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1.
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
2.
Eelgrass (Zostera marina L.) in the Dutch Wadden Sea historically covered an area varying from 65–150 km2 in the eulittoral as well as the sublittoral zones. At present, this area comprises less than 1 km2 eulittoral eelgrass stands, with an associated decrease in habitat diversity. The causes for this decline are presumably
connected with the ‘wasting disease’ and the closure of the former Zuiderzee in the early 1930s resulting in increased tidal
range and increased currents. After a slight recovery of the eelgrass populations on the intertidal flats a definite decline
started in the early 1970s, possibly connected to increased turbidity. The present water quality and turbidity do not negatively
influence eelgrass growth up to a depth of at least 0.6m below Mean Sea Level. Based on mesocosm experiments and field experiments
it is concluded that re-establishment of eelgrass should be possible in sheltered bays and on unexposed tidal flats. The most
suitable depths for a reintroduction are those between 0 and 20–40 cm below mean sea level. 相似文献
3.
Eelgras (Zostera marina L.) in the Dutch Wadden Sea historically covered an area varying from 65–150 km2 in the eulittoral as well as the sublittoral zones. At present, this area comprises less than 1 km2 eulittoral eelgrass stands, with an associated decrease in habitat diversity. The causes for this decline are presumably
connected with the ‘wasting disease’ and the closure of the former Zuiderzee in the early 1930s resulting in increased tidal
range and increased currents. After a slight recovery of the eelgrass populations on the intertidal flats a definite decline
started in the early 1970s, possibly connected to increased turbidity. The present water quality and turbidity do not negatively
influence eelgrass growth up to a depth of at least 0.6m below Mean Sea Level. Based on mesocosm experiments and field experiments
it is concluded that re-establishment of eelgrass should be possible in sheltered bays and on unexposed tidal falts. The most
suitable depths for a reintroduction are those between 0 and 20–40 cm below mean sea level. 相似文献
4.
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
5.
Carbon consumption and nitrogen requirements were estimated for populations of the sandy beach bivalve Donax serra on nine beaches of the west coast of South Africa. Subtidal populations composed mainly of adult clams were responsible for
the bulk of standing stock (3538 g C m−1), annual carbon consumption (13 444 g C m−1 yr−1), faeces production (6478 g C m−1 yr−1 ) and nitrogen regeneration (2525 g N m−1 yr−1). Kelp detritus, bacteria and kelp consumers' faeces available in the water column surpass several times the carbon and nitrogen
requirements of intertidal and subtidal clam populations. Individual Donax serra pop ulations, in turn, may regenerate up to 3.2% of the total nitrogen requirements of all primary producers from kelp beds
and 14% of the requirements of phytoplankton. These high standing stocks of clams are presumably supported mainly by organic
matter originating from kelp which, in contrast to phytoplankton, is in constant supply and comprises the largest proportion
of the annual production of particulate organic matter on this coast. Wide and shallow continental shelves with gentle slopes
probably limit the penetration of upwelled waters to the nearshore waters, decreasing the influence of external inputs and
increasing the importance of internal flows of nutrients and carbon within the nearshore zone. In this context, sandy beaches,
rocky shores and kelp beds may be more closely interlinked compartments of a larger ecosystem encompassing the whole nearshore
than traditionally thought.
Received: 28 August 1996 / Accepted: 7 October 1996 相似文献
6.
Since the early 1980s, the eelgrass, Zostera marina L., population in the saline Lake Gevelingen, The Netherlands, is rapidly declining. An earlier study, in which long-term
data on eelgrass coverage in this former estuary were correlated with several environmental variables, showed only one significant
correlation: coverage was positively related to water column silicon levels. In addition, a negative correlation with salinity
was observed, but this was not significant. In the present study, the effect of silicon and the effect of salinity on the
development of Z. marina were investigated experimentally. Enhancement of dissolved silicon concentrations in the water did not stimulate Z. marina above-ground production or an increase in final above- and below-ground biomass. The highly significant correlation between
eelgrass coverage and water column silicon levels, thus, remains to be explained. The results of the growth experiments did,
however, demonstrate a clear effect of salinity on Z. marina growth. Plants cultured at 22 psu showed a higher production of shoots and leaves, resulting in more above-ground biomass,
than plants grown at 32 psu. In addition, below-ground biomass was also higher at 22 psu. Measurements of chlorophyll a fluorescence, performed with a PAM-fluorometer, indicated a reduction of photosynthesis in the high-salinity treatments.
Thus, low salinity stimulates development of Z. marina from Lake Grevelingen. Eelgrass from such a historically estuarine area may be more sensitive to high salinities than other,
more marine populations. Recovery of the autochthonous eelgrass population is expected to be favoured when the estuarine conditions
of the seagrass area are re-established, or when restoration programmes are carried out with allochthonous ecotypes that are
less sensitive to high salinities.
Received: 23 June 1998 / Accepted: 19 November 1998 相似文献
7.
Annual cycle of biomass of a threatened population of the intertidal seagrass Zostera japonica in Hong Kong 总被引:2,自引:0,他引:2
S. Y. Lee 《Marine Biology》1997,129(1):183-193
The phenology and primary productivity of a population of Zostera japonica (Aschers. & Graebn.) threatened by the construction of Hong Kong's new international airport were studied over a 12-month
period. The need to conserve the population, and the small leaf size of Z. japonica rendered traditional destructive or marking techniques inapplicable for percentage cover and biomass estimation. A nondestructive
method based on image analysis techniques was therefore devised for repeated estimation of percentage cover, biomass and leaf
area index. This technique, which involved random quadrat sampling, photographic recording and image analysis, was able to
provide data on the three parameters with acceptable precision and was cost-effective in the field. Z. japonica demonstrated a strongly seasonal cycle of vegetative growth, with different patterns for leaf density (peak in March) and
overall bed area (peak in June). Total (above- and below-ground) net primary productivity was estimated at between 344 and
688 g AFDW m−2 yr−1. Percentage cover of Z. japonica was negatively correlated with total suspended solids (TSS) in the water column while total bed area was negatively correlated
with water salinity. Increased sedimentation associated with the new airport project was identified as one important factor
affecting the growth of the seagrass, as TSS reached the high level of ≈1 g DW l−1 during the first half of the study period. Sediment traps set in the beds also recorded potential sedimentation rates at
between 2.89 and 14.5 mg cm−2 d−1. This high turbidity resulted in a sharp decrease in the density of Clithon spp., the dominant grazers of epiphytic algae on Z. japonica. Effects of sedimentation and shading on growth of Z. japonica were investigated by field manipulative experiments. Experimental increase of sedimentation rate and shade both resulted
in larger decreases in percentage cover and above-ground AFDW compared with the control.
Received: 3 March 1997 / Accepted: 14 March 1997 相似文献
8.
The population dynamics of zooxanthellae living in the mantle of a giant clam, Tridacna derasa, was studied. The giant clams with shell lengths of 5 to 6 cm which had been reared in the Palau Mariculture Demonstration
Center, in the Republic of Palau, were transferred to aquaria on deck of the R.V. “Sohgen-maru” and kept in running sea water
at 29 to 30 °C. Two clams were removed from the aquaria, and zooxanthellae in the mantle were isolated every 2 h for 24 h.
Numbers of the zooxanthellae in or not in the cell division stage were counted for calculations of the zooxanthellae population
in the mantle and their mitotic index (MI). The MI increased after sunset and reached the maximum values of 6.1 to 11.5% at
03:00 to 05:00 hrs. The specific growth rate, μ, estimated from the MI was 0.083 to 0.14 d−1. Five clams were kept in each of 2 Plexiglas containers in the aquarium for collection of the discharged feces every 3 to
4 h. The discharged zooxanthellae in the feces were counted. The zooxanthellae discharged in 24 h were 0.38 to 1.46% of the
total zooxanthella population in the mantle, and 2.7 to 16.9% of the newly formed zooxanthella population in a day. Increase
of zooxanthella population in the mantle was estimated from clam shell growth rate and from the correlation between zooxanthella
population and clam shell size. Daily increase of zooxanthella population in the mantle was estimated to be approximately
7.6 to 19% of the newly formed zooxanthella population. Therefore, the sum of zooxanthellae populations accounting for daily
increase in the mantle and discharge in the feces was 11 to 36% of the newly formed population. About 64 to 89% of the newly
formed cells were missing; some of these may have been digested by the clam.
Received: 14 July 1996 / Accepted: 19 August 1996 相似文献
9.
The role of birds in intertidal food webs is mediated by effects of tides on the habitat, distribution, and accessibility of food organisms. We studied effects of elevation, sediment characteristics, vegetation, and tidal cycles on waterfowl feeding and food organisms in Boundary Bay, British Columbia, Canada from September to March 1990–1992. Percent dry mass of esophageal contents was mainly Zostera japonica leaves (84%) for American wigeon (Anas americana Gmelin), and leaves of Z. japonica (57%) and Z. marina (41%) for brant (Branta bernicla L.). Northern pintails (A. acuta L.) and mallards (A. platyrhynchos L.) ate mostly the leaves, seeds, and rhizomes of Z. japonica (48 and 72%, respectively) and gastropods (12 and 28%). Green-winged teal (A. crecca L.) ate mainly amphipods (68%) and saltmarsh seeds (19%). The well-sorted fine sand (median 0.125 mm) to medium sand (0.25 mm), and the low organic carbon content (1.31±0.12% dry mass), did not appear to vary sufficiently along 2.1- and 2.6-km transects to affect macroinvertebrate distributions. Three habitat zones were recognized: (1) upper intertidal (sandflats); (2) mid-intertidal (largely monotypic Z. japonica); and (3) lower intertidal (mixed Z. japonica and Z. marina). These zones, although related to elevation, had greater influence on amphipod distributions than did elevation alone or detrital biomass. Biomass and numbers of most invertebrate foods of waterfowl were greatest in the eelgrass zones, with the upper elevational limit of Z. japonica occurring at about Mean Water Level (MWL). Accordingly, wigeon, pintails, and mallards fed mostly below MWL. Because of seasonal tidal cycles, daily accessibility of areas below MWL but within reach of surfacefeeding waterfowl decreased from a mean of 10.8 h in October to 9.6 h in December. In October only 10 d and <12 h available feeding time, whereas in December and January every day had <12 h available feeding time. Seasonal effects of tides on accessibility might limit sufficient feeding by some waterfowl species in intertidal areas, increasing their reliance on alternative feeding sites. 相似文献
10.
Effects of salinity on endogenous rhythm of the Manila clam, Ruditapes philippinarum (Bivalvia: Veneridae) 总被引:1,自引:0,他引:1
The Manila clam Ruditapes philippinarum, an intertidal bivalve, was exposed to different salinity regimes (from 31.0–31.7‰ down to 20‰, 15‰, 10‰, 5‰), and the endogenous
rhythm in its oxygen consumption was studied using an automatic intermittent-flow respirometer. When exposed to salinities
reduced from 31.5‰ to 20‰ and 15‰ under otherwise constant conditions, the clams recovered a clear endogenous circatidal rhythm
in their oxygen-consumption rate after having dampened periods of 12 h and 48 h, respectively. At salinities less than 10‰,
however, the oxygen-consumption rate was depressed greatly at the beginning of the experiment for about 36 h and then increased
to a level higher than normal, but the rhythm of oxygen consumption was not recovered. The results of this study indicate
that the Manila clam, a euryhaline organism, cannot maintain a normal metabolic activity at a salinity lower than 15‰. All
clams were dead after exposure at a salinity of 5‰ for 7 days.
Received: 28 February 2000 / Accepted: 26 August 2000 相似文献
11.
We characterized the prey field and the lipid classes/fatty acids in the flesh of age 0 juvenile cod (Gadus morhua) during their late-summer/fall arrival and settlement into eelgrass (Zostera marina) in coastal Newfoundland. Examination of available prey demonstrated a high abundance of small zooplankton (Acartia, Microsetella and Oithona sp.) with no larger Calanus sp. prey. Breakpoint analysis showed significant changes in the accumulation of relative (mg g−1 wet weight) and absolute (μg fish−1) amounts of lipid with standard length at the time of settlement (~60 mm standard length). Settling juvenile cod showed an
alternate lipid utilization strategy where they catabolized phospholipids (PL) to a greater extent than triacylgylcerols (TAG).
Polyunsaturated fatty acids (PUFA) content in cod flesh decreased as fish grew indicating that nearshore zooplankton quality
was not optimal for PL formation. The dramatic reduction in cod PL was likely due to both catabolism of muscle and a lack
of dietary PUFA suitable for PL synthesis. However, juvenile cod continued to grow, leading to decreased lipid stores and
suggesting that cod settling into eelgrass are under intense selection pressure for growth prior to the onset of winter, possibly
as a means of escaping gape-limited predation. These data contrast better-studied freshwater and estuarine systems in which
lipid storage is critical for successful overwintering. 相似文献
12.
In soft sediment marine communities, fishes frequently bite off extended siphons of buried clams; the consequential shortening
of the siphon is known to reduce burial depth of the clams, secondarily increasing their vulnerability to lethal excavating
predators. In this study, siphon nipping on the yellow clam, Mesodesma mactroides, was simulated by removing the top 6.6–30% of siphons. This caused a burrow reduction in 25–75%, respectively, compared to
control individuals with intact siphons, in field and laboratory trials. To examine subsequent consequences of reduced burial
depth, we exposed nipped and intact clams to potential predators in the laboratory simulating the observed natural clam abundance.
Artificially nipped clams were consumed twice as much as control clams. The present results suggest that sympatric croppers
contribute to the stock recovery failure by facilitation of lethal predation and that re-seeding to increase the local abundance
of M. mactroides should be an essential aspect of conservation efforts in South America. 相似文献
13.
The influence of fresh weight and water temperature on metabolic rates and the energy budget of Meretrix meretrix Linnaeus 总被引:1,自引:0,他引:1
Meretrix meretrix L. was held in the laboratory under simulated natural conditions to measure specific physiological parameters of its energy budget. O2 consumption rate, NH3 excretion rate (NR), ingestion rate, faeces excretion rate and scope for growth (SFG) were negatively related in an exponential manner to the fresh weight of the clams at all water temperatures, while almost all metabolic rates of the clams were positively related in an exponential or e-exponential manner with water temperature. However, the co-relationship between metabolic rates and water temperature was not as close as that between metabolic rates and fresh weight of the clam. The combined effect of fresh weight and water temperature was observed on all metabolic rates except for NR and SFG. At all culture temperatures and for all fresh weights of clams used, respiration took the largest percentage of ingested energy (41.5–51.2%), faeces excretion was second (31.0–42.3%), growth third (12.1–15.5%) and urine production last (2.1–5.6%). 相似文献
14.
Benoit Lebreton Pierre Richard Robert Galois Gilles Radenac Amel Brahmia Géraldine Colli Marig Grouazel Cyril André Ga?l Guillou Gérard F. Blanchard 《Marine Biology》2012,159(7):1537-1550
In an intertidal Zostera noltii Hornem seagrass bed, food sources used by sediment meiofauna were determined seasonally by comparing stable isotope signatures (δ13C, δ15N) of sources with those of nematodes and copepods. Proportions of different carbon sources used by consumers were estimated using the SIAR mixing model on δ13C values. Contrary to δ15N values, food source mean δ13C values encompassed a large range, from −22.1 ‰ (suspended particulate organic matter) to −10.0 ‰ (Z. noltii roots). δ13C values of copepods (from −22.3 to −12.3 ‰) showed that they use many food sources (benthic and phytoplanktonic microalgae, Z. noltii matter). Nematode δ13C values ranged from −14.6 to −11.4 ‰, indicating a strong role of microphytobenthos and/or Z. noltii matter as carbon sources. The difference of food source uses between copepods and nematodes is discussed in light of source accessibility and availability. 相似文献
15.
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
16.
X. de Montaudouin 《Marine Biology》1997,128(4):639-648
Juvenile bivalves may be dispersed by entering a bysso-pelagic phase where they drift through the water mass aided by a long
thread. The ability to resuspend and control the specific weight in two bivalve species, the cockle Cerastoderma edule (L.) and the Japanese clam Ruditapes philippinarum (Adams and Reeves), was documented with juveniles through flume and still-water experiments. Cockle juveniles initially placed
on an unsuitable substratum were exposed to two shear velocities (u
*). At the end of the experiment, 42 (±15)% (for u
*=0.51 cm s−1) and 79 (±9)% (for u
*=0.99 cm s−1) of individuals were retrieved from the sand area which represents only 8% of the total flume surface. Most juveniles (70.5%)
with shell lengths <2.5 mm migrated from the unsuitable Plexiglas substratum to the sand array by resuspension in the water
column. The percentage was lower (21.5%) for larger individuals. The same experimental design was applied to clams, which
immediately adhered to the Plexiglas substratum and remained attach to it. Sinking rates of live and dead specimens of both
species were measured in a 1 m long transparent PVC tube. Cockle fall velocities showed severe deceleration, probably due
to byssus secretion (up to 15-fold slower than dead cockles), sometimes interrupted by brutal acceleration probably due to
byssal rupture. Cockles were able to reduce their sinking rate for shell lengths up to 4.25 mm. By contrast, clam sinking
rates were constant, and similar to dead clam sinking rates. Specific weights of all experimental juveniles were calculated
in relation to their lengths, and their passive motion into the boundary layer was theoretically assessed with Shields curve.
In short, C. edule and R. philippinarum can both exhibit dense populations in the field with a good capacity to colonize, although juveniles display different abilities
to resuspend in the water column.
Received: 27 January 1997 / Accepted: 13 February 1997 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 interaction of sediment ammonium (NH
4
+
) availability and eelgrass (Zostera marina L.) growth, biomass and photosynthesis was investigated using controlled environment and in-situ manipulations of pore water ammonium concentrations. Sediment diffusers were used to create pore water diffusion gradients to fertilize and deplete ammonium levels in sediments with intact eelgrass rhizospheres. Between October, 1982 and September, 1983 controlled environment experiments using plants from shallow (1.3 m) and deep (5.5 m) stations in a Great Harbor, Woods Hole, Massachusetts, USA eelgrass meadow along with in-situ experiments at these stations provided a range of sediment ammonium concentrations between 0.1 and 10 mM (adsorbed+interstitial NH
4
+
). The results of the in-situ experiments indicate that nitrogen limitation of eelgrass growth does not occur in the Great Harbor eelgrass meadow. A comparison of NH
4
+
regeneration rates and eelgrass nitrogen requirements indicates an excess of nitrogen supply over demand and provides an explanation for the lack of response to the manipulations. Results of controlled environment experiments combined with in-situ results suggest that sediment ammonium pool concentrations above approximately 100 mol NH
4
+
per liter of sediment (interstitial only) saturate the growth response of Zostera marina. 相似文献
19.
The giant clam Tridacna crocea harbors in the mantle tissue symbiotic microalgae commonly called zooxanthellae. Isolated zooxanthellae release glycerol
into the medium in the presence of mantle tissue homogenate (MH), but it is not clear whether the cells do so in situ. In
order to determine the photosynthetic products released by zooxanthellae in the mantle of the giant clam we traced photosynthetic
fixation products from 13C- and 14C-bicarbonate both in the clam and in isolated zooxanthellae (IZ) in the presence or absence of MH. After 15 min incubation
in the absence of MH the IZ released less than 0.6% of the fixed labeled carbon, mainly as glucose. The major intracellular
photosynthates were neutral lipids, which constituted 20 to 40% of the total extractable 14C. In the presence of MH, the IZ released up to 5.6% of the total fixed 14C, mostly as glycerol, and the major intracellular photosynthate was glucose. In an intact clam incubated in sea water containing
14C-bicarbonate, 46 to 80% of the fixed 14C was translocated from the zooxanthellae to the host tissues. Most of the 14C in the hemolymph, in the isolated zooxanthellae and in intact mantle tissue (containing zooxanthellae) was recovered as
glucose. No 14C-glycerol was detected in the mantle after 1 to 30 min incubation, and, even after 60 min, far less 14C-glycerol was synthesized than by IZ in the presence of MH. The possibility that in clam tissue glycerol is converted to
glucose was examined by tracing the labeled carbon from 14C-glycerol injected into the adductor muscle. After 5 min incubation, no labeled glucose was found in the hemolymph, but after
60 min, some 20% was found as glucose. Thin slices containing zooxanthellae, cut from the surface of the mantle, fixed inorganic
carbon supplied as NaH14CO3 in the medium and mainly released 14C-glucose. The addition of MH to the surrounding medium did not affect the release rate or form of release product. When the
slices were cut into smaller pieces, however, the ratio of glycerol to glucose in the release product increased. These results
indicate that in the presence of MH the metabolism of isolated zooxan- thellae was different from that of zooxanthellae in
the mantle. In the presence of MH, isolated zooxanthellae release mostly glycerol, whereas in the mantle they release glucose.
Received: 18 February 1998 / Accepted: 4 December 1998 相似文献
20.
When exposed to Prudhoe Bay crude oil in flowing seawater for 180 days, the small intertidal clam Macoma balthica showed behavioral, physical, physiological and biochemical changes. At a high concentration of oil in seawater (3.0 mg l-1) burrowing rate decreased, respiration rate increased, growth was inhibited, and very high mortalities resulted. The lowest concentration of oil in seawater (0.03 mg l-1) inhibited growth and caused reabsorption of gametes. One group of adverse oil effects which was related to sluggishness and disorientation of the clams appeared after a week of exposure to oil; another group related to a negative energy balance was not observed until 60 days. We conclude that chronic exposure of M. balthica to oil-in-seawater concentrations even as low as 0.03 mg l-1 will, in time, lead to population decreases.Please address requests for reprints to Dr. D. G. Shaw at the Institute of Marine Science 相似文献