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1.
L. E. Llewellyn 《Marine Biology》1997,128(4):599-606
A saxitoxin (STX)-binding factor has been found in the haemolymph of the xanthid crabs Lophozozymus pictor, Liomeratristis, Chlorodiella nigra and Actaeodes tomentosus. Lophozozymus pictor and A. tomentosus are both xanthids previously known to be toxic, with the toxins in some L. pictor individuals having been identified as STX analogues. All the individual crabs which had this STX-binding factor did not have
any STX-like activity in their haemolymph or tissues. In contrast, no such factor could be found in two other reportedly toxic
xanthids, Atergatis floridus and Platypodia granulosa, each individual of which did contain STX-like bioactivity. Analysis of saturable 3H-STX-binding, binding kinetics and competition curves in the haemolymph of both Lophozozymus pictor and Liomera tristis indicated that a single, pharmacologically homogeneous population of STX-binding sites was present in each species. The analysis
also revealed that the haemolymph from the non-toxic xanthid Liomera tristis had an affinity for STX of 0.12 nM, which was 20-fold greater than that from Lophozozymus pictor (2 nM). This tighter toxin-binding by Liomera tristis haemolymph predominantly results from a much slower rate of toxin dissociation. The protease trypsin inactivated the toxin-binding
factor in both Lophozozymus pictor and Liomera tristis haemolymph. Tetrodotoxin (TTX) could not displace 3H-STX from any of the haemolymph samples, distinguishing this factor from the voltage-gated sodium channel and a TTX-neutralizing
haemolymph protein previously found in a grapsid crab and a horseshoe crab. Analogues of STX, which may occur in marine organisms,
possess markedly reduced abilities to displace 3H-STX from haemolymph samples. Toxin-binding was inhibited by acidic pH, producing titrations with pKs of 5.5 and 5.1 for
Lophozozymus pictor and Liomera tristis haemolymph, respectively. Binding characteristics are reminiscent of a recently found amphibian plasma protein which belongs
to the transferrin family of proteins and is unrelated to the voltage-gated sodium channel, the only previously known STX-binding
protein. This is the second putative STX-resistance mechanism to be found in this family of crabs.
Received: 19 November 1996 / Accepted: 9 January 1997 相似文献
2.
Herring (Clupea harengus pallasi) spawning sites in Puget Sound, Washington overlap spatially and temporally with blooms of Alexandrium catenella, a toxic dinoflagellate species responsible for paralytic shellfish poisoning. Consequently, newly hatched herring larvae
may be regularly exposed to the suite of dissolved paralytic shellfish toxins that are released into the water column from
toxic cells during blooms. To date, virtually nothing is known about the impacts of these neurotoxins on early developmental
stages of marine fish. In the present study, herring larvae at three ages, 0 days post hatch (dph), 4 dph, and 11 dph, were
exposed to dissolved saxitoxin (STX) in 24-h and multi-day exposures. All larvae were examined for sensorimotor function (i.e.
spontaneous swimming behavior and touch response). Significant reductions in spontaneous and touch-activated swimming behavior
occurred within 1 h of exposure. EC50s at 1 h of exposure were 1,500, 840, and 700 μg STX equiv. l−1 for larvae introduced to STX at 0, 4, and 11 dph, respectively. This progressive age-specific increase in STX-induced paralysis
suggests that older larvae were more sensitive to the toxin than younger larvae. Interestingly, herring larvae at all ages
exhibited a significant degree of neurobehavioral recovery within 4–24 h of continuous exposure relative to the 1-h time point.
This recovery of normal motor behaviors was not observed in previous studies with freshwater zebrafish (Danio rerio) larvae under the same continuous exposure conditions, suggesting that an adaptive detoxification or toxin sequestration
mechanism may have evolved in some species of marine fish larvae. Our data reveal that (1) dissolved STX is bioavailable to
marine finfish larvae, (2) the toxin is a paralytic agent with potencies that differ between developmental stages, and (3)
STX-induced sensorimotor inhibition occurs rapidly but is transient in marine larvae. Collectively, these results suggest
that dissolved algal toxins may have important sublethal effects on marine fish populations. 相似文献
3.
John Humphreys Richard W. G. Caldow Selwyn McGrorty Andrew D. West Antony C. Jensen 《Marine Biology》2007,151(6):2255-2270
The Manila clam Ruditapes philippinarum was introduced to Poole Harbour (lat 50°N) on the south coast of England in 1988 as a novel species for aquaculture. Contrary
to expectations, this species naturalised. We report on individual growth patterns, recruitment, mortality and production
within this population. On the intertidal mudflats the abundance of clams (>5 mm in length) varied seasonally between 18 and
56 individuals m−2. There appear to be two recruitment events per year and there were 6 year classes in the population. A mid-summer decline
in abundance was partly due to increased mortality but probably also a result of down-shore migration in response to high
water temperatures and the development of anoxic conditions. A winter fishery removes c 75% of clams of fishable size (maximum
shell length ≥40 mm) and c 20% of the annual production. The fishery depresses the maximum age and size attained by the clams
but appears to be sustainable. Clam mortality due to factors other than fishing is highest in late-winter to early spring.
The growth of the clams is intermediate in comparison with many published studies but remarkably good given their intertidal
position. As on the coasts of the Adriatic Sea, where the clam is also non-native, the Manila clam has thrived in a shallow,
eutrophic, lagoon-like system on the English coast. While the Poole Harbour population is currently Europe’s most northerly
reported self-sustaining, naturalised population, given forecasts of increasing air and sea temperatures it might be expected
that this species will eventually spread to more sites around the coasts of Northern Europe with associated economic and ecological
consequences. 相似文献
4.
Valerio Matozzo Marta Monari Jurgen Foschi Gian Paolo Serrazanetti Otello Cattani Maria Gabriella Marin 《Marine Biology》2007,151(3):1051-1058
In the present study, the effects of differing salinities on some important functional responses of haemocytes from the clam,
Chamelea gallina, were investigated. The animals were kept for 7 days at 28‰ (hyposalinity), 34‰ (control) and 40‰ salinity (hypersalinity),
and total haemocyte count (THC), haemocyte volume, phagocytosis, lysozyme-like activity (in both haemocyte lysate and cell-free
haemolymph) were measured. The survival-in-air test was also performed. Clams kept at 28‰ showed significantly increased THC
with respect to animals kept at 34 and 40‰. The analysis of haemocyte size frequency distribution highlighted that in clams
kept at 28‰ the haemocyte fraction of about 5 μm in diameter and 50–100 femtolitre in volume increased markedly. Conversely,
in animals kept at 40‰ an increase was observed in the haemocyte fraction having about 8–10 μm diameter and 400–500 femtolitre
volume. Higher phagocytic activity was recorded in haemocytes from control clams, with respect to that of clams kept at 28
and 34‰. Lysozyme-like activity in haemocyte lysate was shown to increase significantly in animals kept at 28‰ with respect
to that of clams kept at 40‰, whereas enzyme activity in cell-free haemolymph from clams kept at 34‰ was significantly higher
with respect to that of clams maintained at 40‰. A relationship between phagocytosis and lysozyme secretion is suggested.
The resistance to air exposure of clams kept at 28 and 40‰ was shown to decrease significantly; LT50 values fell from 7 days in clams kept at 34‰ to 4 and 5 days in those kept at 28 and 40‰, respectively. Results demonstrated
that salinity values far from 34‰ affects the functional responses of haemocytes and reduce the resistance of clams to exposure
to air. 相似文献
5.
Green-Ruiz C Ruelas-Inzunza J Páez-Osuna F 《Environmental geochemistry and health》2005,27(4):321-329
In order to know the concentration of mercury in surface sediments, macroalgae and clams from Guaymas Bay, Mexico, 20 surface
sediment samples and several individuals of Codium amplivesciculatum (3), Enteromorpha clathrata (4), Gracilaria subsecundata (2), Ulva lactuca (2), Chione subrugosa (80) and Crassostrea gigas (40) were collected and their Hg concentration was measured by a cold vapor Hg analyzer, after acid digestion. In addition,
granulometric analysis and quantification of total organic carbon, aluminum, iron and manganese contents in sediments were
performed. A Pearsons correlation matrix was determined and, the enrichment factor, the geoaccumulation index and the biota-sediment
accumulation factor were calculated. Mercury concentrations in sediments ranged from 0.3 to 2.3 μg g−1, with the central and northern portions showing the highest values. Macroalgae had a content of Hg that oscillated from 0.058
to 0.134 μg g−1, while the average concentrations of this metal for clams and oysters were 0.063 and 0.230 μg g−1, respectively. A clear effect of Guaymas City and the anthropogenic activities carried out around the Guaymas Bay has been
observed and the enrichment factor and the geochemical index suggest that sediments from this coastal ecosystem are moderately
to strongly contaminated with Hg. However, according to the figure of the maximum human consumption of Hg per week recommended
by the World Health Organization, people can ingest clams without risk to their health. 相似文献
6.
B. K. Baillie C. A. Belda-Baillie V. Silvestre M. Sison A. V. Gomez E. D. Gomez V. Monje 《Marine Biology》2000,136(5):829-836
We have compared the random-amplified-polymorphic DNA (RAPD) patterns of Symbiodinium isolates from seven species of giant clams to investigate the large genetic variation that we previously reported for this
group of dinoflagellate symbionts using allozyme analysis. Comparisons of 163 RAPD characters by unweighted pair-group arithmetic-average
cluster analysis (UPGMA) corroborate our previous findings that giant clams associate with a large number of genetically distinguishable
algal symbionts, and that the isolates from a single Tridacna gigas individual form a group of closely related algae. However, the overall topology of the UPGMA tree constructed from RAPD data
differs from that of the previous allozyme data, indicating that the combined data we have collected to date are insufficient
to accurately infer phylogenetic affiliations between the isolates studied. Comparisons of our data set with those published
for strains of Gymnodinium catenatum, a toxic dinoflagellate with a sexual life stage, shows that our isolates are even more diverse. Algal isolates from giant
clams have a level of RAPD variation comparable to organisms that are able to undergo sexual recombination. This study demonstrates
the sensitivity of the RAPD technique in detecting genetic diversity in this group of algae, and highlights the need for more
comparative data for the major clades of Symbiodinium.
Received: 24 August 1999 / Accepted: 8 March 2000 相似文献
7.
Mehrzad Keshavarzifard Mohamad Pauzi Zakaria Tan Shau Hwai 《Environmental geochemistry and health》2017,39(3):591-610
The bioaccumulation and bioavailability of polycyclic aromatic hydrocarbons (PAHs) were characterized in sediment and Paphia undulata (short-neck clam) from six mudflat areas in the west coasts of Peninsular Malaysia. The concentrations of total PAHs varied from 357.1 to 6257.1 and 179.9 ± 7.6 to 1657.5 ± 53.9 ng g ?1 dry weight in sediment and short-neck clam samples, respectively. PAHs can be classified as moderate to very high level of pollution in sediments and moderate to high level of pollution in short-neck clams. The diagnostic ratios of individual PAHs and principal component analysis indicate both petrogenic and pyrogenic sources with significant dominance of pyrogenic source. The first PAHs biota-sediment accumulation factors and relative biota-sediment accumulation factors data for short-neck clam were obtained in this study, indicating a preferential accumulation of lower molecular weight PAHs. Evaluation of PAH levels in sediments and short-neck clams indicates that short-neck clam could be introduced as a good biomonitor in mudflats. The results also demonstrated that under environmental conditions, the sedimentary load of hydrocarbons appears to be one of the factors controlling their bioavailability to biota. 相似文献
8.
The influence of silt on growth of juvenile hard clams Mercenaria mercenaria (L.) (9 mm in mean shell length) was investigated in the laboratory using mixed suspensions of algae (50x106
Pseudoisochrysis paradoxa cells l-1) and fine-grained bottom sediments (0 to 44 mg l-1). Growth rates, expressed as percent increase in ash-free dry tissue weight, were not significantly affected by sediment concentrations up to 25 mg l-1. Significant reduction in growth (by 16% relative to controls fed only algae), and condition of clams, occurred at 44 mg silt l-1. The results of the 3-week growth experiment agree well with predictions made in an earlier study by integrating results of shortterm physiological measurements. Growth rates obtained with experimental algal-silt diets at 21°C (2.6 to 3.3% increase in dry tissue weight d-1) were comparable to those determined at ambient concentrations of Great South Bay particulates at 20°C (0.9 to 4.0% d-1). Levels of particulate inorganic matter in seawater from Great South Bay, New York, exhibited pronounced daily changes, and ranged from 6 to 126 mg dry weight l-1. Growth enhancement by the addition of silt to an algal diet, reported in mussels, surf clams and oysters, was not found in M. mercenaria. It is suggested that these three species are better suited than hard clams for culturing efforts in inshore turbid waters above uncompacted, muddy bottoms.Contribution No. 452 from the Marine Sciences Research Center, State University of New York at Stony Brook, USA 相似文献
9.
Susan E. Ford V. Monica Bricelj Christophe Lambert Christine Paillard 《Marine Biology》2008,154(2):241-253
The known negative effects of shellfish toxin-producing dinoflagellates on feeding, burrowing and survival of some bivalve
mollusks has prompted questions concerning whether they might also impair the internal defense system of affected bivalves
and make them more susceptible to disease agents. The primary components of the cellular defense system are hemocytes. Many
toxic dinoflagellates are too large to be ingested whole by hemocytes and would most likely be exposed to intracellular toxins
only after the algae are consumed, broken down, and the water-soluble toxins, released. Therefore, we conducted a series of
experiments in which hemocytes from two suspension-feeding bivalves—the Manila clam, Ruditapes philippinarum, and the softshell clam, Mya arenaria—were exposed in vitro to filtered extracts of one highly toxic paralytic shellfish toxin (PST)-producing and one nonPST-producing
strain of Alexandrium tamarense (isolates PR18b, 76 ± 6 STXeq cell−1 and CCMP115, with undetectable PST, respectively). We measured adherence and phagocytosis, two hemocyte attributes known
to be inhibited by bacterial pathogens and other stressors. We found no measurable effect of a cell-free extract from a highly
concentrated suspension of the PST-producing strain on hemocytes of either bivalve species. Instead, extract from the nonPST-producing
strain had a consistent negative effect on both clams, resulting in significantly lower adherence and phagocytosis compared
to strain PR18b and filtered seawater controls. The bioactive compound produced by strain CCMP115, which has yet to be characterized,
may be similar to the PST-independent allelopathic compounds described for Alexandrium spp., which act on other plankters. These compounds and those produced by other harmful algae are known to cause immobilization,
cellular deformation and lysis of co-occurring target organisms. Thus, nonPST producing Alexandrium spp., which do not cause paralysis and burrowing incapacitation of clams, may still produce a compound(s) that has negative
effects not only on hemocytes, but on other molluscan cell types and their functions, as well. 相似文献
10.
Four 6-mo mark-and-recapture experiments conducted in Long Island Sound, USA, from 1988 to 1990, involving approximately 2250 individual observations, demonstrated that under natural conditions significantly higher mortality (p0.001, chi-square test) occurred amongMya arenaria (L.) with hematopoietic neoplasia than those diagnosed as non-neoplastic. Using a blood-screening technique, the clams were diagnosed and placed in one of three diagnostic groups based on the severity of the disease (the percentage neoplastic cells per total number of blood cells): non-neoplastic (NN), 0%; low-severity neoplastic (LSN), < 50%; high-severity neoplastic (HSN), > 50%. Mortality of those clams initially diagnosed as HSN ranged from 48% to 78%, depending on the test period, as compared to 3% to 21% for the non-neoplastic. Mortality in the LSN treatment varied from 8% to 34%. Both progression and remission were evident in clams at all stages of the disease. Mortality and rates of progression and remission in individuals appeared to be linked to water temperatures. Differential mortality may be responsible for the apparent seasonal cycle of prevalence in populations. 相似文献
11.
The non-indigenous green crab (Carcinus maenas) is an important predator on bivalve wild beds in coastal areas worldwide. This study explored size-dependent green crab
prey preference on American oysters (Crassostrea virginica), blue mussels (Mytilus edulis), and soft-shell clams (Mya arenaria) in a productive coastal system of Atlantic Canada. Using two sizes of prey and three different experimental manipulations,
small, medium, and large green crabs were given a choice among these three bivalves, and their daily feeding rates were monitored
over the course of 3 days. For both prey sizes, green crabs showed an early feeding preference for soft-shell clams and, only
as they declined in numbers, a switch toward mussels and subsequently toward oysters. We found that such changes in the timing
(order) of prey preference are related to prey differences in shell thickness, a fairly reliable indicator of prey shell strength. 相似文献
12.
Attempts were made to analyze the toxin composition of the toxic hiogi scallop Chlamys nobilis. The toxins were partially purified from the digestive glands by column chromatography using Bio-Gel P-2 and Bio-Rex 70 (H+ form), resulting in separation into protogonyautoxin (PX), gonyautoxin (GTX) and saxitoxin (STX) fractions. Their total potencies were scored to be <100 mouse units (MU), 3200 MU and 3700 MU, respectively. A 5-min hydrolysis with 0.1 N HCl enhanced the potencies of PX and GTX fractions to 450 MU and 12000 MU respectively, whereas no enhancement occurred in the STX fraction at all. Electrophoretic, thin-layer chromatographic and high performance liquid chromatographic analyses demonstrated that the PX fraction consisted mainly of GTX8 and its epimer, the GTX fraction of GTX5, GTX6, along with two unidentified toxins, and the STX fraction exclusively of two unidentified toxins. This rather unique composition suggested a complex metabolism of PSP in this species. 相似文献
13.
Bivalves are important in shallow marine habitats, not at least being the major food resource for seaducks such as the common
scoter (Melanitta nigra), thousands of which are wintering on the Western Coastal Banks, near the Belgian-French border (North Sea). Next to this
ecological importance, fishable stocks of one of these bivalves, Spisula subtruncata, occur in the area. This study aimed at investigating S. subtruncata’s spatial distribution, population dynamics and productivity and its implications for a sustainable Spisula fishery in seaduck wintering areas. The spatial distribution of S. subtruncata was studied in 1994 and 1997 in two areas of the Belgian Western Coastal Banks. The population dynamics and production were
investigated by monthly sampling of two stations between April 1995 and April 1996 and a seasonal sampling between April 1996
and April 1998. Spisula subtruncata had a patchy distribution in the deeper (6 m), fine sandy (200 ± 20 μm) sediments of the Abra alba community, mainly found in the western most part of the Western Coastal Banks. In August 1995, an overwhelming and successful
recruitment was observed in this area: local densities were as high as 150,000 ind m−2. Minor, non-successful recruitments were detected in August 1996 and 1997. Due to space limitation, high densities of S. subtruncata are hypothesized to be responsible for the occurrence of aberrant shapes as observed from August 1996 onwards. Growth was
described by a seasonally oscillating version of the von Bertalanffy growth function (VBGF): a growth stop was observed from
late autumn till early spring. The VBGF parameters K (growth constant) and L
∞ (asymptotic length) were estimated at 0.7–0.9 and 31–33 mm. A combination of length and individual biomass increment showed:
(1) a faster length increment of smaller individuals during the second growing period (catching-up phenomenon), (2) a constant
length combined with a decreasing individual biomass during the suboptimal winter periods (except for the first winter, when
the individual biomass slightly increased), (3) a positive relationship between the individual biomass decrease and the seawater
temperature during the winter periods, and (4) a strong increase of the individual biomass in early spring (April 1997 and
1998) because of gametogenesis, followed by a decrease because of spawning (August 1997). The extremely high total production
of the 1995 year class in the tidal gully (Potje) during the study period was estimated at approximately 1,500 g ash-free
dry weight (ADW) m−2 or 600 g ADW m−2 on average per year. Shellfisheries for S. subtruncata within seaduck wintering areas, such as the Western Coastal Banks, should be carefully deliberated since (1) an important
food resource for the seaducks will decrease, (2) the ecologically most diverse and rich macrobenthic A. alba community will be heavily affected, and (3) the recovery of Spisula populations after depletion is expected to be erratic. 相似文献
14.
The surf clam, Spisula solidissima (Dillwyn), population in the estuarine waters of Long Island Sound, New York, USA, was characterized in 1984 and again in 1988 by an age structure restricted to just two age-classes, and an apparent lifespan of only about 10 yr. In the inshore coastal waters off Fire Island, New York, a wide age range from 2 to 22 yr old was present. The age structure at Long Beach, New York, a third geographic region which is coastal but influenced by the Hudson River estuary, was similar to Long Island Sound. Juvenile surf clams grew at similar rates in all three geographic regions. However, adults from the Long Island Sound population grew significantly slower and reached an asymptotic maximum size which was 37% smaller than Fire Island adults. Long Beach adults had intermediate growth rates and maximum sizes. The shells of Long Island Sound clams were also 25% thinner than those from the other two regions. Density dependent effects on growth, evaluated over abundances ranging from 0.5 to 294 ind. m–2, were present but were too small to account for observed regional differences. Results suggest that adult surf clams may be physiologically stressed by the reduced salinity and more extreme temperatures found in estuarine waters. 相似文献
15.
Spatial and temporal genetic homogeneity in the Arctic surfclam (<Emphasis Type="Italic">Mactromeris polynyma</Emphasis>) 总被引:1,自引:0,他引:1
Commercially harvested marine bivalve populations show a broad range of population-genetic patterns that may be driven by
planktonic larval dispersal (gene flow) or by historical (genetic drift) and ecological processes (selection). We characterized
microsatellite genetic variation among populations and year classes of the commercially harvested Arctic surfclam, Mactromeris polynyma, in order to test the relative significance of gene flow and drift on three spatial scales: within commercially harvested
populations in the northwest Atlantic; among Atlantic populations; and between the Atlantic and Pacific oceans. We found small
nonsignificant genetic subdivision among eight populations from the northwest Atlantic (F
ST = 0.002). All of these Atlantic populations were highly significantly differentiated from a northeast Pacific population
(F
ST = 0.087); all populations showed high inbreeding coefficients (F
IS = 0.432). We tested one likely source of heterozygote deficits by aging individual clams and exploring genetic variation
among age classes within populations (a temporal Wahlund effect). Populations showed strikingly different patterns of age
structure, but we found little differentiation among age classes. In one case, we were able to analyze genetic diversity between
age classes older or younger than the advent of intensive commercial harvesting. The results generally suggest spatially broad
and temporally persistent genetic homogeneity of these bivalves. We discuss the implications of the results for the biology
and management of surfclam populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
16.
Blooms of the brevetoxin-producing Karenia brevis in the Gulf of Mexico cause massive fish kills, food poisoning and adverse respiratory effects in humans. Sedimentation of
toxic cells following inert clay application could reduce toxin incorporation by commercially important suspension-feeding
bivalves and thus prevent direct public health impacts, but could potentially lead to brevetoxin (PbTx) accumulation by benthic
deposit-feeders. The goal of this study was therefore to compare suspension- and deposit-feeding as pathways for brevetoxins.
We investigated: (1) the effect of toxic K. brevis on both feeding modes using a facultative deposit-suspension feeding tellinid bivalve, the clam Macoma balthica, as a model species and (2) the relative effectiveness of brevetoxin transfer via suspension- and deposit-feeding over 24-h
exposure. Sedimentation of K. brevis was achieved by treatment with 0.25 g phosphatic clay l−1 and brevetoxin concentrations were measured by ELISA. Karenia brevis reduced both suspension- and deposit-feeding activity. This study demonstrates that brevetoxins can be rapidly accumulated
by a surface deposit-feeding bivalve from sedimented K. brevis cells and that comparable toxin levels can be attained by both suspension- and deposit-feeding modes [1.2–1.6 μg PbTx (g
tissue wet weight)−1]. Deposit-feeding clams generally do not pose a direct threat to humans but may provide a pathway for brevetoxin food web
transfer. 相似文献
17.
Cécile Dang X. de Montaudouin N. Savoye N. Caill-Milly P. Martinez P. G. Sauriau 《Marine Biology》2009,156(4):611-618
In this article, we show how a disease could bias stable isotope analyzes of trophic networks and propose a strategy in the
choice of tissues to be analyzed. In the past few years, a new pathology (brown muscle disease or BMD) affecting the posterior
adductor muscle of Ruditapes philippinarum has emerged in Arcachon Bay. BMD induces a necrosis of muscle tissues which become infused by conchiolin and hence calcified.
As muscle of mollusks are often used for trophic food webs studies through stable isotopic analyzes, this work investigated
the effect of BMD on carbon and nitrogen isotopic ratios of anterior and posterior adductor muscles of clams collected in
February and August 2007. Infected clams displayed a lower condition index and a posterior adductor muscle δ13C enrichment of 1.2‰ in February and 0.7‰ in August. δ15N of posterior muscles was however not affected by the disease. Anterior muscle of diseased clams remained healthy and displayed
the same isotopic signature as both posterior and anterior muscular tissues of healthy clam. Acidification significantly depleted
δ13C in posterior muscles of infected clams, suggesting calcification, contrary to anterior muscles of infected clam and to both
muscles of healthy clams, where no effect was observed. An X-ray diffractometry analysis confirmed the presence of CaCO3 (aragonite). Trophic food web studies relying on stable isotope ratios should utilize only healthy animals or anterior adductor
muscles when expertise in mollusk pathology is lacking. 相似文献
18.
The effects of UV-A and UV-B radiation on photosynthesis of zooxanthellae within the siphonal mantle of the giant clam, Tridacna crocea, and in isolation were studied. While UV-B irradiation (2.4 W m−2, 20 min) completely suppressed photosynthesis of the isolated zooxanthellae, it had little effect on their photosynthetic
ability if they were irradiated while within the siphonal mantle of the host tissue. Chemical analysis of the siphonal mantle
of T. crocea showed the presence of significant amounts of mycosporine-like amino acids (MAAs), which absorb UV-A and -B light. However,
no MAA was detected in the isolated zooxanthellae. MAAs were concentrated in the siphonal mantle and kidney tissues in comparison
with other tissues. In the siphonal mantle, MAA concentrations were the highest in the outermost surface layer where most
of the zooxanthella cells resided. This indicates that the zooxanthellae are protected from UV radiation by a screen of concentrated
MAAs in the host clam. Aside from T. crocea, significant amounts of MAAs were found not only in other zooxanthellate clams, such as T. derasa, Hippopus hippopus, Colculum cardissa and Fragum unedo, but also in a closely related azooxanthellate clam, Vasticardium subrugosum. On the other hand, no MAA was detected in any of the zooxanthellae from these zooxanthellate clams. No MAA was detected
in the tissues of a deep-sea bivalve, Calyptogena soyoae. Although MAAs seem to block strong UV radiation in the shallow-water clam, they are probably not essential for the clam's
life in the dark. MAAs in shallow-water clams may be derived from food and accumulated in their tissues, especially in the
siphonal mantle and kidney.
Received: 29 November 1996 / Accepted: 13 January 1997 相似文献
19.
Influence of algal and suspended sediment concentrations on the feeding physiology of the hard clam Mercenaria mercenaria 总被引:5,自引:0,他引:5
Short-term laboratory feeding experiments were conducted to determine the response of the hard clam Mercenaria mercenaria (L.) (32 mm in mean shell length) to increasing sediment concentrations. Clams were fed mixed suspensions of Pseudoisochrysis paradoxa (50 and 150 cells l-1) and bottom sediments (0 to 44 mg l-1). Algal ingestion rate deelined with increasing sediment loads. This resulted primarily from a reduction in clearance rate, which declined by 0.08 l h-1 g-1 (1.3%) for every 1 mg l-1 increase in sediment load. This reduction was of similar magnitude for juvenile (13 mm) clams. At the algal concentrations tested, pseudofaeces production was intermittent and inconspicuous below about 10 mg silt l-1. Loss of algae in pseudofaeces increased with increasing sediment loads; however, even at the highest silt and algal concentrations, clams lost a maximum of only 18% of the algae cleared from suspension. Thus, pseudofaeces production is not expected to cause significant loss of algal food at the sediment concentrations normally encountered in the natural environment ( ca 40 mg silt l-1). Absorption rate of total organic matter remained constant, at least up to silt concentrations of 20 mg l-1. Experiments using dual 51Cr:14C-formaldehyde-labelled sediment indicated that clams were able to counteract the dilution of algae by absorbing a considerable fraction (21 to 22%) of detrital sedimentary organics. Absorption efficiency of pure P. paradoxa ranged from 82% at 50 cells l-1 to 58% at 150 cells l-1. Integration of physiological rate measurements suggests that at moderate to high algal concentrations (300 g Cl-1), growth improvement by the addition of silt, documented in mussels, surf clams and oysters, is unlikely to occur in M. mercenaria. It is suggested that a suspension-feeding bivalve's success in maximizing its energy gain in a turbid environment depends on the combination of two features: a high selection efficiency and a high rate of pseudofaeces production. It is proposed that species which regulate ingestion primarily by producing pseudofaeces are better adapted to cope with high suspended sediment loads than species such as M. mercenaria, which control ingestion mainly by reducing clearance rate.Contribution No. 451 from the Marine Sciences Research Center, State University of New York at Stony Brook, USA 相似文献
20.
Giant clams form a symbiosis with photosynthetic algae of the genus Symbiodinium that reside in clam mantle tissue. The allometry of symbiont photosynthetic performance was investigated as a mechanism for the increasing percentage of giant clam carbon respiratory requirements provided by symbionts as clam size increases. Chlorophyll fluorescence measurements of symbionts of the giant clam Tridacna maxima were measured during experiments conducted in September of 2009 using specimens 0.5–200 g tissue wet weight (3–25 cm long), collected from waters around southern Taiwan (N 21°36′, E 120°47′) from July to August of 2009. Light-dependent decreases in effective quantum yield (∆F/F m′) calculated as the noontime maximum excitation pressure over PSII (Q m), relative electron transport rates (rETR), and dark-adapted maximum quantum yield (F v/F m) all varied as a quadratic function of clam size. Both Q m and rETR increased as clam size increased up to ~10–50 g then decreased as clam size increased. F v/F m decreased as clam size increased up to ~5–50 g then increased as clam size increased. Chlorophyll fluorescence measurements of rETR were positively correlated with gross primary production measured during chamber incubations. Overall, symbionts of mid-sized clams ~5–50 g exhibited the highest light-dependent decreases in effective photosynthetic efficiencies, the highest relative electron transport rates, and the lowest maximum photosynthetic efficiencies, and symbiont photosynthetic performance is allometric with respect to host clam size. 相似文献