Infected Clams Research Articles

Immune parameters in carpet shell clams naturally infected with Perkinsus atlanticus

Defence parameters of non-infected clams (Ruditapes decussatus) and clams heavily infected withPerkinsus atlanticus were assessed. Cellular (haemocyte density and phagocytic activity) and humoral (lysozyme and anti-bacterial activities, protein concentration and agglutination titre) parameters were measured in clams collected in an area enzootic for P. atlanticus. The infection intensity of each clam was assessed, and the immune parameters measured in the most infected clams were compared with those measured in the non-infected ones. Only the serum anti-bacterial activity and the agglutination titre were significantly different between infected and non-infected clams. The phagocytic rate, haemocyte density, lysozyme concentration and protein concentration were not statistically different but they showed the same trend in the two trials performed. Phagocytic rate, haemocyte concentration and anti-bacterial activity were higher in non-infected clams, while they had lower lysozyme concentration, serum protein concentration and agglutination titre than infected clams. Although infected and healthy clams were not different for every parameter measured, probably due to the high variability among individuals, P. atlanticus seems to affect the clam immune system, at least in advanced stages of the infection.

Identification of proliferating cells in hard clams.

The origin of hemocytes, the circulating “blood cells” of bivalve molluscs, including hard clams (Mercenaria mercenaria) has not been identified (1, 2). Proliferation of hemocytes, however, can be recognized through their increased numbers in diseased animals. Proliferating cell nuclear antigen (PCNA), or cyclin, is a protein produced during the late G1 and S phases of the cell cycle (3, 4). Using antibodies that recognize PCNA in mice, we attempted to identify the origin of hemocytes in the hard shell clams. Quahog parasite unknown (QPX) is a protist that causes severe inflammation and mortality in infected clams (5, 6). We attempted to induce hemocyte proliferation by exposing clams to QPX in a 10-l water column in which 12 ml of undiluted QPX culture (at a concentration of 7p10 cells/ml) were added every 10 days; by injecting QPX between the membranous mantles and the right valves, 3 cm ventral anterior to the siphon and into the pericardial cavities (0.25 ml of undiluted QPX culture); and by injecting an inert particle (India ink, 1:10 dilution in sterile seawater [7, 8]) into the pericardial cavities. The controls consisted of two groups of clams. One group was injected with sterile seawater in the pericardial cavities; the other was untreated. Groups were sampled at 24 h, and at 1, 4, and 8 weeks after the start of the experiment. At sampling, the animals were shucked, fixed in 10% neutral buffered formalin (NBF) for 24 h, and embedded in paraffin. Sections were cut (4–6 mm), mounted onto positively charged slides (Fisherbrand, Superfrost/Plus and ProbeOn Plus slides) and stained either with hematoxylin and eosin (H&E) (9) or with anti-PCNA with a hematoxylin counterstain (Zymed, PCNA Staining Kit). Clams injected with QPX in the pericardial cavities showed mild focal inflammation associated with viable and necrotic QPX organisms. At 2 months post-injection, viable QPX organisms were no longer identified. QPX organisms and associated inflammation were not observed in clams injected in the mantle cavity. After 2 months of water column exposure, only very rare infection by QPX organs with minimal inflammation was observed in mantle tissue. India ink injection caused a minimal inflammatory response. Pools of injected ink in the tissues and vascular spaces were either engulfed by individual hemocytes or surrounded and sequestered by hemocytes (encapsulation), forming thin-walled granulomas (6, 10). Numerous individual hemocytes containing India ink were eliminated from the clams by diapedesis over lumenal epithelial surfaces (Fig. 1A). Thick-walled granulomas (6, 10) were also identified in the gills, pericardial sacs, and other 1 Worcester Polytechnic Institute, Worcester, MA.

Toxicokinetics of 2,4,5-trichlorophenol and benzo(a)pyrene in the clam Pisidium amnicum: effects of seasonal temperatures and trematode parasites.

Several biotic and abiotic stress factors may affect aquatic organisms simultaneously. However, not much is known about the effects of, e.g., low temperatures and parasite infections on the toxicokinetics of organic hydrophobic chemicals. Here we studied the accumulation and depuration of [(14)C]2,4,5-trichlorophenol (TCP) and [(3)H]benzo(a)pyrene (BaP) in the sediment-dwelling freshwater clam Pisidium amnicum. Experiments were made in October (+15 degrees C), April (+4 degrees C), and July (+15 degrees C) both with uninfected clams and clams infected with Bunodera luciopercae (Trematoda). The accumulation rate for both chemicals was slower at 4 degrees C than at 15 degrees C. The depuration of TCP was biphasic, and the slowest depuration occurred at 4 degrees C. For BaP, the depuration was very slow and monophasic at all temperatures. The highest BCFs for both chemicals were found in July at 15 degrees C. Surprisingly, the BCFs for TCP were higher in April at 4 degrees C than in October at 15 degrees C. For BaP, no steady-state was reached in April. Differences in chemical toxicokinetics between the infected and uninfected clams were only minor. However, for both chemicals a trend of slightly lower BCFs in the infected clams was found. In conclusion, low temperatures modify the toxicokinetics of organic chemicals in P. amnicum and the effects depend on hydrophobicity of the chemical. The effects of parasites on toxicokinetics seem to be small.

Alterations in Hemolymph and Extrapallial Fluid Parameters in the Manila Clam, Ruditapes philippinarum, Challenged with the Pathogen Vibrio tapetis

In a recent study, we demonstrated the presence of defense factors, competent hemocytes and high enzymatic activities (peptidases, hydrolases, lytic, etc.), in the extrapallial fluid, located between the mantle and the shell, of the Manila clam, Ruditapes philippinarum. In Europe, this species is affected by brown ring disease, an epizootic disease caused by the bacterium Vibrio tapetis. The present work focused on the effect of the development of the disease on cellular and humoral defense parameters in the hemolymph and the extrapallial fluid of experimentally infected clams. Results indicate significant changes in total and dead hemocyte counts, as well as modifications in lysozyme activity and protein content, in the hemolymph and extrapallial fluid of challenged animals. Hemocyte counts and lysozyme activity increased significantly in the hemolymph, but particularly in the extrapallial fluid, where the highest values were observed. A healing (recalcification) process was observed 7 weeks following challenge, suggesting defense system efficiency at neutralizing the pathogen. These results are discussed with emphasis on the role of extrapallial fluids in the defense process against invading microorganisms.

THE EFFECTS OF PARASITES AND TEMPERATURE ON THE ACCUMULATION OF XENOBIOTICS IN A FRESHWATER CLAM

Freshwater invertebrates are exposed to many stress factors in their habitat. This study is the first attempt to assess the effects of digenean trematode infection on bioaccumulation of (3H)bentzo(a)pyrene (BaP) and ('4C)2,4,5-trichlorophenol (TCP) in the freshwater clam Pisidium amnicum. Static 24-h exposures were carried out in the laboratory both in July (at 20?C) and in February (at 4?C) to see the effect of seasonal temperatures. Three species of digenean trematodes were found in the bivalves. Bunodera luciopercae was the most common parasite with prevalences of 52%. The other two species with prevalences from 2% to 23% were Palaeorchis crassus and Phyllodistomum elongatum. At 20?C the bioconcentration factors (BCFs) of both compounds were higher in uninfected clams when compared to infected ones, but the differences were not significant. The BCFs of TCP were significantly higher at 4?C than at 20?C for both infected and uninfected clams. The concentrations of BaP and TCP in the clam tissue were equal in both infected and uninfected clams, and higher than in their parasites. However, at 20?C the TCP concentration in the tissues of Palaeorchis-infected clams was lower than in the uninfected clams or in the parasite tissue. The differences are explained by the parasites' life cycle and feeding behavior. Our results suggest that both parasite infection and temperature are important for accumulation of organic pollutants and should be considered in aquatic hazard assessment.

Bacciger bacciger (Trematoda, Fellodistomidae) infection in commercial clams Donax trunculus (Bivalvia, Donacidae) from the sandy beaches of the Western Mediterranean

DAO Diseases of Aquatic Organisms Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials DAO 35:37-46 (1999) - doi:10.3354/dao035037 Bacciger bacciger (Trematoda, Fellodistomidae) infection in commercial clams Donax trunculus (Bivalvia, Donacidae) from the sandy beaches of the Western Mediterranean Montserrat Ramón1,*, Mercedes Gracenea2, Olga González-Moreno2 1Institut de Ciències del Mar, Passeig Joan de Borbó, s/n, E-08039 Barcelona, Spain 2Laboratori de Parasitologia, Facultat de Farmàcia, Universitat de Barcelona, E-08028 Barcelona, Spain *E-mail: mramon@icm.csic.es ABSTRACT: Sporocysts of the Fellodistomidae trematode Bacciger bacciger were embedded in gonadal tissue of the bivalve Donax trunculus from the Mediterranean coast of Spain. The overall prevalence of infection was 8.4%, increasing with host size to 23% in D. trunculus from 35 to 36 mm in shell length. Individuals <19 mm long were not infected. No clear seasonality was recognized in prevalence of infection. The proportion of infected individuals of both sexes was similar (6.56% in males and 8.04% in females), although the highest prevalence was in clams of unknown sex (13.47%). The proportion of infected clams reduced to virtual castrates of unknown sex reached 28%. The tegument of the sporocyst and shed cercariae was studied by light and electron microscopy. Scanning electron microscopy revealed a smooth surface on the sporocyst tegument, the area of which was greater due to the presence of circumferential infolds and numerous pits. A birth pore on one side of the sporocyst, uniciliate sensory organs and cup-shaped sensory-like structures were present on the tegument. The cercarial body had spines and uniciliate sensory organs. The ventral sucker of the cercariae had 2 rings of uniciliate sensory organs and tegumental spines. KEY WORDS: Bacciger bacciger · Donax trunculus · Trematode infection · SEM observations · Western Mediterranean Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in DAO Vol. 35, No. 1. Publication date: January 07, 1999 Print ISSN:0177-5103; Online ISSN:1616-1580 Copyright © 1999 Inter-Research.

Cercarial Production of the Trematode Rhipidocotyle fennica in Clams Kept in the Field

The numbers of cercariae that trematodes produce have been previously investigated in the laboratory but not in the field. I studied cercarial production of the bucephalid trematode Rhipidocotyle fennica in the freshwater unionid clam Anodonta piscinalis kept under natural conditions. Naturally infected clams (n=180) were collected and marked in early June 1996. Every 14 days, starting from the collection date and ending in October, these clams were taken to the laboratory where they were monitored for the emergence of trematode cercariae. Between monitoring dates, the clams were returned to the collection site. From a random subsample of infected clams (n=12), the number of cercariae produced was counted during every monitoring. Cercarial production started in late July. The proportion of infected clams releasing cercariae increased from late July to late August. The mean daily production also increased during that period from 140 to 10,400 cercariae, decreasing thereafter. The mean annual production was 290,000+/-26,000 (160,000-440,000) cercariae. Daily production in late August and early September was positively correlated with annual production. Two of the 12 clams appeared to be infected with both R. fennica and Rhipidocotyle campanula. The average annual productions of R. fennica and R. campanula cercariae in double infections were 181,000+/-58,000 and 73,000+/-29,000, respectively.

Observations of a Protistan Disease Similar to QPX inMercenaria mercenaria(Hard Clams) from the Coast of Massachusetts

During the summer and fall of 1995, in clam aquaculture leases at two locations on the coast of Massachusetts, significant mortalities were observed to occur primarily in 112- to 2-year old hard clams (Mercenaria mercenaria,quahog) planted in the leases. Examination of hard clams from those leases suggested a parasite similar to QPX (Quahog Parasite Unknown), as described by Whyte, S. K., Cawthorn, R. J., and McGladdery, S. E. (1994,Can. Dis. Ag. Org.19, 129–136), was responsible for the poor condition of affected clams and the resulting high mortality. In clam tissues, the QPX-like parasite formed thalli surrounded by a mucofilamentous net. Larger thalli underwent endosporulation producing sporangia that contained approximately 40 endospores. Rupture of the sporangium released the endospores into the surrounding tissue. Inflammatory response by the clam to infection was chronic, active, and granulomatous. The occurrence both of phagocytic multinucleated giant inflammatory cells and inflammatory encapsulation of parasites were commonly identified as part of the response. Moderately to severely infected clams showed significantly reduced growth and a poorer condition index as compared to uninfected or mildly infected clams.

Preliminary Evidence for the Effect of Heavy Metal Cations on the Susceptibility of Hard Clam (Meretrix lusoria) to Clam Birnavirus Infection.

The hard clams (Meretrix lusoria) that are cultured in Taiwan have suffered high mortalities each spring and/or summer since 1969. Environmental factors, pollution and infectious diseases have been implicated, but no single factor has been shown to lead directly to large-scale death of the cultured hard clam. In the present study, attempts were made to examine the effects of heavy metals on the susceptibility of the hard clam to birnavirus infection. First we determined the stability of the clam birnavirus in sea, brackish, fresh waters at 4, 15 and 26°C and in solutions containing different concentrations of Zn2+, Cd2+, Cu2+, and Hg2+. For each heavy metal cation, two concentrations which had no influence on clam birnavirus infectivity were selected and used to treat the hard clams before and after virus infection. In experiment I, clams were immersed in 105.0 TCID50 /ml virus solution for 24 h and subsequently exposed to one of the heavy metals. Cumulative mortalities of clams were 20∼52% in most experimental groups although mortalities reached 91% in infected clams exposed to high concentrations of copper. In experiment II, groups of 60 clams were exposed to one of the heavy metals for 7 days and then infected with the virus, while controls were only expose to heavy metals. Mortalities of clams in the experimental groups reached 65∼90% within 28 days, while only 10% mortalities were observed in the groups that were exposed to either heavy metals or virus infection alone.

Perkinsus Protozoan Infecton in Short-necked Clam Tapes (=Ruditapes) philippinarum in Japan.

An infection of Perkinsus (Protozoa : Apicomplexa) was found in the short-necked clam in Kumamoto and Hiroshima prefectures, the first record in Japan. Histology revealed a number of trophozoites with a vacuole, forming cyst-like structures, in connective tissues of the gill, heart, mantle, digestive gland and adductor muscle of the infected clam. The protozoan in the gill enlarged by a culture in Ray's fluid thioglycolate medium and was colored by Lugol's iodine solution. The nucleotide sequences of two internal transcribed spacers with 5.8 SrRNA region were PCR-amplified from DNA of prezoosporangia obtained by a culture of the infected clam tissue. These sequences were almost identical to those of Perkinsus atlanticus and P. olseni. These facts suggest that the Perkinsus protozoan which infected short-necked clam in Kumamoto and Hiroshima, Japan is P. atlanticus or closely related species. We designed a PCR method for diagnosis of this Perkinsus protozoan. The PCR diagnostic method indicated high infection rates (64∼94%) of the parasite in short-necked clam in both area.

An outbreak of intrafamiliar hepatitis A associated with clam consumption: epidemic transmission to a school community.

An outbreak of hepatitis A is described involving thirteen cases in a town in central-northern Italy. The consumption of infected clams, caught in a polluted coastal area of the Adriatic Sea, caused hepatitis A in all five members of a family consisting of mother, father and children, two of whom attended primary school. The epidemic subsequently spread to the primary school with a secondary attack rate of 7.9%, 0 for female pupils and 18.9% for males. The epidemiological and environmental investigations showed that the critical exposure took place in the boys' toilet in the primary school (OR: 32.79, 95% CI: 6.83-157.45). To prevent the spreading of contagion, extra disinfection was carried out in the whole school and health education campaigns were mounted. The good basic hygienic conditions of the homes, together with the cooperation of school staff in surveillance and providing information, allowed the epidemic to be controlled.

Effects of parasites on life history of the freshwater bivalve, Pisidium amnicum, in Eastern Finland

The life history of a freshwater clam, Pisidium amnicum was studied in 1981-1983 and in 1992-1993 in a small river in Eastern Finland, with special focus on reproduction and infection rate by digenean trematodes. The river is ice-covered for ca. 5 months each year. The clam population was found to be infected by three species of digeneans: Bunodera luciopercae was the dominant parasite with prevalences of 34-35 % throughout the year; Palaeorchis crassus (ca. 7.5 %) and Phyllodistomum elongatum (ca. 5 %) were present mainly in the summer. Only 1.5 % of the clams had joint infections by two parasites. The lowest percentage of total trematode infection (ca. 10 %) was found at a host shell length of 5 mm. The percentage increased steeply with increasing host size, and reached 90 % at 7.5 mm shell length (the maximum is 9.3 mm). P. amnicum matured and laid eggs in early August, at the age of ca. 13 months. The eggs developed into embryos in marsupia on the inner gills. The shelled embryos were liberated next June-July at a length of 2 mm. The minimum size of a parent giving birth is 4.5 mm. The number of embryos increased with increasing parent size up to a maximum of 29. The infected clams did not reproduce. Annually the actual production of embryos was ca. 50 % of the potential embryo numbers without digenean infection. Probably the parasite-induced decrease in host fitness is even higher in terms of reproductive biomass production, since the large clams castrated by parasites are expected to have had a potential to produce not only more but larger embryos. Both semelparous and iteroparous populations of P. amnicum have been described. The focal population in Finland had an extended life cycle of 3 years probably because of seasonally low water temperatures, but they reproduced only once in their life because of parasitic castration of large clams. The reproductive effort (number of embryos per parent) in their first (and only) reproduction is as high as with other semelparous populations and much higher than that of another population with extended life cycle but iteroparous reproduction.

Age-, size-, and sex-specific infection of Anodonta piscinalis (Bivalvia: Unionidae) with Rhipidocotyle fennica (Digenea: Bucephalidae) and its influence on host reproduction

A Rhipidocotyle fennica infection in Anodonta piscinalis was studied during 1987–1989 in Lake Saravesi, central Finland. The overall prevalence was 32.3% (n = 1157). Only mature clams, ≥ 3 and ≥ 4 years old in the littoral and sublittoral zones, respectively, were infected. According to log-linear models constructed for the mature clams, there was a statistically significant interaction between prevalence and age of the host, between prevalence and habitat, and between age of the host and habitat; prevalences were higher among old specimens and in the littoral zone than among young clams or in the sublittoral zone. Logit models showed that prevalence increased linearly with host size in both habitats. A relationship between clam growth and infection was also found: fast-growing clams were more often infected or infected clams had grown faster. The quantity of sporocyst tubules increased with the age of the host. Prevalence was higher among female clams than among males. It was estimated that over 50% of mature females in the littoral zone were infected. It was also estimated that there was a 31% reduction in the number of glochidium-bearing clams in the littoral zone of Lake Saravesi due to infection with this parasite.

A comparison of gill and hemolymph assays for the thioglycollate diagnosis of Perkinsus atlanticus (Apicomplexa, Perkinsea) in clams, Ruditapes decussatus (L.) and Ruditapes philippinarum (Adams et Reeve)

Gill and hemolymph assays for the thioglycollate diagnosis of Perkinsus atlanticus in clams ( Ruditapes decussatus and Ruditapes philippinarum) were compared. Gills, hemolymph and the body remains from clams were separately incubated in fluid thioglycollate medium and stained with iodine solution. The intensity of infection was evaluated using the traditional semi-quantitative scale and a recent quantitative technique based on sodium hydroxide digestion of incubated tissues. The semi-quantitative scale was also compared with paraffin histological analysis. No one method detected all of the infections which were found by one or more of the techniques used. The hemolymph assay detected 69%, the gill analysis 90% and the body remains analysis 95% of all infected clams. Of all negative diagnoses from hemolymph, gills and body remains, 46%, 22% and 13%, respectively, were false. Diagnoses by histological sections only detected 61 % of positive gill tests. The semiquantitative Mackin's scale from gill assay exhibited exponential relationships with total body burden. The quantitative gill, hemolymph and body remains analysis showed linear correlations with total clam body burden after a log X-log Y transformation of the data. Results suggest that the gill tissue is better than hemolymph to diagnose P. atlanticus in clams. The semi-quantitative method from gills is easy and shows a high efficacy, but to evaluate infection intensity and avoid false negative diagnoses it is necessary to calculate the total body burden.

The Brown Ring Disease in the Manila Clam, Ruditapes philippinarum: I. Ultrastructural Alterations of the Periostracal Lamina

Brown ring disease (BRD) in the manila clam, Ruditapes philippinarum, is a vibriosis which disturbs the process of shell formation. The etiological agent is a Vibrio sp. named VP1. Light and electron microscope observations of the mantle and periostracal lamina of naturally diseased clams show alterations of the periostracal lamina. An additional layer, rich in vacuoles and cell debris, is found between the periostracum and the fibrous matrix layers. Experimental reproduction of the BRD symptoms, following challenge with VP1, allows us to follow the microscopic modifications of the mantle edge and the periostracal lamina for a period of 2 months. VP1 is detected immunologically at the surface of the mantle edge and the periostracal lamina a short time after challenge. Bacteria adhere to the surface of the periostracal lamina and progressively colonize this secretion. One month after inoculation the periostracum becomes eroded and curls up on itself, and the fibrous matrix is invaded by cells debris and bacteria. The periostracal lamina of experimentally infected clams presents similar alterations to those observed in naturally diseased clams. The reasons behind these modifications are discussed.

Quantity of sporocysts and seasonality of two Rhipidocotyle species (Digenea: Bucephalidae) in Anodonta piscinalis (Mollusca: bivalvia)

The prevalence of Rhipidocotyle campanula in Lake Kuivasjärvi, northern Finland, was 5.7 % ( n = 1486) during 1989. The prevalences of R. campanula and R.fennica in Lake Saravesi, central Finland, during 1987 to 1989 were 1.0 and 33.2 % ( n = 1157), respectively. No clear seasonality in prevalence was found in either species, although miracidia of these digeneans are present only in late summer and autumn. The proportion of infected clams in which the gonad was full of sporocyst tubules was on average 90% for R. campanula and 30% for R. fennica. Clams with only few sporocyst tubules in their gonad were observed most frequently in spring. Old, empty sporocyst ribbons of R.fennica first appeared in the clams during August after the beginning of the cercarial emergence and disappeared slowly thereafter. However, in both species viable sporocyst ribbons with early developmental stages of cercariae were found throughout the year. The emergence of R. fennica cercariae began during July and continued throughout September in Lake Saravesi. The duration of cercariae emergence was found to be up to 72 days in the laboratory. R. campanula cerariae in the northern Lake Kuivasjarvi emerged from mid-June until mid-August.

Changes in Hemolymph Parameters in the Manila Clam Ruditapes philippinarum (Mollusca, Bivalvia) Following Bacterial Challenge

Manila clams, Ruditapes philippinarum, were experimentally challenged with a pathogenic bacterium, Vibrio P1, the causative agent of Brown Ring Disease. Changes in cellular and humoral hemolymph parameters were studied over a 7-week period. Hemocyte concentration increased to a maximum 2 weeks after exposure of the clams to the Vibrio and was considered as hemocytosis in response to the pathogenic stimulus. The hemocyte concentration decreased thereafter and low values were maintained up to 7 weeks. A significant rise of a peptidase activity was observed in the cellular fraction of hemolymph 3 days postchallenge. A peak of serum activity, 1 week postchallenge, probably reflected the release of this peptidase by hemocytes. However, the serum protein concentration in challenged clams did not show any significant variation. There was a conspicuous shift between the early enzymatic response in the cells and the rise of hemocyte concentration, which suggested that the cellular mobilization and the enzymatic responses are controlled by distinct mechanisms. Low peptidase activity levels in both hemocytes and serum were observed 2 weeks following challenge, whereas the number of clams exhibiting the symptoms of Brown Ring Disease increased, indicating the development of the disease. Indeed, both hemocyte concentrations and leucine-aminopeptidase-specific activity in infected clams decreased with increasing infection stages. The depletion of the hemolymph parameters in the late phase may be a consequence of physiological stress due to an harmful effect of Vibrio P1.

Effect of the Castrating Trematode Parasite Rhipido-cotyle fennica on Energy Allocation of Fresh-Water Clam Anodonta piscinalis

If host survival is important to a parasite, it should avoid the use of the host's maintenance energy. Selective use of the host's energy is possible by selecting which part of the host to penetrate and when to be active. We study the effects of the castrating trematode parasite Rhipidocotyle fennica on energetics of fresh-water clam Anodonta piscinalis. Before production of offspring, uninfected clams allocate energy to shell growth and glycogen storage. During offspring production shell growth slows down, clams lose weight and consume the stored glycogen. Concurrently the fat content of clams increases indicating the collection of long-term storage for maintenance during the winter. Infected clams lack glycogen reserves and are lighter, but contain more fat than uninfected clams

Treatments against the Vibrio P1, suspected to be responsible for mortalities in Tapes philippinarum

Since 1987, the brown ring disease has caused mass mortalities on cultured clam-beds on the west coast of France. Our objective was to establish the MIC (minimal inhibitory concentration), the in vivo toxicity and effectiveness of several antiseptic and antibiotic agents, in order to obtain useful information for farmers in controlling epizootics. Among the different drugs tested, furazolidone was the most efficient in the control of this clam disease. Administration of 10 mg/l for 3 days (every day, infected clams were left in filtered (1 μm), sterilized, new, static sea-water supplemented with the determined furazolidone dose) seemed to give 100% protection against the Vibrio.

Trematode (Digenea: Bucephalidae) infection in the burrowing clam Tridacna crocea from the Great Barrier Reef

Larval trematode (Family Bucephalidae) infection of Tridacna crocea (Lamarck 1819) was investigated to determine pathological effects on the host. Of 108 T. crocea gonads examined, 13 (12%) were found to be parasitised. The bucephalid caused castration in heavily infected clams, gonadal tissue being completely replaced by sporocysts. The parasite was also found in the kidney, digestive gland and ctenidia. This is the first record of a bucephalid trematode in a member of the Tridacnidae. The parasite is of potential importance to tridacnid shellfisheries currently being developed.