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1.
Cod (Gadus morhua) were exposed to hypercapnia (water Pco2 = 7.5 mmHg), elevated copper level (0.4 ppm) or a combination of both in order to study extra- and intracellular acid-base
regulation and the influence hereupon of copper. During pure hypercapnia, the extracellular respiratory acidosis was completely
compensated within 12 to 24 h via a chloride-mediated increase in extracellular [HCO3
−]. Exposure to copper in normocapnic seawater caused a large and progressive increase in plasma [Na+] and [Cl−] and a metabolic acidosis. Exposure to copper in hypercapnic seawater was associated with smaller elevations of plasma [Na+] and [Cl−] than in normocapnic seawater, showing that hypercapnia had a protective effect on the copper-induced osmoregulatory disturbances.
The compensation of the hypercapnic acidosis was, however, slow and incomplete in fish exposed to both copper and hypercapnia.
Extracellular pH remained depressed by 0.3 pH units after 72 h. The data reveal that acid-base regulation was immediately
and persistently inhibited by copper. The limited acid-base regulation during combined copper and hypercapnia exposure was
chloride-mediated as during hypercapnia alone. Intracellular pH recovery was complete and very rapid in ventricular and skeletal
muscle tissues during environmental hypercapnia, whereas acid-base compensation in liver tissue was slower, the kinetics being
similar to that in the extracellular compartment. Intracellular pH compensation was significantly slowed down by copper. Copper
concentration increased drastically in gill tissue already at 3 h, while copper concentrations in liver, muscle and plasma
were significantly elevated only after 48 h, with liver showing the largest elevation.
Received: 15 November 1996 / Accepted: 2 December 1996 相似文献
2.
M. H. Depledge A.-K. Lundebye T. Curtis A. Aagaard B. B. Andersen 《Marine Biology》1996,126(2):313-319
An Automated Interpulse Duration Assessment system (AIDA) is described which permits detection of irregularities in cardiac rhythms in selected invertebrates. The sensitivity of AIDA was demonstrated by its ability to detect handling stress in mussels (Mytilus edulis) that was not evident when measuring heart rate alone. Changes in cardiac activity patterns of crabs (Carcinus maenas) held in the laboratory for up to 10 wk was also examined using the new technique. The frequency distribution of interpulse duration changed significantly as the nutritional state changed. Potential applications of the AIDA system are discussed. 相似文献
3.
Influence of cadmium accumulation and dietary status on fatty acid composition in two colour forms of shore crabs, Carcinus maenas 总被引:2,自引:0,他引:2
The effects of cadmium exposure and dietary status on cadmium accumulation, fatty acid (FA) content and profiles were investigated
in two colour forms of the shore crab Carcinus maenas. Groups of shore crabs were either starved or fed with blue mussels, Mytilus edulis, during a 40 d exposure period to 2 or 6 μM Cd2+ (as CdCl2). Starved green individuals accumulated more cadmium in haemolymph and hepatopancreas than did red crabs and green crabs
fed during the experiments. In the red colour form, no difference in cadmium accumulation was observed between starved and
fed individuals. In both colour forms, hepatopancreas contained more FA than gills and muscle. The FAs often present in the
largest amounts in the tissues were 16:0, 16:1ω7, 18:1ω7, 18:1ω9, 20:4ω6, 20:5ω3 and 22:6ω3. However, saturated (SAFA) and
mono-unsaturated fatty acids (MUFAs) were dominant in hepatopancreas, whereas poly-unsaturated fatty acids (PUFAs) were dominant
in gills and muscles. At the beginning of the experiment, the total FA content in the hepatopancreas was 111.6 mg g−1 (dry weight) for red crabs and 78.4 mg g−1 for green shore crabs. During the experiment, however, the FA content decreased in red crabs. This decrease was more pronounced
for starved individuals than for fed individuals. Also, the decrease in FA content was more pronounced in crabs exposed to
6 μM cadmium compared to crabs exposed to 2 μM or crabs not exposed to cadmium. No change in FA content was observed in green shore crabs, irrespective of diet and cadmium
exposure. For both colour forms, no change in FA content was observed for gills and muscle. In red crabs, a decrease was observed
for all FAs in the hepatopancreas. This decrease, however, was more pronounced for SAFAs and MUFAs than for PUFAs, indicating
that the metabolism of FAs during starvation and cadmium exposure is selective. The experiments indicate that green colour
forms of shore crabs are more tolerant of natural stress such as starvation and anthropogenic stress, e.g. cadmium exposure,
than are red colour forms of shore crabs.
Received: 23 September 1999 / Accepted: 29 April 2000 相似文献
4.
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
5.
The morphology and ultrastructure of the otolith settlement-mark was examined in 44 tropical reef-fish species spanning nine
families. A classification scheme based on similar otolith characteristics is presented. Three major categories are identified
based on changes in increment width and optical qualities of the settlement-mark. Of the 44 species examined, 39 possessed
“abrupt” settlement-marks (Type I) characterised by a rapid decrease in increment width (up to 50% reduction) over settlement.
Type I settlement-marks were found in all nine families examined. The 39 species spanned the whole range of possible larval
durations (Pomacentrus moluccensis, 15 d ± 0 SE; Naso hexacanthus, 91.2 d ± 2.97 SE). Four of the 44 species possessed “zonal” settlement-marks (Type II), featuring a band of increments that
are wider than pre-settlement increments. Species in this category are the labrids Corisaygula, Thalassoma bifasciatum, T. lunare and an unidentified acanthurid (Acanthurus sp. 2). One species of acanthurid (N. brevirostris) possessed a “gradual” settlement-mark (Type III), manifest as a gradual decrease in increment width during the settlement
period. A possible fourth type was identified from the literature. Gnatholepis thompsoni and Coryphopterus glaucofraenum possessed a settlement-mark with increment widths that increased post-settlement. Available data suggest a poor relationship
between the structure of the settlement-mark and the magnitude of metamorphosis (previously reported as internal and external
morphological change). Evidence suggests that the increment profile over early development and the increment transitions associated
with the settlement event are taxon-specific and may enable late-larval stage fishes to be identified to species level.
Received: 21 May 1997 / Accepted: 3 February 1999 相似文献
6.
Steven L. Lima Patrick A. Zollner Peter A. Bednekoff 《Behavioral ecology and sociobiology》1999,46(2):110-116
In socially feeding birds and mammals, as group size increases, individuals devote less time to scanning their environment
and more time to feeding. This vigilance “group size effect” has long been attributed to the anti-predatory benefits of group
living, but many investigators have suggested that this effect may be driven by scramble competition for limited food. We
addressed this issue of causation by focusing on the way in which the scan durations of free-living dark-eyed juncos (Junco hyemalis) decrease with group size. We were particularly interested in vigilance scanning concomitant with the handling of food items,
since a decrease in food handling times (i.e. scan durations) with increasing group size could theoretically be driven by
scramble competition for limited food resources. However, we showed that food-handling scan durations decrease with group
size in an environment with an effectively unlimited food supply. Furthermore, this food-handling effect was qualitatively
similar to that observed in the duration of standard vigilance scans (scanning exclusive of food ingestion), and both responded
to changes in the risk of predation (proximity of a refuge) as one might expect based upon anti-predator considerations. The
group size effects in both food-handling and standard scan durations may reflect a lesser need for personal information about
risk as group size increases. Scramble competition may influence vigilance in some circumstances, but demonstrating an effect
of competition beyond that of predation may prove challenging.
Received: 22 September 1998 / Received in revised form: 1 February 1999 / Accepted: 14 February 1999 相似文献
7.
The toxicity of fenitrothion was determined in larvae (nauplii, Zoeae 1 to 3, Mysis 1 to 3), postlarvae (PL stages) and juvenile
shrimp (Penaeus japonicus Bate), in two media, seawater (SW) and diluted seawater (DSW) (1100 and 550 mosM kg−1, ≃ 37 and 19‰ S). The effects of fenitrothion on the osmoregulatory capacities (OC) of juveniles were recorded. A gill and
epipodite histopathological study was also conducted. For larvae in seawater, 24 and 48 h LC50s ranged from 32.9 μg l−1 (Zoeae 2) to 10.7 μg l−1 (Mysis 3), and from 3.9 μg l−1 (Zoeae 3) to 2.0 μg l−1 (Mysis 3), respectively; 48 and 96 h LC50s in postlarvae (PL) at the same salinity ranged from 1.8 μg l−1 (PL1) to 0.6 μg l−1 (PL5), and from 0.3 μg l−1 (PL7) to 0.4 μg l−1 (PL15). In juveniles, 96 h LC50s were 0.8 μg l−1 in seawater and 1.5 μg l−1 in diluted seawater. From hatching to juvenile stages, the overall trend was a rapid decrease (from nauplii to PL5–PL7) followed
by a slight increase (from PL7 to PL15 and juveniles) in the shrimp's ability to tolerate the insecticide. In juveniles kept
in seawater and in diluted seawater, fenitrothion decreased the osmoregulatory capacity (OC = difference between the hemolymph
osmotic pressure and the osmotic pressure of the medium) at both lethal and sublethal concentrations. This effect was time-
and dose-dependent. In SW, the decrease in hypo-OC was ˜ 25% at sublethal concentrations and ˜ 35% at the 96 h LC50. In DSW, the decrease in hyper-OC was ˜ 10 to 15% at sublethal concentrations. In SW, shrimp were able to recover their OC
in less than 48 h when transferred to water free of pesticide. In DSW, recovery at 48 h was only possible after exposure to
the lowest tested sublethal concentration. Haemocytic congestions (thrombosis) of the gills, lamellae necrosis and other alterations
of gills and epipodites (breakage of the cuticle, reduction of the hemolymph lacunae) were noted in juveniles exposed to lethal
and sublethal concentrations of fenitrothion.
Received: 7 October 1996 / Accepted: 13 November 1996 相似文献
8.
The sea urchin Lytechinus variegatus is capable of surviving chronic exposure to sodium phosphate (inorganic phosphate) concentrations as high as 3.2 mg l−1, and triethyl phosphate (organic phosphate) concentrations of 1,000 mg l−1. However, chronic exposure to low (0.8 mg l−1 inorganic and 10 mg l−1 organic phosphate), medium (1.6 mg l−1 inorganic and 100 mg l−1 organic phosphate) or high (3.2 mg l−1 inorganic and 1,000 mg l−1 organic phosphate) sublethal concentrations of these phosphates inhibits feeding, fecal production, nutrient absorption and
allocation, growth and righting behavior. Food consumption and fecal production declined significantly in individuals exposed
to medium and high concentrations of inorganic phosphates and all levels of organic phosphates. Feeding absorption efficiencies
for total organics and carbohydrates decreased significantly in individuals held in the highest concentration of organic phosphate.
Feeding absorption efficiencies for lipids were significantly reduced in the highest inorganic phosphate concentration only,
while they decreased significantly for protein with increasing phosphate exposure. Carbohydrate and lipid levels in gonad
and gut tissues decreased significantly with exposure to increasing phosphate concentrations, potentially impairing both gametogenesis
and nutrient storage in the gut. Moreover, gonad indices significantly decreased in individuals exposed to the highest concentrations
of either phosphate. Growth rates decreased significantly under the influence of all phosphate concentrations, while increasing
in seawater alone. Individuals exposed to increasing phosphate concentrations showed reduced righting responses (a measure
of stress) and no acclimation in righting times during chronic exposure to phosphates over a 4 week period. These findings
indicate that shallow-water populations of L. variegatus subjected to inorganic and organic phosphate pollutants will exhibit stress and be inhibited in their growth and performance
due to reductions in feeding, nutrient absorption and allocation of nutrients to key somatic and reproductive tissues.
Received: 10 April 2000 / Accepted: 2 October 2000 相似文献
9.
E. A. Widder S. Johnsen S. A. Bernstein J. F. Case D. J. Neilson 《Marine Biology》1999,134(3):429-437
To learn how organisms apportion space in the open ocean, biological oceanographers have sought to improve temporal and spatial
resolution of ocean sampling systems. Their objectives are to simultaneously measure physical, chemical and biological structure
in the water column in order to find significant correlations that may reveal underlying processes. Here we report one such
correlation between intense peaks of bioluminescence and density discontinuities in the water column. Intensified video recordings
made in these bioluminescent “hot spots” were analyzed with a computer image-recognition program that identifies organisms
based on the temporal and spatial characteristics of their luminescent displays. Based on this analysis, the source of the
“hot spots” was found to be very thin layers (0.5 m) of the bioluminescent copepod Metridia lucens present at from 5 to 100 times average background concentrations. Given the recent discovery that the vertical distribution
of marine snow is also strongly correlated with density discontinuities in the water column, we suggest that this finding
may provide a possible explanation for the disparity between estimated energy requirements of marine copepods and measurements
of average in situ food concentrations. The energy costs associated with locating food-rich micro-patches is greatly reduced
if those patches are spread out into very thin layers, because the search strategy can be reduced from three dimensions to
one.
Received: 28 December 1998 / Accepted: 12 April 1999 相似文献
10.
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
11.
Copper toxicity was tested on a coastal population of the mysid Praunus flexuosus (Müller) from Southampton Water (Southern England) under winter and summer conditions. Ten-day toxicity tests were performed
on the different life-cycle stages (female, male and juvenile) present in winter (December/February) and summer (August).
The individuals were in winter or summer physiological condition and were exposed to seawater to which 0, 5, 25, 75 and 200 μg l−1 copper was added. There were significantly different copper toxicity effects in winter and summer. In winter mortality was
≤ 1% at all levels of copper exposure, while in summer identical exposure levels caused mortality of up to 93%. The 96 h LC50 was 30.8 μg l−1 copper added in the summer. In winter, the low mortality prevented calculation of LC50. There were differences in responses to copper between the life-cycle stages. Juveniles were more sensitive than adults,
and were severely affected within 24 h. Females were more affected than males at lower doses and shorter exposure times.
Received: 28 April 1999 / Accepted: 22 June 2000 相似文献
12.
E. A. Perry G. B. Stenson S. E. Bartlett W. S. Davidson S. M. Carr 《Marine Biology》2000,137(1):53-58
Harp seals (Pagophilus groenlandicus Erxleben, 1777) comprise three populations based upon whelping areas in the Greenland Sea, White Sea, and Northwest Atlantic.
The last comprises two subpopulations, one whelping in the Gulf of St. Lawrence (“Gulf ”) and one on the pack ice of the southern
Labrador/northern Newfoundland coastal shelf (“Front”). A total of 40 female seals from the four whelping areas were collected
during the 1990 and 1992 whelping seasons. DNA sequence variation was examined in a 307 bp region of the mitochondrial cytochrome
b gene. Eleven variable nucleotide positions defined 13 genotypes: a significant fraction of the genotypic variance (F
ST=0.12, or 0.09 as measured by Weir's coancestry coefficient θ) is attributable to differentiation between Northwest and Northeast
Atlantic populations. There was no significant differentiation between the two whelping areas in the Northwest Atlantic, or
between the Greenland Sea and White Sea. These findings suggest significant reproductive isolation exists between trans-Atlantic
breeding populations.
Received: 18 January 1999 / Accepted: 22 February 2000 相似文献
13.
From September to November 1991, UV-absorbing mycosporine-like amino acids (MAAs) were monitored in a natural population of
the sea urchin Sterechinusneumayeri from a coastal area of Anvers Island (Antarctic Peninsula). MAA concentrations were determined for specific tissues (gonad,
digestive tract and body wall) from adults collected at four depths (intertidal, 8, 15 and 24 m). Four MAAs were identified:
mycosporine-glycine, shinorine, porphyra-334 and paly-thine. Concentrations of MAAs among replicate individuals varied considerably.
Ovaries had high concentrations of MAAs (84 to 1389 μg g−1 dry wt), while testes had non-detectable levels. The relative abundance of specific MAAs in ovaries appeared to be related
to the spawning cycle. Digestive-tract samples had MAA concentrations as high as 3000 μg g−1 dry wt, but the mean MAA content in intertidal individuals decreased by 70% over 3 mo during spring. The body walls of sea
urchins had very low amounts of MAAs (≤ 0.08 μg g−1 dry wt). There were significant depth differences in the␣total MAA content of the ovary ( p <0.001), ( p <0.015), digestive tract ( p <0.001), and body wall with organisms from the intertidal and 8 m depth having the highest concentrations of MAAs. Biological
dosimetry indicated that UV-B (280 to 320 nm) wavelengths penetrated 3 to 7 m below the sea ice during the study period. The
total MAA content in ovaries decreased with depth on all sample dates; however, the MAA content of the digestive tract and
body wall did not exhibit a consistent pattern of change with depth. The MAA content of tissues did not change significantly
with the temporal gradient of light exposure that was established by both ozone depletion and increasing photoperiod, except
in the digestive tract sampled from intertidal specimens. Adult urchins are probably well-protected from UV exposure by the
water column and a calcareous test; however, the results of this study suggest that, even under ice cover, depth of habitation
is a determinant of MAA content in S. neumayeri. Large daily and seasonal fluctuations in the light regime, which are characteristic of Antarctic coastal environments, apparently
do not provide reliable cues to elicit a detectable, temporal, biochemical response.
Received: 19 February 1997 / Accepted: 26 March 1997 相似文献
14.
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
15.
Chemically mediated alarm reactions of the common periwinkle, Littorina littorea (L.), were studied in laboratory experiments during two consecutive summers, and one intermediate autumn season. Responses
to chemical stimuli were detected as crawl-out responses, i.e. movements of snails out of the water. Snails were exposed to
extracts of injured conspecifics, extracts of the mussel Modiolus modiolus (L.), and water conditioned by the predatory crab Carcinus maenas (L.), which had been maintained on different diets. In experiments carried out during the summer, a significantly larger
number of snails moved out of the water when exposed to chemical stimuli from injured conspecifics, compared to chemical stimuli
from injured mussels or filtered seawater. These results suggest that chemical alarm substances are present in L. littorea. Water conditioned by crabs that had been fed L. littorea released significantly more crawl-out responses compared to water conditioned by crabs that had been kept on a fish diet.
When tested in autumn, no significant differences were found in responses to the above-mentioned water samples. Crawl-out
responses under different light regimes were also investigated. All series of experiments carried out in the dark evoked a
higher number of responses compared to series that took place in light. These findings may indicate an adaptation of snails
to night-active predators. In total, the current results suggest that a L. littorea diet may chemically “label” the predator crab with snail alarm substances, and that predator-induced responses of L. littorea are actually responses to conspecific alarm substances released from crabs that have been maintained on a L. littorea diet. The response to the alarm signal, however, appears to be dependent on season and light conditions; some ecological
implications of these findings are also discussed.
Received: 8 January 1999 / Accepted: 29 March 1999 相似文献
16.
In a Kenyan mangrove, we studied the interactions between the gastropod Terebralia palustris and the crab Neosarmatium smithi when foraging on decaying mangrove leaves. Interactions are considerable on account of their wide overlap in zonation (Rhizophora mucronata belt), food items (mangrove leaves) and activity window (diurnal low water). The snails find a leaf by a systematic transecting
of the platform and eat the leaf after crawling on to it, usually en masse. The crabs rarely venture beyond 80 cm from their
burrows, and once they find a leaf they quickly drag it back into their burrow, probably to reduce the strong intra-specific
competition. A crab is able to drag a leaf away even if a number of snails are already feeding on it, by strongly pulling
the leaf away or by pushing the snails off the leaf. The success of the “thief ” depends on both the crab's size and the number
of snails on the leaf.
Received: 25 July 1999 / Accepted: 27 April 2000 相似文献
17.
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
18.
We provide evidence that male lizards can use chemosensory cues to identify individual females and probably therefore maintain
long-term associations with these females in the wild. In the laboratory, males preferentially followed the scent trail of
their vitellogenic female “partner” rather than that of another vitellogenic female. Our 5-year field study of the small viviparous
scincid lizard (Niveoscincus microlepidotus) in alpine Tasmania showed that sexually mature males and females commonly formed “pairs” for long periods (on average 29 days).
These pairs occurred primarily during the mating season, always involved one adult male and one adult female, and usually
involved vitellogenic rather than gravid females. Our laboratory experiments suggest that a significant factor in maintaining
those prolonged partnerships is male scent trailing of partners.
Received: 28 October 1997 / Accepted after revision: 28 May 1998 相似文献
19.
I. B. Kuffner 《Marine Biology》2001,138(3):467-476
The effects of water flow and ultraviolet radiation (UVR, 280–400 nm) on the reef coral Porites compressa Dana were explored in a manipulative flume experiment. The aim of this study was to determine whether this coral responds
to changes in the UVR environment by adjusting the tissue concentration of UV-absorbing compounds (mycosporine-like amino
acids, MAAs), and to see whether such an acclimation is affected by water flow. Also, calcification rate and chlorophyll-a concentration were measured during the experiment to estimate the potential costs (in the form of slowed growth and/or reduced
photosynthetic capacity) to the coral–alga symbiosis of being exposed to UVR and producing MAAs. Branches of P. compressa from a single male colony were exposed to high or low flow (15 cm s−1 and 3 cm s−1, respectively) and ambient or no UVR in an outdoor, continuous-flow seawater system. Chlorophyll-a and MAA concentrations were determined after zero, 3 and 6 weeks of exposure to the experimental conditions. Increase in
buoyant weight during the two 3-week periods was used to calculate calcification rate. The presence of UVR had a significant
positive effect on total MAA concentration in the P. compressa colonies; however, there were significant interactions present. In colonies exposed to UVR, MAA concentration increased and
then decreased to initial levels in high water flow, and increased steadily in low water flow. In colonies receiving no UVR,
MAA concentration decreased steadily, declining 23% in 6 weeks. The absence of UVR did not result in higher chlorophyll-a concentrations, but the calcification rate was slightly affected by UVR. This study supports the putative photoprotective
role of MAAs in P. compressa, and suggests that the costs of mitigating the effects of ambient UVR are detectable, but they are very small.
Received: 29 February 2000 / Accepted: 20 September 2000 相似文献
20.
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