Snail Lymnaea Research Articles

On the status of the study of invertebrate neurons in tissue culture—Phyla mollusca and annelida

1. 1. The utilization of tissue culture in neurobiological studies is discussed for all phyla phylogenetically preceding Phylum Arthropoda. Only two phyla, Mollusca and Annelida, are represented in such studies. 2. 2. The members of Phylum Mollusca which have been so investigated are Aplysia, Helisoma and Lymnaea. 3. 3. The mollusc Aplysia has been used to investigate several processes, including neurosecretion, synaptic transmission and synaptogenesis. 4. 4. Helisoma was employed to study factors regulating neurite growth and the specificity of synapse formation; mechanisms of neurite growth were investigated in the snail Lymnaea. 5. 5. The only member of Phylum Annelida involved in appropriate studies has been the leech Hirudo. This organism was used to investigate axonal regeneration and synaptic mechanisms.

Vertical distribution of young pond snails (Basommatophora: Pulmonata): implications for survival

The vertical distribution of juvenile pond snails (Lymnaea stagnalis and Stagnicola elodes), hatched from egg masses containing known numbers of viable embryos, was recorded daily in artificial containers under outdoor conditions for up to 25 days after hatching. Both species showed an initial vertical movement to the surface of the water with a subsequent return to the bottom sediments after 10–15 days. This pattern was consistent despite differences in the depth of the water column (13 versus 18.5 cm). At 25 days after hatching more than 85% of the population was in the lower half of the container at any one time, almost all being associated with the bottom sediments. The presence of an adult snail of either species in the same container significantly reduced the survival of young snails (from between 85 and 94% to between 1 and 18%). Consumption of the young snails during their first 10 days out of the egg mass, when they were moving to the surface, accounted for the observed differences in survival. Young snails appeared to be ingested incidently by the foraging adults, most often when the former were concentrated at the air–water–glass interface.

Grazing and nutrient interactions in controlling the activity and composition of the epilithic algal community of an arctic lake1

The effects of grazing by the snail Lymnaea and enrichment with N and P were examined in the epilithic algal community of an arctic lake. Increased nutrients raised chlorophyll a levels and primary production and favored the growth of filamentous green algae and coccoid blue‐greens. Intensive grazing reduced algal concentration and activity. Grazing increased the relative abundance of small green and blue‐green coccoid cells at the expense of larger (>20 µm) diatoms.Photosynthetic activity of snail feces was 77–79% that of ungrazed algae per unit mass. Split chamber experiments and measurements of dissolved phosphorus indicated that nutrients released in grazing may be tightly recycled within snail guts or on the rock surface, rather than transferred into the water.Radioisotope tracing was used to develop a simple energy budget for Lymnaea. Despite viable gut passage of some of the algae, the snail was an efficient grazer, assimilating 68% and incorporating 25% of ingested carbon.

Susceptibility of different species of Lymnaea snails to miracidia of Fasciola gigantica and F. hepatica in Iran

Susceptibility of different species of <i>Lymnaea</i> snails to miracidia of <i>Fasciola gigantica</i> and <i>F. hepatica</i> in Iran

Histochemical and ultrastructural studies on the metacercarial cyst of Echinostoma revolutum (Trematoda)

Histochemical and ultrastructural studies were made on the metacercarial cyst of Echinostoma revolutum obtained from the kidney of experimentally infected Physa and Lymnaea snails. Ultrastructural studies revealed three cyst walls, an outer, middle and inner. The outer wall was more electron-dense than the middle, and contained coarser granules than those found in the middle layer. The inner wall was lamellated and contained membranous whorls. Collagenous fibers presumably of host origin surrounded the outer cyst wall. The outer and middle cyst walls stained identically with all histochemical procedures used. These walls contained acid mucopolysaccharides and glycoprotein, whereas the inner cyst wall contained glycoprotein. All cyst walls stained positively with a variety of protein stains.

Molluscs interfering with the capacity of Fasciola hepatica miracidia to infect Lymnaea truncatula

Fasciola hepatica miracidia labelled with radioselenium were used to study aspects of their host-finding capacity by determining radioactivity subsequently taken up by exposed 'target' snails (Lymnaea truncatula). Possible interfering effects exercised by a number of non-host snails and bivalves were examined in linear test channels. The infection rate (radioactivity) among 'target' snails was markedly lowered when non-host Lymnaea species (L. pereger, L. palustris, L. stagnalis) were interposed as 'decoys'. The prosobranch Bithynia tentaculata and the bivalve Sphaerium corneum exhibited a slight decoy effect whereas pulmonate species like Anisus vortex, Gyraulus albus, Planorbis planorbis, Physa fontinalis did not interfere with miracidial host-finding. Other experiments showed that miracidia are more strongly attracted towards L. truncatula than L. pereger. Miracidia are not able to penetrate intact egg clusters of L. truncatula.

Host-induced Variation in Plagiorchis noblei Park, 1936 (Plagiorchiidae: Trematoda)

Eggs of Plagiorchis noblei Park, 1936, used for this study, were recovered from a single worm obtained from a naturally infected red-winged blackbird (Agelaius phoeniceus). Laboratory-reared snails (Lymnaea stagnalis and Stagnicola reflexa) and three genera of insects (Aeschna, Coenagrion and Chironomus) harbored experimental infections of this plagiorchiid. Of the 51 vertebrate species exposed to metacercariae of P. noblei, infections were established in the following avian and mammalian hosts: Gallus gallus, Meleagris gallopavo, Phasianus colchicus, Porzana carolina, Chlidonias niger, Spinus tristis, Cyanocitta cristata, Tyrannus tyrannus, Passer domesticus, Troglodytes aedon, Agelaius phoeniceus, Turdus migratorius, Iridop,rocne bicolor, Sturnella neglecta, Xanthocephalus xanthocephalus, Mus musculus and Rattus norvegicus. Examination of more than 1500 laboratory-reared adults of P. noblei from these definitive hosts reveals the unreliability of body size, size of suckers, position of oral sucker, length of esophagus, size and position of gonads, extent of vitellaria and size and position of cirrus sac as taxonomic characters. Apparently the only stable taxonomic characters in adults of Plagiorchis noblei are the size-ratio of suckers and egg size.