Protective reactions of gastropod molluscs. 1. Cell reactions

Protective reactions of molluscs are traditionally considered in cell and humoral aspects. The paper analyses original data and recent reference data oncell (phagocytic) reactions of gastropod molluscs. The main attention is paid to peculiarities of hemopoiesis, cell elements of hemolymph, and dynamics and mechanics of encapsulating the parasites.     

Ultrastructural and morphometric characteristics of cardiomyocyte mitochondriomes of several invertebrate species. II. Heart ventricle cardiomyocyte mitochondriome of several gastropod mollusks

The mitochondrial ultrastructure in ventricle cardiomyocytes of three gastropod molluscs (Clione limacina, Helix pomatia, Lymnaea stagnalis) has been studied. Mitochondria in cardiomyocytes of these molluscs are connected by intermitochondrial contacts of the same morphology as intermitochondrial contacts in vertebrate cardiomyocytes. Their numbers in cardiomyocytes of the above molluscs being, respectively, 61, 35.1 and 29.2 contacts per 100 mitochondria. In Clione limacina cardiomyocyte contractile elements located on the periphery of cell occupy 21.1% of the cytoplasm volume. Mitochondria form a core making large dense central accumulations taking up 54.9% of the cytoplasm volume. Numerous mitochondria have vesicular or tubular cristae and light matrix. Unlike cardiomyocytes of Clione limacina, in Helix pomatia and Lymnaea stagnalis contractile material predominates in cardiomyocytes occupying 43.7% and 49.2% of the cytoplasm volume, respectively. Mitochondria located on the periphery and in the center of cardiomyocytes in Lymnaea stagnalis and Helix pomatia occupy 31 and 32.5% of the cytoplasma volume, respectively. Mitochondria in cardiomyocytes of both these molluscs have plastic cristae and dense matrix. The differences in cardiomyocyte mitochondriom organization in the studied molluscs can be explained by different functional heart loading in these due to different levels of their locomotor activity.     

Biochemical identification and numerical taxonomy of Aeromonas spp. isolated from environmental and clinical samples in Spain

AIMS: To study the phenotypic characteristics of Aeromonas spp. from environmental and clinical samples in Spain and to cluster these strains by numerical taxonomy. METHODS AND RESULTS: A collection of 202 Aeromonas strains isolated from bivalve molluscs, water and clinical samples was tested for 64 phenotypic properties; 91% of these isolates were identified at species level. Aeromonas caviae was predominant in bivalve molluscs and Aerom. bestiarum in freshwater samples. Cluster analyses revealed eight different phena: three containing more than one DNA-DNA hybridization group but including strains that belong to the same phenospecies complex (Aerom. hydrophila, Aerom. sobria and Aerom. caviae), Aerom. encheleia, Aerom. trota and three containing unidentified Aeromonas strains isolated from bivalve molluscs. CONCLUSIONS:Aeromonas spp. are widely distributed in environmental and clinical sources. A selection of 16 of the phenotypical tests chosen allowed the identification of most isolates (91%), although some strains remain unidentified, mainly isolates from bivalve molluscs, suggesting the presence of new Aeromonas species. Numerical taxonomy was not in total concordance with the identification of the studied strains. SIGNIFICANCE AND IMPACT OF THE STUDY: Numerical taxonomy of Aeromonas strains isolated from different sources revealed the presence of potentially pathogenic Aeromonas spp., especially in bivalve molluscs, and phena with unidentified strains that suggest new Aeromonas species.     

Evolutionary regularities of somatic polyploidy in salivary glands of the Gastropod molluscs. II. Subclass Pectinibranchia: order Anisorbranchia

Salivary glands of 5 species of gastropod molluscs of the order Anisobranchia, the most ancient order within the subclass Pectinibranchia, have been investigated by histological and cytochemical methods, including DNA cytophotometry. Glandular cells of the following types were recognized: granular cells (with glycoproteid granular inclusions), mucocytes-I (including sulfatic acid mucopolysaccharides), mucocytes-II (including neutral and acid polysaccharides and proteins), and epithelial ciliated cells. All the described cell types are considered to be independent and their morphofunctional characteristics coincide with those of salivary gland cells of the gastropod molluscs of subclasses Cyclobranchia and Scutibranchia. It has been shown that somatic polyploidy in salivary glands in the Anisobranchia molluscs, likely as in those of other Archaeogastropoda (Cyclobranchia and Scutibranchia), is actually absent.     

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.     

湖泊富营养化治理的生态工程

1996年对长春南湖的富营养化实施了生治理工作,调查结果表明,通过收获水生高等植物和鱼产品带出湖体的P量分别为149．6和189．9kg,通过蚌体生长固定的P量为153.4kg,三者合计492.9kg,与湖体会年P输入量大体持平,生态工程运转后,水质明显好转,湖水中的总P浓度逐年下降,浮游植物个体密度减小,种类数增加,生态工程是城市湖泊富营养化治理较为理想的方法。     

Coliform bacteria from aquatic sources in Fiji.

Coliform bacteria were abundant in water and bivalve molluscs in the rivers and present to a lesser extent in the coastal areas of Fiji. The rivers fed by treated sewage were highly polluted. There was a noticeable increase in concentration of coliforms in bivalve molluscs. It was also found that these bacteria could survive and grow in river water and seawater over a 5-d period, and had a rapid growth rate in nutrient broth under ideal laboratory conditions. They were characterized by the API 20E identification system.     

Metallothioneins (MTs) in marine molluscs.

The presence of MTs in marine molluscs was firstly hypothesized in oyster and in mussel during the seventies, however mussel's and oysters' MTs were completely purified and sequenced rather later. Already from the first studies it was evident that the purification of molluscan MTs was more difficult than in mammals. Mussel's MTs are characterized by the presence of a monomeric and a dimeric form. Several physiological and biochemical parameters can influence the concentration and the isolation of MT from molluscan tissues. Remarkable variations in MT isolation and quantification might depend on the purification and storage protocol. Because of possible artefacts due to the isolation procedure the establishment of a standard protocol for MT quantification in marine mollusc is still an important goal. In a few species the presence of very low molecular weight metal binding ligands has also been reported, in these cases it cannot be excluded that the native MT has been cleaved by the action of proteases. This review aims to report: 1) importance of a standard method for MT purification and quantification in molluscs; 2) distribution of MT among molluscan species; 3) data concerning oyster's and mussel's MTs which are the two more deeply investigated marine molluscs; 4) biotic and abiotic factors influencing MT concentration, and 5) biological role of MT and use of MT as a biochemical marker of heavy metal pollution.     

Feeding ecology of the diving ducks pochard (Aythya ferina), tufted duck (A. fuligula), scaup (A. mania) and goldeneye (Bucephala clangula) overwintering on Lough Neagh, Northern Ireland

1. The diets of pochard (Aythya ferina), scaup (A. marila) and goldeneye (Bucephala clangula) overwintering on Lough Neagh are dominated by chironomid larvae, while molluscs are more important in that of tufted duck (A. fuligula). 2. Inshore areas of Lough Neagh offer poor feeding conditions for these diving ducks because chironomid larvae and molluscs are of small individual body size or low abundance. These factors lead to all four ducks foraging at least in part at depths greater than those usually exploited. 3. Due to their common consumption of molluscs, the diet of tufted duck shows a higher overlap with that of an introduced roach (Rutilus rutilus) population than with any other duck or fish species. 4. The feeding ecology of tufted duck and roach in Lough Neagh may form an example of distant competition and be at least partly responsible for recent fluctuations in the numbers of tufted duck.     

Modification of the structure of penial glands in males of the intertidal molluscs Littorina saxatilis and L. obtusata under the influence of the infestation by trematode parthenites

Sporocycts of the "pygmaeus" microphallides (Microphallus piriformes) are localized in hepatopancreas and gonads of Littorina molluscs causing total parasitic castration. A histological study of penial glands in Littorina saxatilis and L. obtusata males infested with trematodes M. piriformes has been made. Copulatory organs of noninfested molluscs, molluscs after recent contamination (with not completely formed daughter sporocysts), and molluscs containing mature metacercariae inside daughter sporocysts were examined. Based on the data obtained, probable dynamics of the histological structure of infested glandular apparatus was established. It was shown, that the trematode infestation have an influence on the muscular and secretory parts of penial glands. The wall of the penial gland muscular capsule becomes more fine in infested L. saxatilis. On the contrary, this wall is vastly thicker in infested L. obtusata, as compared with noninfested individuals. Glandular cells of the molluscs' penial glands decreases the amount of granular secret in both species. In L. obtusata the number of secretory cells is shown to be reduced up to their total disappearance. The above pathological changes probably prevent normal function of penial glands.     

Wildlife trade,CITES and the protection of marine molluscs in Indonesia

ABSTRACT

Indonesia is a significant trader in marine molluscs and has a comprehensive legislative framework in place to protect and use molluscs sustainably. The recent inclusion of nautilus in Appendix II of CITES and the general lack of understanding of the level of protection and regulation Indonesia's marine molluscs receive necessitates a review of current laws and agreements. The most relevant are two legally binding international agreements, CITES and the CBD, and Law No 5, and Regulations 8 and 20, dealing with protection, preservation and exploration, respectively. Over the last 30 years, 12 species of mollusc have been legally protected in Indonesia and 7 are included in CITES Appendix II. Species that are not protected can be traded, provided quotas have been set for their commercial exploitation. Seizure data suggest that the illegal trade is considerable – on average almost 10,000 shells/year are confiscated. Seizures do not lead to prosecutions. It is recommended that (a) those involved in the trade of Indonesian marine molluscs need to familiarise themselves better with current legislation and regulation, (b) monitoring of domestic and international trade in marine molluscs needs to be better coordinated and intensified and (c) prosecutions for those trading illegally in marine molluscs need to increase.     

A description of the parthenogenetic metacercaria and cercaria of <Emphasis Type="Italic">Cercaria falsicingulae I</Emphasis> larva nov. (Digenea: Gymnophallidae) from the snails <Emphasis Type="Italic">Falsicingula</Emphasis> spp. (Gastropoda), with speculation on an unusual life-cycle

Previously unknown gymnophallid parthenogenetic metacercariae (PM), referred to as Cercaria falsicingulae I larva nov., were found in the extrapallial cavities of the snails Falsicingula mundana (Yokoyama) and F. athera (Bartsch) on coasts of Sakhalin and the Kuril Islands. Unlike all other known PM, rather than producing metacercariae infective to the definitive host, their furcocercariae emerge into the environment. The developing cercariae and metacercariae of C. falsicingulae I are described and compared with other gymnophallid larvae from littoral molluscs in the region. Experimental evidence and analysis of metacercarial group composition in naturally infected molluscs indicate that some cercariae leave their molluscan hosts and penetrate other specimens of Falsicingula in which they develop into new cercariae-producing PM. Metacercariae with developing hermaphroditic reproductive organs were never observed in naturally infected molluscs. A probable life-cycle for C. falsicingulae I is presented in which cercarial/metacercarial production is switched seasonally in order to enable the infection of the definitive hosts by PM. Importantly, the 'cercaria - PM - cercaria' component of the life-cycle appears to be somewhat autonomous.     

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.     

An Early Cambrian problematic fossil: Vetustovermis and its possible affinities

The Early Cambrian problematic fossil Vetustovermis (Glaessner 1979 Alcheringa3, 21-31) was described as an annelid or arthropod. Anatomical analysis of 17 new specimens from the Lower Cambrian Maotianshan Shale at Anning, Kunming (South China) does not support its affinities with annelids or arthropods. Anatomical features instead resemble other animal groups including modern flatworms, nemertines and molluscs. The presence of a pelagic slug-like form and ventral foot, as well as a head with eyes and tentacles indicates a possible affinity with molluscs, but these characters are not present only in molluscs; some of them are shared with other animal groups, including flatworms and nemertines. For example, a ventral foot-like structure is found in nemertines, 'turbellarians', and some polychaete groups. The well differentiated head is seen in separate bilaterian groups, but among molluscs it did not occur before the evolutionary level of the Conchifera. Unlike the ctenia-gills in molluscs, the gills in Vetustovermis are bar-like. All the characters displayed in this 525 million-year old soft-bodied animal fail to demonstrate clear affinity with molluscs or any other known extant or extinct animal groups, but argue for representing an independently evolved animal group, which flourished in Early Cambrian and possibly in Middle Cambrian time.     

Bacteria of the genus Acinetobacter in the marine environment and in hydrobiontic mollusks

The study of Acinetobacter bacteria in sea water and in aquatic molluscs of the southern climatic zone has revealed ecological differences in the species A. calcoaceticus and A. lwoffi and the appearance of the ecological niche for Acinetobacter in molluscs.     

Cadmium accumulation in organs of the scallop Mizuhopecten yessoensis--I. Activities of phosphatases and composition and amount of lipids

Maintenance of Mizuhopecten yessoensis in water with 0.5 mg Cd/l for 60 days increased Cd concentration in the mantle and ovaries about 200 times, in gills 70 times and hepatopancreas 20 times. Alkaline phosphatase activity was inhibited in all organs except the hepatopancreas after a 1-month exposure to Cd and became equal to the control in all the organs after 2 months exposure. Molluscs transferred to flowing water showed a considerable decrease in the activity of alkaline and acid phosphatases. The activity of both acid phosphatase and Mg2+-ATPase decreased in all the organs of experimental molluscs after exposure to Cd. The amount of phospholipids and cholesterol in the organs of control and experimental molluscs did not essentially differ.     

Nociceptive behavior and physiology of molluscs: animal welfare implications

Molluscs have proven to be invaluable models for basic neuroscience research, yielding fundamental insights into a range of biological processes involved in action potential generation, synaptic transmission, learning, memory, and, more recently, nociceptive biology. Evidence suggests that nociceptive processes in primary nociceptors are highly conserved across diverse taxa, making molluscs attractive models for biomedical studies of mechanisms that may contribute to pain in humans but also exposing them to procedures that might produce painlike sensations. We review the physiology of nociceptors and behavioral responses to noxious stimulation in several molluscan taxa, and discuss the possibility that nociception may result in painlike states in at least some molluscs that possess more complex nervous systems. Few studies have directly addressed possible emotionlike concomitants of nociceptive responses in molluscs. Because the definition of pain includes a subjective component that may be impossible to gauge in animals quite different from humans, firm conclusions about the possible existence of pain in molluscs may be unattainable. Evolutionary divergence and differences in lifestyle, physiology, and neuroanatomy suggest that painlike experiences in molluscs, if they exist, should differ from those in mammals. But reports indicate that some molluscs exhibit motivational states and cognitive capabilities that may be consistent with a capacity for states with functional parallels to pain. We therefore recommend that investigators attempt to minimize the potential for nociceptor activation and painlike sensations in experimental invertebrates by reducing the number of animals subjected to stressful manipulations and by administering appropriate anesthetic agents whenever practicable, welfare practices similar to those for vertebrate subjects.     

Heavy metal complexation in polluted molluscs I. Limpets (Patella vulgata and Patella intermedia)

The accumulation of cadmium, zinc and copper by the marine gastropod molluscs Patella vulgata and Patella intermedia has been studied by gel permeation chromatography of water-soluble extracts of environmentally contaminated shellfish.A major proportion of the water-soluble cadmium and copper in these molluscs is associated with a protein of molecular weight 10 800 daltons. Evidence is presented supporting the similarity of this protein with mammalian metallothionein. This protein contained only a small proportion of the zinc found in the samples.     

Parasitism of Molluscs by Nematodes: Types of Associations and Evolutionary Trends

Although there are no confirmed fossil records of mollusc parasitic nematodes, diverse associations of more than 108 described nematode species with slugs and snails provide a fertile ground for speculation of how mollusc parasitism evolved in nematodes. Current phylogenic resolution suggests that molluscs have been independently acquired as hosts on a number of occasions. However, molluscs are significant as hosts for only two major groups of nematodes: as intermediate hosts for metastrongyloids and as definitive hosts for a number of rhabditids. Of the 61 species of nematodes known to use molluscs as intermediate hosts, 49 belong to Metastrongyloidea (Order Strongylida); of the 47 species of nematodes that use molluscs as definitive hosts, 33 belong to the Order Rhabditida. Recent phylogenetic hypotheses have been unable to resolve whether metastrongyloids are sister taxa to those rhabditids that use molluscs as definitive hosts. Although most rhabditid nematodes have been reported not to kill their mollusc hosts prior to their reproduction, some species are pathogenic. In fact, infective juveniles of Phasmarhabditis hermaphrodita vector a lethal bacterium into the slug host in which they reproduce. This life cycle is remarkably similar to the entomopathogenic nematodes in the families Steinernematidae and Heterorhabditidae. Also, the discoveries of Alloionema and Pellioditis in slugs are interesting, as these species have been speculated to represent the ancestral forms of the entomopathogenic nematodes. Development of the infective stage appears to be an important step toward the acquisition of molluscs as definitive hosts, and the association with specific bacteria may have arisen in conjunction with the evolution of necromeny.