frank W. Sellke, and William C. Aird. "Vascular bed-specific endothelium-dependent vasomomotor relaxation in the hagfish, Myxine glutinosa." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 293, no. 2 (August 2007): R894—R900. http://dx.doi.org/10.1152/ajpregu.00080.2007.

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The last common ancestor of hagfish and gnathostomes was also the last common ancestor of all extant vertebrates that lived some time more than 500 million years ago. Features that are shared between hagfish and gnathostomes can be inferred to have already been present in this ancestral vertebrate. We recently reported that hagfish endothelium displays phenotypic heterogeneity in ultrastructure, lectin binding, and mechanisms of leukocyte adhesion. Thus, phenotypic cell heterogeneity evolved as an early feature of the endothelium. In the present study, we wanted to extend these observations by determining whether hagfish endothelium plays a role in mediating vasomotor tone. Response of mesenteric and skeletal muscle arteries to a variety of mediators was assayed by videomicroscopy. Phenylephrine and acetylcholine induced vasoconstriction of mesenteric and skeletal muscle arteries. Bradykinin (BK) and ADP promoted vasorelaxation in precontracted mesenteric arteries but not those from skeletal muscle. BK- and ADP-mediated vasorelaxation of the mesenteric artery was abrogated by mechanical denudation of the endothelium but was unaffected by NG-nitro-l-arginine methyl ester. Indomethacin significantly inhibited the vasodilatory response to ADP but not BK. The nitric oxide donor sodium nitroprusside resulted in endothelium-independent relaxation of both mesenteric and skeletal muscle arteries. Together, these data suggest that site-specific endothelium-dependent vasorelaxation is an evolutionarily conserved property of this cell lineage.

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Mito, M., G. Miyazaki, H. Morimoto, Chong Khoon Tee, and Sam Yong Park. "The structure of Hagfish hemoglobin." Seibutsu Butsuri 40, supplement (2000): S47. http://dx.doi.org/10.2142/biophys.40.s47_3.

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34

Girondot, Marc, Sidney Delgado, and Michel Laurin. "Evolutionary analysis of “hagfish amelogenin”." Anatomical Record 252, no. 4 (December 1998): 608–11. http://dx.doi.org/10.1002/(sici)1097-0185(199812)252:4<608::aid-ar11>3.0.co;2-o.

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35

Knight, K. "Adhesive constrains hagfish thread skeins." Journal of Experimental Biology 217, no. 8 (April 15, 2014): 1199–200. http://dx.doi.org/10.1242/jeb.105841.

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36

Knight, K. "RECIPE FOR HAGFISH SLIME DISCOVERED." Journal of Experimental Biology 213, no. 7 (March 12, 2010): ii. http://dx.doi.org/10.1242/jeb.043919.

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37

Pancer, Z., N. R. Saha, J. Kasamatsu, T. Suzuki, C. T. Amemiya, M. Kasahara, and M. D. Cooper. "Variable lymphocyte receptors in hagfish." Proceedings of the National Academy of Sciences 102, no. 26 (June 17, 2005): 9224–29. http://dx.doi.org/10.1073/pnas.0503792102.

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Cleemann, Lars, Sarah Haviland, Ronnie Dalsgaard, and Martin Morad. "The persistently beating hagfish heart." Biophysical Journal 96, no. 3 (February 2009): 258a. http://dx.doi.org/10.1016/j.bpj.2008.12.1274.

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39

Yano, Kiichiro, Daniel Gale, Steffen Massberg, Pavan K. Cheruvu, Rita Monahan-Earley, Ellen S. Morgan, David Haig, Ulrich H. von Andrian, Ann M. Dvorak, and William C. Aird. "Phenotypic heterogeneity is an evolutionarily conserved feature of the endothelium." Blood 109, no. 2 (September 21, 2006): 613–15. http://dx.doi.org/10.1182/blood-2006-05-026401.

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Abstract Mammalian endothelial cells (ECs) display marked phenotypic heterogeneity. Little is known about the evolutionary mechanisms underlying EC heterogeneity. The last common ancestor of hagfish and gnathostomes was also the last common ancestor of all extant vertebrates, which lived some time more than 500 million years ago. Features of ECs that are shared between hagfish and gnathostomes can be inferred to have already been present in this ancestral vertebrate. The goal of this study was to determine whether the hagfish endothelium displays phenotypic heterogeneity. Electron microscopy of the aorta, dermis, heart, and liver revealed ultrastructural heterogeneity of the endothelium. Immunofluorescent studies demonstrated marked differences in lectin binding between vascular beds. Intravital microscopy of the dermis revealed histamine-induced adhesion of leukocytes in capillaries and postcapillary venules, but no such adhesion in arterioles. Together, these data suggest that structural, molecular, and functional heterogeneity of the endothelium evolved as an early feature of this cell lineage.

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FORSTER, M. E. "Myocardial Oxygen Consumption and Lactate Release by the Hypoxic Hagfish Heart." Journal of Experimental Biology 156, no. 1 (March 1, 1991): 583–90. http://dx.doi.org/10.1242/jeb.156.1.583.

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Myocardial oxygen consumption (MOO2)and lactic acid release were measured in the isolated heart of a hagfish (Eptatretus cirrhatus Forster) perfused in vitro. Two different ranges of partial pressures of oxygen were employed (PIOO2 3.87-5.87 and 1.60-2.67 kPa). All hearts released lactate into the perfusate, but the rate of release was greater and MOO2 was depressed at the lower PIOO2. When energy production through the glycolytic pathway to lactate is converted to oxygen equivalents and added to measured oxygen consumption rates, over a wide range of power outputs and different values of POO2, the data can be fitted to a single linear regression line. The rate of oxygen consumption of the hagfish myocardium, so obtained, is similar to values reported for teleost fish. The unusual ability of the hagfish myocardium to support perhaps up to 50 + of its maximal power output through anaerobic metabolism is related to its extremely low cardiac energy demand.

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41

Peters, T., R. E. Forster, and G. Gros. "Hagfish (Myxine glutinosa) red cell membrane exhibits no bicarbonate permeability as detected by (18)O exchange." Journal of Experimental Biology 203, no. 10 (May 15, 2000): 1551–60. http://dx.doi.org/10.1242/jeb.203.10.1551.

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The bicarbonate permeability of the plasma membrane of intact hagfish (Myxine glutinosa) red blood cells and the intracellular carbonic anhydrase activity of these cells were determined by applying the (18)O exchange reaction using a special mass spectrometric technique. When the macromolecular carbonic anhydrase inhibitor Prontosil-Dextran was used to suppress any extracellular carbonic anhydrase activity, the mean intracellular acceleration of the CO(2) hydration/HCO(3)(−) dehydration reaction over the uncatalyzed reaction (referred to as intracellular carbonic anhydrase activity A(i)) was 21 320+/−3000 at 10 degrees C (mean +/− s.d., N=9). The mean bicarbonate permeability of the red blood cell membrane (P(HCO3)-) was indistinguishable from zero. It can be concluded that CO(2) transport within hagfish blood does not follow the classical scheme of CO(2) transport in vertebrate blood. It is suggested that the combination of considerable intraerythrocytic carbonic anhydrase activity and low P(HCO3)- may serve to enhance O(2) delivery to the tissue in the exceptionally hypoxia-tolerant hagfish.

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42

Fleury, Aharon G., Eva M. MacLennan, Rylan J. Command, and Francis Juanes. "Reproductive biology and ecology of Pacific hagfish ( Eptatretus stoutii ) and black hagfish ( Eptatretus deani )." Journal of Fish Biology 99, no. 2 (April 24, 2021): 596–606. http://dx.doi.org/10.1111/jfb.14748.

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Uyeno, T. A., and A. J. Clark. "On the fit of skins with a particular focus on the biomechanics of loose skins of hagfishes." Canadian Journal of Zoology 98, no. 12 (December 2020): 827–43. http://dx.doi.org/10.1139/cjz-2019-0296.

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There is a considerable diversity in how skins fit. Here, we review the function of both tight and loose skins and note that the latter are poorly understood. Analysis of loose skin examples suggest five functional categories: (I) freedom of movement, (II) surface area enhancement, (III) increased structural extensibility, (IV) lubrication, and (V) maladaptive examples arising through sexual or artificial selection. We investigate the skins of hagfishes as a model for understanding loose skin function by examining its structure using histology, standardized puncture resistance testing using the ASTM F1306 protocol, and the effect of internal pressure using a simple inflated balloon model. Skins of hagfishes are composed of multiple layers of cross-helically wound connective tissue fibers of a 45° angle to the longitudinal axis, resulting in a skin that functions as fabric cut “on the bias”. Hagfish skins are relatively yielding; however, skin looseness adds a “structural extensibility” that may allow hagfishes to compensate for low puncture resistance. Physical balloon models, with stiff cores that limit length changes, show that only low pressures allow short loop radii without local buckling. Hagfishes represent ideal organisms for studying loose skin function because their skins seem to fit in all functionally adaptive categories.

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Riegel, J. A. "Secretion of primary urine by glomeruli of the hagfish kidney." Journal of Experimental Biology 202, no. 8 (April 15, 1999): 947–55. http://dx.doi.org/10.1242/jeb.202.8.947.

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Adrenaline and noradrenaline increased the perfusion pressure (Pperf) and single glomerulus filtration rate (SGFR) of perfused hagfish glomeruli. Small amounts (0.1 % or 0.5 %) of bovine serum albumin (BSA) in perfusion fluids containing Ficoll 70 did not diminish the loss of colloid from hagfish glomerular capillaries as has been reported for other perfused capillaries. However, replacement of Ficoll 70 with an osmotically equivalent amount (3 %) of BSA appreciably reduced colloid loss. It was concluded that adrenaline and colloids enhanced flow through the urine-forming capillaries. Whereas adrenaline elevated the SGFR, colloid lowered the SGFR probably by a direct effect on the fluid permeability of the capillary walls. The flow-enhancing effect of adrenaline was used to ensure the exposure of urine-forming capillaries to two inhibitors of active fluid transport, ouabain and 2,4-dinitrophenol (DNP). Both substances lowered the single glomerulus filtration fraction (SGFF), probably by affecting a fluid secretion mechanism. In addition, DNP diminished the flow-enhancing effect of adrenaline. This study provides relatively unequivocal evidence that fluid secretion underlies the formation of primary urine by the hagfish.

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45

Foster, Glen D., and T. W. Moon. "Enzyme activities in the Atlantic hagfish, Myxine glutinosa: changes with captivity and food deprivation." Canadian Journal of Zoology 64, no. 5 (May 1, 1986): 1080–85. http://dx.doi.org/10.1139/z86-162.

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Selected Krebs cycle enzymes and carbohydrate, amino acid, and lipid metabolizing enzymes were assayed in the muscle and liver of newly captured (April, 4 °C; August, 15 °C), fed (for 7 months), and food-deprived (for 7 and 11 months) hagfish, Myxine glutinosa. Seasonal differences were found in the glycogen content of the muscle and liver of newly captured hagfish (lower in the cold temperature), while consistently high levels were maintained in the fed group. Food deprivation decreased the content. All enzymes measured were found in both tissues, except glucose-6-phosphate dehydrogenase (liver only) and glycerol kinase (absent in both tissues). Activities of the enzymes were lower than teleost values, except for pyruvate kinase, citrate synthase, and 3-hydroxyacyl-CoA dehydrogenase, for which activities resembled teleost levels. Enzyme values from the fed fish (7 months) were generally the same as the newly captured group, and food deprivation increased phosphoenolpyruvate carboxykinase activities without altering other enzyme levels. These results support the view that hagfish are anoxia tolerant with low metabolic potential and demonstrate that the muscle and liver rely on carbohydrate and lipid reserves during fasting.

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46

Bernier, N., J. Fuentes, and D. Randall. "Adenosine receptor blockade and hypoxia-tolerance in rainbow trout and Pacific hagfish. II. Effects on plasma catecholamines and erythrocytes." Journal of Experimental Biology 199, no. 2 (February 1, 1996): 497–507. http://dx.doi.org/10.1242/jeb.199.2.497.

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The purpose of this study was to examine the role of adenosine receptors (ARs) in (1) the regulation of catecholamine secretion and (2) the modulation of blood oxygen capacitance by catecholamines. To this end, we assessed the response of rainbow trout and Pacific hagfish treated with either an AR blocker, theophylline, or saline under hypoxic and normoxic conditions. Compared with the control hypoxic rainbow trout, AR blockade resulted in a smaller increase in haematocrit and haemoglobin (Hb) concentration of the blood, smaller red blood cell transmembrane pH differences and mean cellular [Hb] (MCHC), as well as a 16-fold higher plasma adrenaline concentration after only 10 min of acute hypoxic exposure. In hypoxic hagfish, AR blockade had no effect on the [Hb] of the blood, and there was no regulation of red blood cell pH or changes in MCHC. However, whereas plasma [adrenaline] did not change following exposure to a PwO2 of 1.33 kPa in the hypoxic sham group, the concentration increased 3.8-fold within 10 min in the theophylline-injected group. These results suggest that adenosine modulates the circulating level of catecholamines in both hypoxic rainbow trout and hypoxic Pacific hagfish.

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Furlong, Rebecca F., and John F. Mulley. "ParaHox Cluster Evolution — Hagfish and Beyond." Zoological Science 25, no. 10 (October 2008): 955–59. http://dx.doi.org/10.2108/zsj.25.955.

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48

Jensen, David. "THE ANEURAL HEART OF THE HAGFISH*†." Annals of the New York Academy of Sciences 127, no. 1 (December 16, 2006): 443–58. http://dx.doi.org/10.1111/j.1749-6632.1965.tb49418.x.

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OTA, KINYA G., SATOKO FUJIMOTO, YASUHIRO OISI, and SHIGERU KURATANI. "Late Development of Hagfish Vertebral Elements." Journal of Experimental Zoology Part B: Molecular and Developmental Evolution 320, no. 3 (February 8, 2013): 129–39. http://dx.doi.org/10.1002/jez.b.22489.

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50

Jørgensen, J. M., M. Shichiri, and F. A. Geneser. "Morphology of the Hagfish Inner Ear." Acta Zoologica 79, no. 3 (July 1998): 251–56. http://dx.doi.org/10.1111/j.1463-6395.1998.tb01163.x.

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Journal articles on the topic 'Hagfish'

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