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At least 19 recordsLinked to original sources
PubMed1990

Photoperiod and temperature interaction in the determination of reproduction of the edible snail, Helix pomatia.

Snails were kept in self-cleaning housing chambers in an artificially controlled environment. Mating was frequent under long days (18 h light) and rare under short days (8 h light) regardless of whether the snails were kept at 15 degrees C or 20 degrees C. An interaction between photoperiod and temperature was observed for egg laying. The number of eggs laid (45-50/snail) and the frequency of egg laying (90-130%) were greater in long than in short days (16-35/snail and 27-77%) but a temperature of 20 degrees C redressed, to some extent, the inhibitory effect of short days. At both temperatures only long photoperiods brought about cyclic reproduction over a period of 16 weeks, confirming the synchronizing role of photoperiod on the neuroendocrine control of egg laying in this species of snail.

Animals↗
PubMed1997

Morphology of interneurons in the procerebrum of the snail Helix aspersa.

Terrestrial snails have a highly developed sense of olfaction. Because the procerebrum has a large number of cells and is located at the entry site of the olfactory nerve into the brain, the structure is thought to have a significant role in the processing of olfactory stimuli. The morphology of the procerebral neurons in the snail Helix aspersa was investigated through intracellular injections of biocytin. No formal categorization of neuronal types was possible, but some cells were seen to have neurites entirely intrinsic to the procerebrum, whereas others had both intrinsic and extrinsic arborizations, and still others had only extrinsic arborizations. These interneurons were previously thought to have arborizations restricted to the procerebral lobe. We demonstrated the extent of the neurite projections outside of the procerebral lobe by making focal injections of biocytin or Neurobiotin into various regions of the cerebral ganglion. This technique revealed subsets of cells that send neurites not only in the ipsilateral ganglion but also through the cerebral commissure into the contralateral cerebral ganglion. Our results demonstrate not only that the procerebral cell population is heterogeneous but also that the procerebrum interacts more directly with the rest of the central nervous system than was formerly believed.

Animals↗
PubMed1994

Acid-base status of a pulmonate land snail (Helix aspersa) and a prosobranch amphibious snail (Pomacea bridgesi) during dormancy.

Changes in metabolism and acid-base status were compared during dormancy in the pulmonate land snail Helix aspersa and a prosobranch amphibious snail Pomacea bridgesi. The typical condition of higher blood PCO2 and bicarbonate levels for air-breathing versus water-breathing vertebrates was shown for the two snail species. When exposed to dry air for 24 hr, both species depressed oxygen uptake by about 65%. In Pomacea, hypercapnia (increase in hemolymph PCO2 from 5.5 to 18 torr) resulting from dormancy produced no significant change in pH due to large increases in bicarbonate (over 17 mmol/l). In Helix, on the other hand, hypercapnia (increase in hemolymph PCO2 from 13 to 18 torr) resulting from dormancy produced a significant decrease in pH and a less than 7 mmol/l increase in bicarbonate. Pre-existing high levels of bicarbonate in Helix may prevent compensation of hypercapnia resulting from dormancy, similar to the case described for air-breathing vertebrates. Complete compensation of respiratory acidosis during the first 24 hr of dormancy in Pomacea suggests that metabolic rate suppression is independent of pH.

Acid-Base Equilibrium↗
PubMed1983

Behavioral effects of opiates on the land snail Helix aspersa.

The terrestrial snail Helix aspersa appears to have an endogenous opiate system involved with regulating its locomotor activities as well as its responses to tactile stimulations. In animals which were repeatedly injected with the same dose of morphine, tolerance developed. Injection of the opiate antagonist, naloxone, resulted in a gradual reversal of the morphine induced behavioral characteristics. In addition, the effect of morphine on locomotor activity can be considered biphasic. At higher doses morphine induced a state of muscular rigidity in the organisms whereas at lower doses the animals were hyperactive.

Animals↗
PubMed1992

Accumulation and excretion of aluminium and iron by the terrestrial snail Helix aspersa.

1. The snail Helix aspersa was fed one 24 hr meal containing Al, Fe or both together in barley flour pellets. Accumulation and distribution within the digestive gland, kidney, crop and remaining soft tissues were examined over the subsequent 30 days using atomic absorption spectroscopy (A.A.S.). 2. The digestive gland contained significantly (P < 0.05) elevated levels of Al and Fe for 8 and 12 days. The digestive gland is the major sink for both Al and Fe in Helix. 3. The kidney rapidly accumulated Al and Fe but the increase was short-lived. The kidney may therefore be involved in the elimination of metal not incorporated into the digestive gland. 4. Iron was absorbed by the crop but Al was not. This may indicate a route of uptake of Fe into the digestive gland not shared with Al. 5. No obvious pattern of accumulation of Al and Fe were seen in the remaining soft tissues or the blood of Helix. 6. Aluminium is present in the faeces for 12 days suggesting that Al is released relatively slowly. 7. Presence of both Al and Fe in the feed induced a change in the pattern of accumulation in the digestive gland but not in the kidney, crop and remaining soft tissues. 8. The distribution of Al is discussed in relation to the suggestion that Al follows the ferretin pathway during accumulation.

Aluminum↗
PubMed1984

Patterns of accumulation, distribution and liberation of Zn, Cu, Cd and Pb in different organs of the land snail Helix pomatia L.

The snail Helix pomatia was fed lettuce enriched with zinc, cadmium, lead and copper for 32 days, followed by a feeding period of 40-50 days with uncontaminated lettuce. The time-dependent distribution of the four metals during loading and unloading was determined in all major organs. Four general types of response to metal loading have been distinguished. Another general feature is the rhythmic nature of accumulation and de-accumulation of metals in several organs. On the other hand, each metal also elicits specific responses which can be described in terms of acute or delayed reaction and long-term accumulation. Lead is accumulated by most organs and redistributed after loading has stopped, but a single organ, the midgut gland, accumulates about 90% of this metal. Zinc accumulates in most organs during the first part of the loading period and is then redistributed to the midgut gland which may hold up to 70% of the metal at the end of the experiment. Cadmium is not taken up at all by a number of organs but the midgut gland and anterior gut keep accumulating it. After loading has been terminated the metal appears to move from the midgut gland to the gut. Copper is distributed more evenly than the other metals in the organs of the snail, the midgut gland not playing a dominant role in the storage of this metal.

Animals↗
PubMed2005

Seasonal modulation of free radical metabolism in estivating land snails Helix aspersa.

We investigated the regulation of free radical metabolism in Helix aspersa snails during a cycle of 20-day estivation and 24-h arousal in summer in comparison with estivation/arousal in winter-snails. In winter-snails (J. Exp. Biol. 206, 675-685, 2003), we had already observed an increase in the selenium-dependent glutathione-peroxidase (Se-GPX) activity in foot muscle and hepatopancreas and in the contents of hepatopancreas GSH-equivalents (GSH-eq=GSH+2 GSSG) during estivation compared with 24-h aroused snails. Summer-estivation prompted a 3.6-fold increase in Se-GPX activity in hepatopancreas, though not in foot muscle. Total-superoxide dismutase and catalase activities in hepatopancreas decreased (by 30-40%) during summer-estivation; however, no changes occurred in the activities of glutathione reductase, glutathione S-transferase and glucose-6-phosphate dehydrogenase in the two organs. GSH-eq levels were increased (by 54%) in foot muscle during estivation, but were unchanged in hepatopancreas. In contrast with winter-snails, oxidative stress markers (lipid peroxidation, carbonyl protein, and the GSSG/GSH-eq ratio) were unaltered during estivation/arousal in summer. These results demonstrate that seasonality modulates not only the absolute activities/levels of antioxidants (enzymes and GSH-eq) in H. aspersa, but also the regulatory process that controls the snail's antioxidant capacity during estivation/arousal. These results suggest that H. aspersa has an "internal clock" controlling the regulation of free radical metabolism in the different seasons.

Animals↗
PubMed1989

Sugar and amino acid intestinal transport systems in land snail Helix aspersa.

The intestine of Helix aspersa snail is able to actively transport sugars and amino acids. D-glucose, D-galactose and 3-oxymethylglucose share the same transport system with competitive inhibition between them, which is strictly Na(+)-dependent. Phlorizin has high affinity for that system and inhibits it competitively. D-fructose and L-arabinose are not actively transported, do not inhibit the transport of other sugars, and enter the tissue at a lineal rate with their concentration, which coincides with that of mannitol and with that of actively transportable sugars in the presence of 10(-4)M phlorizin. Galactose seems to enter the tissue from the serosal side through another carrier, with different specificity, Na(+)-independent, inhibited by phloretin but not by phlorizin. There are also transport systems for neutral amino acids, for the basic ones and for imino acids. Neutral amino acids present affinity for the other systems, whereas the basic ones and the imino acids seem to use only those proper to them. The system for imino acids is strictly Na(+)-dependent, but neutral amino acids and the basic ones continue to be transported and accumulated, although to a lesser extent, in the absence of Na+. Transport of sugars and amino acids is scarcely O2 dependent, although it is inhibited by 10(-4)M DNP. It is also partially inhibited by harmaline and by ouabain.

Amino Acids↗
PubMedDate not supplied

[The Na,K pump regulates a decrease in the cholinosensitivity of the neurons in the snail Helix lucorum taurica Kryn in a cellular analog of habituation: its dependence on intracellular calcium].

In Helix lucorum snail we studied the effects of ouabain, inhibitor of Na,K-pump, on the depression of cholinosensitivity in command neurons of withdrawal behavior and the role of the intracellular free Ca2+. The cellular analog of the negative learning (habituation) was used Transmembrane integral inward currents were recorded from the identified LPa2, LPa3, RPa3, and RPa2 neurons in ganglia preparation using two-electrode voltage clamp technique. Acetylcholine (ACh) was locally applied iontophoretically. Reduction of neuronal cholinosensitivity was estimated as a depth of depression of the ACh-induced inward current during rhythmic local application of ACh (interstimulus interval of 1-3 min) onto the somatic membrane. Bath application of ouabain (0.1 mM) produced an increase in depression in one group of neurons and its decrease in another group. After 60-150 min of spontaneous diffusion of a calcium ion chelator BAPTA (1 mM) from the intracellular microelectrode, ouabain produced only the increase in depression. If CaCl2 (100 mM) was added to the solution of the voltage-recording intracellular microelectrode, 60 min later ouabain produced only the reduction of the depression of the ACh current. The conclusion is drawn that the inhibition of the Na,K-pump by ouabain modifies the depression of neuronal cholinosensitivity in the cellular analog of habituation. The direction of the modulatory effect depends on the basal concentration of the intracellular free Ca2+.

Acetylcholine↗
PubMed1977

Isolation of nematode inhibitor from hemolymph of the snail, Helix aspersa.

Hemolymph plasma of the snail Helix aspersa which inhibits maturation and reproduction of its mantle cavity-inhabiting nematode, Rhabditis maupasi, was separated biochemically for the active proteinaceous component. Isolation of the active inhibitor was performed using ion-exchange chromatography in combination with subsequent gel filtration. The isolated peaks were bio-assayed in vitro on nematode larvae. The fractions harboring inhibitory protein suppressed larval growth and adult reproduction in vitro. The isolated fraction was purified by gel filtration and characterized on the basis of a single band on starch zone electrophoresis and positive reaction only with folin-phenol reagent.

Animals↗
PubMedDate not supplied

Neuropharmacological studies on identified central neurones of the snail, Helix aspersa.

Central neurones of the snail, Helix aspersa, possess both synaptic and somatic receptors to a wide range of classical transmitters and neuroactive peptides. The range of receptors and the type of response is reasonably constant for a specific neurone. This review will provide data concerning the pharmacology of acetylcholine, serotonin, dopamine, noradrenaline, octopamine, glutamate, GABA and purine receptors on identified neurones. Many of these neurones also respond to neuroactive peptides including molluscan peptides, e g, AMPMLRLamide, LSSFVRIamide, SGQSWRQGRPFamide, FMRFamide; coelenterate peptides, e g, pQGRFamide; echinoderm peptides, e g, GFNSALMFamide; and nematode peptides, e g, KNEFIRFamide, KHEYLRFamide, SDPNFLRFamide. Using this data, the pharmacological profiles of identified neurones will be summarised.

Animals↗
PubMed1995

In vitro effects of methionine-enkephalin, somatostatin and insulin on cultured gonadal cells of the snail Helix aspersa.

Isolated snail gonadal cells were cultured in the presence of synthetic neuropeptides in order to determine the subsequent effect of these substances on gonadal synthetic activities. Gonadal cells were incubated for 24 h in concentrations of methionine-enkephalin, somatostatin and insulin ranging from 10(-4) M to 10(-9) M, in medium 199 supplemented with 6% Ultroser G. Synthesis of DNA and protein by the cultured cells were simultaneously estimated by measuring incorporation of 3H thymidine and 35S methionine. The rate of labelled precursor incorporation was measured using the liquid scintillation technique. All substances tested exerted a dose-dependent effect. The synthetic activity of the cultured cells was highest when the concentration of the peptides added to the medium approximated the physiological levels. Methionine-enkephalin, somatostatin and insulin at 2 x 10(-8) M significantly increased 3H thymidine incorporation, by 62%, 69% and 69% respectively, and protein synthesis by 42%, 57% and 57%, respectively. In the case of juvenile gonadal cultured cells, a similar increase in 3H and 35S incorporation was registered for a 10(-7) M peptide concentration. Both lower and higher peptide concentrations inhibited 3H thymidine and 35S methionine incorporation. Pharmacological studies suggest the existence of methionine-enkephalin and somatostatin-like receptors on snail gonadal cells. These results indicate that our gonadal cell culture model provides a useful tool for the study of the neuroendocrinological control of the activity of snail gonadal cells.

Age Factors↗
PubMed1978

The accumulation of DL-glutamate by the central nervous system of the snail Helix pomatia.

Isolated snail ganglia are capable of maintaining their free amino acid levels steady for the first 60 min of incubation in physiological saline. Within this time the ganglia also possess an uptake mechanism for DL-glutamate which can be divided into sodium-sensitive and -insensitive components. The accumulation of DL-glutamate showed saturation kinetics typical of a carrier-mediated process. The Vmax value for the uptake is 1.5 x 10(-8) mole/g/min and the Km value 1.1 x 10(-4) M. The amino acid accumulation is quite specific towards L-dicarboxylic acids and insensitive to a number of metabolic inhibitors. It is unlikely to be due to a homoexchange phenomenon because the ganglia are capable of achieving a net uptake of glutamate and the efflux of DL-[3H]glutamate is not increased by the addition of non-radioactive L-glutamate to the incubation medium.

Amino Acids↗
PubMed1983

Transport of pinocytic vesicles in the eye of a snail, Helix aspersa.

The heads of small adult snails, Helix aspersa, were injected with horseradish peroxidase (HRP) for one to five hours before extirpating the eyes and preparing them cytochemically for electron microscopy. There was internalization of tracer by pinocytic vesicles (pinosomes) at the bases of types-I and -II sensory cells, ganglion cells and, in lesser amounts, by pigmented supportive cells. Vesicles and vacuoles filled with HRP were transported in two directions: lensward as far distad as the ends of the cells (retrograde) and brainward down the optic nerve (anterograde). We believe that the numerous reacted vacuoles in the cell somata are formed by fusion of vesicles, tubules and C-shaped organelles filled with tracer; we present evidence that they become secondary lysosomes. Sensory cell type II possesses more HRP-reacted vacuoles distally than the other retinal cells. Other vesicles are also described. There was no uptake of tracer by the distal ends of the retinal cells following injection HRP into the hemolymph. The swelling of the optic nerve, immediately behind the eye, contains more HRP-filled pinosomes and vacuoles than does the nerve below the dilatation. The significance of endocytosis and transport of pinosomes within the eye and down the optic nerve is discussed.

Animals↗
PubMed1990

Structural studies on the galactan from the snail Helix pomatia.

1. The galactan of the snail Helix pomatia was subjected to two cycles of Smith-degradation and the resulting products were isolated by gel filtration and thin layer chromatography. 2. The structures of the low molecular weight oligosaccharides were elucidated being identical to those obtained from Lymnaea stagnalis galactan. However, the quantities released differed significantly between the two species. The high molecular fractions comprising about 66% of the material were not obtained in a similar degradation of the Lymnaea stagnalis galactan. 4. Thus the observed structural differences can explain easily the species-specific reactivity among the two polysaccharides seen earlier with lectins, enzymes and antibodies.

Animals↗
PubMed2003

Sensory innervation of the ovotestis in the snail Helix aspersa.

Because oviposition in the land snail Helix aspersa is a metabolically expensive process coupled to a high fixed cost, one expects oviposition to occur only when the clutch size surpasses a minimum value at which the reproductive benefit exceeds the cost. We propose that neural innervation of the gonad allows H. aspersa to monitor oocyte production and ensure an adequate supply of gametes prior to ovulation. The ovotestis is innervated by a branch of the intestinal nerve in which the majority of axon fibres measure <0.2 microm in diameter. We found a strong positive correlation between the number of mature oocytes in the ovotestis and the frequency of spontaneous afferent spikes in the nerve branch. Tactile stimulation of the ovotestis resulted in a 20-fold increase in afferent spikes and an efferent reflex directed towards the ovotestis and the pericardium. Afferent activity also increased 10-fold after an experimentally induced increase in the volume of the ovotestis. These results suggest that the growing oocytes expand the walls of the acini and trigger action potentials in the mechanosensitive nerve terminals that lie within the acinar walls. We hypothesize that the resulting tonic signal is permissive for ovulation. In addition, a phasic sensory signal may occur during ovulation to trigger CNS motor output related to oviposition.

Action Potentials↗
PubMed1977

[Differentiation of the prostate in the snail Helix aspersa Müll].

The differentiation of the snail Helix aspersa prostate gland is studied in animals from one to six months old. After the presentation of organogenesis the primary stage of secretion (3 months) and a stage where the prostate gland shows abundant secretions (6 months) were described; but the oviduct is still indifferentiated. The ultrastructural analysis shows the formation of secretory and ciliated cells in epithelioid prostatic tubes.

Animals↗