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1.
The experiments were undertaken to measure, for the first time, cardiac output in yellowtail (Seriola quinqueradiata) during exposure to a harmful red tide flagellate (Chattonella marina). The responses were compared with those during exposure to environmental hypoxia to evaluate the significance of the drop of arterial oxygen partial pressure (PaO2) in the fish-kill mechanisms by C. marina. PaO2 immediately decreased, whereas heart rate (HR) was maintained until shortly before death during exposure to C. marina. Suffocation developing during the exposure resulted from a decrease in blood oxygen content, but not from lowered blood flow to the tissue. Although exposure to both C. marina and hypoxia immediately decreased PaO2, arterial oxygen content (CaO2) and pH (pHa) were significantly lower, whereas HR and cardiac output (&Qdot;) remained significantly higher, for the C. marina-exposed fish than for hypoxia-exposed fish. Although the drop in PaO2 appears to play a pivotal role in the mechanisms of fish death by C. marina, other physiological response(s) should also be considered. 相似文献
2.
Echinoderms are major predators of anemones in temperate ecosystems. The fate of two algae, zooxanthellae and zoochlorellae, after their host anemone (Anthopleura elegantissima Brandt) was consumed by the leather star Dermasterias imbricata Grube was determined in experiments conducted in July and August 2004. Productivity, photosynthetic pigments, and mitotic index (percent of cells dividing) were used as indicators of algal health; algae released after leather stars consumed their host were compared with algae freshly isolated from anemones. Two types of waste products contained algae: pellets resulting from extraoral digestion, and feces. Zooxanthellae and zoochlorellae isolated from these waste products were photosynthetic, although to different extents. For algae from feces and pellets, light-saturated photosynthetic rates (P
max) were 85 and 13%, respectively, of P
max of freshly isolated zooxanthellae; and were 20 and 46%, respectively, for zoochlorellae. The photosynthetic pigments and mitotic index (percent of dividing cells) were not altered by the feeding activities of the leather star. These results show that algae released by seastar predation on their hosts remain viable, and are hence available for establishing symbioses in A. elegantissima and other potential hosts. 相似文献
3.
A strain of Alexandrium leei Balech that was isolated in October 2002 from Singapore coastal waters and identified by light and scanning electron microscopy and phylogenetic analysis using LSU rDNA sequences, is toxic to Asian sea bass fingerlings (Lates calcarifer Bloch). The ichthyotoxicity of the algal cells obtained by filtration (15 μm mesh net) and rinsed with sterile culture medium indicated that the toxicity of A. leei was probably not due to bacterial contamination, which was further supported by a negative correlation between the time to death of the fish and the dosage of algal cells applied. Paralytic shellfish toxins (PST) could not be detected indicating that PST was not the cause of fish mortality. Fish bioassays using frozen culture, heat-treated cultures, cell-free culture medium, and hexane, ethyl acetate, and water extracts of algal cells indicated that A. leei produces a heat-stable, polar ichthyotoxin(s) which can be released from the algal cells into the culture medium. Phylogenetic analysis based on the LSU rDNA sequences of A. leei confirmed its identification and indicated that the Singapore strain is more similar to isolates from Malaysia than to a geographically distant strain from Korea. This is the first evidence of icthyotoxin production by A. leei. 相似文献
4.
Bruna Plese Vladislav A. Grebenjuk Heinz C. Schröder Hans J. Breter Isabel M. Müller Werner E. G. Müller 《Marine Biology》2008,153(6):1219-1232
The cDNA sequence coding for tauropine dehydrogenase (TaDH) [belonging to the family of opine dehydrogenases] has been determined.
Using the demosponge Suberites domuncula, we describe for the first time the tauropine dehydrogenase gene (of length 2,992 kb) from a eukaryote, consisting of two
introns flanked by three exons. Moreover, two allelic variants have been identified, which are present in the different specimens
either in a homozygotic or in a heterozygotic way; the data suggest an intermediary type of heritance. Phylogenetic analyses
indicate that S. domuncula TaDH is only distantly related to the opine dehydrogenases from marine invertebrates; rather it comprises high sequence similarity
to bacterial ornithine cyclodeaminases (OCD). In addition, expression studies revealed that the steady-state level of TaDH
dropped drastically in animals, which had been exposed to elevated aeration. Antibodies raised against the recombinant sponge
TaDH were used to demonstrate that S. domuncula expresses high levels of this enzyme in almost all cells. If tissue samples were kept under additional aeration no immuno-signals
could be identified. A strong accumulation of the enzyme was seen around the bacteria, existing in bacteriocytes, indicating
that under aerobic conditions the bacteria might produce taurine. These data suggest involvement of the sponge TaDH in the final step of the glycolytic pathway, more specifically, in regeneration of NAD(+) under anaerobic conditions. Furthermore,
potential mutual influences between bacteria and sponge are discussed, claiming a horizontal gene transfer of the gene from
a bacterium to the sponge.
The following sequences from Suberites domuncula have been deposited (EMBL/GenBank): the cDNA encoding the tauropine [(carboxyethyl)-taurine/derived from sulfhydryl-amino
acids] dehydrogenase (SD_TaDH) under AM712888; the corresponding gene under AM712889; and the fragments of the sponge-associated bacteria comprising the
opine dehydrogenase domain: SUBDO_BAC1 (AM712890), SUBDO_BAC2 (AM712891), SUBDO_BAC3 (AM712892), SUBDO_BAC5 (AM712894), SUBDO_BAC6
(AM712895), SUBDO_BAC7 (AM712896), SUBDO_BAC8 (AM712897) and SUBDO_BAC9 (AM712898). 相似文献
5.
While qualitative observations of jellyfish intraguild predation abound in the literature, there are only few rate measurements
of these interactions. We quantified predation rates among two common jellyfish in northern boreal waters, Cyanea capillata and its prey Aurelia aurita, both of which also feed on crustacean zooplankton and fish larvae. A series of incubation experiments using a wide range
of prey concentrations (0.38–3.8 m−3) in large containers (2.6 m3) was carried out. By replenishing the prey continuously as they were captured we maintained a nearly constant prey concentrations.
Ingestion rates increased linearly up to prey concentrations of 1.92 m−3, yielding maximum clearance rates of ∼2.37 ± 0.39 m3 predator−1 h−1 for C. capillata predators 16 ± 2.3 cm in diameter. Mean ingestion rate at saturated prey concentrations (1.92–3.85 m−3) was 4.01 ± 0.78 prey predator−1 h−1. Behavioral observations suggested that predators did not alter their swimming behavior during meals, and thus that feeding
rates were generally handling limited rather than encounter limited. Predators captured more prey than needed, and semi-digested
prey was often discarded when fresh prey was encountered. 相似文献
6.
Andrea Gori Sergio Rossi Elisa Berganzo Joan Lluis Pretus Mark R. T. Dale Josep-Maria Gili 《Marine Biology》2011,158(1):143-158
Most of the current knowledge on Mediterranean gorgonians is restricted to investigations of those populations found within
shallow sublittoral waters, and only limited data are available for populations located below scuba depth. To overcome this
lack of information, the occurrence and abundance of the gorgonians Eunicella singularis, Paramuricea clavata, and Leptogorgia sarmentosa were investigated in northwestern Mediterranean benthic communities over a wide geographical (60 km of coastline) and bathymetrical
(0–70 m deep) extent using a remotely operated vehicle (ROV). The greatest occurrence and abundances of E. singularis and P. clavata were concentrated in areas that are directly exposed to strong near-bottom currents. E. singularis was the most common and abundant species and displayed great plasticity and amplitude in its environmental preferences. Conversely,
P. clavata showed a very patchy distribution that was associated with vertical rocky walls. Only isolated colonies of L. sarmentosa were observed in the study area. Hot spots of abundance of E. singularis and P. clavata were identified below a depth of 40 m, which demonstrates the importance of studying the distribution of benthic species
over a wide geographical and bathymetrical extent. 相似文献
7.
Fine-scale movement patterns in penaeid prawns are rarely observed in situ, but are essential in understanding habitat use,
foraging, and anti-predator behaviour. Acoustic telemetry was applied to examine the activity, space utilization, and habitat
use of the eastern king prawn Penaeus (Melicertus) plebejus, at small temporal and spatial scales. Tracking of sub-adult P. plebejus (n = 9) in Wallagoot Lake (36.789°S, 149.959°E; 23 April–12 May 2009) and calculation of a minimum activity index (MAI) revealed high variation in activity rates across diel periods and in different habitats. Elevated activity rates and movement
indicated foraging in unvegetated habitats during the night. Areas within the 95 and 50% space utilization contours averaged
2,654.1 ± 502.0 and 379.9 ± 103.9 m2, respectively, and there was a significant negative relationship between these areas and prawn activity rates in unvegetated
habitats. This study provides the first estimates of prawn activity rates and space utilization in the field. Application
of acoustic telemetry can increase knowledge of prawn movements and their interactions with other marine species in different
habitats. 相似文献
8.
Structure and complexity of the substrate are important habitat characteristics for benthic epifauna. The specific growth and mortality rates and inducible defence characters on medium-sized blue mussels (Mytilus edulis L.) exposed to shore crabs (Carcinus maenas L.) were examined on three different substrate types in combined field and laboratory experiments. The experiments showed that complexity of the substrate increased blue mussel survival significantly, through a decrease in predation pressure. However, increased intraspecific competition for food on the complex substrate resulted in significantly lower growth rates of the mussels. Inducible defence characters were also influenced by substrate type. Blue mussels were more affected by predators on the structurally simple substrate, where they developed thicker shells and a larger posterior adductor muscle. 相似文献
9.
Baraka Kuguru Gidon Winters Sven Beer Scott R. Santos Nanette E. Chadwick 《Marine Biology》2007,151(4):1287-1298
Corallimorpharians may dominate some habitats on coral reefs and compete with stony corals for access to light, yet little
is known concerning their photosynthetic traits. At Eilat in the northern Red Sea, we observed that the abundance of individuals
of the corallimorpharian Rhodactis rhodostoma decreased significantly with depth on the reef slope. Field and laboratory experiments revealed that they employ several
mechanisms of photoadaptation to high irradiance on the shallow reef flat. Their endosymbiotic microalgae (zooxanthellae)
varied significantly in both abundance and chlorophyll content with level of irradiance. Use of a diving pulse amplitude modulated
fluorometer revealed that the zooxanthellae of R. rhodostoma effectively disperse excess light energy by expressing significantly higher values of non-photochemical quenching and maximum
excitation pressure on photosystem II when experimentally exposed to high light (HL) versus low light (LL). Host corallimorpharian
tissues mediated this response by shielding the algal symbionts from high irradiance. The endoderm of host tentacles thickened
significantly and microalgal cells were located further from the mesoglea in HL than in LL. The clades of zooxanthellae hosted
by the corallimorpharians also varied with depth. In shallow water, all sampled individuals hosted clade C zooxanthellae,
while in deep water the majority hosted clade D. The photosynthetic output of individuals of R. rhodostoma was less affected by HL than was that of a stony coral examined. When exposed to both high temperature (HT) and HL, individuals
of R. rhodostoma reduced their maximum quantum yield, but not when exposed to HL at low temperature (LT). In contrast, colonies of the scleractinian
coral Favia favus reduced their photosynthetic output when exposed to HL in both temperature regimes. After 2 weeks of HT stress, R. rhodostoma polyps appeared to bleach completely but re-established their zooxanthella populations upon return to ambient temperature.
We conclude that mechanisms of photoadaptation to high irradiance employed by both the endosymbiotic zooxanthellae and host
corallimorpharians may explain in part the abundance of R. rhodostoma on some shallow reef flats. The ability to survive for weeks at HT while bleached also may allow corallimorpharians to repopulate
shallow reef areas where scleractinians have been killed by thermal stress.
B. Kuguru and G. Winters contributed equally to this work. 相似文献
10.
Mirna H. R. Seleghim Simone P. de Lira Patrícia T. Campana Roberto G. S. Berlinck Marcio R. Custódio 《Marine Biology》2007,150(5):967-975
Ascidians are a notable source of nitrogen-bearing secondary metabolites with a wide range of biological activities. Although
many biologically active compounds have been isolated from ascidians, it is often unclear whether the animal or associated
microbial symbionts such as bacteria or fungi are the true biosynthetic source of the metabolites. We have addressed the question
of the biosynthetic source of the alkaloids granulatimide and isogranulatimides by localizing these compounds within the ascidian.
In this work, we demonstrate that granulatimide is stored in Didemnum
granulatum tunic bladder cells. Analysis by confocal fluorescence microscopy at the granulatimide emission range indicated the presence
of fluorescent cells as highly vacuolated cells found dispersed in the ascidian tunic. Since this is the most exposed ascidian
tissue, it is possible that these alkaloids may have a protective role, either as sunscreens and/or as feeding deterrents. 相似文献
11.
The euphausiids Thysanoessa inermis (Kroyer 1846), Thysanoessa spinifera (Holmes 1900), and Euphausia pacifica (Hansen 1911) are key pelagic grazers and also important prey for many commercial fish species in the Gulf of Alaska (GOA).
To understand the role of the euphausiids in material flows in this ecosystem their growth rates were examined using the instantaneous
growth rate (IGR) technique on the northern GOA shelf from March through October in 2001–2004. The highest mean molting increments
(over 5% of uropod length increase per molt) were observed during the phytoplankton bloom on the inner shelf in late spring
for coastal T. inermis, and on the outer shelf in summer for T. spinifera and more oceanic E. pacifica, suggesting tight coupling with food availability. The molting rates were higher in summer and lower in spring, for all species
and were strongly influenced by temperature. Mean inter-molt periods calculated from the molting rates, ranged from 11 days
at 5°C to 6 days at 8°C, and were in agreement with those measured directly during long-term laboratory incubations. Growth
rate estimates depended on euphausiid size, and were close to 0 in early spring, reaching maximum values in May (0.123 mm day−1 or 0.023 day−1 for T. inermis) and July (0.091 mm day−1 or 0.031 day−1 for T. spinifera). The growth rates for E. pacifica remained below 0.07 mm day−1 (0.016 day−1) throughout the season. The relationship between T. inermis weight specific growth rate (adjusted to 5°C) and ambient chlorophyll-a concentration fit a Michaelis–Menten curve (r
2 = 0.48) with food saturated growth rate of 0.032 day−1 with half saturation occurring at 1.65 mg chl-a m−3, but such relationships were not significant for T. spinifera or E. pacifica. 相似文献
12.
Fleur E. Champion de Crespigny Nina Wedell 《Behavioral ecology and sociobiology》2007,61(8):1229-1235
The maternally inherited bacterium Wolbachia pipientis generates strong reproductive incompatibilities between uninfected females and infected males (cytoplasmic incompatibility),
significantly reducing both female and male reproductive success. Such fitness costs are thought to place selective pressure
on hosts to evolve pre-copulatory preferences for mating with compatible mates, thereby enabling them to avoid the reproductive
incompatibilities associated with Wolbachia. Therefore, uninfected females are predicted to prefer mating with uninfected males, whereas infected males are predicted
to prefer mating with infected females. Despite these predictions, previous investigations of pre-copulatory mate preferences
in Wolbachia-manipulated Drosophila have not found evidence of female preference for uninfected or compatible males. However, none of these studies utilised
a design where focal individuals are provided with a simple choice in a relatively non-competitive situation. We examined
both female and male pre-copulatory mate preference based on mate infection status in Drosophila simulans and D. melanogaster using simple choice assays involving between 30–50 replicates per treatment. Although we found no evidence of female pre-copulatory
mate preferences in either species, male D. simulans exhibited some preference for mating with females of the same infection status. However, this preference was not evident
when we repeated the experiment to confirm this finding. Consequently, we conclude that neither male nor female D. melanogaster and D. simulans exhibit significant Wolbachia-associated pre-copulatory mate preferences. 相似文献
13.
Susanna Andersson 《Chemoecology》2003,13(1):1-11
Summary. For butterflies to be efficient foragers, they need to
be able to recognize rewarding flowers. Flower signals such as colours
and scents assist this recognition process. For plant species to attract
and keep butterflies as pollinators, species-specific floral signals are
crucial. The aim of this study is to investigate foraging responses to
floral scents in three temperate butterfly species, Inachis io L.
(Nymphalidae), Aglais urticae L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae), in behavioural choice
bioassays. The butterflies were allowed to choose bet-ween flower models
varying in scent and colour (mauve or green). Flowers or vegetative
parts from the plants Centaurea scabiosa L. (Asteraceae),
Cirsium arvense (L.) (Asteraceae), Knautia arvensis (L.)
(Dipsacaceae), Buddleja davidii Franchet (Loganicaeae), Origanum vulgareL. (Lamiaceae), Achillea millefolium L. (Asteraceae), and
Philadelphus coronarius L. (Hydrangiaceae) were used as scent
sources. All visits to the models — those that included probing and
those that did not — were counted, as was the duration of these
behaviours. Both flower-naive and flower-experienced (conditioned to
sugar-water rewards, the colour mauve, and specific floral scents)
butterflies were tested for their preference for floral versus
vegetative scents, and to floral scent versus colour. The butterflies
were also tested for their ability to switch floral scent preferences in
response to rewards. Flower-naive butterflies demonstrated a preference
for the floral scent of the butterfly-favourable plants C.
arvense and K. arvensis over the floral scent of the non-favourable
plants Achillea millefolium (Asteraceae), and Philadelphus
coronarius cv. (Hydrangiaceae). Most of the butterflies that were
conditioned to floral scents of either C. arvense, K. arvensis,
or B. davidii readily switched theirfloral scent preferences to
the one most recently associated with reward, thus demonstrating that
floral scent constancy is a result from learning. These findings suggest
that these butterflies use floral scent as an important cue signal to
initially identify and subsequently recognize and distinguish among
rewarding plants.
Received 2 September 2001; accepted 9 September 2002. 相似文献
14.
Short-term (3 h) changes in concentration of chlorophylls and their derivatives in stage V Pseudodiaptomus euryhalinus and their fecal material were followed by HPLC during a 24 h experiment. Copepodites were fed with the prasinophyte Tetraselmis suecica. Intact chlorophyll a and b were found in animals and fecal material and had similar dynamics of accumulation over time. The extent of transformation of chlorophyll a and b to colorless compounds was different with chlorophyll a being more extensively degraded. Additionally, several chlorophyll derivatives (pheophytin and pyropheophytin-like pigments) were found. Pyropheophytin a was the most abundant followed by pheophytin b, pheophytin a, and pheophorbide a. Relative amounts of pheopigments were different in copepodites and fecal material, and pheophytin a, pheophorbide a, and pheophytin b concentrations were low and variable. The amount of ingested chlorophyll recovered as chlorophyll a and its derivatives in fecal and copepodite pools was generally low (<5%), with one exception occurring after 9 h, when it accounted for >70%. These data suggest individual pheopigments are produced at different rates and that chemical or enzymatic mechanisms in the gut of copepodites act on the two chlorophylls in different ways. 相似文献
15.
Susanna Andersson 《Chemoecology》2003,13(1):13-20
Summary. To better understand the biological role of floral scents for
butterflies, electrophysiological responses to floral scents were
investigated using combined gas chromatography and electroantennographic
detection (GC-EAD). The antennal responses of three butterfly species,
Aglais urticae L. (Nymphalidae), Inachis io L. (Nymphalidae), and
Gonepteryx rhamni L. (Pieridae) to floral scent compounds from both
natural and synthetic mixtures were examined. Floral scents were
collected from the butterfly nectar plants Cirsium arvense (L.)
(Asteraceae), and Buddleja davidii Franchet cv. (Loganicaeae) with
dynamic head-space methods on Tenax-GR and eluted with pentane. These
eluates, composed of natural floral scent blends, represent an array of
compounds in their natural state. In the GC-EAD analyses eleven
compounds were identified from C. arvense with the benzenoid compound
phenylacetaldehyde in highest abundance. Seventeen compounds were
identified from B. davidii with the irregular terpene oxoisophorone in
highest abundance. Thirty-nine synthetic floral scent compounds were
mixed in pentane, in equal amounts; about 35 ng were allowed to reach
the antennae. The butterflies showed antennal responses to most of the
floral scent compounds from both natural and synthetic blends except to
the highly volatile monoterpene alkenes. Certain benzenoid compounds
such as phenylacetaldehyde, monoterpenes such as linalool, and irregular
terpenes such as oxoisophorone, were emitted in relatively large amounts
from C. arvense and B. davidii, and elicited the strongest antennal
responses. These compounds also elicited strong antennal responses when
present in the synthetic scent blends. Thus, the butterflies seem to
have many and /or sensitive antennal receptors for these compounds,
which points to their biological importance. Moreover, these compounds
are exclusively of floral scent origin. For B. davidii, which depends
highly on butterflies for pollination, the exclusive floral scent
compounds emitted in high abundance could be the result of an adaptive
pressure to attract butterflies.
Received 2 Septemter 2001; accepted 9 September 2002. 相似文献
16.
R. Allen Brooks Martha S. Nizinski Steve W. Ross Kenneth J. Sulak 《Marine Biology》2007,152(2):307-314
The occurrence and relative abundance of tissue (arm) regeneration in the ophiuroid, Ophiacantha bidentata (Retzius), was examined in individuals collected primarily among colonies of the deep-water coral Lophelia pertusa off the southeastern United States. Seven deep-water coral sites (384–756 m), located between Cape Lookout, NC, and Cape
Canaveral, FL, were sampled in June 2004 using a manned submersible. The presence of regenerative tissue was evaluated by
visual inspection of each individual ophiuroid, and the proportion of regenerating arms per individual was examined relative
to size of individual, geographic location, and depth of collection. Ophiacantha bidentata, the dominant brittle star collected, commonly displayed signs of sublethal injury with over 60% of individuals displaying
some evidence of regeneration. These levels of regeneration rival those reported for shallow-water ophiuroids. Larger individuals
(>6.5 mm disc size) had a higher incidence of regeneration than smaller individuals. Size of individual and percent of regeneration
were negatively correlated with depth. Although O. bidentata was significantly less abundant in southern versus northern sites, ophiuroid abundance did not appear to be influenced by
amount or density of coral substratum. Presence of dense aggregations of O. bidentata indicates that they are an important component of the invertebrate assemblage associated with deep-water coral habitat especially
in the northern part of the study area. Assuming that observed frequencies of injury and subsequent regeneration represent
predation events then dense ophiuroid aggregations in deep-water coral habitats represent an important renewable trophic resource
within these communities. 相似文献
17.
J. Arrontes 《Marine Biology》2002,141(6):1059-1067
The intertidal brown alga Fucus serratus is naturally expanding its distributional range along the north shore of Spain. Shores being colonised by F. serratus harbour saturated algal communities, with almost no free space. Processes responsible for the successful expansion were investigated in a locality where the alga was experimentally introduced. After a short period, the number of F. serratus plants increased exponentially at a monthly intrinsic rate of 0.111. At early and intermediate stages of invasion, colonisation occurred by the growth of patches of the invader around the transplant points. F. serratus is a bad disperser, with most of propagules settling in near proximity to parent plants. Colonisation of manipulated and control areas was influenced by the proximity of propagule sources. Experimental removals of canopies, irrespective of whether the turf was removed or left intact, accelerated the expansion, as this component of the community had a negative influence on recruitment of both F. serratus and F. vesiculosus. The unmanipulated algal beds were, however, invasible, as some control quadrats close (<10 m) to F. serratus patches had a 100% cover of F. serratus at the end of the study. Prior or concurrent to increases of F. serratus, a decrease in cover of F. vesiculosus and other resident macroalgae was evident. No formal competition experiment was done but results suggest that F. serratus outcompetes F. vesiculosus and Bifurcaria bifurcata at mid-tidal levels. In scraped quadrats, in which both Fucus species recruited at large densities, F. serratus grew at a higher rate than F. vesiculosus and eventually monopolised the experimental surfaces. 相似文献
18.
Corals harbouring genetically mixed communities of endosymbiotic algae (Symbiodinium) often show distribution patterns in accordance with differences in light climate across an individual colony. However, the
physiology of these genetically characterised communities is not well understood. Single stranded conformation polymorphism
(SSCP) and real time quantitative polymerase chain reaction (qPCR) analyses were used to examine the genetic diversity of
the Symbiodinium community in hospite across an individual colony of Acropora valida at the spatial scale of single polyps. The physiological characteristics of the polyps were examined prior to sampling with
a combined O2 microelectrode with a fibre-optic microprobe (combined sensor diameter 50–100 μm) enabling simultaneous measurements of O2 concentration, gross photosynthesis rate and photosystem II (PSII) quantum yield at the coral surface as a function of increasing
irradiances. Both sun- and shade-adapted polyps were found to harbour either Symbiodinium clade C types alone or clades A and C simultaneously. Polyps were grouped in two categories according to (1) their orientation
towardps light, or (2) their symbiont community composition. Physiological differences were not detected between sun- and
shade-adapted polyps, but O2 concentration at 1,100 μmol photons m−2 s−1 was higher in polyps that harboured both clades A and C symbionts than in polyps that harboured clade C only. These results
suggest that the acclimatisation of zooxanthellae of individual polyps of an A. valida colony to ambient light levels may not be the only determinant of the photosynthetic capacity of zooxanthellae. Here, we
found that photosynthetic capacity is also likely to have a strong genetic basis and differs between genetically distinct
Symbiodinium types. 相似文献
19.
Great scallop, Pecten maximus, and blue mussel, Mytilus edulis, clearance rate (CR) responses to low natural seston concentrations were investigated in the laboratory to study (1) short-term
CR variations in individual bivalves exposed to a single low seston diet, and (2) seasonal variations in average CR responses
of bivalve cohorts to natural environmental variations. On a short temporal scale, mean CR response of both species to 0.06 μg L−1 chlorophyll a (Chl a) and 0.23 mg L−1 suspended particulate matter (SPM) remained constant despite large intra-individual fluctuations in CR. In the seasonal study,
cohorts of each species were exposed to four seston treatments consisting of ambient and diluted natural seston that ranged
in mean concentration from 0.15 to 0.43 mg L−1 SPM, 0.01 to 0.88 μg L−1 Chl a, 36 to 131 μg L−1 particulate organic carbon and 0.019 to 0.330 mm3 L−1 particle volume. Although food abundance in all treatments was low, the nutritional quality of the seston was relatively
high (e.g., mean particulate organic content ranged from 68 to 75%). Under these low seston conditions, a high percentage
of P. maximus (81–98%) and M. edulis (67–97%) actively cleared particles at mean rates between 9 and 12 and between 4 and 6 L g−1 h−1, respectively. For both species, minimum mean CR values were obtained for animals exposed to the lowest seston concentrations.
Within treatments, P. maximus showed a greater degree of seasonality in CR than M. edulis, which fed at a relatively constant rate despite seasonal changes in food and temperature. P. maximus showed a non-linear CR response to increasing Chl a levels, with rates increasing to a maximum at approximately 0.4 μg L−1 Chl a and then decreasing as food quantity continued to increase. Mean CR of M. edulis also peaked at a similar concentration, but remained high and stable as the food supply continued to increase and as temperatures
varied between 4.6 and 19.6°C. The results show that P. maximus and M. edulis from a low seston environment, do not stop suspension-feeding at very low seston quantities; a result that contradicts previous
conclusions on the suspension-feeding behavior of bivalve mollusks and which is pertinent to interpreting the biogeographic
distribution of bivalve mollusks and site suitability for aquaculture. 相似文献
20.
We examined the effects of elevated temperature under different exposure periods on larval settlement and post-settlement
survival in scleractinian corals, Acropora solitaryensis and Favites chinensis. In the first experiment with the subtropical coral, A. solitaryensis, the numbers of larvae settling and those dead were examined daily for 5 days at 20, 23 (ambient), 26 and 29°C conditions.
Larval settlement of A. solitaryensis was initially greater at higher temperature conditions, but the peak in number of settled larvae shifted from 29 to 26°C
by day 5, due to ca. 90% post-settlement mortality at 29°C condition. In order to determine the effects under short-term exposure,
larvae of F. chinensis were exposed to 27 (ambient), 31 or 34°C only for one hour in the second experiment. The number of larvae settling for 24 h
after the exposure and their survivorship over subsequent week was monitored in the ambient temperature condition. Larvae
of F. chinensis exhibited greater settlement at higher temperature treatments and constantly low post-settlement mortalities (< ca. 17%)
in all temperature treatments, resulting in the highest number of settled larvae at 34°C treatment. These results suggested
two different effects of elevated temperature on the early stages of recruitment process of scleractinian corals; (1) the
positive effect on larval settlement and (2) the negative effect on post-settlement survival under prolonged exposure. 相似文献