Academic literature on the topic 'Radula (zoologie) – Morphologie (biologie)'

Abstract. Sudarmono. 2018. Short Communication: Pollen diversity in the Bogor Botanic Gardens, Indonesia. Biodiversitas 20: 931-936. Pollen morphology influenced the process of plants evolution. Bogor Botanic Gardens has many living collections in terms of pollen diversity. The purpose of this study was observed at the diversity of pollen morphology at the Bogor Botanic Gardens and its implications for the pollen conservation of plants in the collection. The method used is cleaning the pollen using Glacial Acetic Acid (AAG), then examined using a light microscope in the tissue culture laboratory of Bogor Botanic Gardens. There were 35 specimens that were analyzed and the results were randomly shaped pollen from radial symmetry or bilateral symmetry to its combination with monocolpate, tricolpate, pericolpate and stephanocolpate. While aperture types were the monoporate type with 5 specimens, monocolpate 10 specimens, tricolpate 11 specimens, stephanocolpate 4 specimens, periporate 4 specimens, and syncolpate 1 specimen. Three specimens families Caesalpiniaceae (order Fabales) has the shape of pollen vary, i.e radial symmetry monocolpate and radial symmetry tricolpate. Similarly, two specimens of the family Araliaceae (Apiales) different shapes, namely radial symmetry and bilateral symmetry tricolpate. In Asteraceae and Asclepiadaceae has the same shape, the radial symmetry tricolpate. Overall of 35 specimens then there are 22 specimens of radial symmetry and 13 specimens of bilateral symmetry. For the same family have the same ornamentation, for example in the Lamiaceae, Malvaceae, and Rutaceae. But the uniqueness occurs in the family of Arecaceae or palm family that show the diversity in the shape and size of pollen in each genus. Pollen morphology analysis through a combination of morphological data, palynology, and molecular samples more would be better. Pollen bank as pollen in the living collections of Bogor Botanic Gardens is needed to germplasm conservation of endangered plants in Indonesia.

The two small white (W) cells in the buccal ganglia of Tritonia hombergi can initiate and modulate cyclic activity in the pattern generating neurones which drive feeding activity in the buccal mass. They also make extensive monosynaptic connections with the buccal motoneurones, generating EPSPs on protractor (P) cells, IPSPs on retractor (R) cells, and EIPSPs on the small radula flattener (F) cells. Two F motoneurones receive a chemically mediated, facilitating EPSP from the W cells. Inactive W cells receive weak excitatory feedback from the pattern generating network interneurones (FPG) in phase I of the feeding cycle and also from some F cells. Prolonged depolarization of one W cell recruits the other. When both are active they adopt a patterned burst mode with a common inhibitory input in phase I.

Cartilaginous fishes continuously replace their teeth throughout their life (polyphyodonty) and often show a sexually dimorphic dentition that was previously thought to be an invariant sex character. Radial vector analysis of tooth shape in the polyphyodontic stingray Dasyatis sabina across a consecutive 24 month period shows a stable molariform morphology for females but a periodic shift in male dentition from a female-like molariform to a recurved cuspidate form during the reproductive season. The grip tenacity of the male dentition is greater for the cuspidate form that occurs during the mating season than for the molariform dentition that occurs during the non-mating season. Dental sexual dimorphism and its sex-dependent temporal plasticity probably evolved via polyphyodontic preadaptation under selective pressures on both sexes for increased feeding efficiency and sexual selection in males to maximize mating success. These phenomena are important considerations for the identification and classification of cartilaginous fishes and possibly other polyphyodontic vertebrates in the fossil record.

Establishment of culture systems with type A spermatogonial cells has focused primarily on the use of testicular cells from prepubertal animals. The objective of this study was to evaluate various culture systems on development of testicular cells derived from prepubertal and adult bulls. Testicular cells (were harvested from 3–4 mo-old prepubertal bulls (PB; Dairy; single fresh testis weight: 24.1 ± 0.1 g) and adult bulls (AB; Beef; 399.0 ± 0.5 g). After purification using a discontinuous Percoll density gradient, testicular cells (50 × 103 cells well–1; 24-well plate) were kept separate according to origin (prepubertal or adult) and were cultured in the presence (FL) or absence (NF) of a feeder monolayer (mitomycin C-treated male bovine fetal fibroblasts) with either embryonic-like stem cell media (ELSC; DMEM high glucose) or regular media (RCC; DMEM low glucose) supplemented with regular fetal bovine serum (FBS-S) or charcoal stripped (FBS-SF). Colony number, size and type (round, radial, and irregular) were examined on Days 4, 7 or 15 of culture. Data were analyzed using a randomized block design with factorial treatment arrangement. Depending on variable of interest, fixed treatment effects were feeder monolayer, fetal bovine serum type, media type, bull type, day of culture (4, 7, and 15 d) and interactions. Cell viability and percentage of germ and somatic cells at seeding were used as covariates. Plate (bull type × day) were random blocking factors. Cells from prepubertal bulls had greater viability than adult bulls (P < 0.0001) immediately after digestion (92.0 ± 0.1 and 84.9 ± 0.1%, respectively) and immediately after Percoll purification (78.8 ± 0.2 and 44.9 ± 0.2%, respectively). Following digestion and cell purification, percentage of cultured testicular cells staining positive for protein gene product 9.5 was 11.5 ± 0.17% for prepubertal bulls and 15.5 ± 0.19% for adult bulls (P < 0.0001). Colonies in culture presented similar morphological characteristics and timing of formation as those observed by Izadyar et al. (2003 Biol. Reprod. 68, 272–281) when culturing bovine type A spermatogonia from prepubertal bulls. Number of colonies increased from Day 4 to 15 of culture and was not affected by bull type. Overall, radial colonies were the most predominant type of colony in culture (P < 0.0001). The maximum number and size of colonies were obtained on a FL with RCC media containing FBS-S in prepubertal and adult bulls (P < 0.0001). Data illustrate that isolation and culture of testicular cells from mature bulls resulted in colony formation, similar to prepubertal animals. Although cell cultures were a mixed population, colonies with morphologies appearing similar to those previously reported in the literature suggest that a portion were likely stem cells in origin. Efforts are currently underway to use markers to further define colony populations. Nonetheless, these findings suggest that culture of testicular cells in the presence of a feeder layer with regular culture media containing FBS with steroids was beneficial in colony formation regardless of bull type.

1. The mechanism of dipteran flight has been investigated in a comparative study involving thorax manipulation, analysis of high-speed films and direct observation of tethered flies under stroboscopic illumination. 2. The click action observed in CCl4-anaesthetized Calliphora was found to be due to an interaction between the radial stop and the pleural wing process at the top of the upstroke. The movements occurring during unanaesthetized tethered flight were quite different as these structures were vertically separated except towards the bottom of the downstroke (Miyan & Ewing, 1985a,b). 3. Results of observations on tethered insect flight and on morphology did not give full support to either the click mechanism (Boettiger & Furshpan, 1952) or the model of Miyan & Ewing. 4. A novel model for the wingbeat is proposed. Distortion of the thorax brought about by the flight muscles results in upward and outward movement of the lateral scutum during the downstroke and inward and downward movement during the upstroke. In more advanced flies flexion lines result in a differentiated scutellar lever and parascutal shelf. Distortion is thereby limited largely to the posterior scutum. The parascutal shelf moves as a part of the scutal distortion, not as an independent element in the articulation, and the system is not bistable. 5. The automatic changes in angle of attack are caused by inertial and aerodynamic forces acting around the torsional axis of the wing during the beat, which twist the compliant wing base.

The fast-start escape response is a rapid, powerful body motion used to generate high accelerations of the body in virtually all fishes. Although the neurobiology and behavior of the fast-start are often studied, the patterns of muscle activity and muscle force production during escape are less well understood. We studied the fast-starts of two basal actinopterygian fishes (Amia calva and Polypterus palmas) to investigate the functional morphology of the fast-start and the role of intramuscular pressure (IMP) in escape behavior. Our goals were to determine whether IMP increases during fast starts, to look for associations between muscle activity and elevated IMP, and to determine the functional role of IMP in the mechanics of the escape response. We simultaneously recorded the kinematics, muscle activity patterns and IMP of four A. calva and three P. palmas during the escape response. Both species generated high IMPs of up to 90 kPa (nearly 1 atmosphere) above ambient during the fast-start. The two species showed similar pressure magnitudes but had significantly different motor patterns and escape performance. Stage 1 of the fast-start was generated by simultaneous contraction of locomotor muscle on both sides of the body, although electromyogram amplitudes on the contralateral (convex) side of the fish were significantly lower than on the ipsilateral (concave) side. Simultaneous recordings of IMP, escape motion and muscle activity suggest that pressure change is caused by the contraction and radial swelling of cone-shaped myomeres. We develop a model of IMP production that incorporates myomere geometry, the concept of constant-volume muscular hydrostats, the relationship between fiber angle and muscle force, and the forces that muscle fibers produce. The timing profile of pressure change, behavior and muscle action indicates that elevated muscle pressure is a mechanism of stiffening the body and functions in force transmission during the escape response.

AbstractIn the bodies of seed plants, lateral organs of the shoot, for example cotyledons, leaves, and floral organs, are determinate and exhibit localized planer growth resulting in breaking of radial symmetry and asymmetric development. Localized planer growth in the leaf generates the leaf blade, the principle site of photosynthesis in most plants. Development of flat and expanded lamina is an important physiological process. In these processes, a few kind of meristems cooperate with regulating leaf development. In this work, with transfer sense ASL11, sense ASL38 and antisense ASL15 under 35S promoter to to Arabidopsis (Col-0), we found a series of radial symmetric needle-like rosette leaves. By analyzing the anatomical and the epidermal cell features, our data suggests that in these malformed leaf blades, a few meristem tissues all can be suppressed or accelerated, and normal leaf blade morphology disappears. Pro ASL11:GUS expression further suggests that this process may be triggered by misexpression of a few transcription factors (Tfs).

La masse buccale des ammonites recèle des données utilisables en paléobiologie et en phylogénie. L'exploration des chambres d'habitation de spécimens remarquablement bien préservés, a permis la découverte de plusieurs éléments de la masse buccale chez Didymoceras, Rhaeboceras et Baculites et une nouvelle organisation de la microstructure a été identifiée chez les ammonites. Grâce à l'utilisation de techniques d'imagerie 3D utilisées pour la première fois chez les ammonites (CTscan, PPC-SR-μCT), la morphologie de la radula a été observée chez 3 spécimens de Baculites et un spécimen de Rhaeboceras. Une hypothèse de mode alimentaire pour les ammonites possédant une mâchoire de type aptychus a été proposée, leur alimentation reposerait sur des organismes appartenant au plancton s. L. Et plus particulièrement au zooplancton. Elle est renforcée par la découverte de restes d'organismes dans la masse buccale d'un spécimen de Baculites
The buccal mass of ammonites can be used for paleobiological and phylogenetical studies. The exploration of the body chamber of exceptionally well-preserved specimens allowed to discover new buccal mass elements in Didymoceras, Rhaeboceras and Baculites and a new type of microstructre was identified in ammonites. Thanks to 3D imaging, used for the first time in ammonites (CTscan, PPC-SR-μCT), the morphology of the radula could be observed in three specimens of Baculites and one specimen of Rhaeboceras. After the morphological analyses of the jaw elements and the comparison with recent cephalopods, it was suggested that ammonites with aptychus jaws fed on organisms belonging to the plankton sl. , and more precisely zooplankton. It was reinforced by the discovery of organisms rests that could belong to the zooplankton in the buccal mass of one specimen of Baculites

Les espèces de coraux du genre Pocillopora sont notoirement difficiles à identifier. Pour tenter d'y remédier, les génomes mitochondriaux de deux individus ont été séquencés, révélant la présence de deux régions variables : un cadre ouvert de lecture de fonction inconnue et la région de contrôle putative. Par ailleurs, une méthode nouvelle pour le séquençage direct de mélanges d'haplotypes a été mise au point et appliquée à l'analyse de quatre marqueurs nucléaires (l’ITS2 et trois introns) : de manière inattendue, pour chacun de ces marqueurs plus de deux séquences ont été détectées chez certains individus. L’analyse d’échantillons récoltés en diverses localités de l’océan Pacifique (Okinawa, Philippines, Nouvelle Calédonie, Hawaii, Clipperton et Mexique) suggère un nombre d'espèces de Pocillopora inférieur à ce que la variation morphologique laissait supposer, et remet en question l'hypothèse d'un centre de biodiversité du genre localisé dans le Pacifique Est
Corals of the genus Pocillopora are notoriously difficult to identify down to species level. In the present study, the complete mitochondrial genomes of two individuals of contrasting morphologies were sequenced, revealing the presence of two variable regions: the putative D-loop and a novel ORF of unknown function. Moreover, a method was discovered allowing for direct sequencing of haplotype mixtures and applied to the development and analysis of four nuclear sequence markers (the ITS2 region and three introns): unexpectedly, for each of them more than two sequences were detected in some individuals. Analysis of these markers for a set of samples collected across the Pacific Ocean (Okinawa, Philippines, New Caledonia, Hawaii, Clipperton and Mexico) suggests that Pocillopora species are fewer than inferred from morphology and challenges the hypothesis of an eastern Pacific center of biodiversity for this genus

Die Morphologie der Buchlungen von Arachniden (Arachnida Lamarck, 1801 – Arthropoda, Chelicerata) wurde in der vorliegenden Dissertation einer streng vergleichenden Analyse unterzogen, welche mit Hilfe moderner Methoden eine neue Sicht auf die Phylogenie der Arachniden eröffnet. Aus dem Vergleich mit den potentiellen Schwestergruppen (Xiphosura, Eurypterida) und mit Skorpionsfossilien erweist sich der einmalige Landgang eines gemeinsamen Vorfahrens aller rezent terrestrischen Arachniden. Buchlungen-Daten von 200 rezenten + 2 fossilen Skorpionen, 16 Geißelspinnen (Amblypygi), 17 Geißelskorpionen (Thelyphonida), einem Schizomiden (Schizomida), einem ausgestorbenen Trigonotarbiden (Trigonotarbida) und der Außengruppe, den rezenten Pfeilschwanzkrebsen (Xiphosura), wurden zu einem illustrierten Katalog zusammengestellt. Die unüberschaubare Vielfalt der oft graduell variierenden Strukturen macht die eindeutige Definition der Merkmale und auftretenden Merkmalszustände notwendig. Es wurden folgende 5 Merkmale definiert: (1) die Oberflächen der Atemlamellen, (2) der Lamellenrand, (3) der posteriore Stigmenrand, (4) der anteriore Stigmenrand und (5) die Wand des Atriums. Hierbei tragen die Merkmale 1-3 mit ihrer unerwarteten Fülle innerhalb der Skorpione maßgeblich zur Aufklärung ihrer Verwandtschaftsverhältnisse bei. Ähnliches wird von den Merkmalen 4 und 5 bezogen auf die Uropygi s. lat. vermutet. Ein sechstes Merkmal (Sensillen/Poren) wurde definiert, doch nur vereinzelt erfasst. Raster-Elektronenmikroskopie diente der Erfassung der cuticulären Feinstruktur der Buchlungen. Die Struktur der Buchlungen im Gesamten wurde mittels histologischer Schnittserien und mit auf µCT basierenden 3D-Rekonstruktionen untersucht. Für die Untersuchung von Trigonotarbiden-Fossilien wurde eine Methode entwickelt, die 3D-Rekonstruktion aus Sequenzen von Mikrofotos in unterschiedlichen Fokusebenen generiert.
Strict comparative analyses of the morphology of arachnid book lungs (Arachnida Lamarck, 1801 - Arthropoda: Chelicerata) were carried out in the present doctoral thesis using modern methods, resulting in a new perspective on arachnid phylogeny. Comparisons with potential aquatic sistergroups (Xiphosura and/or Eurypterida) and fossil scorpions give rise to the hypothesis of the unique terrestrialization of ancestors, which is common for all arachnids. Data from 200 Recent + 2 extinct scorpions, 16 whip spiders (Amblypygi), 17 whip scorpions (Thely-phonida), 1 schizomid (Schizomida), 1 extinct trigonotarbid (Trigonotarbida) and 1 outgroup - horseshoe crab (Xiphosura) are assembled into an illustrated catalogue of arachnid book lungs. Following the observations of these gradually differing cuticular structures the vast variation of book-lung fine structure across Arachnida requires unequivocal definition of characters and character states. Five characters are defined, which are assigned to distinct homologous book-lung structures: (1) the surface structure of the respiratory lamellae, (2) structure of the distal edges of the lamellae, (3) the posterior edge of the spiracle, (4) the anterior edge of the spiracle and (5) the structure of the wall lining the atrial chamber. Especially the book-lung characters 1-3 contain unexpected information, which helps resolve relationships within Scorpiones to a high degree, and characters 4 and 5 are of considerable importance for Uropygi s. lat. One sixth character (sensilla/pores) is mentioned, but sporadically examined. However, cuticular book-lung fine structure is studied using SEM, the gross morphology is reassessed using histological sectioning and 3D-reconstructions based on µCT. For investigations on trigonotabid fossils a new method yielding 3D-reconstructions from stacks of subsequent focal layers was developed.

L’embranchement Hemichordata regroupe les classes Enteropneusta et Pterobranchia. Hemichordata constitue, avec l’embranchement Echinodermata, le groupe-frère des chordés. Les entéropneustes sont des organismes vermiformes solitaires qui vivent sous ou à la surface du substrat et s’alimentent généralement par déposivorie, alors que les ptérobranches sont des organismes coloniaux filtreurs habitant dans un réseau de tubes appelé coenecium. Ce mémoire présente trois études dont le point commun est l’utilisation des hémichordés actuels pour répondre à des questions concernant l’évolution des hémichordés, des chordés, et du super-embranchement qui les regroupe, Deuterostomia. Notre première étude démontre que les fentes pharyngiennes, l’organe pré-oral cilié (POCO) et le pharynx de l’entéropneuste Protoglossus graveolens sont utilisés pour l’alimentation par filtration. Le système de filtration de P. graveolens permet la capture de particules jusqu’à 1.3 um, à un débit de 4.05 mm.s-1, pour une demande énergétique de 0.009 uW. Les similarités structurales et fonctionnelles avec le système de filtration des céphalochordés suggèrent que la filtration pharyngienne est ancestrale aux deutérostomes. Lors de notre deuxième étude, nous avons exploré l’hypothèse selon laquelle le POCO des entéropneustes, une structure ciliée pré-buccale au rôle possiblement chémorécepteur, serait homologue au « wheel organ » des céphalochordés et à l’adénohypophyse des vertébrés. Pour cela, nous avons déterminé par immunohistochimie l’expression de Pit-1, un facteur de transcription spécifique à ces deux structures, chez l’entéropneuste Saccoglossus pusillus. Pit-1 est exprimé dans des cellules sensorielles du POCO, mais aussi dans des cellules épithéliales distribuées dans le proboscis, collet et tronc. Ce patron d’expression ne permet pas de confirmer ou rejeter l’homologie du POCO et de l’adénohypophyse des vertébrés. Lors de notre troisième étude, nous avons caractérisé l’ultrastructure du coenecium des ptérobranches Cephalodiscus hodgsoni, Cephalodiscus nigrescens et Cephalodiscus densus par microscopie électronique à transmisison et à balayage. Cephalodiscus est le groupe frère de Graptolithina, un groupe qui inclut les graptolithes éteints ainsi que les ptérobranches du genre Rhabdopleura. Nous avons décrit les types de fibrilles de collagène présents, leur taille et leur organisation, ainsi que l’organisation globale du coenecium. Nous avons ainsi démontré la présence chez Cephalodiscus d’une organisation similaire au paracortex, pseudocortex et eucortex des graptolithes. La présence chez Cephalodiscus de ce type d’organisation suggère que le cortex est ancestral à la classe Pterobranchia. Ces trois études illustrent plusieurs axes importants de la recherche sur les hémichordés, qui en intégrant des données morphologiques, fonctionnelles et moléculaires permet de reconstruire certains évènements clés de l’évolution des deutérostomes.
The phylum Hemichordata comprises the classes Enteropneusta and Pterobranchia. Together with echinoderms, hemichordates are the sister-group to chordates. Enteropneusts are worm-shaped solitary deposit feeders. Pterobranchs are colonial filter feeders that live in a secreted collagenous domicile called a coenecium. In this thesis, three studies are presented. These studies are based on observations of extant hemichordates, and adress a variety of issues relating to the evolution of hemichordates, chordates, and the super-phylum to which they belong: Deuterostomia. Our first study demonstrates that the gill slits, pre-oral ciliary organ (POCO), and lining of the pharynx of the enteropneust Protoglossus graveolens are used in filter feeding. The filter-feeding system of P. graveolens enables particle capture down to 1.3 um, at a rate up to 4.05 mm.s-1, with a power consumption of 0.009 uW. Structural and functional similarities with the cephalochordate filter-feeding system suggest that pharyngeal filter-feeding is ancestral to the deuterostomes. In our second study, we address the hypothesis that the enteropneust POCO, a putative chemosensory structure located anterior to the mouth, is homologous to the cephalochordate wheel organ and vertebrate adenohypophysis. We characterized the expression pattern of the adenohypophysis-specific transcription factor Pit-1 in the adult enteropneust Saccoglossus pusillus with immunohistochemistry. Pit-1 is expressed in sensory cells of the POCO and in scattered epithelial cells of the proboscis, collar and trunk. This expression pattern does not allow to confirm or reject the homology of the POCO with the vertebrate adenohypophysis. In our third study, we characterized the ultrastructure of the coenecium of the pterobranchs Cephalodiscus hodgsoni, Cephalodiscus nigrescens and Cephalodiscus densus using transmission and scanning electron microscopy. Cephalodiscus is the sister-group to the Graptolithina, which includes the extinct graptolites and the extant pterobranch genus Rhabdopleura. We described the fibril types, size and organization, as well as the general organization of the coenecium. We demonstrated that the coenecium of Cephalodiscus shows similarities with the graptolite eucortex, paracortex and pseudocortex. The cortical-like organization of the coenecium of Cephalodiscus suggests that the cortex is ancestral to the Pterobranchia. Together, these three studies illustrate different axes of hemichordate research, and show how integrating morphological, functional and molecular data allows us toinfer key events in the evolution of deuterostomes.

Cette étude comparative est une révision de la famille des Harrimaniidae basée sur les caractères morphologiques d'espèces connues et nouvelles provenant des collections de William E. Ritter, Theodore H. Bullock et Kandula P. Rao rassemblées au cours du 20e siècle. Les descriptions présentées ici portent le total des genres de cinq à neuf par l'ajout de Horstia n. gen., Mesoglossus n. gen., Ritteria n. gen et Saxipendium, un genre auparavant attribué à la famille monospécifique des Saxipendidae. Le nombre d'espèces est porté à 34 par la description de cinq nouvelles espèces du Pacifique oriental: Horstia kincaidi, Mesoglossus intermedius, Mesoglossus macginitiei, Protoglossus mackiei et Ritteria ambigua. La description d'une sixième espèce, Stereobalanus willeyi Ritter et Davis, 1904 (nomen nudum) est présentée ici pour la première fois, ainsi qu'une description abrégée de Saxipendium coronatum. Quatre espèces précédemment attribuées au genre Saccoglossus sont transférées au genre Mesoglossus: M. bournei, M. caraibicus, M. gurneyi, et M. pygmaeus et Saccoglossus borealis est transféré au genre Harrimania. Une hypothèse phylogénétique sur la famille des Harrimaniidae est émise, présentant l'évolution possible des caractères morphologiques au sein du groupe. Finalement, des notes sur la distribution géographique étendue mais discontinue de plusieurs espèces suggère que les entéropneustes auraient pu avoir une distribution ancienne continue et plus grande qui aurait été fragmentée par la suite.
This comparative study is a revision of the family Harrimaniidae based on morphological characters of described and undescribed species from the collections of William E. Ritter, Theodore H. Bullock and Kandula P. Rao, gathered in the 20th century. The new descriptions bring the total number of genera to nine by the addition of Horstia n. gen., Mesoglossus n. gen., Ritteria n. gen and Saxipendium, a genus previously assigned to the monospecific family Saxipendidae The number of species is increased to 34, resulting from the description of five new species from the eastern Pacific: Horstia kincaidi, Mesoglossus intermedius, Mesoglossus macginitiei, Protoglossus mackiei and Ritteria ambigua. The description of a sixth species, Stereobalanus willeyi Ritter et Davis, 1904 (nomen nudum) is presented here for the first time and a brief description of Saxipendium coronatum is also presented. Four species previously assigned to the genus Saccoglossus are transfered to the genus Mesoglossus: M. bournei, M. caraibicus, M. gurneyi, and M. pygmaeus, while Saccoglossus borealis is transfered to the genus Harrimania. A phylogenetic hypothesis on the Harrimaniidae is postulated presenting the possible evolution of morphological characters within the group. Finally, notes on the wide but spotty distribution of several species suggest that the Enteropneusta may have once had a wider distribution that has since become fragmented.