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1.
The relationship between intermoult duration (coloration), sex, size and seasonal variations in fatty acid (FA) profiles
was studied in a population of shore crabs, Carcinus maenas, inhabiting the Isefjord, Denmark. For male shore crabs, the total hepatopancreas FA content was high in July and December
(12.7 to 16.0 mg g−1 dry weight, dw) but lower in May and September (7.3 to 10.0 mg g−1). This indicates that male shore crabs are in relatively good condition before winter, when the crabs migrate off shore,
but in relatively poor condition when they return to shallow waters during spring. The hepatopancreas FA content also decreased
over the mating season. After the mating season the hepatopancreas FA content of males had decreased to approximately 60%
of that prior to the mating season. Female shore crabs had significantly higher hepatopancreas FA levels than males in May
(11.7 mg g−1 dw), September (12.6 mg g−1 dw) and December (17.9 mg g−1 dw) but lower levels in July (9.5 mg g−1 dw). This indicates that the spawning season is the most energy-demanding part of the female reproductive cycle. For all
seasons, the hepatopancreas FA content of green shore crabs was significantly higher than that of red shore crabs. For both
colour forms, the amount of polyunsaturated fatty acids (PUFAs) was significantly higher than that of saturated fatty acids
(SAFAs) and monounsaturated fatty acids (MUFAs), with the relative proportion of PUFAs increasing when the total hepatopancreas
FA content decreased. For both genders and colour forms, the most dominating SAFA was palmitic acid (16:0). Palmitoleic acid
(16:1ω7), vaccenic acid (18:1ω7) and oleic acid (18:1ω9) were the three MUFAs found in highest concentrations. The most dominating
PUFA was eicosapentaenoic acid (EPA, 20:5ω3). Docosahexaenoic acid (DHA, 22:6ω3) and arachidonic acid (AA, 20:4ω6) were also
abundant in all samples. The results demonstrated that season, sex, size and intermoult duration all influence the amount
of FAs present in the hepatopancreas of shore crabs.
Received: 23 September 1999 / Accepted: 29 April 2000 相似文献
2.
Cadmium accumulation in the female shore crab Carcinus maenas during the moult cycle and ovarian maturation 总被引:2,自引:0,他引:2
The influence of moulting and ovarian maturation on cadmium accumulation in the tissues of female shore crabs Carcinus maenas exposed to 1 mg Cd l−1 in the water was investigated. Cadmium accumulation in all tissues examined was markedly increased in crabs in the postmoult
stages (A and B) compared to crabs in all other moult stages. During the moult cycle, average cadmium accumulation in the
midgut gland ranged from 29 μg Cd g−1 dw at premoult stage (D2) to 589 μg Cd g−1 dw at postmoult stage (A). Average cadmium concentrations in the haemolymph ranged from 0.56 μg Cd ml−1 at intermoult stage (C4) to 4.6 μg Cd ml−1 at postmoult stage (A), while the gills accumulated from 103 μg Cd g−1 dw in intermoult stage (C3) to 352 μg Cd g−1 dw in postmoult stage (A). Cadmium concentration in gills and haemolymph was also significantly higher in crabs in late premoult
stage (D3) compared to C4-crabs, while midgut gland cadmium concentration remained elevated in C1- and C3- intermoult stages relative to C4. During ovarian maturation the cadmium accumulation in midgut gland, gills, ovaries and haemolymph decreased. Average cadmium
concentration in the midgut gland decreased from 63 μg g−1 dw in ovarian Stage I to 19 μg g−1 dw in ovarian Stage VI. The same pattern was observed for gills, haemolymph and ovaries. The present study demonstrates that
cadmium accumulation in the female shore crab strongly depends on the physiological status of the animal. A possible association
between physiological calcium requirements and cadmium accumulation during moulting is discussed.
Received: 20 January 2000 / Accepted: 20 July 2000 相似文献
3.
P. Bjerregaard 《Marine Biology》1990,106(2):199-209
Accumulation and binding of cadmium in the tissues of the shore crabCarcinus maenas (L.) were investigated in a series of laboratory experiments. The relation between the physiological condition of individual crabs and their ability to transport cadmium from haemolymph to hepatopancreas was specifically addressed. Cadmium was removed from the haemolymph with a half-life of approximately 10 h, and half of the cadmium removed from the haemolymph was taken up in the hepatopancreas. The efficiency with which individual crabs transported cadmium from the haemolymph to the hepatopancreas was strongly related to physiological parameters, such as concentrations of calcium and magnesium in the hepatopancreas and haemolymph volume and haemolymph protein concentration. The transport of cadmium from the haemolymph to the hepatopancreas was saturated in crabs exposed to more than 2 to 4 mg Cd l–1 in the sea water. In the hepatopancreas of unexposed crabs, cadmium was bound mainly in the insoluble tissue fraction (40%) and in the protein fraction with a molecular weight of approximately 6000 D (50%). Exposure to 0.25 to 1.5 mg Cd l–1 for 2 w led to dose-dependent increases of the amounts of cadmium bound in the high-molecular weight protein fraction and in the insoluble tissue fraction. Modes of internal cadmium transport and accumulation in tissues and variability in physiological parameters are discussed. 相似文献
4.
Calanoid copepod eggs in sea-bottom muds. IV. Effects of some environmental factors on the hatching of resting eggs 总被引:4,自引:0,他引:4
During cadmium uptake by the shore crab Carcinus maenas (L.), cadmium appears in both haemolymph and urine within 1 h, and comes into equilibrium with the haemolymp after some 60 h. The equilibrium concentration for haemolymph cadmium is always considerably less than that of the external medium, whether the latter is close to background level or at the artificially high concentration of 2.2 mg l-1. Despite earlier evidence that cadmium entering the haemolymph is mainly bound to protein, current results show most of this to be freely labile and quickly displaced by cadmium taken up subsequently. There is some evidence to suggest that cadmium is passed on from the haemolymph to the hepatopancreas. A large proportion of whole-body cadmium is adsorbed onto the exoskeleton and gills. The comparatively rapid efflux of 109Cd from loaded crabs over a period of 1 week is mainly due to desorption of this cadmium from the outer body surface. 相似文献
5.
The effect of photosynthetic available radiation (PAR) levels, light quality, ultraviolet (UV) radiation, and temperature
on photosynthesis, growth, and chlorophyll fluorescence was evaluated in red and green morphotypes of the rhodophyte Kappaphycus alvarezii (Doty) Doty under controlled conditions. Chlorophyll a and phycoerythrin (PE) levels were similar in the red and green morphotypes cultured under the same conditions, but phycocyanin
(PC) and allophycocyanin (APC) levels were 2-fold greater in the green than in the red morphotype. Pigment characterization
indicated that the overexpression of PC and APC masked the red pigmentation in the green morphotype. Maximum photosynthesis
and photosynthetic efficiency were similar between the two morphotypes assayed at a wide temperature range, which was reflected
in the similar growth rates observed in outdoor culture systems. In the green morphotype, photosynthetic efficiency increased
2-fold relative to the red morphotype when assayed with red light (λ > 600 nm), indicating that photosynthetic characteristics
are modified as a result of pigment variation in these morphotypes. Such increase in photosynthetic efficiency in the green
morphotype, however, did not result in greater growth rates when cultured under white light. Short exposure to high levels
of solar radiation (UV-A + UV-B + PAR), and filtered solar radiation (UV-A + PAR or PAR) decreased effective quantum yield
(ΔF/F
m′) in both morphotypes. The reduction of ΔF/F
m′ values in the red and green morphotypes was accounted for by high levels of PAR and not by the UV-A + UV-B + PAR and UV-A + PAR
treatments. Photoinhibition caused by UV-A, UV-B, or PAR was completely reversed within 30 h after incubations. Recovery rates
from photoinhibition, however, were significantly reduced in the green morphotype when incubated with UV-B radiation. The
results here suggest that the overexpression of pigments do not necessarily increase photosynthesis and growth in these morphotypes.
Received: 19 June 2000 / Accepted: 28 November 2000 相似文献
6.
Subcellular distribution of zinc and cadmium in the hepatopancreas and gills of the decapod crustacean Penaeus indicus 总被引:1,自引:0,他引:1
The decapod crustacean Penaeus indicus accumulated Cd and Zn in different subcellular compartments of hepatopancreas and gill cells. Most of the Cd and part of the Zn accumulates within the soluble fraction of the cells, while the remainder of the Zn is found in insoluble inclusions, associated with P, Ca, Mg and Si in B-, F- and R-cells in the hepatopancreas, and haemocytes, nephrocytes and epithelial cells in the gills. No presence of Cd was observed in metal-rich inclusions in any cell analysed. Metallothionein-like proteins (MTLP), analysed by differential pulse polarography, were present in the hepatopancreas (12–18 mg g−1) and gills (7–8 mg g−1) of metal-exposed prawns. Binding to MTLP is the detoxification mechanism for cadmium, while the detoxification of zinc involves both binding to MTLP and incorporation into insoluble metal-rich inclusions. 相似文献
7.
Automated interpulse duration assessment (AIDA) in the shore crab Carcinus maenas in response to copper exposure 总被引:1,自引:0,他引:1
The effects of acute (24 h) and chronic (4␣weeks) copper exposure and subsequent recovery in “clean” conditions on cardiac
activity were examined in shore crabs ( Carcinus maenas). Cardiac activity was monitored by automated interpulse duration assessment (AIDA) which permits detection of irregularities
in cardiac rhythms in selected invertebrates. Mean interpulse durations, maximum interpulse durations and coefficients of
variation were significantly affected by exposure to copper for 24 h and 4 weeks. Mean interpulse durations decreased reflecting
an increase in heart rate, whereas maximum interpulse durations and coefficients of variation increased with increasing exposure
concentration. Recovery of normal cardiac activity was evident following a 6-week recovery period in “clean” conditions. However,
high levels of mortality were seen among crabs exposed to the two highest copper concentrations (0.6 and 0.8 mg l−1 Cu). The extent of recovery was assessed by subjecting the surviving crabs to a physiological challenge. There were no apparent
differences in circulatory response to physiological challenge between crabs previously exposed to copper and control crabs.
Gill copper concentrations were significantly elevated in crabs that had previously been exposed to copper, despite their
return to “clean” sea water for 6 weeks. Midgut gland wet weight/dry weight ratios, haemolymph total protein and midgut gland
metallothionein concentrations did not reflect the previous copper exposure. The findings of the present study indicate that
AIDA may be a valuable tool for use in toxicity testing.
Received: 24 March 1997 / Accepted: 21 October 1997 相似文献
8.
The relations between genetic variation, physiological condition, size and metal status in the shore crab Carcinus maenas (L.) were investigated. Shore crabs were collected at three sites around the island of Funen, Denmark, and carapace width, colour, moulting stage and major ions and protein in the haemolymph were determined. Concentrations of water, cadmium, copper and zinc in midgut glands, muscles and gills were measured, and allozyme variation at 15 loci was studied. Generally, tissue water content and copper, zinc and cadmium concentrations decreased from the moulting stages C3 over C4 to D crabs, whereas the opposite was true for copper and zinc concentrations in gills and muscle. However, the water content of the tissues increased with the size of the crabs. Since tissue water contents changed consistently over moulting stages, conclusions on changes in metal concentrations sometimes diverged when expressed on a dry versus wet weight basis. Regarding allozymes, esterase, malate dehydrogenase and phosphoglucomutase were polymorphic. The crabs showed a low level of genetic variability for both polymorphism (0.14) and for heterozygosity (0.07) at the three sites. Allelic frequencies showed very low levels of differentiation among the samples, no evidence of inbreeding and no population subdivision. Multilocus heterozygosity was positively correlated with size. Concentrations of copper and zinc in midgut gland, muscle tissue and gill were not correlated with genotype, whereas a weak correlation between phosphoglucomutase genotypes and concentrations of cadmium in the midgut gland was found.Communicated by M. Kühl, Helsingør 相似文献
9.
I. M. Davies G. Topping W. C. Graham C. R. Falconer A. D. McIntosh D. Saward 《Marine Biology》1981,64(3):291-297
The distribution of cadmium within captive crabs (Cancer pagurus) exposed experimentally to cadmium-contaminated food and water is described and illustrated by triangular diagrams. Crabs from the Orkney Islands (Scotland) are known to contain relatively high levels of cadmium (up to 62 g g-1 wet wt) in the hepatopancreas. The distribution of cadmium between the hepatopancreas, gonad, gill, carapace, claw muscle, heart, and haemolymph, is described in crabs collected during 1978, and compared with similar data from crabs exposed to cadmium for ca. 300 d (September 1978 – June 1979) experimentally. It is concluded that the dominant uptake route of cadmium to Orkney crabs is through their diet. 相似文献
10.
RNA:DNA ratios of larval and juvenile red drum (Sciaenops ocellatus) collected from nursery habitats in the Aransas Estuary, Texas, in 1994 were quantified using a highly sensitive ethidium-bromide
fluorometric technique. RNA:DNA ratios of wild red drum were evaluated by comparing individual values to a linear regression
model derived for starved laboratory-reared red drum. Wild red drum were in relatively good condition with <5% of the RNA:DNA
ratios within or below the 95% prediction interval of 4 to 5 d starved red drum. A multiple-regression model explained 54%
of the variability in the RNA:DNA ratio of wild red drum, and identified length and water temperature (midday) as significant
factors. RNA:DNA ratios increased with fish length [≃1.1 mm−1, over the size range investigated (5␣to 20 mm)]. The effect of temperature on the RNA: DNA ratio was assessed on different
sampling trips, and ratios increased with increasing temperature. Abundance of larval and juvenile red drum in the Aransas
Estuary varied as a function of both habitat (shoal grass Halodule wrightii, turtle grass Thalassia testudinum) and site (Aransas Bay, Redfish Bay); however, no differences in RNA:DNA ratios were detected between habitats or between
sites. It is postulated that the nutritional condition of newly settled red drum from the Aransas Estuary in 1994 was relatively
high, and that starvation was of minor importance.
Received: 19 August 1996 / Accepted: 23 August 1996 相似文献
11.
Weapon size versus body size as a predictor of winning in fights between shore crabs, Carcinus maenas (L.) 总被引:4,自引:0,他引:4
Lynne U. Sneddon Felicity A. Huntingford Alan C. Taylor 《Behavioral ecology and sociobiology》1997,41(4):237-242
Relative body size (carapace width) and weapon size (chela length) were used as indicators of resource holding potential (RHP)
in the agonistic behaviour of male shore crabs, Carcinus maenas (L.). Weapon size was found to be a more reliable predictor of the outcome of pairwise fights than body size. Crabs with
longer chelae than their opponents were more likely to win fights than crabs with relatively larger bodies. Body size had
less influence on the outcome of fights. Relative body and weapon size did not influence initiation of contests but did affect
the likelihood of winning; however, this was significant only for weapon size. Winning crabs had heavier claws with greater
surface area than losing crabs. There was no relationship between relative size and fight duration. The frequency of cheliped
display increased with chela length and win- ners performed significantly more displays than losers.
Received: 5 February 1997 / Accepted after revision: 20 May 1997 相似文献
12.
This study was carried out between January and March 1995 on the intertidal sand flats of Tang Khen Bay, Phuket, South Thailand,
where the soldier crab Dotilla myctiroides (H. Milne-Edwards) occurs in densities of up to 120 m−2. In this bay, long, ribbon-like sand waves (wavelength 40 m, height 0.4 m) are interspersed with shallow pools, running approximately
parallel to the shore. During daylight low-tides, exposure of the sand waves is followed 15 to 20 min later by the emergence
of the crabs which have been buried under the sediment surface during high tide. Their subsequent burrowing and feeding activity
results in the production of large numbers of sand pellets on the sediment surface. Most crabs retreat down their burrows,
and some also plug the burrow entrance, prior to being covered by the incoming tide. The crab burrows have a distinct distribution
on the sand waves. Burrows are most dense at the top of each sand wave, and a band of unburrowed sediment adjoins the adjacent
tidal pools. Crabs are most abundant between mean high-water neap-tide level and mean low-water neap-tide level, where the
median particle size of the surface sediment is ∼2 . Measurements of water-table depth below the sand waves and the exposure
time of the sediment indicated that, where sediment size is suitable, the main factor controlling crab distribution is the
duration of daytime exposure. This observation is in contrast to those of many previous studies, which have suggested that
water-table height and sediment drainage are the main factors controlling the distribution of D. myctiroides.
Received: 14 January 1998 / Accepted: 6 May 1999 相似文献
13.
Chitobiase activity in the epidermis and hepatopancreas of the fiddler crab Uca pugilator during the molting cycle 总被引:5,自引:0,他引:5
The activity of chitobiase, also known as N-acetyl-β-glucosaminidase, in the epidermis and hepatopancreas of the fiddler crab Uca pugilator (Bosc, 1802), during the molting cycle, was investigated. A pH optimum of 5 to 6 was found for the enzymatic activity in
both the epidermis and hepatopancreas. The temperature optimum for epidermal and hepatopancreatic chitobiase activities was
50 to 60 °C. The K
m values for epidermal and hepatopancreatic chitobiase activities at 19 °C were 0.190 ± 0.027 and 0.203 ± 0.016 mM 4-methylumbelliferyl-N-acetyl-β-glucosaminide, respectively. Hepatopancreatic chitobiase activity was significantly higher than epidermal enzymatic
activity in all the molt cycle stages tested except Postmolt Stage A-B. Chitobiase activity varied significantly during the
molting cycle, with the epidermal enzymatic activity in Premolt Stage D3–4 significantly higher than in Stage C (intermolt) and Premolt Stage D0, whereas hepatopancreatic chitobiase activity in Premolt Stage D3–4 was significantly higher than in all other molt stages tested. The patterns of chitobiase activity in the epidermis and hepatopancreas
correlate well with the hemolymph titer of ecdysteroids in U. pugilator during the molting cycle; this suggests that chitobiase activity in both tissues is regulated at least in part by the steroid
molting hormones.
Received: 6 May 1998 / Accepted: 12 September 1998 相似文献
14.
Activity pattern and spatial strategy in Pachygrapsus marmoratus (Decapoda: Grapsidae) from Mediterranean and Atlantic shores 总被引:2,自引:0,他引:2
The spatial strategies and activity patterns of two populations of Pachygrapsus marmoratus (Fabricius), from Italy and Portugal, were studied in the field. The Mediterranean site was a non-tidal splash zone about
30 cm wide, while the Atlantic site was a 30 m wide intertidal belt. Almost all P. marmoratus of both populations were active on the emerged rocks, rarely entering the sea. The Mediterranean crabs actively fed on the
algal turf throughout the 24 h, while in Portugal active crabs were more numerous at night. In the Italian population, all
crabs were packed together, although large males had larger activity areas than females and smaller males. In Portugal, the
large males were more concentrated in the sublittoral fringe, while both small males and females were confined to the eulittoral
and littoral fringe. The Italian P. marmoratus performed feeding loops within areas smaller than 9 m2. Although most Portuguese crabs showed the same spatial strategy, some of them performed feeding migrations to the sublittoral
fringe, covering distances of up to 20 m. Environmental factors (e.g. temperature), physical factors (e.g. refuge availability)
and biotic factors (e.g. competitors and predators) of the different shores probably determine the behavioural plasticity
of␣P.␣marmoratus.
Received: 1 February 1998 / Accepted: 13 November 1998 相似文献
15.
Physiological studies were made on the crabs Ucides cordatus (L.) and Callinectes danae sampled from populations living in “polluted” mangroves on the southeast littoral of Brazil. Analysis of Cu, Cd, Zn, and
Fe of sediments and crab tissues showed interspecific differences in tissue concentrations, and significantly higher levels
of Cu, Cd, and Zn in “polluted” populations compared to “unpolluted” crabs living in uncontaminated mangrove in the same geographical
area. Individuals of both species from the polluted site showed significantly greater capacities for regulating blood osmotic
concentrations at low salinity (9‰). However, U. cordatus showed a reduced hypo-regulatory ability in 34‰S. Differences in ionoregulation were also seen. “Polluted”C. danae showed significantly higher Na/ K-ATPase levels in posterior gills compared to “unpolluted” crabs. Oxygen consumption rates
(M˙
O2) were elevated in U. cordatus, but depressed in C. danae from the “polluted” population. Individuals of both species from this site showed significantly lower O:N ratios, mainly
because of an increased net efflux of ammonia. Adenylate energy charge (AEC) values of muscle and hepatopancreas in “unpolluted”
and “polluted” populations of both species were not significantly different. These physiological differences are discussed
in relation to the known acute physiological and metabolic effects of heavy metals in crustaceans, and interpretated in the
light of possible adaptive changes following long-term exposure to contamination.
Received: 6 August 1999 / Accepted: 22 June 2000 相似文献
16.
Perfusing and bathing isolated gills of shore crabs Carcinus maenas with artificial saline or sea (brackish) water enabled us to determine potential differences (PDs) between ambient bathing medium and perfusion solution. Establishment of diffusional PDs was avoided by employment of the same solution on the internal and external side. The PDs measured were therefore of an active nature. We compared the properties of the PDs with the well-known properties of the Na-K-ATPase: dependence on biological energy (ATP), on salinity and sodium concentration, susceptibility of PD to depletion of internal K and to the addition of 5 mM internal ouabain. Considering also the magnitude of the PDs measured, the results obtained indicate that it is the Na-K-ATPase that generates an active transport potential for Na in the gills of shore crabs. This PD represents the driving force for the active uptake of Na in crabs that hyperregulate their body fluids when they inhabit environments of reduced salinity regimes or fluctuating salinities in tidal estuaries. This process counteracts diffusional losses of Na in crabs exposed to dilute media. 相似文献
17.
A key regulatory mechanism underlying the switch between aerobic and anaerobic metabolism amongst anoxia-tolerant marine
molluscs is reversible protein phosphorylation. To assess the role of cAMP-dependent protein kinase (PKA) in aerobic–anaerobic
transitions, the effects of anoxia on the activity and subcellular distribution of PKA were assessed in foot and hepatopancreas
of the marine periwinkle, Littorina littorea. Exposure to N2 gas at 5 °C caused a rapid decline in the percentage of total enzyme present as the free catalytic subunit (PKAc) in both
tissues; the percentage of PKAc fell from ∼30% in controls to 3% after 1 h anoxia and remained low over 72 h. Total PKA also
fell by 30% after 72 h anoxia in hepatopancreas but rebounded during aerobic recovery. Freezing at −8 °C elicited parallel
results for both percentage of PKAc and total PKA, suggesting that PKA responses to freezing were stimulated by the ischemia
that develops when hemolymph freezes. Anoxia also led to a shift in PKA subcellular distribution in hepatopancreas (but not
in foot), the percentage of total PKA activity associated with the nuclear fraction dropping from 25% in controls to 8% in
12 h anoxic snails with opposite changes in the cytosolic fraction. The catalytic subunit (PKAc) of foot PKA was purified
to a final specific activity of 63.5 nmol phosphate transferred per minute per milligram protein. Enzyme properties included
a molecular weight of 33 to 35 kDa, an activation energy from Arrhenius plots of 65.1 ± 4.8 kJ mol−1, and substrate affinity constants of 151 ± 6 μM for the phosphate acceptor, Kemptide, and 72 ± 9 μM for Mg.ATP. Activity was strongly reduced by mammalian PKA inhibitors (H-89, PKA-I), by neutral chloride salts (I50 values 165 to 210 mM) and by NaF (I50 62 mM). Reduced PKA activity under anoxic or freezing conditions would facilitate the observed suppression of the activities of
numerous enzymes that are typically PKA-activated and thereby contribute to the overall anoxia-induced metabolic rate depression.
Received: 19 November 1997 / Accepted: 30 September 1998 相似文献
18.
N. Aizawa 《Marine Biology》1998,131(3):523-532
In several species of ocypodid crabs, including Ilyoplax pusilla (De Haan), waving displays tend to be synchronized among neighboring individuals. However, no quantitative study has yet
been conducted. In this study, responses of I. pusilla males to waving of video and real crabs were examined. Spontaneous, periodic waving was observed even when no stimulus waves
were present. When single isolated waves of the video crab were randomly delivered (single pulse perturbation), crabs waved
either immediately after the stimuli or after some time had elapsed. Assuming that waves immediately after the stimuli were
triggered prior to those stimuli, crabs typically responded after a roughly constant delay from the onset of each stimulus.
The delay (response time) was close to, but slightly shorter than, the spontaneous wave period. Dependency of response time
upon timing of the stimulus (stimulus time) was at most weak. Responses of crabs to periodic waves of the video crabs and
waves of␣the real crabs were basically consistent with the results of single pulse perturbation, although there was a consistent
tendency for stimulus time and response time to be negatively correlated near stimulus time = 0 s. Overall, these results
demonstrate that males of I. pusilla adjust signal timing relative to a neighbor in a manner of phase delay synchrony. The similar response pattern has also been
noted in synchronous flashing of fireflies and the calling of katydids. Moreover, these experiments with I.␣pusilla demonstrate the value of video playback as a research tool in this species.
Received: 4 April 1997 / Accepted: 17 December 1997 相似文献
19.
The euryalinid brittle-star (snake star) Astrobrachion constrictum (Farquhar) lives coiled around the branches of black coral (Antipathes fiordensis) colonies. Twenty-two vertical transects, 10 m wide by 30 m deep, were swum in Doubtful Sound over a 2.5 yr period from 1993
to 1995. Numbers, disc diameters and colour morphotypes of brittle-stars inhabiting coral colonies were recorded. 36.3% of
the coral colonies >200 mm tall (n = 292) hosted ≥1 Astrobrachion constrictum (range 0 to 12). Overall, the population was patchily distributed on the available coral habitat. The dark red colour morphotype
of A. constrictum was most common (87%, n = 279) followed by the yellow, striped, and then spotted varieties. The population was comprised mainly of large (≥10 mm
disc diam) individuals, and juveniles were rarely encountered, indicating low rates of recruitment or a high mortality of
recruits. Disc-diameter data gathered from this and previous studies indicated that growth in A. constrictum is initially rapid, with individuals reaching a disc diameter of 15 mm in ≃2.5 yr; growth decreases with age, as in other
deep-sea ophiuroids. Growth rate within years, however, was not constant, with faster growth in the spring/summer. Maximum
size for A. constrictum is reached in ≃8 yr at ˜23 mm disc diam. Anecdotal evidence indicates that A. constrictum may not be confined solely to black coral colonies.
Received: 25 September 1996 / Accepted: 16 October 1996 相似文献
20.
Juvenile lesser blue crabs, Callinectes similis Williams, were exposed to a range of salinities for measurement of survival and bioenergetics. Effects of salinity on survival
were determined by exposing juvenile crabs to salinity treatments ranging from 0 to 74‰. All crabs survived 21 d of exposure
to 5 and 45‰S. The 21 d LC50 values for salinity tolerance (calculated from survival data) were 2.6 and 60.8‰S at low and high salinities, respectively.
Energy-budget components and scope for growth were determined for crabs exposed to 2.5, 10, 25, 35 and 50‰S. Energetic absorption
rates were highest at 2.5 and 35‰S. Energetic expenditure rates (energy lost to respiration and excretion) were greatest at
2.5‰S, and decreased as salinity increased. Respiration constituted the majority of energetic expenditure at all salinities
(92.3% average). Scope for growth was significantly affected by salinity and was highest in crabs exposed to 35‰S. Increased
respiration at low salinity may indicate that C. similis incurs greater costs due to osmoregulation. The results of this study indicate that C. similis is capable of surviving and growing in waters with salinities as low as 10‰.
Received: 10 January 1997 / Accepted: 11 February 1997 相似文献