Land Slug Research Articles

The internal defense system of the land slug: A mophological analysis : K. Yamaguchi, E. Furuta ∗ and A. Shimozawa ∗. Laboratory of Medical Science, and ∗Department of Anatomy, Dokkyo University School of Medicine, Mibu, Tochigi 321-02, Japan

The internal defense system of the land slug: A mophological analysis : K. Yamaguchi, E. Furuta ∗ and A. Shimozawa ∗. Laboratory of Medical Science, and ∗Department of Anatomy, Dokkyo University School of Medicine, Mibu, Tochigi 321-02, Japan

Regulation of body volume by the peripheral nervous system of the terrestrial slug Ariolimax columbianus

AbstractResponses to mechanical and chemical stimulation have been studied in an in vitro preparation of the body wall of the land slug Ariolimax columbianus. This preparation (posterior chamber, PC) is separated from the head ganglia and therefore has only peripheral nervous control. The volume contained within the PC (normally filled with viscera and hemolymph) is determined by 1) contraction or relaxation of muscle cells, causing exchange of fluid between the PC and the attached manometer that controls pressure within the PC; 2) secretion by epithelial channel cells moving fluid from inside the PC to the outside across the epithelial surface.The PC maintained at constant internal pressure responded to mechanical stimulation (at ca. 1 Hz) of the epithelium with a brief burst of secretion. Prolonged (45 minutes) stretch of the body wall by maintenance at 11 torr or above resulted in intermittent pulses of secretion and muscle contraction. At very high pressure muscle contraction was suppressed, and secretion volumes were huge, gradually restoring the volume of the PC to its initial value (autoregulation).When PCs were immersed in fluid containing garlic extract, skin receptors responded, initiating secretion comparable to the effects of mechanical stimulation in both amount and duration. Other chemicals (including capsaicine, cysteic acid, and geraniol) known to be aversive to pulmonates in vivo did not activate the secretory response.

Osmolyte processing in the gut and an important role of the rectum in the land slug, Ariolimax columbianus (pulmonata; arionidae)

AbstractExperiments were carried out to investigate the role of the gut in the osmotic balance of the land slug Ariolimax columbianus. Previous investigators have shown that absorption of nutrients, calcium, and some heavy metals occurs in the slug's digestive gland and intestine. The only function suggested for the rectum, beyond transfer of the fecal mass, has been its possible involvement in lipid absorption. We collected hemolymph and fluids contained in different regions of the gastrointestinal tract and compared these with respect to osmotic pressure as well as to concentrations of ions (sodium, potassium, calcium, and chloride), glucose, and amino acids. The osmotic pressure of rectal contents was found to average one‐quarter the values of other fluids. In in vitro experiments sacs of intestine and rectum exposed to 1:4 mucosa:serosa osmotic gradients for 1 h showed transfer of fluid across the sac wall into the surrounding fluid. This transfer was significantly enhanced in the case of the rectum but not of the intestine, after dehydration or loss of hemolymph, and during immersion of the sacs in media containing the gastropod neurotransmitters FMRFamide, norepinephrine, and 5‐hydroxytryptamine, as well as arginine vasotocin. The data indicate that the rectum of the slug serves as a small but ready source of water available for use under conditions of acute water deficiency.

Function of the Epithelial Channel Cells of the Body Wall of A Terrestrial Slug, Ariolimax Columbianus

ABSTRACT The body wall of the land slug Ariolimax columbianus Gould (Arionidae) secretes fluid in response to mechanical stimulation. This fluid is a product of specialized channel cells, with addition of mucus. Channel cell function can be explained in terms of ultrafiltration of blood components into the central channel, and modification of this ultrafiltrate, prior to extrusion from the body surface, by cellular transport of univalent ions but without change in osmotic pressure. Sodium and chloride ions are conserved, and potassium and bicarbonate ions are transferred out into the channel cell product. Agents known to affect epithelial transports and ion processing in a variety of animals - ouabain, amiloride, furosemide, SITS and acetazolamide - depress the function of the slug channel cells.

Neurophysiological mechanisms underlying habituation of the tentacle retraction reflex in the land slug Ariolimax.

Habituation of the tentacle retraction reflex was studied at the following response levels: (1) Muscle tension elicited in the tentacle retractor muscle by repeated stimulation of a cerebral nerve (at 60-sec intervals) declined in parallel with evoked activity of the largest unit in the tentacle retractor nerve. (2) The largest unit in the tentacle retractor nerve (L4) showed spontaneous recovery and dishabituation. The rate of response decrement was inversely related to the strength of stimulus, and an optimal interstimulus interval ca. 60 s was found. Retention of habituation for 24 h was exhibited. (3) The major retractor motoneurons (L2, L3, L4) all showed habituation, dishabituation, and spontaneous recovery. The decline of L4 activity was parallelled by a decline in muscle response. (4) Compound EPSPs elicited in the retractor motoneurons by stimulation of sensory pathways showed habituation and dishabituation. (5) Unitary EPSPs elicited by stimulation of cerebral nerves and connectives with minimal stimulus strengths also showed habituation and were unaffected by spontaneously occurring EPSPs. Dishabituation by another pathway was also shown. (6) Depolarization of L4 by a constant current produced spike trains of constant firing rate and evoked a constant level of muscle tension in repeated trails, suggesting the absence of habituation in a peripheral nerve net or at the neuromuscular junction.

Cerebral motoneurons mediating tentacle retraction in the land slug Ariolimax columbianus

(1) Tentacle retraction in the land slug Ariolimax columbianus can be elicited by stimulation of all nerves and connectives of the ipsi-and contralateral cerebral ganglia. (2) Six neurons in the left cerebral ganglion were classified as tentacle retraction motoneurons because their action potentials are followed one-for-one with constant delay be action potentials in the left tentacle retractor nerve and their depolarization causes retraction of the ipsilateral tentacle. The motoneurons can be identified by size, pattern of pigmentation, position, and physiological characteristics. (3) Each retractor motoneuron discharges at a rather constant rate and had more than one source of excitatory input, but no IPSPs were observed. No synaptic connections between the six retractor motoneurons were found. The nerve action potentials that correspond to each motoneuron are distinguishable by waveform and size rank. (4) Each motoneuron elicits visible contractions in a particular region of the ipsilateral retractor muscle, but the motor fields of some motoneurons overlap. Some motoneurons mediate relatively rapid contractions while other cause slower responses. (5) There is one-for-one correspondence between action potentials of the largest unit recorded extracellularly in the retractor nerve and excitatory junction potentials recorded from the retractor muscle. No evidence of a peripheral neural plexus was found in serial sections of the retractor muscle.

Two new species ofPseudaneitacockerell (Athoracophoridae : Gastropoda) from New Zealand

Abstract Two new species of Pseudaneitea are described, P. leva from Mid-Canterbury, P. nodosa from the Outer Chetwode Is. An account of the anatomy of each is given, and their affinities are discussed. Land slugs belonging to the Family Athoracophoridae are found in the Admiralty Is., New Britain, New Hebrides, New Caledonia, the east coast of Australia, New Zealand, and the subantarctic islands. The most distinctive character of the family is the presence of a dorsal tracheate lung, consisting of a pulmonary cavity from whose floor thin-walled pulmonary diverticula radiate out to form the roof of a blood sinus. The first species described in this paper was found in a beech forest near Staveley by Mr P. M. Johns, of the University of Canterbury. The other species was found on the Outer Chetwode Is. by Mr G. S. Hardy, of Victoria University of Wellington. Both very kindly supplied the writer with all the material they collected.

Steroids of invertebrates IV. On the optic tentacle-gonadal axis in the control of the male-phase ovotestis in the slug ( Ariolimax californicus)

The giant land slug, Ariolimax californicus, is a protandrous hermaphrodite. The role of the optic tentacles in affecting the sexual status of the ovotestis in other gastropods has been investigated ( Pelluet and Lane (1961); Pelluet (1964). The present study was undertaken to determine if the optic tentacles exert a hormonal influence upon the male phase of the ovotestis, and whether steroids are implicated in determining the presumptive capacity of the optic tentacle to influence the gonad. The experimental approach used was to follow histological changes occurring in the ovotestis of immature slugs under the following conditions: (1) optic tentacle removal and replacement therapy; (2) administration of steroids to animals with and without optic tentacles; (3) the effect of Metopirone in the presence and absence of optic tentacles. The results of these investigations strongly suggested that the optic tentacle exerts a profound influence upon the ovotestis of immature animals. Optic tentacle removal in immature slugs produced maturation of the testicular elements of the gonad within 21 days to a stage histologically comparable with that occurring normally in animals almost three times the age and body weight; precocious spermatogenesis was induced. Similar results were obtained by administering dehydroepiandrosterone and 11-ketotestosterone (presumptively identified by GLC techniques in male-phase gonads) to slugs with and without optic tentacles. Optic tentacle homogeneates apparently halted further precociously induced spermatogenesis, but may also have caused spermiation to occur. Metopirone, when administered to young males in increasing dose levels in the presence of the optic tentacles, caused progressive disorganization of spermatogenesis. Histologically, this appeared as an apparent hyperplasia of the gonial cells lining the tubule walls. No similar effects were seen in animals without optic tentacles treated with Metopirone. These results suggested that tentacular control of the male phase of the ovotestis might be limited to that portion of the gonad cycle up to the point of spermiation. Steroids appeared to influence the effect of this tentacular regulator or modifier of ovotesticular development. The evidence suggested that the male phase in A. californicus ovotestis is controlled partially by the optic tentacle.

Slug and Snail Control with Experimental Poison Baits1

Metaldehyde, a long-established specific molluscicide for land slug and snail control, is not satisfactory under moist weather conditions. The search for a more effective molluscicide has resulted in a laboratory screening technique, simulating natural conditions, by which experimental baits are presented to various species of land molluses. The brown garden snail, Helix aspersa Muller and the European black slug Arion ater (L.), are laboratory reared for the tests, while other species are field collected in season. five experimental carbamate materials have shown outstanding activity against land molluses to date: Bay 37344 (4-(methylthio)-3,5-xylyl methylcarbamate), UC 20047A (Tranid® (exo-(5-chloro-6-oxoendo 2-norbornanecarbonitrile O-(methylcarbamoyl) oxide), EP-332 (m [[ (dimethyl amino) methylene]amino] phenyl methylcarbamate hydrochloride), EP-316 (m-cym-5-yl methyicarbamate), and IN-1179 (methyl N-[(methyicarbamoyl) oxy] thioacetimidate). All established chlorinated hydrocarbon and organophosphate pesticides tested have shown little or no toxicity to slugs and snails.

Revision of the Giant West Coast Land Slugs of the Genus Ariolimax Moerch (Pulmonata: Arionidae)

The giant West Coast land slugs have a complex genital physiology (Heath, 1916), the details of which are unknown, except that they frequently gnaw off the penis at the close of copulation. The first step in a study of this behavior undertaken by the author was to examine critically a great number or specimens not only to familiarize himself with the genital morphology of the several species in the hypertrophied, atrophied, and immature states, but to attempt to find a structural explanation for this unique practice. Examination of large series of live specimens afforded great advantages which earlier workers unfortunately had not enjoyed; consequently the literature contains not only serious errors regarding the taxonomic status of the group, but also many morphological misinterpretations based on examinations of very limited and often poorly preserved material. For this reason, it was thought advisable to publish first a revision of the taxonomy of this genus with adequate information on its speciation, phylogeny, and distribution. In this paper the morphological aspects are limited to those external and internal structures, which are or have been considered of taxonomic importance. Other structures, including especially the apical genital structures, will be treated in a later paper dealing with the biology and genital physiology of the genus.

Colpoda steini, a Facultative Parasite of the Land Slug, Agriolimax agrestis

While examining land slugs for parasites during the autumn of I933 numerous holotrichous ciliates were observed in the alimentary tract and other regions of the mollusc's body. The ciliate was identified as Colpoda steini. Since this had always been considered a free-living species a series of experiments were planned for the purpose of obtaining data relative to its proclivities as a facultative parasite.

On the Occurrence of Onchidella celtica (Cuvier) on the Cornish Coast

Onchidella celtica (Cuvier) is the only representative of its genus found on our shores. Included in the Sub-order Stylommatophora of the Pulmonates, it is believed to be a land mollusc that has reverted to a marine habitat. It is quite devoid of a shell and closely allied to the land slugs.