Short-necked Clam Tapes Research Articles

Accumulation and Elimination Profiles of Paralytic Shellfish Poison in the Short-necked Clam Tapes japonica Fed with the Toxic Dinoflagellate Gymnodinium catenatum

The paralytic shellfish poison (PSP)-producing dinoflagellate Gymnodinium catenatum (Gc) was fed to the short-necked clam Tapes japonica, and the accumulation, transformation and elimination profiles of PSP were investigated by means of high-performance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FLD). The short-necked clams ingested most of the Gc cells (4 x 10(6) cells) supplied as a bolus at the beginning of the experiment, and accumulated a maximal amount of toxin (181 nmol/10 clams) after 12 hr. The rate of toxin accumulation at that time was 16%, which rapidly decreased thereafter. During the rearing period, a variation in toxin composition, derived presumably from the transformation of toxin analogues in the clams, was observed, including a reversal of the ratio of C2 to C1, and the appearance of carbamate (gonyautoxin (GTX) 2, 3) and decarbamoyl (dc) derivatives (decarbamoylsaxitoxin (dcSTX) and dcGTX2, 3), which were undetectable in Gc cells. The total amount of toxin contained in clams and residue (remaining Gc cells and/or excrement in the rearing tank) gradually declined, and only about 1% of the supplied toxin was detected at the end of the experiment.

Accumulation and depuration profiles of PSP toxins in the short-necked clam Tapes japonica fed with the toxic dinoflagellate Alexandrium catenella

A toxic dinoflagellate responsible for paralytic shellfish poisoning (PSP), Alexandrium catenella ( Ac) was fed to the short-necked clam Tapes japonica, and the accumulation and depuration profiles of PSP toxins were investigated by means of high-performance liquid chromatography with postcolumn fluorescence derivatization (HPLC-FLD). The short-necked clams ingested more than 99% of the Ac cells (4×10 7 cells) supplied once at the beginning of experiment, and accumulated a maximal amount of toxin (185 nmol/10 clams) after 12 h. The rate of toxin accumulation at that time was 23%, which rapidly decreased thereafter. Composition of the PSP toxin accumulated in the clams obviously different from that of Ac even 0.5 h after the cell supply, the proportion of C1+2 being much higher than in Ac, although the reason remains to be elucidated. In contrast, a higher ratio of gonyautoxin (GTX)1+4 than in Ac was detected in the toxin profiles of clam excrements. The variation in toxin composition derived presumably from the transformation of toxin analogues in clams was observed from 0.5 h, such as reversal of the ratio of C1 to C2, and appearance of carbamate (saxitoxin (STX), neoSTX and GTX2, 3) and decarbamoyl (dc) derivatives (dcSTX and dcGTX2, 3), which were undetectable in Ac cells. The total amount of toxin distributed over Ac cells, clams and their excrements gradually declined, and only 1% of supplied toxin was detected at the end of experiment.

Paralytic Shellfish Poison (PSP) Profiles and Toxification of Short-necked Clams Fed with the Toxic Dinoflagellate Alexandrium tamarense

As a part of our studies on paralytic shellfish poison (PSP) accumulation kinetics in bivalves, short-necked clam Tapes japonia was experimentally contaminated with PSP by being fed with the toxic dinoflagellate Alexandrium tamarense for 2, 4, 6, 8 and 10 days, and the processes of PSP accumulation and bioconversion were investigated: the toxicity level was determined by mouse bioassay and toxin components were identified by high-performance liquid chromatography (HPLC). The strain of A. tamarense used in this study possessed a specific toxicity of 186.7 +/- 81 (mean +/- S.D., n = 5) x 10(-6) MU/cell. Total toxin concentration of this strain was 140.4 +/- 61 (mean S.D., n = 5) fmol/cell. The toxicity level of short-necked clams increased almost in parallel with the abundance of A. tamarense, reaching 1.8, 3.2, 3.8, 3.5 and 4.6 MU/g meat for 2, 4, 6, 8 and 10 days of feeding, respectively. The accumulation rates of PSP toxins, which are the ratio of the total amount of toxins accumulated in the bivalves to the estimated intake in each feeding experiment, were 7.5, 8.1, 5.7, 4.2 and 4.4% for 2, 4, 6, 8 and 10 days, respectively. At the end of each exposure period, many undigested algal cells were found in pseudofeces under microscopic observation. There was a remarkable difference in the relative proportions of the predominant toxin components between A. tamarense and short-necked clams. The most notable difference was the change in the relative amounts of C2 (carbamoyl-N-sulfo-11beta-hydroxysaxitoxin sulfate), GTX1 and GTX 4 during the first two days. In the toxic bivalves, the amount of C2, which is dominant in A. tamarense, decreased to below half a percent after being ingested. Subsequently, the amount of GTX1 in the shellfish meat reached 50.1 mol%, while that of GTX4 decreased to about half of that in A. tamarense. As for the configuration of 11-hydroxysulfate, PSP components in A. tamarense exist almost exclusively as beta-epimers (GTX3, GTX4, C2 and C4), accounting for 72.8 mol% of the total. This contrasts with the case of the short-necked clams, where the beta-epimers represented 25.8, 33.8, 30.8, 36.8 and 28.5 mol% of the total after 2, 4, 6, 8 and 10 days, respectively. PSP components seemed to be converted rapidly at an early stage of the feeding of A. tamarense.

Identification of antihypertensive peptides from peptic digest of the short-necked clam Tapes philippinarum and the pearl oyster Pinctada fucata martensii

Identification of antihypertensive peptides from peptic digest of the short-necked clam Tapes philippinarum and the pearl oyster Pinctada fucata martensii

Impact of Tapes philippinarum farming on nutrient dynamics and benthic respiration in the Sacca di Goro

The introduction of the short-necked clam Tapes philippinarum into the Sacca di Goro has over a short period made this coastal environment one of the top European clam production sites. In recent years, this activity has been seriously impacted due to the appearance in the lagoon of large macroalgal beds and the occurrence of dystrophic events causing anoxia and massive deaths of molluscs in the cultivated areas.

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.

Appearance of Gymnodinium catenatum in Association with the Toxification of Bivalves in Kamae, Oita Prefecture, Japan

In spring of 1996, three species of bivalves, scallop Chlamys nobilis, mussel Mytilus edulis, and short-necked clam Tapes japonica, were toxified in Kamae, Oita Prefecture, Japan. In this bay, the cultured scallop C. nobilis has been infested with the dinoflagellate Alexandrium catenella almost every year, but the plankton was not seen this year. Instead, at the beginning of April 1996, a toxic dinoflagellate, which was later identified as Gymnodinium catenatum, appeared (maximal density: 44, 350 cells/L). The toxicity score of C. nobilis specimens reached the maximum (81MU/g, digestive gland) in early May, while M. edulis and T. japonica showed the maximum scores of 253MU/g and 28MU/g at the end of April, respectively. The toxins from the three species of bivalves closely resembled each other, consisting of C1 (Protogonyautoxin 1, PX1), C2 (PX2) and Gonyautoxin 6 (GTX6) as the major components. The toxin profile of G. catenatum was similar to that of the bivalves. This result indicates that G. catenatum may be a causative dinoflagellate for the PSP infestation of bivalves in Kamae.

Novel tetraamines, pentaamines and hexaamines in sea urchin, sea cucumber, sea squirt and bivalves

1. 1. Polyamines were extracted from the guts and ovaries of the sea urchin Anthocidoris crassispina, and the guts and flesh of the sea cucumber Stichopus japonicus and the sea squirt Halocynthia roretzi, the oyster Crassostrea gigas and the short-necked clam Tapes philippinarum, and analyzed by ion-exchange high-performance liquid chromatography and gas chromatography-mass spectrometry. 2. 2. Norspermidine and norspermine as well as putrescine, cadaverine, spermidine, spermine and agmatine were the ubiquitous polyamines in these invertebrates. These results suggest the widespread distribution of norspermidine and norspermine in invertebrates. 3. 3. Thermopentamine, thermohexamine and homothermohexamine were found in the sea urchin. This in the first report on the occurence of thermopentamine and hexaamine in invertebrates. 4. 4. Homospermidine, canavalmine, aminopropylhomospermidine, homospermine, caldopentamine, homocaldopentamine and aminopropylcanavalmine were found in the sea cucumber. Homospermidine, aminopropylhomospermidine and homospermine were found in the squirt. This is the first report on the occurence of canavalmine, aminopropylhomospermidine, homospermine, homocaldopentamine and aminopropylcanavalmine in invertebrates.

Volatile components of boiled and roasted short-necked clam Tapes philippinarum.

The volatile components were experimentally produced by heating short-necked clam (Tapes philippinarum) with glass beads. Three flavor concentrates, obtained by distillation at three temperature ranges (98-101, 101-115, and 115-160°C), were analyzed by GC-MS. A total of 76 compounds were identified. They included 9 acyclic nitrogen compounds, 9 pyrazines, 6 pyridines, 6 pyrroles, 5 pyrrolidines, 5 acyclic sulfur compounds, and 1-methylpyrrolidine-2, 5-dione. The last concentrate (115-160°C) gave a pleasant roasted odor of short-necked clam was char-acterized by the following flavor components: 3, 4, 5, 6-tetrahydro-2, 4, 6-trimethyl-2H-1, 3, 5-thiadiazine, 5, 6-dihydro-2, 4, 6-trimethyl-4H-1, 3, 5-dithiazine, 2-methyl-2-thiazoline, 3-hydroxy-2-methyl-4H-pyrone (maltol), and N, N-dimethylglycine methyl ester. While the second concen-trate (101-115°C) having the boiled odor of the clam contained some pyrazines, some pyridines, and the ester as major flavor components.

PSP components of toxified short-necked clams in Yamagawa Bay, Kagoshima Prefecture.

Our efforts were made to clarify the cause of a food poisoning in which a person provoked numbness in the mouth by ingesting the short-necked clam Tapes japonica from Yamagawa Bay, Kagoshima Prefecture.The toxic shellfish specimens which were collected from Yamagawa Bay were shucked and extracted with 80% ethanol acidified with acetic acid. After being defatted with chloroform, the aqueous extract was purified by chromatography on Bio-Gel P-2 and Bio-Rex 70. The toxins prepared were analyzed by cellulose acetate strip electrophoresis and thin-layer chromatography on silica gel. The results indicated that toxins contained protogonyautoxins (PXs) 1-4 as the major components, together with gonyautoxins (GTXs) 1-6 as the minor, on molar basis.We thus came to a conclusion that the aforementioned poisoning was caused by the paralytic shellfish poisons (PSPs) accumulated in the short-necked clam.

Accumulation and retention of antimony-125 in the short-necked clam.

Accumulation and retention of 125Sb by short-necked clam Tapes japonica were investigated in order to elucidate the uptake mechanism of the nuclide in marine bivalves. It was found that the accumulation of 125Sb by the clam from the environmental water showed an initially relative rapid increase, followed by a gradual increasing pattern during the experimental period. The concentration factors for 125Sb in the clam at the end of the experimental period were obtained as 1.2 for the soft part and 4.2 for the shell. The loss of 125Sb accumulated in the whole clam showed an initial decrease, followed by two slow elimination patterns. The long-lived biological half-life for 125Sb in the clam was approximately 58 days. Regarding the influence of chelating agent and co-existing element on the accumulation of 125Sb by the clam, it was observed that the addition of stable antimony to the rearing sea watere enhanced the accumulation of 125Sb by the soft part and shell of the clam to some extent; whereas, the accumulation of 125Sb by the soft part and shell was not depressed in the presence of EDTA. The accumulation of 125Sb by the shell depends mostly on the surface adsorption phenomenon rather than that via metabolic process.

Accumulation of mercury by tissues in the short-necked clam Tapes japonica.

After the rearing of short-necked clams Tapes japonica in sea water containing mercury chloride (HgCl2) or methyl mercury chloride (MeHgCl), the accumulation of mercury was examined with seven different tissues (adductor muscle, foot, mantle, siphon, gill, mid-gut gland, and others). Two tissues, gill and mid-gut gland, exhibited a remarkably higher accumulation of mercury than the other tissues. Moreover, regardless of the tissues, much higher accumulation of mercury was found in the case of rearing in MeHgCl-containing sea water, than in the case of rearing in HgCl2-containing sea water. When reared in HgCl2-containing sea water, only inorganic mercury was accumulated in shellfish. On the other hand, when reared in MeHgCl-containing sea water, about a half of the mercury accumulated in shellfish was MeHg and the rest inorganic mercury, indicating that MeHgCl ingested by shellfish is partly converted into inorganic mercury by rapid demethylation in shellfish themselves. Unlike in the case of mammals, no metallothionein was produced in shellfish as they ingested mercury.

浜名湖産アサリのセルカリア３種の形態と寄生状況

Three marine cercariae, Cercaria pectinata, Cercaria tapidis and Cercaria sp. were found in the short-necked clam Tapes philippinarum from Lake Hamana, Japan. These cercariae are the first reported marine cercariae from the area. Of 3, 200 clams examined, 110 infections for C.pectinata, three for C.tapidis and one for Cercaria sp. occurred. C.pectinata is a yellowish, non-oculate, trichocercous, fellodistomid cercaria, developing in large saccular sporocyst in the host gonad. C.tapidis is an oculate cercaria with long tail of five times as body, and Cercaria sp. is a non-oculate, furcocercous, gymnophallid cercaria, and both species develop in sporocyst.The infection rate by C.pectinata showed a seasonal change, being low(0-1.2%)from May to August and relatively high (2.0-3.6%)from September to March. Histologically, sporocysts in early stage were found in inter-follicular spaces, and were observed to grow in size in situ with the duration of time and to occupy finally the greater part of the gonad;ripe sporocysts with numerous mature cercariae were observed from March to April.

Studies on the chemical preferences of the shore crab, Carcinus maenas (L.)

Experiments conducted with a simple two-choice maze suggest that the flesh of the teleost fish, Gadus morrhua Day, and of the mollusc Crepidula fornicata (L.) are highly attractive to Carcinus maenas (L.). Further experiments show that an entirely synthetic mixture of chemicals, based on the composition of the short-necked clam Tapes japonica, is also highly attractive to Carcinus maenas. Evidence is presented that the attractiveness of this mixture is greater than that of any one of its major components.