Species Of Bivalve Molluscs Research Articles

Guidelines for routine mercury speciation analysis in seafood by gas chromatography coupled to a home-modified AFS detector. Application to the Andalusian coast (south Spain)

A home-modified atomic fluorescence detector (mAFS) has been employed for mercury and methylmercury determination in bivalves from the Andalusian coast (south Spain). This modification consists on the inclusion of a quartz flow cell into the detector, which increases the concentration of mercury atoms in the detector and therefore enhances sensitivity about two fold. Two analytical approaches for mercury speciation based on the coupling of gas chromatography on-line pyrolysis and mAFS (GC–Pyro–mAFS) have been tested. The first approach ( Method 1) is based on aqueous ethylation followed by extraction into an organic solvent, and the second one ( Method 2) in the extraction of monoalkylated mercury as chloride. Method 1 is a rapid procedure but not sensitive enough for the analysis of methylmercury in non-polluted sites (detection limit: 20 ng g −1 as mercury, wet basis). The second one is quite more sensitive (detection limit: 0.2 ng g −1, wet weight), but sample treatment is cumbersome and time-consuming. The optimum range for mercury determination for both methods are complementary and exhibit an overlapping measurable concentration range (OMCR) in which methylmercury can be indistinctly determined (75–100 ng g −1 as mercury, wet basis). The suitability of both methods has been assayed with spiking experiences at levels within the OMCR with good recoveries. Both approaches have been validated with two certified reference materials (BCR-463, mercury and methylmercury in tuna fish; and NIST-2977, organic contaminants and trace metals in mussel tissue). Both procedures have been used for the analysis of three species of bivalve molluscs collected along the Andalusian coast (south Spain), all of them employed for human consumption ( Chamelea gallina, Donax trunculus and Scrobicularia plana), and their potential use in routine analysis has been established.

Update of the marine Bivalvia Mollusca checklist in Greek waters

Species of marine bivalve molluscs identified in the last nine years in the Greek waters have been used to update the checklist published in 1996 (Fauna Graeciae VII) by inserting necessary changes and adding new records. The updated version includes 13 new species among which three are exotics (non-Mediterranean species), five rare, two new deep sea and one previously considered a fossil species. Also, as a result of new resources, the distributions of pre-existing native molluscs have been updated to include new habitat areas. The nomenclature is also up to date based on the CLEMAM Database. Thus five species are now excluded either because they are junior synonyms of pre-existing valid species (2) or because of old spurious records (3 species). Additions and corrections of the 1996 checklist have resulted in a total of 308 bivalves in Greek waters.

Heavy metal concentrations in molluscs from the Atlantic coast of southern Spain

Trace metals were determined in the two most abundant species of bivalve molluscs along the Atlantic coast of southern Spain ( Donax trunculus and Chamelea gallina) and in the sediments where they live. The results show that the area near the mouth of the Huelva estuary is where the highest metal concentrations are found in sediments and in the two bivalve species. This is not surprising, considering that the Huelva estuary is the mouth of the Tinto and Odiel rivers, which have one of the highest levels of metal pollution of all the rivers of Europe. The two species of bivalves have different amounts of metals in their tissues. The concentrations of Cr, Cu, Pb, Zn, As and Hg in D. trunculus were significantly higher ( p < 0.05) than in C. gallina; however, C. gallina contained more Ni and Cd. In both species the most abundant elements were Cu and Zn, while Hg showed the lowest values. There is a significant correlation ( p < 0.05) for concentrations of Cu, Pb, Zn and Hg in D. trunculus and C. gallina relative to their concentrations in surface sediments.

Effects of GABA and epinephrine on the settlement and metamorphosis of the larvae of four species of bivalve molluscs

Competent larvae of different marine bivalve species were treated with GABA and epinephrine at different concentrations and times of exposure to test the ability of the drugs to induce settlement and metamorphosis. GABA induced both settlement and metamorphosis in the mussel Mytilus galloprovincialis, the clams Venerupis pullastra and Ruditapes philippinarum and the oyster Ostrea edulis. Maximum induction of settlement (>39%) was achieved after exposure of V. pullastra larvae to 10 −4 M GABA; this concentration of GABA also induced the highest percentages of metamorphosis in the four species studied. Epinephrine was identified as an active inducer of settlement and metamorphosis in bivalve molluscs. Exposure to 10 −5 M epinephrine induced significant levels of settlement in Mytilus, Venerupis and Ostrea. In contrast, epinephrine failed to induce settlement behaviour in Ruditapes. Maximum induction of metamorphosis was produced by 10 −5 M epinephrine in mussels, clams and oysters; Ruditapes showed the highest percentage of metamorphosis (>78%). This is the first report in which the involvement of GABA in the settlement and metamorphosis of bivalve molluscan larvae is demonstrated. It was also recognised that epinephrine plays a role not only in inducing metamorphosis but also in initiating settlement.

Upstream dams and downstream clams: growth rates of bivalve mollusks unveil impact of river management on estuarine ecosystems (Colorado River Delta, Mexico)

We studied how the extensive diversion of Colorado River water, induced by dams and agricultural activities of the last 70 years, affected the growth rates of two abundant bivalve mollusk species ( Chione cortezi and Chione fluctifraga) in the northern Gulf of California. Shells alive on the delta today (‘Post-dam’ shells) grow 5.8–27.9% faster than shells alive prior to the construction of dams (‘Pre-dam’ shells). This increase in annual shell production is linked to the currently sharply reduced freshwater influx to the Colorado River estuary. Before the upstream river management, lower salinity retarded growth rates in these bivalves. Intra-annual growth rates were 50% lower during spring and early summer, when river flow was at its maximum. Growth rates in Chione today are largely controlled by temperature and nutrients; prior to the construction of dams and the diversion of the Colorado River flow, seasonal changes in salinity played an important role in regulating calcification rates. Our study employs sclerochronological (growth increment analysis) and geochemical techniques to assess the impact of reduced freshwater influx on bivalve growth rates in the Colorado River estuary. A combination of both techniques provides an excellent tool to evaluate the impact of river management in areas where no pre-impact studies were made.

Sulphide mining by the superextensile foot of symbiotic thyasirid bivalves.

In a symbiotic association between an invertebrate host and chemoautotrophic bacteria, each partner has different metabolic requirements, and the host typically supplies the bacteria with necessary reduced chemicals (sulphide or methane). Some combination of anatomical, physiological and behavioural adaptations in the host often facilitates uptake and transport of reduced chemicals to the symbionts. We have studied five species of bivalve molluscs of the family Thyasiridae (that is, thyasirids) three of which harbour chemoautotrophic bacteria. Here we show that the symbiotic bivalves extend their feet to form elongated and ramifying burrows in the sediment, most probably to gain access to reduced sulphur. Closely related bivalves (including some thyasirid species) without bacterial symbionts show no comparable foot extension behaviour. The length and number of burrows formed by chemosymbiotic thyasirids are related to the concentration of hydrogen sulphide in the sediment. The burrows are formed by the foot of each bivalve, which can extend up to 30 times the length of the shell, and may be the most extreme case of animal structure elongation documented to date.

Peroxisome proliferation as a biomarker in environmental pollution assessment.

Peroxisome proliferators comprise a heterogeneous group of compounds known for their ability to cause massive proliferation of peroxisomes and liver carcinogenesis in rodents. In recent years it has become evident that other animals may be threatened by peroxisome proliferators, in particular aquatic organisms living in coastal and estuarine areas. These animals are exposed to a variety of pollutants of industrial, agricultural and urban origin which are potential peroxisome proliferators. Both laboratory and field studies have shown that phthalate ester plasticizers, PAHs and oil derivatives, PCBs, certain pesticides, bleached kraft pulp and paper mill effluents, alkylphenols and estrogens provoke peroxisome proliferation in different fish or bivalve mollusc species. The response appears to be mediated by peroxisome-proliferator activated receptors, members of the nuclear receptor family, recently cloned in fish. Based on these results it is proposed that peroxisome proliferation could be used as a biomarker of exposure to a variety of pollutants in environmental pollution assessment. This is illustrated by a case study in which mussels, used worldwide as sentinels of environmental pollution, were transplanted from reference to contaminated areas and vice versa. In mussels native to an area polluted with PAHs and PCBs, peroxisomal acyl-CoA oxidase (AOX) activity and peroxisomal volume density were 2-3 fold and 5-fold higher, respectively, compared to the reference site. When animals were transplanted to the polluted station, with increased concentration of organic xenobiotics, a concomitant significant increase of AOX was recorded. Conversely, in animals transplanted to the cleaner station, AOX activity and peroxisomal volume density decreased significantly. These results indicate that peroxisome proliferation is a rapid (i.e., two days) and reversible response to pollution in mussels. Before peroxisome proliferation can be implemented as a biomarker in biomonitoring programs, a well-defined protocol should be established and validated in intercalibration and quality assurance programmes. Furthermore, the influence of biotic and abiotic factors, some of which are known to affect peroxisome proliferation (season, tide level, interpopulation and interindividual variability), should be taken into consideration. The possible hepatocarcinogenic effects as well as the potential adverse effects on reproduction, development, and growth of peroxisome proliferators are unknown in aquatic organisms, thus providing a challenge for future investigations.

Biology and immature stages of the clam-killing fly, Renocera pallida (Diptera: Sciomyzidae)

The larva of the Palaearctic Renocera pallida (FallĂŠn, 1820) is confirmed as a predator of small species of bivalve molluscs of the family Sphaeriidae. To date only the larvae of three Nearctic Renocera species (and larvae of two other species of Sciomyzidae in two genera) are known to have the same food preference. The life cycle, biology, larval feeding and behaviour are described for the first time and compared with that of the Nearctic Renocera. The systematic position and biology of Renocera in general are discussed. Descriptions of the egg, second and third larval instars and the puparium of R. pallida are presented, the main features of the egg and larvae are illustrated by scanning electron micrographs.

A pilot model for neogene and paleogene bivalve cenozones of the Northwestern Pacific

By means of taxonomically and geochronologically revised species lists (a total of 793 valid species of bivalve molluscs were considered) from 178 formations (‘Suites’) of Neogene and Paleogene deposits in the Russian Far East and characteristic and index species distinguished on this basis, the molluscan cenozones are established. These allow the construction of a preliminary stratigraphical scheme for the northwestern Pacific (western and eastern Kamchatka, south and north Sakhalin, Koryak 0Upland). The following cenozones are established: 1—extant species; 2— Fortipecten takahashii– Yoldia ( Cnesterium) kuluntunensis; 3— Acila ( Truncacila) marujamensis– Lucinoma acutilineata; 4— Mya cuneiformis– Acila ( Truncacila) gottschei; 5— Mytilus ( Tumidimytilus) tichanovitchi– Macoma osakaensis; 6— Megayoldia ( Hataiyoldia) tokunagai– Neilonella ( Borissia) sakhalinensis; 7— Periploma ( Aelga) besshoensis– Yoldia ( Yoldia) kovatschensis; 8— Papyridea ( Profulvia) harrimani– Ciliatocardium asagaiense; 9— Megayoldia ( Portlandella) watasei– Yoldia ( Nampiella) takaradaiensis; 10— Nuculana ( Saccella) gabbii– Corbula ( Cuneocorbula) formosa; 11— Lucina washingtonensis– Nuculana ( Saccella) alaeformis. On the basis of bivalve distribution patterns, it is assumed that the boundary between the Neogene and the Paleogene lies at the base of the Kuluven Horizon in western Kamchatka, the base of the lower Nevelisk sub-Horizon in south Sakhalin and at the lower part of the Pakhachin Horizon in eastern Kamchatka and Koryak Upland.

Flow cytometric comparison of haemocytes from three species of bivalve molluscs

Haemocyte subpopulations from three bivalve species (the clams Ruditapes philippinarum andMercenaria mercenaria and the oyster, Crassostrea virginica) were characterised using light-scatter flow cytometry and a standard set of methods. Two parameter (forward and side scatter) plots for the three species were very similar and resembled plots for mammalian white blood cells. Two haemocyte groups (granulocytes and agranulocytes) were found in both the haemolymph and the extrapallial fluid of the clams while those two groups and an additional third group were found in the haemolymph of the oyster. All subpopulations were sorted on to glass slides, identified, photographed, and measured microscopically. Sorting of the bivalve granulocyte and agranulocyte groups indicated varying degrees of heterogeneity within each population in terms of either size or granularity, or both. However, subsorting of selected regions within the major groupings produced highly pure haemocyte populations. The comparison showed both similarities and differences among species. For instance, a distinct subpopulation of small granulocytes was present only in oysters and a subpopulation of spindle-shaped haemocytes, only inM. mercenaria . The haemocyte subpopulations delineated by light-scatter flow cytometry underscore questions about cell lineages, but the instrument also offers a powerful technique for answering them.

Correlated evolutionary divergence of egg size and a mitochondrial protein across the Isthmus of Panama.

An explicit assumption of studies that employ a mitochondrial DNA (mtDNA) molecular clock is that mtDNA evolves independently of morphology. Here we report a very strong correlation between egg size divergence and cytochrome c oxidase-1 (CO1) amino acid sequence divergence among sister species of bivalve molluscs separated by the Central American Isthmus (i.e., "geminate" species). Analyses of the molecular data reveal that CO1 sequences likely did not diverge as a function of time or evolve in response to positive natural selection. Given that an excess of CO1 amino acid polymorphism exists within species (as expected if most mutations are only slightly deleterious), a third hypothesis is that reductions in effective population size could simultaneously increase the fixation rate of nearly neutral mtDNA polymorphisms and in some way also facilitate egg size evolution. The remarkable strength of the relationship between egg size and CO1 amino acid sequence demonstrates that, even in the absence of an obvious functional relationship or clock-like evolution, the amounts of molecular and morphological change can be tightly correlated, and therefore may reflect common processes. Accordingly, the assumption that the evolutionary divergence of molecules and morphology are independent must always be carefully examined.

Effects of plasma from bivalve mollusk species on the in vitro proliferation of the protistan parasite Perkinsus marinus.

The in vitro culture of the Eastern oyster parasite Perkinsus marinus has provided a unique opportunity to examine its susceptibility to putative recognition and effector defense mechanisms operative in refractory bivalve species. In this study, we report the effect of supplementing the culture medium with plasma from: (1) uninfected to heavily infected Eastern oysters; (2) oyster species considered to be disease-resistant; and (3) bivalve mollusk species that are naturally exposed to the parasite but show no signs of disease. We also examined in vitro the interaction between hemocytes from Crassostrea virginica and C. gigas and P. marinus trophozoites. Our results revealed a significant decrease (32%) in proliferation of P. marinus in the presence of plasma from heavily infected C. virginica oysters. The inhibitory effects were less pronounced with plasma from moderately infected and uninfected oysters. In contrast, plasma from C. rivularis and C. gigas enhanced P. marinus proliferation. Proliferation was significantly reduced in media supplemented with plasma from Mytilus edulis, Mercenaria mercenaria, and Anadara ovalis. The highest inhibitory activity was apparent in M. edulis, for which 5% plasma-supplemented medium reduced growth by 35% relative to the controls. M. edulis active component(s) was heat-stable, yet pronase-sensitive. The significantly higher uptake of live P. marinus trophozoites by hemocytes from C. virginica, relative to those from C. gigas, suggests a certain level of specificity in the recognition/endocytosis of the parasite by its natural bivalve host species.

System of principles for conservation of the biogeocenotic function and the biodiversity of filter-feeders.

An ecologically substantiated system of protectedterrestrial and water areas is an essential component ofbiodiversity conservation [1].Studies by many authors [2–4] and our own works[6, 7] showed that filter-feeders play an important rolein elimination of suspended particles from water and itspurification. Therefore, filter-feeders provide habitatsfor other species in aquatic ecosystems. This impliesthat the problem of conservation of the filtration func-tion in the population of hydrobionts should be prop-erly taken into account when developing the system ofconservation of terrestrial and aquatic areas.The goal of this work was to formulate and substan-tiate the suggestion that the system of protected terres-trial and aquatic areas should be supplemented by sitesintended to conserve the filtration function of filter-feeding hydrobionts (filter-feeders of zoobenthos, inparticular). An additional goal of this work was to for-mulate and substantiate the system of basic principlesand conditions of their protection.Emphasis should be placed on the following aspectsof this problem: the state of the population of filter-feeders (bivalve mollusks, in particular); the factorsmaking it necessary to protect populations of filter-feeders; and basic requirements for the conditions oftheir protection. The state of the populations of filter-feeders (asexemplified by bivalve mollusks).Some species of bivalve mollusks are included inthe Red Data Books of Russian Federation (34 taxa, in2000) [8] and some other states of the former SovietUnion. In the North America and Western Europe,many populations of bivalve mollusks are also endan-gered and included in the IUCN Invertebrate Red DataBook [9].In many aquatic ecosystems, there is a trend towarda decrease in the populations and biomass of bivalvemollusks at polluted sites. This concerns both freshwa-ter [7] and marine [4] ecosystems.The state of filter-feeding hydrobionts should betaken into account in the context of the general state ofaquatic ecosystems. Even in some reserves, the state ofmany aquatic ecosystems is far from satisfactory. Usingthe methods based on the morphometric characteristicsof aquatic organisms such as the roach ( Rutilus rutilus )and the lake frog ( Rana ridibunda ), it has been shownthat the state of aquatic ecosystems in the VoronezhskiiState Natural Reserve is unsatisfactory [10]. The stateof aquatic ecosystems was also found to be unsatisfac-tory in many places outside state natural reserves: thetown of Voronezh, Lake Kostomukshinskoe (Karelia), alake in the Zheleznogorsk raion of the Kursk oblast,etc. [10]. Factors making it necessary to protect popula-tions of filter-feeders. There are several factors mak-ing it necessary to protect populations of filter-feeders(including bivalve mollusks), including:conservation of the gene pool as a part of biodiver-sity;conservation of the gene pool as a resource and areserve for aquaculture; andconservation of water self-purification in naturalwater bodies.Various aspects of conservation of the gene pool wereconsidered in the preceding works on the general prob-lems of conservation of biodiversity [11, 12] and morespecific problems of conservation of invertebrates [9].Let us consider the third factor in more detail. Therole of invertebrates in self-purification of water bodieswas studied by many researchers (for review, see [2–7,13–15]). The whole volume of water in many largeaquatic ecosystems can be filtrated by bivalve molluskswithin the time interval from 0.7 (South San FranciscoBay) to 25 days (Narragansett Bay) [5]. Within oneyear, marine bivalve mollusks are capable of eliminat-ing, from water column above 1 m

Ultrastructural Characteristics of Interneuronal Connections of the Central Nervous System of Bivalve Molluscs

Ultrastructure and peculiarities of interneuronal contacts are studied in visceral ganglia of two species of bivalve molluscs, Anadara broughtoni and Mactra sulcatoria. Gap, desmosome-like, symmetrical, and classic synaptic junctions between neuronal bodies and their main processes are described. The major part of interneuronal junctions in the ganglia of the molluscs studied are symmetrical. Complex synaptic complexes formed by specialized and non-specialized junctions are observed.

Interactions between the toxic estuarine dinoflagellate Pfiesteria piscicida and two species of bivalve molluscs

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 245:1-10 (2002) - doi:10.3354/meps245001 Interactions between the toxic estuarine dinoflagellate Pfiesteria piscicida and two species of bivalve molluscs Jeffrey J. Springer1,*, Sandra E. Shumway2, JoAnn M. Burkholder1, Howard B. Glasgow1 1Center for Applied Aquatic Ecology, North Carolina State University, 620 Hutton Street, Suite 104, Raleigh, North Carolina 27606, USA 2Department of Marine Sciences, University of Connecticut, 1080 Shennecossett Road, Groton, Connecticut 06340, USA *Email: jeff_springer@ncsu.edu ABSTRACT: Toxic strains of Pfiesteria spp. produce toxin(s) that can cause finfish death, but much less is known about impacts of Pfiesteria on shellfish. Here we conducted 4 experiments to examine interactions between shellfish and toxic (actively toxic or TOX-A from finfish-killing cultures and potentially toxic or TOX-B from cultures without finfish) and non-inducible (NON-IND, apparently incapable of killing fish via a toxic effect) strains of P. piscicida. First (Expt 1), we documented direct physical attack by P. piscicida TOX-A, TOX-B, and NON-IND zoospores on larvae of the bay scallop Argopecten irradians (Lamarck, 1819) and the eastern oyster Crassostrea virginica (Gmelin, 1791). Within 5 min zoospores swarmed around larvae that had discarded their vela, and attached with their peduncles. Within 15 min they had penetrated into the shellfish visceral cavity and had begun to feed aggressively; after 30 min all shellfish tissues except the adductor muscle had been consumed. Second, we tested the response of scallop larvae to P. piscicida (TOX-A or TOX-B) or cryptomonads (as controls) that were held in dialysis tubing (0.22 µm porosity) to prevent direct contact. After 60 min larval survival was 0% in the TOX-A treatment, 100% in the cryptomonad control, and intermediate in TOX-B and TOX-B + cryptomonad treatments. The data indicate a toxic effect of P. piscicida zoospores on the larvae, separate from the physical effect shown in Expt 1. Third, we compared grazing by juvenile and adult oysters on TOX-A, TOX-B, and NON-IND P. piscicida zoospores from the medium. After 60 min, grazing by juvenile oysters significantly differed as NON-IND >> TOX-B >> TOX-A. In contrast, adult oysters grazed significantly fewer TOX-A zoospores and maintained comparable grazing on TOX-B and NON-IND zoospores. Thus juvenile oysters, but not adults, were sensitive to residual toxicity of TOX-B zoospores, and both life-history stages were sensitive to TOX-A zoospores. The adverse effects of toxic strains on larval survival and juvenile grazing indicate that P. piscicida could potentially affect shellfish recruitment. Fourth, we assessed zoospore survival after passage through the digestive tract of adult oysters. The feces contained many temporary cysts from zoospores, and within 24 h >75% of the cysts produced motile cells. The data indicate that adult oysters would be poor biocontrol agents of P. piscicida, given the high survival of ingested zoospores following gut passage and fecal elimination; and that oysters could act as vectors of toxic P. piscicida strains if transported from affected estuaries to other waters. KEY WORDS: Argopecten irradians · Crassostrea virginica · Oyster · Pfiesteria · Scallop · Shellfish · Temporary cyst · Toxic dinoflagellate Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 245. Online publication date: December 18, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Seasonal Dynamics of Soft Bottom Macrobenthic Communities of the Sublittoral in Peter the Great Bay, Sea of Japan

Seasonal dynamics of macrobenthos were studied at five stations located at depths of 10–60 min in the Far East State Marine Reserve (southern Peter the Great Bay) during 1984–1987. Sampling was conducted at stations once per season. Stable seasonal fluctuations of the population density and the biomass in basic taxonomic groups were found. As a rule, the quantitative parameters were augmented in spring and summer, and decreased in fall and winter. This was caused, first of all, by summer fluctuations of the number of small and short-lived species of polychaetes and bivalve molluscs. The amplitude of fluctuations decreased with increasing depth. Variation in the quantitative parameters was significant at the community level only at the most shallow-water stations. It was assumed that this phenomenon might be caused by the seasonal consumption of macrobenthos by bottom fish and by the periodicity of detritus supply to the bottom from the water column with a background of varying environmental temperature parameters and of mass settling of benthic larvae. The seasonal changes in parameters began and ceased earlier in 1986–1987 than 1984–1985, which was related to an appreciable decrease in water temperature in 1986. During the period of study, an increasing trend of parameters, apparently part of a long-term cycle, was recorded both for individual groups and for entire communities, and was the most appreciable at greater depths (47–60 m).

DNA content, karyotypes, and chromosomal location of 18S-5.8S-28S ribosomal loci in some species of bivalve molluscs from the Pacific Canadian coast.

The DNA content of 10 species of bivalve molluscs from British Columbia coast was determined by image analysis, and the karyotypes of the horse clam Tressus capax, the bent-nose macoma Macoma nasuta, and the nuttall's mahogany clam Nuttallia nuttallii are described here for the first time. We also have analyzed the location of rDNA loci using a 28S-5.8S-18S probe in four of these species: Mytilus californianus, M. trossulus, Macoma nasuta and N. nuttallii. Results obtained report new data about cytogenetic characteristics of bivalve molluscs.

Environmental Genotoxicity in Klaipėda Port Area

Genotoxic effects were evaluated in the somatic and gonadal cells of five bivalve and gastropod mollusc species inhabiting various sites of Klaipėda port area, differing by ecotoxic impacts. Aneuploidy, polyploidy of cells, meiotic injures, centromere dissociation and fragmented polyploid nuclei were assessed as cytogenetic disturbances. The highest level of environmental genotoxicity was observed in the cells of Lymnaea ovata snails inhabiting Malkų Bay in 1995 and 1996. Dredging and removal of contamined sediments from Malkų Bay resulted in marked decrease of cytogenetic damage in molluscs, which were studied in 1997 and 1998. In 1997 the aneugenic effects were more frequent in the tissues of Bithynia tentaculata from Smeltė River than those collected from Malkų Bay and Klaipėda passage. The level of cytogenetic damage in molluscs from Vilhelmo Channel was increasing from 1995 to 1998.

Environmental Genotoxicity in Klaipėda Port Area

Genotoxic effects were evaluated in the somatic and gonadal cells of five bivalve and gastropod mollusc species inhabiting various sites of Klaipe˙da port area, differing by ecotoxic impacts. Aneuploidy, polyploidy of cells, meiotic injures, centromere dissociation and fragmented polyploid nuclei were assessed as cytogenetic disturbances. The highest level of environmental genotoxicity was observed in the cells of Lymnaea ovata snails inhabiting Malkų Bay in 1995 and 1996. Dredging and removal of contamined sediments from Malkų Bay resulted in marked decrease of cytogenetic damage in molluscs, which were studied in 1997 and 1998. In 1997 the aneugenic effects were more frequent in the tissues of Bithynia tentaculata from Smelte River than those collected from Malkų Bay and Klaipeda passage. The level of cytogenetic damage in molluscs from Vilhelmo Channel was increasing from 1995 to 1998.

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.