Nudibranch Mollusc Research Articles

Motor organization of Tritonia swimming. I. Quantitative analysis of swim behavior and flexion neuron firing patterns.

Motor organization of Tritonia swimming. I. Quantitative analysis of swim behavior and flexion neuron firing patterns.R I Hume, P A Getting, and M A Del BeccaroR I Hume, P A Getting, and M A Del BeccaroPublished Online:01 Jan 1982https://doi.org/10.1152/jn.1982.47.1.60MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySerial-section atlas of the Tritonia pedal ganglionChristopher Brandon, Matthew Britton, David Fan, Andrew R. Ferrier, Evan S. Hill, Adrian Perez, Jean Wang, Nengding Wang, and William N. Frost21 September 2018 | Journal of Neurophysiology, Vol. 120, No. 4Homology and Variation in Neural Control of Swimming in Nudipleura MollusksHikaku seiri seikagaku(Comparative Physiology and Biochemistry), Vol. 35, No. 2Role of Membrane Potential in Calcium Signaling During Rhythmic Bursting in Tritonia Swim InterneuronsEvan S. Hill, and Paul S. Katz1 March 2007 | Journal of Neurophysiology, Vol. 97, No. 3Long-Term Habituation in the Marine Mollusc Tritonia diomedeaThe Biological Bulletin, Vol. 210, No. 3Field Behavior of the Nudibranch Mollusc Tritonia diomedeaThe Biological Bulletin, Vol. 210, No. 2Short-term synaptic dynamics promote phase maintenance in multi-phasic rhythmsNeurocomputing, Vol. 52-54Swimming Behavior of the Nudibranch Melibe leoninaThe Biological Bulletin, Vol. 203, No. 2Neural Correlates of Swimming Behavior in Melibe leoninaThe Biological Bulletin, Vol. 203, No. 2Identified Serotonergic Neurons in the TritoniaSwim CPG Activate Both Ionotropic and Metabotropic ReceptorsStefan Clemens, and Paul S. Katz1 January 2001 | Journal of Neurophysiology, Vol. 85, No. 1Multi-Joint Coordination During Walking and Foothold Searching in the Blaberus Cockroach. I. Kinematics and ElectromyogramsAndrew K. Tryba, and Roy E. Ritzmann1 June 2000 | Journal of Neurophysiology, Vol. 83, No. 6The PD programs: a method for the quantitative description of motor patternsJournal of Neuroscience Methods, Vol. 19, No. 1 More from this issue > Volume 47Issue 1January 1982Pages 60-74 https://doi.org/10.1152/jn.1982.47.1.60PubMed7057225History Published online 1 January 1982 Published in print 1 January 1982 Metrics

An ultrastructural study of spermatogenesis in the nudibranch mollusc Spurilla neapolitana.

The ultrastructural features of spermatogenesis were investigated in the nudibranch mollusc Spurilla neapolitana. Sperm develop in the proximal half of numerous sac-like acini which are radially arranged within about ten ovotestis lobes. Accessory cells line the inner wall of the testicular portion of each acinus and are connected to developing sperm by numerous desmosomes. Stages of spermatid development have been divided into precup, cup, postcup, and elogate stages depending on the general shape of the nucleus. Nuclear differentiation includes the formation of anterior and posterior nuclear plaques, condensation of chromatin fibrils into nuclear lamellae, the insertion of the developing flagellar axoneme into a shallow, nuclear implantation fossa, and eventual formation of an elongated sperm head with a terminal twist. Spermiogenesis also includes the differentiation of an anterior, perinuclear structure having the characteristics of an acrosome, the appearance of peculiar arrays of ER cisternae, and the fusion of mitochondria into a large mitochondrial derivative which eventually encircles the axoneme, forming a crystalline-like periaxonemal sheath.

Change in a specific phosphoprotein band following associative learning in Hermissenda.

Although cellular neurophysiological studies of invertebrates have provided some understanding of the cellular basis of modifiable behaviour (for reviews, see refs 1–5), little is known about biochemical changes in the specific neural pathways accompanying alterations in behaviour. The nervous systems and sensory structures of invertebrates are especially suitable to an analysis of the biochemical mechanisms involved in behavioural modification because they typically contain a relatively small number of neurones, some of which have large, identifiable somata, and because associative learning has been studied in several invertebrate preparations6–10. Studies with the nudibranch mollusc Hermissenda crassicornis have demonstrated a short-term non-associative change in phototactic behaviour after training with light and rotation11. More recently8,12, an example of associative learning in Hermissenda was produced by the temporal association of light and a presumed aversive stimulus. This associative learning is accompanied by neurophysiological changes in the B-type photoreceptors12. We now report that there is also a change in the level of incorporation of 32P in a 20,000-molecular weight (MW) phosphoprotein; as the eye of Hermissenda consists of only five photoreceptors, a lens and a few pigment and epithelial cells, a biochemical change specific to associative learning has thus been localized to a few cells within a nervous system.

Biology and relationships of the nudibranch mollusc Notobryon wardi in South Africa, with a review of the Scyllaeidae

The Scyllaeidae is an important but little understood family of dendronotacean nudibranchs distinguished principally by having one or two pairs of latero‐dorsal flattened cerata which bear mesial arborescent gills. Most published records of scyllaeids have related to the world‐wide species of Scyllaea found in association with Sargassum, feeding upon attached hydroids. Other scyllaeids belonging to the genera Crosslandia and Notobryon are predominantly benthic, although they may swim to escape predators. Very little is known about them; on the South African coast, for example, benthic scyllaeids have been confused with Scyllaea pelagica. The present paper includes an investigation of these South African animals, with observations from life. Furthermore, a comparative account is given of living material of Crosslandia from Tanzania and of Scyllaea from the Gulf of Mexico. It is concluded that Scyllaea, Crosslandia and Notobryon are all valid and well founded genera; they are re‐defined in the light of the present study.

Mechanisms of pattern generation underlying swimming in Tritonia. I. Neuronal network formed by monosynaptic connections.

Mechanisms of pattern generation underlying swimming in Tritonia. I. Neuronal network formed by monosynaptic connections.P A GettingP A GettingPublished Online:01 Jul 1981https://doi.org/10.1152/jn.1981.46.1.65MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByHomology and Variation in Neural Control of Swimming in Nudipleura MollusksHikaku seiri seikagaku(Comparative Physiology and Biochemistry), Vol. 35, No. 2Two interconnected kernels of reciprocally inhibitory interneurons underlie alternating left-right swim motor pattern generation in the mollusk Melibe leoninaAkira Sakurai, Charuni A. Gunaratne, and Paul S. Katz15 September 2014 | Journal of Neurophysiology, Vol. 112, No. 6Hidden synaptic differences in a neural circuit underlie differential behavioral susceptibility to a neural injury11 June 2014 | eLife, Vol. 3Transient Enhancement of Spike-Evoked Calcium Signaling by a Serotonergic InterneuronEvan S. Hill, Akira Sakurai, and Paul S. Katz1 November 2008 | Journal of Neurophysiology, Vol. 100, No. 5Parameter Space Analysis Suggests Multi-Site Plasticity Contributes to Motor Pattern Initiation in TritoniaRobert J. Calin-Jageman, Mark J. Tunstall✠, Brett D. Mensh, Paul S. Katz, and William N. Frost1 October 2007 | Journal of Neurophysiology, Vol. 98, No. 4Potentiation Phase of Spike Timing-Dependent Neuromodulation by a Serotonergic Interneuron Involves an Increase in the Fraction of Transmitter ReleaseAkira Sakurai*, Robert J. Calin-Jageman*, and Paul S. Katz1 October 2007 | Journal of Neurophysiology, Vol. 98, No. 4Serotonin-Immunoreactive CPT Interneurons in Hermissenda: Identification of Sensory Input and Motor ProjectionsLian-Ming Tian, Ryo Kawai, and Terry Crow1 July 2006 | Journal of Neurophysiology, Vol. 96, No. 1Field Behavior of the Nudibranch Mollusc Tritonia diomedeaThe Biological Bulletin, Vol. 210, No. 2Cycle Period of a Network Oscillator Is Independent of Membrane Potential and Spiking Activity in Individual Central Pattern Generator NeuronsPaul S. Katz, Akira Sakurai, Stefan Clemens, and Deron Davis1 September 2004 | Journal of Neurophysiology, Vol. 92, No. 3Behavioral Plasticity: Modulation Occurs across TimeCurrent Biology, Vol. 14, No. 5Comparative Psychology of Motor Systems15 April 2003G Protein Signaling in a Neuronal Network is Necessary for Rhythmic Motor Pattern ProductionStefan Clemens, and Paul S. Katz1 February 2003 | Journal of Neurophysiology, Vol. 89, No. 2The use of elevated divalent cation solutions to isolate monosynaptic components of sensorimotor connections in AplysiaJournal of Neuroscience Methods, Vol. 120, No. 1Inhibitory Synchronization of Bursting in Biological Neurons: Dependence on Synaptic Time ConstantRobert C. Elson, Allen I. Selverston, Henry D. I. Abarbanel, and Mikhail I. Rabinovich1 September 2002 | Journal of Neurophysiology, Vol. 88, No. 3Physiology and pathophysiology of cortico-basal ganglia–thalamocortical loops: Theoretical and practical aspectsProgress in Neuro-Psychopharmacology and Biological Psychiatry, Vol. 26, No. 4Activation and Reconfiguration of Fictive Feeding by the OctopamineContaining Modulatory OC Interneurons in the Snail LymnaeaÁgnes Vehovszky, and Christopher J. H. Elliott1 August 2001 | Journal of Neurophysiology, Vol. 86, No. 2Identified Serotonergic Neurons in the TritoniaSwim CPG Activate Both Ionotropic and Metabotropic ReceptorsStefan Clemens, and Paul S. Katz1 January 2001 | Journal of Neurophysiology, Vol. 85, No. 1Dopamine Activates Two Different Receptors to Produce Variability in Sign at an Identified SynapseNeil S. Magoski, and Andrew G. M. Bulloch1 March 1999 | Journal of Neurophysiology, Vol. 81, No. 3Central Pattern Generator for Escape Swimming in the Notaspid Sea Slug Pleurobranchaea californicaJian Jing, and Rhanor Gillette1 February 1999 | Journal of Neurophysiology, Vol. 81, No. 2Learning model for coupled neural oscillators9 July 2009 | Network: Computation in Neural Systems, Vol. 10, No. 3A ternary logic model for recurrent neuromime networks with delayBiological Cybernetics, Vol. 73, No. 2A neuronal network from the mollusc Lymnaea stagnalisBrain Research, Vol. 645, No. 1-2Principles of organization of neural systems controlling automatic movements in animalsProgress in Neurobiology, Vol. 39, No. 1Statistical neurodynamics of the oscillatory circuit underlying central pattern generationNeuronal models of cognitive functionsCognition, Vol. 33, No. 1-2Central patterning of speech movementsExperimental Brain Research, Vol. 71, No. 3Induction of rhythmic activity in motoneurons of crayfish thoracic ganglia by cholinergic agonistsNeuroscience Letters, Vol. 77, No. 1Properties of the serotonergic cerebral ganglion neurons of the gastropod mollusc, Philine apertaComparative Biochemistry and Physiology Part C: Comparative Pharmacology, Vol. 76, No. 1 More from this issue > Volume 46Issue 1July 1981Pages 65-79 https://doi.org/10.1152/jn.1981.46.1.65PubMed6267210History Published online 1 July 1981 Published in print 1 July 1981 Metrics

An infraciliary network in statocyst hair cells.

Ultrastructural analysis of the statocyst, a primitive vestibular organ, of the nudibranch mollusc Hermissenda crassicornis, indicates that in addition to the basal foot, there is an infraciliary rootlet system between basal bodies of adjacent sensory cilia. These rootlets project perpendicularly from the basal bodies and parallel to the cell surface in an astral array. A polarity within the network also appears to exist; the array is longest and most extensive on the side of the basal body directed away from the cell centre, but the overall arrangement of the basal bodies indicates a multidirectional sensitivity for each of the 13 sensory cells. This rootlet system, in conjunction with the attachment system of the basal bodies to the cell membrane (button anchors), may serve an integrative function for the mechanical stimuli experienced by sensory cells and/or be involved with their transductive processes by maximizing the stress to, and membrane distortion of, the transductive site caused by weighting of the cilia. Evidence was also obtained for the intracellular synthesis of statoconia by the nonsensory supporting cells.

Isoguanosine: isolation from an animal.

Isoguanosine (oxyadenosine or crotonoside), previously known to occur in nature only in the croton bean, was isolated from an animal, the marine nudibranch mollusk Diaulula sandiegensis.

Polyp mimicry in a new species of aeolid nudibranch mollusc

A new species of aeolid mollusc of the genus Cuthona (Tergipedidae) is described from New South Wales, Australia. It feeds on the tubulariid hydroid Zyzzyzus spongicola, and its cerata have developed two circlets of epithelial “tentacles” making the cerata remarkable mimics of the hydroid polyp on which they feed.

Calcium-dependent potassium conductance in the photoresponse of a nudibranch mollusk

1. 1. The response to light of Hermissenda photoreceptors when recorded intracellularly without interference from synaptic and action potentials consisted of three phases: an early depolarization (ED) followed by hyperpolarization (dip) and subsequent depolarization (tail). 2. 2. The ED and the dip were associated with increased membrane conductance while decreased membrane conductance was involved with the tail. 3. 3. The dip reversal potential was − 82.1 ± 5.3 mV and its amplitude varied inversely with the log of [K +]. 4. 4. Perfusing with agents which block K + current like 4AP, Quinine, Quinidine or injection of TEA eliminated the dip and its associated increased membrane conductance, thus further supporting the role of K + conductance in producing the dip. 5. 5. The dip was enhanced by increased [Ca 2+] o, reduced by decreased [Ca 2+] o and abolished together with its associated increased membrane conductance when perfused with either D600, Cd 2+, Mg 2+, Mn 2+, or Co 2+, which block transmembrane Ca 2+ current. 6. 6. The dip and its associated increased membrane conductance were abolished by intracellular injection of EGTA and enhanced by perfusion with Ruthenium red. 7. 7. Intracellular injection of Ca 2+ mimicked the dip: membrane conductance was increased and the cell hyperpolarized. 8. 8. These results indicate that the increase in intracellular [Ca 2+] is primarily responsible for the light-induced increase of K + conductance during the dip. The possible source of the Ca 2+ is, at least in part, extracellular due to activation of an inward Ca 2+ current.

CELLULAR ANALYSIS OF A GASTROPOD (HERMISSENDA CRASSICORNIS) MODEL OF ASSOCIATIVE LEARNING

Intuitive formulations concerning the nature of cellular substrates for associative learning are considered. Invertebrate models of vertebrate learning are discussed. A cellular analysis of a long-term associative behavioral change is reviewed for the nudibranch mollusc Hermissenda crassicornis. Convergence of neuronal pathways which mediate natural sensory stimuli used for associative training have been determined. Primary biophysical changes within single identified neurons are analyzed for their causal role in learning behavior. A sequence of neural processes is proposed to underlie acquisition and retention of an associative behavioral change of Hermissenda. Paired sensory stimuli enhance voltage-dependent currents by means of converging sensory pathways. Repeated pairings cause progressive membrane depolarization, which in turn causes long-lasting conductance changes. Biochemical correlates of these phenomena are presented.

Motile statocyst cilia transmit rather than directly transduce mechanical stimuli.

We have investigated the role of motile cilia in mechanotransduction by statocysts of the nudibranch mollusk Hermissenda crassicornis. Movement of the cilia that experience the weight of statoconia causes increased variance of voltage noise and membrane depolarization of the statocyst hair cell. Two complementary approaches were used to immobilize the cilia. Vanadate anion was iontophoretically injected into hair cells. This reversible inhibitor of vibratile form and to assume a more classic, pliable beat pattern. Voltage noise decreased as the cilia slowed and bent more extremely, nearly disappearing as motility was lost. When the intracellular vanadate concentration approached 10(-5) M, the cilia were arrested in an effective stroke against the cell membrane. The cell no longer depolarized upon gravitational or local mechanical stimulation. Rapid reversal of ciliary inhibition by norepinephrine or slow reversal with time restored both the voltage noise and depolarization response. Cilia were rendered rigid and upright by covalent cross-linkage of their membrane "sleeve" to the 9 + 2 axoneme, using the photoactivated, lipophilic, bifunctional agent 4,4'-dithiobisphenyl azide. In the initial stages of cross-linkage, the cilia remained vibratile but slowed and moved through wider excursions. Voltage noise decreased in frequency but increased in amplitude. When the cilia were fully arrested, voltage noise was minimized while the resting potential and membrane resistance remained essentially constant. Mechanical stimulation of the rigid cilia, normal to the cell membrane, elicited a generator potential of the same amplitude but of greater duration than before treatment. Because cilia that are partially arrested by vanadate undergo increased bending, although the hair cell shows decreased noise, neither the axoneme nor the ciliary membrane proper would appear to be sites of direct transduction. In cells with beating but stiffened cilia, however, the voltage noise becomes amplified, implying an increased efficiency of transduction. We suggest that active but rigid flexure of the axoneme is involved in amplification and continuous signal detection. The basal insertion area is the most likely transduction site, being the terminal leverage point through which force is applied to the plasma membrane via the flexing ciliary shaft.

Physiological basis of feeding behavior in Tritonia diomedea. II. Neuronal mechanisms.

1. The nudibranch mollusk Tritonia diomedea feeds by biting and drawing pieces of coelenterate sea whips into its buccal cavity. It then swallows them in a series of cyclic ingestion movements. The coordinated pattern of swallowing can be elicited in reduced preparations by stimulation of identifiable neurons in cerebral or buccal ganglia. 2. Swallowing normally proceeds as a cyclic pattern of protraction and retraction movements driven by alternating bursts in odontophore-radula protractor and retractor motor neurons (MNs), with simultaneous coordination of many other major neurons. 3. Brief or prolonged constant-current stimulation of certain individual buccal ganglion (SW) premotor neurons reliably triggers one or more complete cycles of impulse bursts in motor neurons with coordinated movements of the jaws and buccal mass. The MN bursts produced in this way resemble the ones seen during feeding. Some SW neurons trigger responses that greatly exceed the duration of the stimulus; others drive cyclic output in the motor system whose duration corresponds closely to the duration of the depolarizing current. As well, the rate of MN bursting can be modulated by steady currents of different amplitudes injected into these SW neurons. There are, however, alternative sensory and motor routes independent of SW neurons by which the motor pattern may be elicited and modulated. 4. A search for the source of the feeding rhythm resulted in the identification of a pair of motor neurons (B5) that have prominent burst and pattern-generating capabilities independent of SW activation. They fire vigorous impulse bursts on rebound from spontaneously occurring IPSP waves or from imposed hyperpolarizing potentials of similar amplitude and duration. 5. Constant prolonged depolarizing currents injected into B5 result in the production of repetitive bursts in other MNs that resemble in amplitude and time course those seen during feeding. Cyclic bursting generated in this way apparently entrains other parts of the feeding motor generator since a coordinated output of appropriately phased hyperpolarizing waves, antagonistic EPSP volleys, motor bursts, and movements is simultaneously recorded in other, unstimulated motor neurons of the system. However, the SW neurons are not always entrained by such MN-generated bursting. 6. Brief stimulation of B5 (sufficient to elicit one or a few impulses) also results in the appearance of a depolarizing afterpotential, which is itself capable of regenerating further impulses. When prolonged, constant currents are applied, the impulses that result form bursts whose durations and interburst intervals depend on the amplitude of the stimulating currents. The spike and burst-generating qualities of these neurons (which may include endogenous and interactive components) are sufficient to serve as a source of timing and phasing for the motor pattern.

Two new species of nudibranchiate molluscs from the west coast of North America, with a revision of the family Cuthonidae

Two species of nudibranch molluscs are described from the northeastern Pacific Ocean on the west coast of North America. These are: a new aeolid species of Cuthona Alder & Hancock, 1855 (family Cuthonidae) from the Oregonian marine zoogeographical province and a new dorid species of Acanthodoris Gray, 1850 (family Onchidorididae) from the Panamic province in the Gulf of California. The internal anatomy and external features of each species are compared with related species. Differences in structure of the radula, reproductive system and other morphological aspects are described. A revision of the family Cuthonidae is included. Evidence is presented to include the genera Trinchesia Ihering, 1879, and Precuthona Odhner, 1929, within the genus Cuthona. Cuthona alpha Baba & Hamatani, 1963, is synonymized with Catriona columbiana (O'Donoghue, 1922). We consider the New World Cuthonidae to be composed of the following five genera: Catriona Winckworth, 1941; Cuthona Alder & Hancock, 1855; Embletonia Alder & Hancock, 1851; Tenellia Costa, 1877; and Tergipes Cuvier, 1805.

Ultrastructure of photoreceptors in the eye of Hermissenda labelled with intracellular injections of horseradish peroxidase.

The terminal processes of single and of pairs of identified photoreceptors in the eyes of the nudibranch mollusc Hermissenda crassicornis were studied by light and transmission electron microscopy after their somata were labelled by intracellular iontophoresis of horseradish peroxidase (HRP). The HRP spread from the somata into the axons and fine terminal processes within the neuropil of the cerebropleural ganglia. The photoreceptors ended in extensive secondary branches in the neuropil where previous electrophysiological studies had indicated the probable site of synaptic interactions between photoreceptors. Clear round vesicles (54-126 nm diameter) within labelled processes were similar to the vesicles found in the somata and axon hillocks. The terminal processes of pairs of type B photoreceptors contained different intensities of the HRP label. Uniform intensities of the HRP label were found in the terminal processes of single type B photoreceptors. These differences in intensity suggested that the terminal processes were from different type B photoreceptors. This finding suggests that the connections between type B photoreceptors are probably monosynaptic.

Homologous neurons control movements of diverse gill types in nudibranch molluscs

A comparison of central neurons controlling circumanal gill movements in 5 species of dorid nudibranch molluscs with those known to control movements of the dorsal gill tufts in the dendronotid nudibranchTritonia, suggests that the neurons controlling these two gill types are homologous. Four symmetrical pairs of neurons, 2 in the pleural ganglia and 1 each in the cerebral and pedal ganglia, were found to control the circumanal gills in the dorids; three of these pair (pedal and pleural) correspond to similar neurons inTritonia. InTriopha carpenteri, a dorid nudibranch having dorsal tufts as well as circumanal gills, the same neurons control both types of gill. The common neural control of dorsal tufts and circumanal gills revealed here, coupled with the widely observed conservatism in neural evolution, supports the hypothesis that these two gill types have a common evolutionary origin.

Cholinergic features of photoreceptor synapses in Hermissenda.

1. A number of observations, as listed below, suggested a cholinergic basis for inhibitory interactions between photoreceptors of the eye in the nudibranch mollusk Hermissenda crassicornis. 2. The isolated eyes synthesized and accumulated acetylcholine but not other putative neurotransmitter substances. Synthesis and accumulation were determined by electrophoretic separation of products that incorporated radioactive label. Electron microscopic visualization of clear round vesicles within the photoreceptors' somata and axon hillocks was consistent with synthesis and storage of acetylcholine within these cells. 3. Pharmacologic experiments indicated the presence of cholinergic receptors on the terminal branches of the photoreceptors, which are pre- and postsynaptic to each other. Carbachol or nicotine produced hyperpolarization of the photoreceptors' membrane accompanied by a reduction of the input resistance. The reversal potential of carbachol-induced hyperpolarization coincided with the reversal potentials of the IPSPs that followed, one for one, impulses of neighboring photoreceptors. Eserine often caused blockade of the IPSPs. This blockade was associated with substantial membrane hyperpolarization and reduction of membrane resistance. 4. Neuronal endings within the optic tract in the area of the photoreceptor's terminal branches stained for acetylcholinesterase. 5. The results of these different experiments, especially when considered together, strongly suggest, although by no means unequivocally demonstrate, that the neurotransmitter of the photoreceptors is acetylcholine.

Retention of an associative behavioral change in Hermissenda.

The nudibranch mollusk Hermissenda crassicornis is normally attracted to a test light. Three days of training consisting of 50 trials per day of light paired with a rotational stimulus led to a significant increase, lasting for days, in the animal's response latency to enter a test light. The group that received light associated with rotation was significantly different from groups subjected to nonassociative control procedures. Modifications of well-known sensory networks may be related to a behavioral change that shares several operational features with associative learning.

Central neuronal control of cilia in Tritonia diamedia.

CONSIDERABLE evidence indicates that the beating of cilia of a wide variety of animals is under neural control1, but no recordings have yet been made of the central neurones which actually control or influence ciliary beating. Several invertebrates of several phyla locomote by means of ciliary beating2,3; among these are included members of several families of gastropods4–7. The pedal cilia of these gastropods must be under central nervous control, but apart from some early experiments demonstrating that central control does exist4,5 it has received little attention8. I report here that the nudibranch mollusc Tritonia diomedia locomotes by pedal ciliary action, and that re-identifiable ‘cilia motor neurones’ in the central nervous system stimulate the beating of the pedal cilia.

Changes in Spatial Pattern of an Intertidal Population of the Nudibranch Mollusc Onchidoris muricata in Relation to Life-Cycle, Mortality and Environmental Heterogeneity

Changes in Spatial Pattern of an Intertidal Population of the Nudibranch Mollusc Onchidoris muricata in Relation to Life-Cycle, Mortality and Environmental Heterogeneity

Interaction of chemosensory, visual, and statocyst pathways in Hermissenda crassicornis.

Neurons in the cerebropleural ganglia (CPG), photoreceptors in the eye, optic ganglion cells, and statocyst hair cells of the nudibranch mollusk Hermissenda crassicornis responded in specific ways, as recorded intracellularly, to stimulation of the chemosensory pathway originating at the tentacular chemoreceptors as well as to stimulation of the visual pathway originating at the photoreceptors. Synaptic inhibition of photoreceptors occurs via the chemosensory pathway. The possible significance of such intersensory interaction is discussed with reference to preliminary investigation of the animal's gustatory behavior and possible neural mechanisms of behavioral choice.