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1.
Symbiotic dinoflagellate algae (Symbiodinium sp.) isolated from the scleractinian coral Plesiastrea versipora and incubated in homogenized host tissue released 4 to 7 times as much glycerol (14 to 46 nmol glycerol/106 algae) as those incubated in seawater (3 to 6 nmol glycerol/106 algae) after 4 h incubation in the light. During this period, no release of triglycerides was detected. Intracellular glycerol
increased 2- to 3-fold in algae incubated in host homogenate, but remained unchanged in algae incubated in seawater at a concentration
of 0.82 ± 0.47 nmol glycerol/106 algae. In each incubation condition, intracellular triglyceride levels increased. However, in algae incubated in host homogenate,
the intracellular levels of triglycerides reached only about 75% of the amount reached in algae incubated in seawater (max.
18.55 ± 2.40 nmol glycerol/106 cells). Host homogenate did not stimulate the release of glycerol from algae during dark incubation. These data show that
the glycerol released by algae incubated in host-tissue homogenate was derived from increased synthesis of glycerol or from
diversion of some glycerol or other photosynthetic intermediates from incorporation into algal triglyceride stores, and did
not come from existing stores.
Received: 20 December 1996 / Accepted: 9 January 1997 相似文献
2.
In the Red Sea, the zooxanthellate sponge Cliona vastifica (Hancock) is mainly present at >15 m depth or in shaded areas. To test whether its scarcity in unshaded areas of shallower
waters is linked to the functional inefficiency of its photosymbionts at high irradiances, sponges were transferred from 30 m
to a six times higher light regime at 12 m depth, and then returned to their original location. During this time, photosynthetic
responses to irradiance were measured as rapid light curves (RLCs) in situ by pulse amplitude modulated (PAM) fluorometry
using a portable underwater device, and samples were taken for microscopic determinations of zooxanthellar abundance. The
zooxanthellae harboured by this sponge adapted to the higher irradiance at 12 m by increasing both their light saturation
points and relative photosynthetic electron transport rates (ETRs). The ETRs at light saturation increased almost fourfold
within 15–20 days of transfer to the shallower water, and decreased back to almost their original values after the sponges
were returned to 30 m depth. This, as well as the fact that the photosynthetic light responses within an individual sponge
were in accordance with the irradiance incident to specific surfaces, shows that these photosymbionts are highly adaptable
to various irradiances. There was no significant change in the number of zooxanthellae per sponge area throughout these experiments,
and the different photosynthetic responses were likely due to adaptations of the photosynthetic apparatus within each zooxanthella.
In conclusion, it seems that parameters other than the hypothesised inability of the photosymbionts to adapt adequately to
high light conditions are the cause of C. vastifica's rareness in unshaded shallow areas of the Red Sea.
Received: 25 April 2000 / Accepted: 13 October 2000 相似文献
3.
When symbiotic dinoflagellate algae (Symbiodinium sp., isolated from the coral Plesiastrea versipora) were incubated with NaH14CO3 in the light in seawater, they released 22.69±9.16 nmol carbon/106 algae. Release of photosynthetically fixed carbon was stimulated more than six-fold for algae incubated in host-tissue homogenate
(148.54±97.03 nmol C/106 algae) and more than four-fold (102.00±49.16 nmol C/106 algae) for algae incubated in a low molecular weight fraction (≤1 000 M
r
) prepared from host homogenate. Soluble released 14C-labelled products, as determined by chromatography and autoradiography, were the same when algae were incubated in either
host homogenate or the low molecular weight fraction. After 4 h incubation in the light (300 mol photons m−2 s−1),␣intracellular␣glycerol increased in algae incubated with the low molecular weight fraction (an increase of 0.39 to␣0.67 nmol glycerol/106 algae) compared with little or no increase in algae incubated in seawater (0 to 0.12 nmol glycerol/106 algae). Partial inhibition of triglyceride synthesis (up to 51%) was also observed when algae were incubated in the low molecular
weight fraction. All these effects are the same as those observed when algae were incubated in host homogenate. These data
indicate that the “host release-factor” activity of P.␣versipora is a compound of low molecular weight.
Received: 13 February 1997 / Accepted: 24 October 1997 相似文献
4.
Allozymes were examined in quantitative lunar monthly collections of larval recruits of the western rock lobster Panulirus cygnus George over three recruitment seasons at two sites nearly 350 km apart in Western Australia. At Alkimos, the southern site,
recruitment occurs in a relatively narrow peak early in the spring, whereas at the northern Houtman Abrolhos Islands, recruitment
extends into the summer months. In the 1995/1996 recruitment season, the frequency of the GPI
*
100 allele increased from early to late in the season, but the frequencies were indistinguishable at the two sites in each monthly
collection. The combination of this temporal variation in allelic frequencies with the contrasting patterns of recruitment
at the Abrolhos Islands and Alkimos resulted in genetically different cohorts at the two sites. This pattern was ephemeral,
as it was not repeated in the subsequent two years. Thus, ephemeral genetic patchiness in P. cygnus can be generated by the locally-specific genetic mix of recruits obtained from a common larval pool. This mechanism is the
probable explanation of previously observed temporal and possible spatial genetic variation in adult P. cygnus, and highlights the importance of studying recruitment in order to understand the genetic structure of marine species.
Received: 22 February 1999 / Accepted: 8 June 1999 相似文献
5.
The localisation of halogenated furanones, the biologically active secondary metabolites from the red alga Delisea pulchra (Greville), was determined by a combination of fluorescence microscopy, culture studies and quantitative chemical analyses.
All types of evidence showed that furanones are localised in the central vesicle of gland cells in D. pulchra. These cells release furanones onto the surface of the plant, where they can be quantified using a newly developed surface
extraction-technique. Levels of furanones on the surface of the plant were highest near the apical tips (≃100 ng cm−2), and decreased towards the base of the alga. Variation in furanone levels within the plant and variation in the number of
gland cells followed a similar pattern. The localisation of furanones within gland cells in D. pulchra and the presence and concentrations of furanones on the surface of the plant are consistent with furanones functioning as
antifoulants and in mediating other ecological interactions at the surface of the alga.
Received: 5 March 1998 / Accepted: 10 September 1998 相似文献
6.
Territorial Parma microlepis (Günther) (Pomacentridae) were collected at different depths, at three sites in each of four estuaries near Sydney, Australia.
Element concentrations were measured by induc- tively-coupled–plasma mass spectrometry. Significant differences in concentrations
of Mn and Ba were found in the otoliths of fish sampled in different depth strata, with concentrations generally greatest
in fish found in water <4 m deep. Depth-related differences varied among estuaries (e.g. 0 to 1.2 μg Ba g−1 otolith). In most estuaries there was a negative linear relationship between concentrations of Mn and Ba in otoliths and
actual depth. Great variation was found within an estuary among sites separated by 0.5 to 3 km. In the eye lenses, concentrations
of Rb differed according to depth of capture of fish. The age of fish (1+ to 34 yr) had no influence on the concentrations
of elements in otoliths or lenses. Multivariate comparisons of elemental composition (= fingerprints) detected significant
differences among depth strata. Fish collected from shallow water had the clearest multivariate classification according to
depth. There was a close match between our shallow strata and the average depths reached by low-salinity/high-temperature
estuarine plumes. The element composition of whole otoliths and lenses represents average concentrations experienced by the
fish. The temporal resolution of differences in ambient conditions is likely to be coarse in the fish (i.e. months to years).
Received: 9 April 1999 / Accepted: 29 February 2000 相似文献
7.
Field sampling and laboratory experiments examined whether ultraviolet radiation (UVR) affects the reproduction or the accumulation
of mycosporine-like amino acids (MAAs) and ascorbic acid in ovaries of the green sea urchin Strongylocentrotus droebachiensis (Müller). Ovaries of sea urchins sampled across a depth gradient (0.5–10 m) in March 1998 did not differ in their gonadal
index, or in concentrations of MAAs, or ascorbic acid. Concentrations of MAAs and ascorbic acid in ovaries were higher in
sea urchins collected from a kelp bed compared with those collected from a community of crustose coralline algae. The concentrations
of MAAs in ovaries varied seasonally, peaking in March, when sea urchins had high gonadal indices just before spawning. Ovaries
of sea urchins maintained on controlled diets from October 1997 to April 1998 accumulated significantly higher concentrations
of MAAs when fed a diet rich in MAAs than did ovaries of sea urchins fed an alga lacking MAAs, but the gonadal indices did
not differ between diets. Sea urchins accumulated principally one MAA, shinorine, but not others that were available in high
concentrations in their diet. Neither the gonadal index nor the ovarian concentrations of MAAs were affected by daily exposure
of adult urchins to UVR for 6 months. Concentrations of ascorbic acid in ovaries did not differ among diets or UV-treatments.
The percentages of nutritive phagocytes and gametic cells were not affected by diet or UVR, and did not co-vary with concentrations
of MAAs or ascorbic acid in ovaries. These data support previous demonstrations that female sea urchins accumulate MAAs from
their diet of macroalgae, but further show that the accumulation is selective for specific MAAs, particularly shinorine, and
that adult S. droebachiensis do not accumulate MAAs in their ovaries or eggs in response to UV-exposure. These are also the first experimental studies
to address whether MAAs are affected by or regulate gametogenesis, and indicate that they do not.
Received: 5 May 2000 / Accepted: 29 September 2000 相似文献
8.
Geographic variation in polyphenolic levels of Northeastern Pacific kelps and rockweeds 总被引:1,自引:0,他引:1
K. L. Van Alstyne J. J. McCarthy III C. L. Hustead D. O. Duggins 《Marine Biology》1999,133(2):371-379
Brown algal polyphenolic compounds are secondary metabolites whose functions may include protecting plants from pathogens
or damage by UV radiation, and deterring feeding by herbivores. We present here the first analysis of spatial variation (at
scales from tens of meters to hundreds of kilometers) in concentration of these compounds in two orders of brown algae from
the northeastern Pacific Ocean. In kelps (order Laminariales), variation among sites was significant in only 25% of species
examined and was consistent within families (high in the Alariaceae and low in the Laminariaceae and Lessoniaceae). In rockweeds
(order Fucales, family Fucaceae), site variation was high in three of four species examined. Both the proportion of high polyphenolic
kelp species and the magnitude of spatial variation within species from both kelps and rockweeds were much higher than would
have been predicted from previous studies in other regions. In one kelp (Laminaria groenlandica), significant differences between sites occurred at scales of only tens of meters. No latitudinal clines were observed. Differences
in phenolic concentrations of kelps spanned nearly an order of magnitude in one species, Hedophyllum sessile. Phenolic levels were significantly higher in members of the Fucales than the Laminariales, but showed no significant differences
between intertidal and subtidal species.
Received: 22 July 1996 / Accepted: 26 October 1998 相似文献
9.
We used random amplified polymorphic DNA (RAPDs) to examine small-scale spatial genetic structure in the red alga Delisea pulchra (Greville) Montagne at two locations near Sydney, Australia. We examined genetic structure among plants at four spatial scales
ranging from 2 km apart down to <50 cm apart between locations, among sites within locations, among quadrats within sites,
and among plants within quadrats. Haploid stages of D. pulchra were absent from the populations studied, suggesting that they are maintained through asexual reproduction of diploid plants.
Consistent with this, we found that 19 RAPD phenotypes scored in this study had multiple individuals, indicating the presence
of clones in these populations. However, there were no RAPD phenotypes common to two locations separated by only 2 km. Analysis
of molecular variance revealed that strong genetic differences occurred between plants from these two locations, with 46.3%
of the total genetic variation occurring at this scale, most probably reflecting limited gene flow. Within each location,
<25% of the genetic variation was attributable to differences among sites or quadrats, indicating gene flow at those smaller
scales. Most of the variation within each location occurred at the smallest spatial scale, among plants within 0.25 m2 quadrats. Nonetheless, some pairwise genetic distances (φST) between sites or quadrats within locations were large, indicating some genetic divergence on smaller scales. Genetic distance
was independent of spatial distance within both locations, suggesting that fine-scale differences within locations were most
probably caused by variation in fine-scale patterns of water movement or fine-scale natural selection. We assessed the impact
of one potential selective agent, grazing sea urchins, on the fine-scale genetic structure of D. pulchra. There was no evidence that grazing by sea urchins affected the genetic structure of D. pulchra. In combination with demographic data, our results indicated that local populations of D. pulchra within locations were relatively open and that fine-scale genetic structure was probably constrained by gene flow. At the
larger scale however, strong genetic differentiation indicated little gene flow between locations and restricted dispersal
of spores.
Received: 22 April 1999 / Accepted: 29 November 1999 相似文献
10.
The relative contribution of dissolved nitrogen (ammonium and dissolved free amino acids DFAAs) to the nitrogen budget of
the reef-building coral Pocillopora damicornis was assessed for colonies growing on control and ammonium-enriched reefs at One Tree Island (southern Great Barrier Reef)
during the ENCORE (Enrichment of Nutrient on Coral Reef; 1993 to 1996) project. P. damicornis acquired ammonium at rates of between 5.1 and 91.8 nmol N cm−2 h−1 which were not affected by nutrient treatment except in the case of one morph. In this case, uptake rates decreased from
80.5 to 42.8 nmol cm−2 h−1 (P < 0.05) on exposure to elevated ammonium over 12 mo. The presence or absence of light during measurement did not influence
the uptake of ammonium ions. Nitrogen budgets revealed that the uptake of ammonium from concentrations of 0.11 to 0.13 μM could completely satisfy the demand of growing P. damicornis for new nitrogen. P. damicornis also took up DFAAs at rates ranging from 4.9 to 9.8 nmol N cm−2 h−1. These rates were higher in the dark than in the light (9.0 vs 5.1 nmol m−2 h−1, P < 0.001). Uptake rates were highest for the amino acids serine, arginine and alanine, and lowest for tyrosine. DFAA concentrations
within the ENCORE microatolls that received ammonium were undetectable, whereas they ranged up to 100 nM within the control microatolls. The contribution of DFAAs to the nitrogen budget of P. damicornis constituted only a small fraction of the nitrogen potentially contributed by ammonium under field conditions. Even at the
highest field concentrations measured during this study, DFAAs could contribute only ≃11.3% of the nitrogen demand of P.␣damicornis. This contribution, however, may be an important source of nitrogen when other sources such as ammonium are scarce or during
periods when high concentrations of DFAAs become sporadically available (e.g. cell breakage during fish-grazing).
Received: 22 April 1998 / Accepted: 3 November 1998 相似文献
11.
Nutrients were added separately and combined to an initial concentration of 10 μM (ammonium) and/or 2 μM (phosphate) in a series of experiments carried out with the giant clam Tridacna maxima at 12 microatolls in One Tree Island lagoon, Great Barrier Reef, Australia (ENCORE Project). These nutrient concentrations
remained for 2 to 3 h before returning to natural levels. The additions were made every low tide (twice per day) over 13 and
12 mo periods for the first and second phase of the experiment, respectively. The nutrients did not change the wet tissue
weight of the clams, host C:N ratio, protein content of the mantle, calcification rates or growth rates. However, ammonium
(N) enrichment alone significantly increased the total population density of the algal symbiont (Symbiodinium sp.: C = 3.6 · 108 cell clam−1, N = 6.6 · 108 cell clam−1, P = 5.7 · 108 cell clam−1, N + P = 5.7 · 108 cell clam−1; and C = 4.1 · 108 cell clam−1, N = 5.1 · 108 cell clam−1, P = 4.7 · 108 cell clam−1, N + P = 4.5 · 108 cell clam−1, at the end of the first and second phases of the experiment, respectively), although no differences in the mitotic index
of these populations were detected. The total chlorophyll a (chl a) content per clam but not chlorophyll a per cell also increased with ammonium addition (C = 7.0 mg chl a clam−1, N = 13.1 mg chl a clam−1, P = 12.9 mg chl a clam−1, N + P = 11.8 mg chl a clam−1; and C = 8.8 mg chl a clam−1, N = 12.8 mg chl a clam−1; P = 11.2 mg chl a clam−1, N + P = 11.3 mg chl a clam−1, at the end of the first and second phases of the experiment, respectively). The response of clams to nutrient enrichment
was quantitatively small, but indicated that small changes in inorganic nutrient levels affect the clam–zooxanthellae association.
Received: 2 June 1997 / Accepted: 9 June 1997 相似文献
12.
Pure compounds isolated from the cyanobacterium Lyngbya majuscula Gomont were evaluated in an artificial diet for their influence on the feeding preferences of the sea hare Stylocheilus longicauda (Quoy and Gaimard, 1824), which lives in and feeds on this filamentous cyanobacterium (blue-green alga). Microcolin B, ypaoamide,
malyngolide and other natural products acted as feeding deterrents at natural concentrations. At lower concentrations, sea
hares were indifferent to ypaoamide and malyngolide in their diets. In contrast, barbamide stimulated sea hare feeding at
the concentrations normally found in L. majuscula. Malyngamides and majusculamides, the most common natural products found in samples of L. majuscula from Guam, increased sea hare feeding at low concentrations and inhibited feeding at the higher concentrations that occurred
in some collections of L. majuscula. Dietary selection of cyanobacteria by S. longicauda may be regulated by the concentration of specific chemical cues produced by L. majuscula.
Received: 28 January 1997 / Accepted: 24 April 1998 相似文献
13.
This paper reports data on 28 allozyme loci in wild and artificially reared sea bass (Dicentrarchus labrax) samples, originating from either coastal lagoon or marine sites in the Mediterranean Sea. F
ST analysis (θ estimator) indicated strong genetic structuring among populations; around 34% of the overall genetic variation
is due to interpopulation variation. Pairwise θ estimates showed that, on average, the degree of genetic structuring was much
higher between marine populations than between samples from lagoons. Six polymorphic loci showed differences in allele frequencies
between marine and lagoon samples. Multivariate analyses of individual allozymic profiles and of allele frequencies suggested
that different arrays of genotypes prevail in lagoons compared to marine samples, particularly at those loci that, on the
basis of previous acclimation experiments, had been implicated in adaptation to freshwater. On the other hand, variation at
“neutral” allozyme loci reflects to a greater extent the geographic location of populations. Allozyme differentiation was
also studied in a D. labrax population from the Portuguese coast. Average genetic distance between this population and the Mediterranean populations
was quite high (Nei's D = 0.236) and calls into question the taxonomic status of the Portuguese population. Finally, genetic relationships between
D. labrax and D. punctatus were evaluated. Average Nei's D was 0.648, revealing high genetic differentiation between the two species, even for two sympatric populations of these species
in Egypt; thus gene flow was not indicated between species.
Received: 24 October 1996 / Accepted: 27 November 1996 相似文献
14.
The blue mussels Mytilus edulis L. and M. galloprovincialis Lmk. hybridize in western Europe. Within hybrid populations nuclear alleles specific to M. galloprovincialis increase in frequency with age and size. This relationship changes with tidal height; alleles from M. galloprovincialis occur more frequently high in the intertidal zone, while M. edulis alleles predominate in the low intertidal zone. We tested the hypotheses that larvae with M. galloprovincialis alleles tend to settle higher in the intertidal zone, or that mussels redistribute themselves with respect to tidal height
after initial larval settlement. We sampled recently metamorphosed mussels every 2 weeks in a hybrid mussel population at
Whitsand Bay in southwest England throughout the summer of 1996. We observed four cohorts of newly settled mussels. There
was no evidence of differential settlement of mussels with different genotypes in connection with tidal height, or into shaded
versus unshaded microsites. Therefore, we rejected the preferential settlement hypothesis. There was substantial movement
of juvenile mussels in the first 4 weeks following initial settlement, but this “secondary settlement” did not result in genetic
differentiation with respect to tidal height. Further, significant differences in allele frequencies were found between primary
and secondary spat. This allele frequency change was in the opposite direction of that seen in the adult population, suggesting
newly settled larvae may be experiencing different selective pressures than adults. We propose that the genetic structure
of hybrid mussel populations with respect to tidal height is the consequence of differences in selection intensity.
Received: 30 April 1999 / Accepted: 5 May 2000 相似文献
15.
S. K. Wilson 《Marine Biology》2000,136(3):431-437
An evaluation of the dietary resources available to, and selected by, blennies of the tribe Salariini was used to assess
their trophic status on the Great Barrier Reef. Gut-content analysis of nine species of blennies found detrital aggregates
to be the dominant item ingested. Samples of the dietary resources available to one of these species, Salarias patzneri, were compared biochemically. Of the two main dietary categories (detrital aggregates and filamentous algae), detrital aggregates
were the major resource available, accounting for 53 ± 4.6% (SE) of the organic matter present. The mean C:N values for detrital
aggregates (17.2 ± 0.8) and filamentous algae (20.0 ± 1.8) were very similar, as were protein concentrations (1.8 ± 0.1 and
2.1 ± 0.1 μg mg−1, respectively). However, mean carbohydrate concentrations were much lower in the aggregates than the filamentous algae (19 ± 2
and 76 ± 13 μg mg−1, respectively). Comparison of the inorganic particles ingested to those available indicated that S. patzneri selectively fed on particles <125 μm, (predominantly detrital aggregates) and avoided particles >250 μm, (predominantly algal
filaments). The patterns of resource availability, nutritional quality and selectivity suggest that salariin blennies utilise
detrital aggregates as their primary dietary resource.
Received: 24 May 1999 / Accepted: 29 November 1999 相似文献
16.
We measured the uptake kinetics of four metals (Cd, Cr, Se and Zn) in two marine macroalgae (the green alga Ulva lactuca and the red alga Gracilaria blodgettii). Metal uptake generally displayed a linear pattern with increasing exposure time. With the exception of Cr, which exhibited
comparable uptake rate constants at different concentrations, uptake rate constants of Cd, Se and Zn decreased with increasing
metal concentration, indicating that the seaweeds had a higher relative uptake at lower metal concentration. Uptake of Cd
and Zn was higher in U. lactuca than in G. blodgettii, whereas uptake of Cr and Se was comparable between the two species. Only Cd and Zn uptake in U. lactuca was significantly inhibited by dark exposure. A decrease in salinity from 28 to 10‰ enhanced the uptake of Cd, Cr, Se and
Zn in U. lactuca 1.9-, 3.0-, 3.6-, and 1.9-fold, respectively. In G. blodgettii, Cd uptake increased twofold when salinity was decreased from 28 to 10‰, whereas uptake of Cr and Zn was not significantly
affected by salinity change. The calculated depuration rate constants of metals in U. lactuca were 0.01 d−1 for Cd, 0.05 to 0.08 d−1 for Cr, 0.14 to 0.16 d−1 for Se, and 0.12 to 0.15 d−1 for Zn, and were relatively independent of the metal body burden in the algae. The predicted bioconcentration factor was
3 × 104 for Cd, 2 × 103 for Cr, 40 to 150 for Se, and 1 to 2 × 104 for Zn in U. lactuca. Our kinetic study suggested that U. lactuca would be a good biomonitor of Cr and Zn contamination in coastal waters.
Received: 14 September 1998 / Accepted: 29 May 1999 相似文献
17.
Artemia franciscana was grown on Isochrysis galbana Green (clone T. Iso) at saturated food concentrations (13 to 20 mg C l−1) for 11 d at 26 to 28 °C, and 34 ppt salinity. Three groups of brine shrimp were used in the feeding experiments: metanauplius
III and IV (Group 1), post-metanauplius II and III (Group 2) and post-metanauplius VIII (Group 3), corresponding to 4-, 7-
and 11-d-old animals, respectively. The ingestion rate, clearance rate and carbon balance were estimated for these stages
at different concentrations of 14C-labeled I. galbana ranging from 0.05 to 30 mg C l−1. The handling time of algae was determined for all three groups. The ingestion rate (I, ng C ind−1 h−1) increased as a function of animal size and food concentration. In all three groups, the ingestion rate increased to a maximum
level (I
max) and remained constant at food concentrations ≥10 mg C l−1 (saturated food concentrations). The clearance rate (CR, μl ind−1 h−1) increased with increasing food concentration up to a maximum rate (CR
max), after which it decreased for even higher food concentrations. The functional response of A. franciscana was most consistent with Holling's Type 3 functional response curve (sigmoidal model), which for the two oldest groups (Group 2
and 3) differed significantly from a Type 2 response (p < 0.05). The gut passage time for the three groups of A. franciscana, feeding on saturated food concentration (20 mg C l−1), varied between 24 and 29 min. As the nauplii developed to pre-adult stage the handling time of the algae increased as a
function of animal size. The assimilation rate (ng C ind−1 h−1) in the youngest stages (Group 1 and 2) increased with increasing food concentrations, reaching a maximum level close to
10 mg C l−1. At higher food concentrations the assimilation rate decreased, and the proportions of defecated carbon increased, reaching
60 to 68% in the post-metanauplius stages (Group 3). The assimilation efficiency (%) was high at the lowest food concentrations
in all three groups (89 to 64%). At higher concentrations, the assimilation efficiency decreased, reaching 56 to 38% at the
highest concentrations.
Received: 2 February 2000 / Accepted: 25 March 2000 相似文献
18.
Comparison of herbivory in the closely-related marine fish genera Girella and Kyphosus 总被引:2,自引:0,他引:2
Specimens of the nominally herbivorous, closely-related, fish genera Girella and Kyphosus were collected from Australian waters in 1994 and 1995. The diet of three Girella species (G. cyanea, G. elevata, and G. tricuspidata) consisted mainly of chlorophytes and rhodophytes, with an animal component of␣15.9 ± 4.2% in G. tricuspidata. The diet of four species of Kyphosus (K. bigibbus, K. cinerascens, K. sydneyanus, and K. vaigiensis) included phaeophytes, chlorophytes and rhodophytes, and almost no animal material. Concentration of total short-chain fatty
acids in the posterior intestine was <11.4 mM in the Girella spp. and >39.2 mM in the Kyphosus spp. These results suggest that microbial fermentation plays a role in algal digestion in Kyphosus spp., but not in Girella spp. Girellids and kyphosids appear to function quite differently as herbivores. Girellids should be considered as omnivores
that complement readily-available energy from algae with protein from invertebrates. Kyphosids appear to be strict herbivores
that can derive adequate nutrition from algae poor in easily assimilable energy, through microbial fermentation in the hindgut.
Received: 8 July 1996 / Accepted: 2 August 1996 相似文献
19.
Cell density, chemical composition and toxicity of Chrysochromulina polylepis (Haptophyta) in relation to different N:P supply ratios 总被引:2,自引:0,他引:2
The influence of different N:P supply ratios on cell accumulation, chemical composition and toxicity of the marine haptophyte
Chrysochromulina polylepis was examined in semi-continuous cultures. A non-axenic strain of C. polylepis was exposed to five different N:P supply ratios (N:P = 1:1, 4:1, 16:1, 80:1 and 160:1, by atoms), in order to create a range
of N- and P-limited conditions. The toxicity per cell in C. polylepis was determined on four occasions at steady state cell density using the haemolytic activity of the cells expressed as saponin
nanoequivalents. Haemolytic activity was demonstrated in all treatments, and increased in the algae when cell growth was nutrient
limited (N:P = 1:1, 4:1, 80:1 and 160:1), compared to cells grown under non-limiting conditions (N:P = 16:1). This occurred
regardless of the growth-limiting nutrient (N or P) and became more pronounced as nutrient limitation increased. In P-limited
cultures the haemolytic activity per cell increased linearly with the cellular N:P ratio, whereas the N-limited cultures showed
an opposite trend. The haemolytic activity per cell showed an inverse relationship with both cellular N and cellular P content.
Cells limited by P showed a higher haemolytic activity than cells limited by N. The results suggest that toxicity in C. polylepis is strongly influenced by the physiological state of the algae. This may partially explain the large variability previously
observed in the toxicity of C. polylepis blooms. The potential ecological significance of our findings is also discussed.
Received: 18 November 1998 / Accepted: 5 July 1999 相似文献
20.
When aseptically-cultured sea anemones, Aiptasia pulchella, were incubated with 14C-labelled glucose, aspartate and glutamate, radioactivity was incorporated into animal protein. Radioactivity was recovered
from all amino acids in the protein hydrolysates of A. pulchella bearing the symbiotic alga Symbiodinium sp., and from all but seven of the amino acids in A. pulchella experimentally deprived of their algae. These data suggest that these seven amino acids (histidine, isoleucine, leucine,
lysine, phenylalanine, tyrosine and valine) may be synthesized by the symbiotic algae and translocated to the sea anemone's
tissues; and that methionine and threonine, two amino acids traditionally considered as dietary essentials for animals, are
synthesized by A. pulchella. Essential amino acid translocation from the symbiotic algae to the animal host is a core element in symbiotic nitrogen-recycling.
Its nutritional value to the animal host is considered in the context of the amino acid biosynthetic capacity of the host.
Received: 26 October 1998 / Accepted: 28 June 1999 相似文献