Academic literature on the topic 'Statocyst'

1. In the marine mollusk Clione limacina the "statomotor system" (named by analogy with the oculomotor system) has been found. This system includes a muscle that is directly attached to the statocysts connecting them with each other and with the inner surface of the body. 2. The statocyst muscle consists of four electrically coupled, mononuclear cells. Statocyst muscle cells do not generate spike-like potentials but only excitatory junctional potentials. 3. The motor input to the statocyst muscle correlates with the activity of the locomotor generator. This suggests that in the soft-bodied Clione contraction of the statocyst muscle stabilizes the statocysts into a standard "working" position in relation to coordinates of the body. This statocyst stabilization is important for Clione's spatial orientation during swimming.

The two equilibrium receptor organs (statocysts) of Nautilus are ovoid sacks, half-filled with numerous small, free-moving statoconia and half with endolymph. The inner surface of each statocyst is lined with 130 000 to 150 000 primary sensory hair cells. The hair cells are of two morphological types. Type A hair cells carry 10 to 15 kinocilia arranged in a single ciliary row; they are present in the ventral half of the statocyst. Type B hair cells carry 8 to 10 irregularly arranged kinocilia; they are present in the dorsal half of the statocyst. Both type of hair cells are morphologically polarized. To test whether these features allow the Nautilus statocyst to sense angular accelerations, behavioural experiments were performed to measure statocyst-dependent funnel movements during sinusoidal oscillations of restrained Nautilus around a vertical body axis. Such dynamic rotatory stimulation caused horizontal phase-locked movements of the funnel. The funnel movements were either in the same direction (compensatory funnel response), or in the opposite direction (funnel follow response) to that of the applied rotation. Compensatory funnel movements were also seen during optokinetic stimulation (with a black and white stripe pattern) and during stimulations in which optokinetic and statocyst stimulations were combined. These morphological and behavioural findings show that the statocysts of Nautilus , in addition to their function as gravity receptor organs, are able to detect rotatory movements (angular accelerations) without the specialized receptor systems (crista/cupula systems) that are found in the statocysts of coleoid cephalopods. The findings further indicate that both statocyst and visual inputs control compensatory funnel movements.

In mollusks, statocyst receptor cells (SRCs) interact with each other forming a neural network; their activity is determined by both the animal's orientation in the gravitational field and multimodal inputs. These two facts suggest that the function of the statocysts is not limited to sensing the animal's orientation. We studied the role of the statocysts in the organization of search motion during hunting behavior in the marine mollusk, Clione limacina. When hunting, Clione swims along a complex trajectory including numerous twists and turns confined within a definite space. Search-like behavior could be evoked pharmacologically by physostigmine; application of physostigmine to the isolated CNS produced “fictive search behavior” monitored by recordings from wing and tail nerves. Both in behavioral and in vitro experiments, we found that the statocysts are necessary for search behavior. The motor program typical of searching could not be produced after removing the statocysts. Simultaneous recordings from single SRCs and motor nerves showed that there was a correlation between the SRCs activity and search episodes. This correlation occurred even though the preparation was fixed and, therefore the sensory stimulus was constant. The excitation of individual SRCs could in some cases precede the beginning of search episodes. A biologically based model showed that, theoretically, the hunting search motor program could be generated by the statocyst receptor network due to its intrinsic dynamics. The results presented support for the idea that the statocysts are actively involved in the production of the motor program underlying search movements during hunting behavior.

1. An interneurone specifically sensitive to substratum vibration was identified in the crayfish circumoesophageal connective. The interneurone, called B1 in this paper, received excitatory input from the statocysts on both sides. Electrical stimulation of the statocyst nerve elicited several spikes in the interneurone with latencies that depended on which side was stimulated. 2. B1 responded phasically to artificial bending of the statocyst sensory hairs. The response was similar to that of the phasic-type receptor in the statocyst 3. The morphology of B1 was studied by an intracellular staining technique using nickel chloride and subsequent silver intensification. The interneurone projects its neurite arborization to the dorsal part of the deutocerebrum and parolfactory lobe on both sides, where the statocyst primary afferents also project. The overlapping of central projections, together with the properties of the response of B1 suggests that the interneurone receives excitatory input from the phasic-type receptors and transmits information about phasic body movement, but not static positional information, to the posterior ganglia 4. Branches of B1 also project to the antennal and tegumentary lobes ipsilateral to the axon. B1 may receive additional mechanosensory information from the cuticular sensory hairs on the antennae and the cephalic body surface

In the puerulus of Jasus edwardsii, the statocyst opens onto the dorsal surface of the basal segment of the antennule. The opening is bordered by two types of setae. The cavity contains many minute hardened statoliths, which are devoid of a mineral or crystalline core and are not cemented together. There are no sensory hairs, secretory pores or fluid within the cavity; these are found among other decapods, but it appears that the Palinuridae are an exception. Knowledge of the statocyst in crustaceans in general is briefly reviewed. Extra keyword: statolith.

1. When the crayfish Procambarus is rolled with legs not upon a substratum, uropod opener muscles on the lifted side are activated in co-contraction whereas antagonistic closer muscles on the same side are all relaxed simultaneously. The closers are activated and the openers are relaxed on the lowered side. 2. This reciprocal pattern is also observed in the motor neurone activity: the contraction of opener muscles on the lifted side and closer muscles on the lowered side is caused by an increase in the activity of excitatory motor neurones innervating these muscles, whereas the relaxation of their antagonists on each side is caused by a decrease in the activity of excitatory motor neurones innervating them. Deafferentation by cutting all roots of the terminal ganglion has no significant effect on the steering pattern. 3. The decrease in the excitatory motor neurone activity during steering was found to be due to an increase in the inhibitory input to the motor neurones. 4. During body rolling, the statocyst receptors on the lifted side increase their activity while those on the lowered side decrease it (Takahata & Hisada, 1979). We conclude that the opener motor neurones receive excitation and inhibition respectively from the ipsilateral and the contralateral statocyst, whereas the closer motor neurones receive excitation and inhibition respectively from the contralateral and ipsilateral statocyst. From these results, the connections between the motor neurones and the identified statocyst interneurones were deduced. 5. The normal, bilaterally organized steering pattern of the uropod muscle activity seems to be produced by the statocysts of both sides, whose information is mediated by a bilateral set of interneurones having different connections to individual motor neurones.

The temporal characteristics of statocyst and leg proprioceptive inputs to the uropod motor system were investigated in crayfish using behavioural and electromyographic analyses to elucidate their functional roles in the control of the uropod steering response under natural conditions. When the animal, which was suspended in the air without a footboard, was actively extending its abdomen, prolonged stimulation of the statocysts by body rolling elicited a maintained asymmetrical configuration of the bilateral uropods. Prolonged stimulation of the walking legs by footboard tilting with the animal body held in the upright position elicited a transient uropod response. When the treadmill was tilted while the animal was walking on it in the upright position, the uropods showed the same transient response. However, when the animal body was rolled, together with the treadmill, while the animal was walking on it, the uropods showed a transient response which was reversed in direction compared with that observed during body rolling without a footboard. This transient response was abolished by the removal of the statoliths. The results show that the statocysts and leg proprioceptors exert sustained and transient control effects, respectively, on the uropod motor system during walking. It is also suggested that the uropod response to body rolling during walking is controlled primarily by leg proprioceptor signals which result from statocyst-induced changes in the leg position.

The statocyst of an undescribed species of Luridae is described by electron microscopy. it is located between the brain and the intestine, suspended on a cytoplasmic band, and contains a nucleus and three statoliths. The statoliths are surrounded by many mitochondria. Fibres from the brain enter the statocyst wall through dark lamellae with a lamellate substructure, and form part of the wall that contains many basal bodies with short axonemes which, however, do not protrude into the statocyst cavity as free cilia. It is not clear whether intestinal cells contribute to the formation of the statocyst wall. Three small statoliths, also surrounded by many mitochondria, lie in cytoplasm latero-posteriorly to the statocyst.

Global change is the origin of increased occurrence of disturbance events in natural communities, with biological invasions constituting a major threat to ecosystem integrity and functioning. The apple snail (Pomacea maculata) is a freshwater gastropod mollusk from South America. Considered one of the 100 most harmful invasive species in the world, due to its voracity, resistance, and high reproductive rate, it has become a global problem for wetland crops. In Catalonia, it has affected the rice fields of the Ebre Delta since 2010 with significant negative impact on the local economy. As a gastropod mollusc it possesses statocysts consisting of a pair of sacs, one located on each side of the foot, that contain multiple calcium carbonate statoconia. This study shows the first ultrastructural images of pathological changes in the sensory epithelium of the statocyst of apple snail adults with an increase in the severity of the lesions over time after exposure to low frequency sounds. Sound-induced damage to the statocyst could likely result in an inhibition of its vital functions resulting in a potential reduction in the survival ability of the apple snail and lead to an effective mitigation method for reducing damage to rice fields.

A dorsal light reflex is described in the squid Lolliguncula brevis. When illuminated from the side in visually homogeneous surroundings, a free-swimming squid rolls the dorsal side of its head and trunk 10-20 degrees towards the light. With the trunk restricted in a holder, the squid rolls its head 4-5 degrees towards the light; this reaction increases by about 50% when the statocysts are bilaterally removed and increases further when the neck receptor organ is also destroyed. The results indicate a multi-modal interaction of visual, statocyst and proprioceptive inputs during postural control.

Controlled Exposure Experiments revealed lesions in the statocysts of four cephalopod species of the Mediterranean Sea (Sepia officinalis, Loligo vulgaris, Illex coindetii and Octopus vulgaris), when exposed to relatively low intensity low frequency sounds. The analysis was performed through: scanning (SEM) and transmission (TEM) electron microscopy techniques of the whole inner structure of the cephalopod statocysts, especially on macula and crista; SEM of the epidermal lines of cephalopod hatchlings; and proteomic studies (2DE/MALDI –MS) of the statocyst’s endolymph. All exposed adult individuals presented the same lesions and the same incremental effects over time, consistent with a massive acoustic trauma observed in land species that were exposed to much higher intensities of sound. Immediately after exposure, the damage was observed in the macula statica princeps (msp) and in the crista sensory epithelium. Kinocilia on hair cells were either missing or were bent or flaccid. A number of hair cells showed protruding apical poles and ruptured lateral plasma membranes, most probably resulting from the extrusion of cytoplasmic material. Hair cells were also partially ejected from the sensory epithelium, and spherical holes corresponding to missing hair cells were visible in the epithelium. The cytoplasmic content of the damaged hair cells showed obvious changes, including the presence of numerous vacuoles and electron dense inclusions not seen in the control animals. The appearance of these lesions became gradually more pronounced in individuals after 12, 24, 48, 72, and 96 hours. Special attention was given to validate these findings with control animals that were caught, maintained and sequentially sacrificed following the same protocol as the exposed individuals. The statocyst ultrastructure was therefore revisited and a comparative analysis was carefully conducted to assess the lesions triggered by the exposure to noise This study also presents preliminary results of the sound effects on epidermal lines of cephalopod hatchlings. The lesions, consistent with an acoustic trauma, were identic in the three species that were exposed, but their evolution over time, in opposition with what was observed in the statocysts, were different, suggesting that the animal size and metabolic response might play a role in a possible recovery process. The analysis of noise effects in the statocyst endolymph by proteomic techniques was only conducted on Sepia officinalis. The presence of differential staining of gels from control and subjected to sound exposure individuals demonstrate that the injuries could be related to a possible physiological imbalance that would affect the protein levels of the endolymph. The lesions and findings described here are new to cephalopod pathology. Given that lowfrequency noise levels in the ocean are increasing (e.g. due to shipping, offshore industry, and naval maneuvers), that the role of cephalopods in marine ecosystems is only now beginning to be understood, and that reliable bioacoustic data on invertebrates are scarce, the present study and future investigations will bring an important contribution to the sustainable use of the marine environment.<br>Després de sotmetre'ls a experiments d'exposició controlada a sons de baixa intensitat i baixa freqüència es van observar lesions en els estatocists de quatre espècies de cefalòpodes de la mar Mediterrània (Sepia officinalis, Loligo vulgaris, Illex coindetii i Octopus vulgaris). L'anàlisi es va realitzar per mitjà de de microscòpia electronica d'escombratge (SEM) i de transmissió (TEM) de tota l'estructura interna de l'estatocist dels cefalòpodes, especialment en la màcula i en la crista, per SEM de les línees epidèrmiques de les larves dels cefalòpodes i per tècniques de proteòmica (2DE/MALDI-MS), de l'endolimfa de l'estatocist. Tots els estatocists d'individus adults de cefalòpodes exposats presentaven les mateixes lesions i aquests efectes eren més greus a mesura que passava el temps després de l'exposició als sons. Tots els animals exposats al soroll van mostrar lesions consistens amb trauma acústic massiu observat en altres espècies terrestres que havien estat exposades a intensitats molt més altes de so. Immediatament després de l'exposició, es van observar danys a la macula statica princeps (msp) i en l'epiteli sensorial de la crista. Els quinocilis de les cèl·lules ciliades desapareixien o es doblegaven i es tornaven flàccids. Un nombre important de cèl·lules ciliades mostraven els pols apicals sobresortint de l'epiteli sensorial, així com el trencament de les membranes plasmàtiques laterals, molt probablement com a resultat de l'extrusió de material citoplasmàtic. Les cèl·lules ciliades també van ser parcialment expulsades de l'epiteli sensorial deixant visibles forats esfèrics en el mateix. El contingut citoplasmàtic de les cèl·lules ciliades danyades va mostrar canvis obvis, com ara la presència de nombrosos vacúols i inclusions electrodenses que no es veien en els animals control. L'aparició d'aquestes lesions es va tornar gradualment més pronunciada en els individus analitzats després de 12, 24, 48, 72 i 96 hores. Es van validar curosament aquests resultats per mitjà de la comparació amb els animals control que van ser capturats, mantinguts i sacrificats de forma seqüencial seguint el mateix protocol que els individus exposats. La ultraestructura de l'estatocist va ser revisada i es va dur a terme un curós anàlisi comparatiu per tal d'avaluar les lesions provocades per l'exposició al soroll. Aquest estudi també presenta els resultats preliminars dels efectes del so en les línies epidèrmiques de cefalòpodes recent nascuts. Les lesions, consistens amb trauma acústic, eren idèntiques en les tres espècies que van ser exposades, però la seva evolució en el temps, en oposició amb el que es va observar en els estatocists, era diferent, cosa que suggereix que la grandària dels animals i la resposta metabòlica podria tenir influència en un possible procés de recuperació. L'avaluació dels efectes en l'endolimfa de l'estatocist per tècniques de proteòmica es va dur a terme només en Sepia officinalis. La presència de taques diferencials en els gels dels individus control i els sotmesos a exposició a so demostren que les lesions podrien estar relacionades amb un possible desequilibri fisiològic que tindria repercusions en els nivells proteics de l'endolimfa. Les lesions descrites aquí són noves pel que fa a la patologia dels cefalòpodes. Atès que els nivells de soroll de baixa freqüència a l'oceà estan augmentant (per exemple, a causa del transport, la indústria petrolera i les maniobres navals), que el paper dels cefalòpodes en els ecosistemes marins només ha començat a ser entès recentment, i que les dades bioacústiques fiables sobre els invertebrats són escasses, el present estudi i les investigacions futures aportaran una important contribució a l'ús sostenible del medi marí.