Defensive reactions of gastropod molluscs. Humoral reactions

Humoral protective reactions and their mechanisms in gastropod mollusks are considered based on the results of various investigations. It is important to note that lectines in molluscs, as well as in other invertebrates, are functional analogues of immunoglobulins in vertebrates.     

Aminergic systems in pulmonate gastropod molluscs

Summary Histochemical fluorescence (Falck-Hillarp) and microspectro-fluorometric (MSF) methods were used to characterize different types of catecholamine-containing cellular elements located in the reproductive system of fresh-water snails (Bulinus truncatus, Planorbarius corneus) and land snails [Archachatina marginata, Helix (Cryptomphalus) aspersa]. Transverse sections through the genital tract display a common structural pattern of tubular differentiations: (1) an internal epithelium bordering the lumen and containing variable numbers of monoaminergic cells; (2) an enveloping sheath of connective and muscular tissue containing fine nerve fibers in the form of a network that exhibits a variable degree of density.MSF determinations showed that the formaldehyde-induced fluorophores of the intraepithelial aminergic cells belong to the following classes: (1) the DOPA/dopamine group in the duct of the albumen gland of B. truncatus and the carrefour of A. marginata; and (2) the norepinephrine/epinephrine group in the duct of the albumen gland and in the oviduct sac of P. corneus. In the reproductive systems of B. truncatus and P. corneus (duct of the albumen gland, oviduct sac, vagina), A. marginata and H. aspersa (duct of the fertilization pocket, origin of the receptaculum seminis, carrefour), the MSF analysis revealed norepinephrine/epinephrine-containing intramural nerve fibers. On the other hand, the small neurons in the vagina of B. truncatus belong to the DOPA/dopamine group.The authors wish to express their gratitude to Prof. A. Oksche who facilitated this collaborationThe investigations of H.G.H. were supported by grants from the Deutsche Forschungsgemeinschaft (-HA 726/5-) and the Stiftung Volkswagenwerk (I/35582). The investigations of P.B. and J.P.C. were supported by the University of Poitiers and CNRS (L.A. CNRS n 290)     

Diversity of trematode larvae in gastropod molluscs in water bodies of Belarus

The analysis of literary data and own investigations of gastropod molluscs on existence of cercariae of trematodes in Belarus was carried out. 13 856 specimens of 11 species and 2 species complexes of freshwater gastropod molluscs were examined on infection with cercariae of trematodes in 2010 by the authors of this article. Total infestation was 13.1% and infection of some molluscs species varied from 0.4% (Dnieper River, Gomel region) to 66.7% (Lukomskoe reservoir, Vitebsk region). The cercariae of 90 trematode species were found. The majority (51 species) at the adult stage parasitize birds. The cercariae of 14 trematode species have medical significance.     

Sieve structure of slit diaphragms of podocytes and pore cells of gastropod molluscs

Summary The ultrastructure of the slit diaphragms between the pedicels of the podocytes of the prosobranch Viviparus viviparus and between the cytoplasmic tongues of the haemocyanin producing pore cells of the pulmonate Lymnaea stagnalis was investigated. In both cell types 2 diaphragms are present in the slits. They form a 3-dimensional sieve structure with holes of respectively 90 × 110 Å (podocyte) and 200 × 220 Å (pore cell). Injection experiments showed that the size of the holes of the pore cell sieve matches that of particles which can be ingested by this cell type. The substructure of the sieves of the molluscs is compared to that of the 2-dimensional sieve of the podocytes of the mouse and the rat.The authors thank Mrs. J.E. Vlugt-van Dalen for technical assistance and Mr. G.W.H. van der Berg for drawing the diagrams. Thanks are furthermore due to Miss B.E.C. Plesch for correcting the English text     

Evolutionary regularities of somatic polyploidy manifestation in salivary glands of gastropod molluscs. I. Subclasses Cyclobranchia and Scutibranchia

By means of histological and cytochemical methods, including DNA cytophotometry, the salivary glands of 11 species of molluscs of two old gastropod subclasses--Cyclobranchia and Scutibranchia (limpets)--have been investigated. In spite of some anatomical differences, the glandular epithelium of investigated molluscs includes functionally similar cell types: granular cells (with glycoproteid granular inclusions), mucocytes-I (that include sulfatic acid mucopolysaccharides), mucocytes-II (that include neutral and acid polysaccharides and proteins) and also the epithelial ciliated cells. Data of experiments on starvation and synchronous feeding of molluscs testify that all described cell types are independent. According to DNA cytophotometry data, the glandular cell nuclei are diploid in the main; only small part of the nuclei, varying in different species from 0.5 to 5.0%, displayed tetraploid DNA mass. A conclusion is made that in the oldest subclasses of gastropods (Cyclobranchia and Scutibranchia) somatic polyploidy, as a factor of tissue growth in salivary glands, is actually absent.     

Evaluation of the ligand specificity of hemolymph hemoagglutinins and hemolysins of gastropod and bivalve molluscs

The study deals with evaluation of ligand specificities of hemoagglutinins and hemolysins of hemolymph of three species of gastropods(Planorbius corneus, Lymnaea stagnalis, andAchatina fulica) and one species of bivalve molluscs(Anodonta cygnea). The hemoagglutinin titer was estimated from hemoagglutination reaction, the hemolysin titer, spectrophotometrically, from release of hemoglobin from sheep erythrocytes. The ligand specificity of hemoagglutinins and hemolysins was evaluated by an inhibitory modification of the hemoagglutination reaction. It has been shown that hemoagglutinins and hemolysins of pulmonary gastropod molluscs have different spectra of ligand specificity to the substances of the carbohydrate nature. Hemoagglutinins and hemolysins of the bivalve molluscAnodonta cygnea have the same spectrum of ligand specificity. Among the ligands of these lectins, terminal N-acetylated sugars and monosaccharides predominate. Components of bacterial cell walls, lipopolysaccharide and phosphorylcholine, have been revealed among specific ligands of hemolymph hemoagglutinins and hemolysins.     

A pioneer survey and DNA barcoding of some commonly found gastropod molluscs on Robben Island

Nineteen species of abundant gastropods were collected at Robben Island, including introduced dune snails and European brown garden snails. They were identified using morphology and DNA barcoding. It was expected that the species recorded would be similar to those from the Cape peninsula, South Africa, but we were surprised to find some exceptions: the very abundant invasive mussel species in South Africa, the South American bisexual mussel (Semimytilus algosus), and the beaded topshells (Oxystele impervia) were not found on Robben Island. Possible explanations are presented for these differences.     

Dyssymmetrical cytotomy and orientation of the spindles in early isolated blastomeres of gastropod molluscs]

While removing the vitelline membrane mechanically or by trypsinization, one or two blastomeres were isolated from two-, four- and eight-celled embryos Lymnaea stagnalis, Physa fontinalis and Ph. acuta. If a pair of blastomeres was isolated prior to the formation of the III and IV cleavage spindles, it became similar to a two-cell embryo; the spindles oriented in parallel to each other and the contact zone of blastomeres preserving the previous localization of the nuclei and the subsequent division was equal. If a pair of blastomeres was isolated in metaphase, the localization of spindles did not change and the relative size of sister blastomeres after the subsequent division resembled the normal size (in particular, the III division was unequal). In the course of division of isolated single blastomeres, as well as pairs of blastomeres with parallel spindles, mutual turns of sister cells along the plane of new furrow, always dexiotropic in Lymnaea and laetropic in Physa, were observed in all cycles. The ability of dissymmetrical invariant turns during cytotomy, shown earlier when studying the whole embryos, is, thus, inherent to each blastomere irrespective of the neighbour ones but is supressed during the normal development after the III division mechanically due to the dense cellular packing projected by the orientation of spindles.     

Transaminase reactions and glutamate dehydrogenase in gastropod hepatopancreas

Summary In toads,Bufo bufo L., ACTH (1 I.U.) causes a retardation of extinction compared with Ringer administration irrespective of whether the animals have received the ACTH injection before or at the end of acquisition. Treatment with ACTH 20 min prior to acquisition lowers the starting activity. Therefore, habituation is completed earlier than in Ringer controls. The effect of ACTH treatment is stimulus-specific, as toads habituated to a wormlike stripe show normal turning activity to a triangle even under the influence of ACTH.The conformity of these results with the ACTH effect on complex learning behaviour especially in rats may indicate an underlying common principle. It is concluded that ACTH and, possibly, related peptides elicite neuronal events which favour learning and memory processes even in lower vertebrates.We thank Prof. Dr. W. Hanke, Karlsruhe, for fruitful discussions.     

Use of isolated digestive-gland cells in the study of biochemical and physiological processes in gastropod molluscs

We describe a method for preparation and maintenance of isolated digestive-gland cells in the abalone, Haliotis kamtschatkana. Viability of the isolated cells was confirmed by the fact that 18 h after preparation the cells exhibited less than 5% staining with trypan blue and actively synthesized glycogen following the addition of glucose substrate. Use of the method in a 15-month study of metabolic activity of the digestive gland of H. kamtschatkana showed significant differences in oxygen consumption of isolated-cell preparations correlated with seasonal differences in somatic and gametogenetic growth, and with relative size of the digestive gland.     

Ligand displacement reactions of oxyhemocyanin: comparison of reactivities of arthropods and molluscs.

The ligand displacement reactions of oxyhemocyanin have been compared over a series of arthropods and molluscs. The arthropods (with the exception of $\text{Limulus}$) are found to be more reactive than the molluscs, (k_cancer = .04 hr^?1, k_busycon = .002 hr^?1, k_limulus ? 10^?4hr^?1 N₃^? reactions). Correlation of the spectral properties of the oxy sites require these to be extremely similar with small differences being associated with shifts in the dd transition energies. The met produced by ligand displacement contains variable amounts of EPR detectable, group 2 exogenous ligand damaged sites (arthropods 25–35%, molluscs 3–9%, $\text{Limulus}$ <1%). A parallel (arthropod > mollusc ～ $\text{Limulus}$ ～ 0) group 2 ligand damaged site is also reported for the half met derivatives.     

Brefeldin A or monensin inhibits the 3D organizer in gastropod,polyplacophoran, and scaphopod molluscs

In molluscs, the 3D vegetal blastomere acts as a developmental signaling center, or organizer, and is required to establish bilateral symmetry in the embryo. 3D is similar to organizing centers in other metazoans, but detailed comparisons are difficult, in part because its organizing function is poorly understood. To elucidate 3D function in a standardized fashion, we used monensin and brefeldin A (BFA) to rapidly and reversibly interfere with protein processing and secretion, thereby inhibiting the signaling interactions that underlie its specification and patterning. In the gastropods, Patella vulgata and Lymnaea stagnalis, the polyplacophoran, Mopalia muscosa, and the scaphopod, Antalis entalis, treatments initiated before the organizer-dependent onset of bilateral cleavage resulted in radialization of subsequent development. In radialized P. vulgata, L. stagnalis, and M. muscosa, organizer specification was blocked, and embryos failed to make the transition to bilateral cleavage. In all four species, the subsequent body plan was radially symmetric and was similarly organized about a novel aboral–oral axis. Our results demonstrate that brefeldin A (BFA) and monensin can be used to inhibit 3D’s organizing function in a comparative fashion and that, at least in M. muscosa, the organizer-dependent developmental architecture of the embryo predicts subsequent patterns of morphogenetic movements in gastrulation and, ultimately, the layout of the adult body plan.     

Change of hemoagglutinin and hemolysin titers in hemolymph of gastropod molluscs in response to immunization with sheep erythrocytes

This work deals with analysis of changes of the levels of hemoagglutinins (HA) and hemolysins (HL) in hemolymph of three gastropod species,Planorbius corneus, Lymnea stagna-lis, andAchatina fulica, in response to immunization with sheep erythrocytes (ShE). The levels of HA and HL were determined before immunization and 3, 5, 10, and 15 days after the antigen administration. The HA titer was estimated from hemoagglutination reaction, the HL titer was measured spectrophotometrically from release of hemoglobin from ShE. It has been found that after immunization the titer of HA falls by 72–88% for the first 3–5 days, but returns to the initial values or even exceeds them statistically significantly by the10–15th days. The time of the decrease of the HA titers correlates inversely with the body mass of the animals, while the amplitude of this decrease is directly proportional to the body mass. The HL titer either changes parallel to the HA titer (inL. stagnalis) or increases statistically significantly by 60–65% during the entire period of observation (in two other species studied). It is suggested that inP. coneus andA. fulica, HA and HL are different compounds.     

Somatic polyploidy in neurons of the gastropod molluscs. II. Dynamics of DNA synthesis in the process of postnatal growth of CNS neurons in Succineid snail

A study was made of the age dynamics of polyploidization and dynamics of DNA synthesis in neuron cell nuclei during the postnatal growth of the gastropod pulmonate snail Succinea lauta. According to cytophotometrical results, the degree of polyploidization in neuron nuclei increases from young to adult individuals, varying from 2c to 16,384c. In the visceral complex, the maximum and medium ploidy values of the neuron nuclei are higher by almost 4-8 times than those in cerebral and pedal ganglia. The medium level of ploidy in adult snails increases by 5.7 times in the visceral complex of ganglia and by 4.1-4.2 times in the pedal and cerebral ganglia. According to 3H-thymidine autoradiography, DNA synthesis in neuron nuclei occurs during the whole life of the snail. In young individuals the neurons have the highest activity of DNA synthesis--the index of labeled nuclei of neurons making in total 50.2%. In older age, a steady decrease in the index of labeled nuclei is observed--in total to 35.8% and 7.0% in small and large adult snails, respectively. The state of summer hibernation completely stops DNA syntheses in neurons, but emergency from hibernation is accompanied by restoration of DNA syntheses.