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1.
R. Lundheim 《Marine Biology》1997,128(2):267-271
The ice nucleation temperatures of different homogenised organs of the mussel Mytilus edulis L. were examined. The stomach and the hemolymph had the highest nucleation temperatures. In the homogenised stomach the nucleation
temperatures were fairly constant throughout the year, whereas the nucleation temperatures of the hemolymph increased in the
cold season. Bacterial growth experiments, microfiltration, and experiments using antibiotics indicated that the nucleators
were not of bacterial origin. The nucleation temperatures of natural seawater were approximately −9 °C, whereas seawater made
from distilled water and sea salt had nucleation temperatures of about −17 °C. The nucleation temperatures of the seawater
were reduced when the seawater was filtered by the mussels. However, no clear indication that the nucleators in the stomach
were obtained from the seawater was found. Stomach homogenates from mussels kept in nucleator-free water had the same supercooling
points as stomach homogenates from mussels kept in natural seawater. This indicates that the nucleators in the stomach are
not obtained from the seawater. The temperature and light conditions examined in the present study did not significantly influence
the hemolymph ice nucleation temperatures of mussels kept in the laboratory.
Received: 24 October 1996 / Accepted: 16 November 1996 相似文献
2.
The accumulation and depuration of Cs in the green mussels (Perna viridis) commonly found in the subtropical and tropical waters were studied under the laboratory conditions using radiotracer techniques.
Following an initial rapid sorption onto the mussel's tissues, uptake of Cs exhibited linear patterns over a short exposure
time (8 h) at different ambient Cs concentrations. The concentration factor was independent of ambient Cs concentration. The
calculated uptake rate and initial sorption constant of Cs were directly proportional to the ambient Cs concentration. The
calculated uptake rate constant from the dissolved phase in the mussels was as low as 0.026 l g−1 d−1. Uptake rates of Cs in the mussels were inversely related to the ambient salinity. Uptake increased about twofold when the
salinity was reduced from 33 to 15 ppt. The effect of salinity on Cs uptake was primarily due to the change in ambient K+ concentration. The uptake rate decreased in a power function with increasing tissue dry weight of the mussels, although the
initial sorption was not related to the mussel's body size. The efflux rate constant of Cs in the mussels was 0.15 to 0.18 d−1, and was the highest recorded to date among different metals in marine bivalves. The efflux rate constant also decreased
in a power function with increasing tissue dry weight of mussels. A simple kinetic model predicted that the bioconcentration
factor of Cs in the green mussels was 145, which was higher than measurements taken in their temperate counterparts. The bioconcentration
factor also decreased in a power function with increasing tissue dry weight of mussels.
Received: 27 October 1999 / Accepted: 16 June 2000 相似文献
3.
The accumulation of lipofuscin, which is an indictor of physiological age, in the brain of juvenile European lobster (Homarus gammarus L.) was monitored for 22 mo in three experimental temperature regimes that simulated seasonal variation in temperature in
the geographic range of this species. Metabolic rate responses to changes in temperature were estimated by measuring the activity
of the electron transport system (ETS) in muscle tissue and in vivo rates of oxygen consumption. Lipofuscin accumulation oscillated
with simulated seasonal changes in temperature and was described by seasonalised von Bertalanffy growth functions. The incremental
accumulation in lipofuscin between sampling dates was linearly related to the number of degree days that accumulated between
dates, irrespective of the amplitude of temperature fluctuation that had occurred. ETS activity increased with acclimation
temperature and was modelled using a polynomial function. This indicated a lower temperature sensitivity in the temperature
mid-range (12 to 16 °C), although the Q10 for this mid-range was 2.1. ETS activity in lobsters acclimated to 8 and 18 °C and assayed at 13 °C was similar, indicating
no compensation for changes in environmental temperature. Oxygen consumption rate was significantly higher at 14 °C than at
10.5 °C and had a Q10 of 3.6, again suggesting no compensation to temperature change. The absence of metabolic compensation in response to temperature
change in H. gammarus is consistent with the predictability of changes in temperature and food availability in the sub-littoral environment of
this species. As lipofuscin accumulates according to metabolic rate, and metabolic rate in H. gammarus is directly correlated with temperature, geographic differences and long-term temporal trends in temperature will need to
be considered when converting physiological age indices, obtained from lipofuscin estimates, to a chronological scale.
Received: 27 April 2000 / Accepted: 21 July 2000 相似文献
4.
Calcium carbonate transfer was experimentally examined in hydrothermal mussels Bathymodiolus azoricus, which were collected from 850 m depth at Menez Gwen hydrothermal vent site (31°31′W, 37°50′N) on the Mid Atlantic Ridge in
May 2007. In each of four 10-day experiments, groups of mussels were maintained at atmospheric pressure or re-pressurised
to depths relevant to their site of occurrence, i.e. 850 m depth at Menez Gwen, 1,750 m at Lucky Strike (31°31′W, 37°18′N)
and 2,300 m at Rainbow (31°31′W, 36°13′N). The shells of experimental mussels were perforated and mantle tissue was fixed
for light and TEM studies at days 7 and 10 following the injury. Simultaneously, haemocytes from the extrapallial fluid (EPF)
at the site of induction were studied. At day 7 the response was most intense in the middle fold of the mantle margin and
possibly proportional to hydrostatic pressure. At day 10 the epithelial cells on the mantle surface facing the body cavity
produced copious organic secretions that avidly bound calcium. Haemocyte migration was noted within the mantle tissue, and
the haemocytes at the mantle surface facing the shell had a Ca-positive granular content. Large haemocytes were detected in
the EPF at the injury site, and some showed evidence of an immune reaction while others showed Ca-positive granular content.
These results suggest that haemocytes are involved in shell repair in these deep-sea mussels just as in some freshwater and
shallow marine molluscs. 相似文献
5.
The use of the egg production rate of herbivorous copepods as an important parameter for understanding population dynamics
and as an index of secondary production requires knowledge of the regulatory mechanisms involved and of the response to changes
in food concentrations and temperature. Furthermore, the effects of season and generation on egg production have to be studied.
In this context data are presented for Calanus finmarchicus from the northern North Atlantic. Prefed and prestarved females were exposed to different concentrations of the diatom Thalassiosira antarctica over 1 to 2 wk at 0 or 5 °C, and egg deposition was controlled daily. Egg production increased with higher food concentrations,
but much less when prestarved. The effect of temperatures between −1.5 and 8 °C on egg production was studied in females maintained
at optimum feeding conditions. Egg production rate increased exponentially over the whole temperature range by a factor of
5.2, from 14.2 to 73.4 eggs female−1 d−1, and carbon-specific egg production by 4, from 2.1 to 8.5% body C d−1. The response to starvation was also temperature dependent. In both the temperature and feeding experiments egg production
rate was regulated mainly by changes of the spawning interval, while changes of clutch size were independent of experimental
conditions. Different responses to optimum feeding conditions were observed in females collected in monthly intervals on three
occasions between March and May. The March females deposited more clutches than the April and May females. In May, >50% of
the females did not spawn at all. Maximum egg production rates were never >25% of the rate expected at 5 °C, indicating endogenous
control of egg production in addition to food and temperature effects.
Received: 4 August 1996 / Accepted: 11 September 1996 相似文献
6.
To understand how regeneration in corals may be affected by intrinsic and extrinsic factors, the process of repair of experimentally
induced tissue lesions was investigated in the solitary scleractinian coral Fungia granulosa. Three lesion sizes were inflicted in situ on large, sexually mature individuals (>5.5 cm diameter) and in small sexually
immature (<5.0 cm) individuals. Repair was monitored using photography and computerized image analysis. This procedure was
carried out in fall (September to November; post-reproductive months), and repeated with a new set of corals in spring (March
to May; gametogenic months). Reproductive effort was investigated histologically 1 to 2 months following lesion infliction.
In field experiments, there was a significant difference in percent of tissue coverage 8 weeks after lesion infliction between
spring and fall for all lesion sizes in large corals. During the fall, all lesion sizes in large corals were repaired within
8 weeks. Large lesions in small corals did not undergo repair regardless of season. During the spring, none of the corals
underwent complete repair regardless of coral size, and many of the small corals died. In laboratory experiments, 83.3% of
the corals kept at 25 °C and 16.7% of those kept at 21 °C underwent repair during the fall. None of the corals maintained
at 21 °C and only 16.7% of those corals maintained at 25 °C underwent complete repair during spring. Though both fecundity
and tissue regeneration were significantly reduced, gametogenesis continued in corals that had previously undergone experimental
injury. These results indicate that in fungiid corals, regeneration is affected by intrinsic factors such as size and reproductive
state as well as by environmental factors such as ambient water temperatures. Moreover, it is possible that, following injury,
energetic resources are diverted from repair towards the maintenance of reproductive effort.
Received: 21 March 2000 / Accepted: 28 July 2000 相似文献
7.
Cephalopod mollusks exhibit highly plastic life cycle traits influenced primarily by the interactive effects of food availability,
light cycle and temperature, with the latter perhaps the most influential. Hatchlings of the tropical reef squid Sepioteuthis lessoniana were hatched from field-collected eggs in the laboratory and cultured at different temperatures to evaluate the effect of
temperature on growth rates. All groups showed rapid, sustained growth rates from hatching to a size of 10–25 g. Beyond this
size range, growth was slower and not clearly exponential in form. Growth rate was closely linked to temperature. Squids grown
at approximately 27 °C attained a size of 10 g in as little as 45 days at sustained growth rates of 12.2% body weight day−1 (%bw day−1), while squids cultured at 20 °C required almost 100 days to attain the same size at rates of 5.7%bw day−1. At an age of 55 days and approximately 1 g body weight, juvenile squids cultured at 20 °C were able to accelerate growth
rates from 5.7%bw day−1 to over 12%bw day−1 when temperature was raised to 27 °C. They maintained this growth rate to a size of about 10 g and an age of at least 75 days
post-hatching, indicating that body size and not age is the limiting factor for this rapid post-hatching growth. By comparison,
conspecifics cultured near 27 °C from hatching had shifted out of the rapid post-hatching growth phase by day 50 at sizes
between 10 and 50 g. The hatchlings from temperate to subtropical Japan had consistently higher growth rates at comparable
temperatures than hatchlings from tropical Okinawa. When plotted as growth rate versus temperature, the Japanese group had
a clearly higher slope to the relationship than the tropical populations, equivalent to a 2%bw day−1 difference in growth rate at 25 °C. Age at first egg-laying was decreased at higher culture temperatures; however, overall
life span was not.
Received: 21 February 2000 / Accepted: 6 September 2000 相似文献
8.
To examine the impact of development rate on swimming performance, escape response, and morphology, yolk-sac larvae of American
plaice (Hippoglossoides platessoides, Fabricius) were reared at two temperatures (5 and 10 °C). Videomicroscopy and silhouette collimation videography were used
to examine swimming, escape behaviour, and morphology (standard length, finfold area, and yolk-sac area) of individual larvae.
Larvae were examined from 0 d post hatch (dph) to 14 dph for the 5 °C treatment group and from 0 to 6 dph for the 10 °C treatment
group (3 August to 17 August 1996). Since larvae were not fed, yolk-sac reserves were essentially exhausted by 14 and 6 dph
for the 5 and 10 °C treatment groups, respectively. To control for the effect of testing temperature on behaviour, larvae
from each temperature treatment were tested at both 5 and 10 °C. Testing temperature had an effect on some swimming parameters
but not on escape response. Swimming performance, escape response, and morphology varied with age, while only morphology and
escape response varied with development rate. Morphology and swimming performance, and morphology and escape response were
found to be correlated as determined by canonical correlation. This study suggests that both types of swimming behaviours
should be examined when developing models of the impacts of predation on the early life history of larval fish.
Received: 13 September 1999 / Accepted: 21 June 2000 相似文献
9.
Animals that bore into calcareous material can cause considerable damage to molluscan shells. In contrast, smaller microbial
phototrophic endoliths have until recently been thought of as relatively benign. Phototrophic endoliths (primarily cyanobacteria)
infest the shells of 50 to 80% of midshore populations of the mussel Perna perna (L.) in South Africa. This infestation causes clearly visible shell degradation, and we record here ecologically important
lethal and sub-lethal effects (e.g. changes in growth and reproductive output) of the endoliths on their mussel hosts. Endolith
infestation reduced the strength of shells significantly and also affected shell growth. In situ marking of shells, using
the fluorochrome calcein, showed that infested and non-infested mussels increased in shell length at the same rate. However,
the rate of increase in shell thickness (associated with shell repair) was significantly faster in infested than in uninfested
individuals. This increase in the rate of shell thickening was not sufficient to compensate for rapid endolith-induced shell
degradation and, around the site of adductor muscle attachment, infested shells were thinner than their uninfested counterparts.
The shells of 18% of recently dead mussels had holes induced by endolith erosion. This effect was highly size dependent, and
the proportion of mortality due to endoliths rose to almost 50% for the largest mussels. The re-routing of energy due to shell
repair had important sub-lethal effects on the reproductive rates of mussels. During the reproductive period, mean dried flesh
mass for large (>70 mm), non-infested P. perna was substantially higher than for infested individuals. This difference was almost entirely due to differences in gonad mass,
which was approximately 100% higher for non-infested mussels. We conclude that, by attacking the shell, phototrophic endoliths
reduce both the longevity and reproductive output of large mussels on the midshore.
Received: 26 January 1999 / Accepted: 17 August 1999 相似文献
10.
Life history of Gonatus onyx (Cephalopoda: Teuthoidea): deep-sea spawning and post-spawning egg care
A reproductive strategy consisting of deep- water spawning and egg-care was inferred for the midwater squid Gonatus onyx Young, 1972. Brooding females and associated eggs and hatchlings, captured between 1250 and 1750 m depth off southern California,
are described. Brooding females appear to be senescent and lack tentacles. Large eggs of this species (3 mm) at cold temperatures
(3 °C at capture depth) may require as long as 9 mo to develop. The high lipid content of the digestive gland in adult females
of this species may provide fuel to support such an extended “brooding” period.
Received: 22 February 1999 / Accepted: 25 May 2000 相似文献
11.
A prey-localization test allowed the observation of the foraging behaviour of Coscinasterias muricata in the presence of Mytilus edulis and the disruption of this behaviour following oil exposure. Asteroids were exposed to dilutions of water-accommodated fractions
(WAF) of Bass Strait stabilised crude oil (control, 2%, 10%). Effects of exposure (4 d) and depuration (20 d) were quantified
using circular statistical analyses. Observations suggested that disruption of behaviour might be concentration-dependent.
Control asteroids successfully located mussels during tests. A small proportion (3 of 16) of asteroids exposed to 2% WAF also
located the mussels, while asteroids exposed to 10% WAF did not. Following depuration, exposed asteroids recovered their chemoreception
capacities. It is concluded that (1) Coscinasterias muricata is able to locate prey mussels through chemoreception, (2) exposure to oil disrupts its foraging behaviour, and (3) the effect
is reversible.
Received: 4 March 1998 / Accepted: 25 November 1998 相似文献
12.
Differential increment-deposition rate in embryonic statoliths of the loliginid squid Loligo vulgaris 总被引:2,自引:0,他引:2
R. Villanueva 《Marine Biology》2000,137(1):161-168
Apart from one study that reported growth of less than one increment per day in statoliths of the squid Alloteuthis subulata, most studies so far have presumed that one increment was laid down per day in the statoliths of the squid species they examined.
The present study provides evidence of differential daily growth rates in embryonic statoliths of the squid Loligo vulgaris Lamarck, 1798, thus confirming a previous report for A. subulata. Incremental growth rates of L. vulgaris statoliths differ as a function of temperature. Squid embryos were incubated in the laboratory at three temperatures (12.0,
15.5 and 21.1 °C), and tetracycline staining was used to follow statolith growth. This growth slowed in squid exposed to the
lowest temperature, but recovered when the squid were returned to warm conditions, indicating statolith adaptation. Statolith
growth rate after incubation at 12 °C was 1.3% d−1 and reached 6.1% d−1 for squids exposed to 21.1 °C. Statoliths from embryos incubated at 15.5 °C yielded a rate of 1 increment d−1 and a mean daily growth of 2.2 μm in the dorsal dome area of the statolith. In contrast, the slow growth of statoliths incubated
at 12 °C yielded a mean daily growth of only 0.9 μm in the dorsal dome and the readings resulted in a less-than-daily increment-deposition
rate.
Received: 9 October 1999 / Accepted: 30 March 2000 相似文献
13.
Intraspecific physiological variability of the gastropod Littorina saxatilis related to the vertical shore gradient in the White and North Seas 总被引:1,自引:0,他引:1
Physiological responses to desiccation and temperature stress as well as behavioural responses to fast and abrupt environmental
changes were investigated in high- and low-shore Littorina saxatilis (Olivi) from several populations from the White and North Seas. Variations in evaporation rates, resistance to air exposure
and to acute and chronic temperature stress between animals from different shore levels were similar in White and North Sea
periwinkles, consistent with the adaptive nature of these variations. High-shore snails were found to be able to conserve
body water reserves better, to resist higher temperatures and to survive longer under conditions of combined temperature and
desiccation stress than their low-shore counterparts. In a temperature range of 25 to 35 °C, the rate of evaporative water
loss was positively correlated with temperature in low-shore snails while being largely temperature-independent in high-shore
snails. Median lethal time during air exposure in L. saxatilis was negatively but not linearly related to the temperature of exposure. In a temperature range of 30 to 38 °C, the resistance
to heat exposure in air was only slightly dependent on the temperature, with Q
10 = 1.4 for the median lethal time; the heat resistance dropped drastically at temperatures above 38 °C, with Q
10 = 593.8. This suggests different mechanisms of temperature resistance in different parts of the studied temperature range.
In contrast, behavioural response to extreme salinity fluctuations was not uniform in the high- and low-shore periwinkles
from the White and North Seas, which may reflect specific environmental conditions at different shore levels in the two areas
studied. Observed physiological and behavioural variations are discussed from the viewpoint of different adaptive strategies
employed by eulittoral and eulittoral-fringe animals within populations of a single species.
Received: 13 December 1999 / Accepted: 11 April 2000 相似文献
14.
Effect of temperature fluctuations and food supply on the growth and metabolism of juvenile sea scallops (Placopecten magellanicus) 总被引:1,自引:0,他引:1
On the eastern shore of Nova Scotia late summer atmospheric systems cause upwelling of shelf water; the associated temperature
variations of 10 °C with a 6 to 8 d period are comparable in magnitude to the seasonal variation. A laboratory study was undertaken
to assess the effects of these temperature fluctuations on sea scallop (Placopecten magellanicus) growth and metabolism. In a factorial design, scallops were subjected to constant (10 °C) or a variable (6 to 15 °C) 8 d
temperature cycle, and either a low (seston in filtered seawater) or high (seston supplemented with cultured phytoplankton)
food diet. During the 48 d experiment scallop mortality was low and growth positive in all treatments. Shell and total tissue
growth rate did not differ between temperature treatments, but growth in the high food treatments was 40 to 50% higher than
in the low food treatments. However, soft tissue (excluding adductor) growth did show a temperature treatment effect; growth
rates were significantly higher in the fluctuating temperature treatment, due in part to greater gonad development. Weight-standardized
rates of scallop oxygen consumption (V
sO2 , μmol O2 g−1 h−1) were 20 to 25% higher in high food than in low food treatments, consistent with the expected increase in respiration due
to the higher growth rates. Scallop metabolism did not acclimate to the fluctuating temperature cycle; V
sO2 and ammonium excretion (V
sNH+
4, μmol O2 g−1 h−1) remained dependent on ambient temperature throughout the experiment. V
sNH+
4 Q10 (2.77) was higher than V
sO2 Q10 (2.01) which was reflected in a decrease in the O:N ratio at 15 °C, indicating a shift toward increased protein catabolism
and a stressed state. At 10 °C, V
sO2 and V
sNH+
4 in the variable temperature treatments were 15 to 18% lower than in the constant temperature treatments, a difference that
was not detected in growth measurements. Results demonstrate that the metabolism of Placopecten magellanicus, unlike some bivalve species, is tightly coupled to fluctuations in ambient temperature. Although an absence of compensatory
acclimation had a minimal effect on growth in this study, if high temperatures were combined with low food conditions a reduction
in scallop production could result.
Received: 23 June 1998 / Accepted: 8 February 1999 相似文献
15.
Importance of cysts in the population dynamics of the red tide flagellate Heterosigma akashiwo (Raphidophyceae) 总被引:7,自引:0,他引:7
To elucidate roles of cysts in occurrences of Heterosigma akashiwo blooms, cyst dynamics were studied in northern Hiroshima Bay, the Seto Inland Sea of Japan, where H. akashiwo regularly forms red tide in June. Monthly measurements of seasonal changes in the densities of vegetative cells of H. akashiwo and their germinable cysts in surface sediments (top 1-cm layer) were made for 2 years at three stations. Vegetative cells
of H. akashiwo could be detected from April through December throughout the water column, and the existence of vegetative cells was confirmed
in surface waters even in winter after incubation of sampled seawater in culture medium. Germinable cysts, enumerated by the
extinction dilution method, existed in sediments in all seasons, even before and after the seasonal bloom. The effects of
incubation temperature on the germination of natural cysts of H. akashiwo in sediments were examined. Germination was not observed at 5 °C, was low at 10 °C, while it increased at 15 °C, and maintained
a high level to 25 °C. The bottom water temperature reached 15 °C (suitable for the germination of cysts) and the surface
about 18 °C or more (suitable for the growth of vegetative cells) 2 to 3 weeks before the blooms. The dark survival of H. akashiwo cysts was tested, and it was found that the cysts were viable for at least 650 d at 11 °C, and for 165 d at 25 °C, indicating
a significant role of cysts in the survival during winter and summer seasons. The cysts presumably also play an important
role in seeding primary populations into water columns when the bottom water reaches a suitable temperature (around 15 °C);
thereafter the populations develop with great annual regularity to bloom in June. These results suggest that initiation of
H. akashiwo red tides in the Seto Inland Sea could be triggered by bottom water temperature.
Received: 3 July 1998 / Accepted: 12 January 1999 相似文献
16.
Short-term effects of temperature and irradiance on oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat were investigated with O2 microsensors in a laboratory. The effect of temperature on O2 fluxes across the mat–water interface was studied in the dark and at a saturating high surface irradiance (2162 μmol photons
m−2 s−1) in the temperature range from 15 to 45 °C. Areal rates of dark O2 consumption increased almost linearly with temperature. The apparent activation energy of 18 kJ mol−1 and the corresponding Q
10 value (25 to 35 °C) of 1.3 indicated a relative low temperature dependence of dark O2 consumption due to mass transfer limitations imposed by the diffusive boundary layer at all temperatures. Areal rates of
net photosynthesis increased with temperature up to 40 °C and exhibited a Q
10 value (20 to 30 °C) of 2.8. Both O2 dynamics and rates of gross photosynthesis at the mat surface increased with temperature up to 40 °C, with the most pronounced
increase of gross photosynthesis at the mat surface between 25 and 35 °C (Q
10 of 3.1). In another mat sample, measurements at increasing surface irradiances (0 to 2319 μmol photons m−2 s−1) were performed at 25, 33 (the in situ temperature) and 40 °C. At all temperatures, areal rates of gross photosynthesis saturated
with no significant reduction due to photoinhibition at high irradiances. The initial slope and the onset of saturation (E
k = 148 to 185 μmol photons m−2 s−1) estimated from P versus E
d curves showed no clear trend with temperature, while maximal photosynthesis increased with temperature. Gross photosynthesis
was stimulated by temperature at each irradiance except at the lowest irradiance of 54 μmol photons m−2 s−1, where oxygenic gross photosynthesis and also the thickness of the photic zone was significantly reduced at 40 °C. The compensation
irradiance increased with temperature, from 32 μmol photons m−2 s−1 at 25 °C to 77 μmol photons m−2 s−1 at 40 °C, due to increased rates of O2 consumption relative to gross photosynthesis. Areal rates of O2 consumption in the illuminated mat were higher than dark O2 consumption at corresponding temperatures, due to an increasing O2 consumption in the photic zone with increasing irradiance. Both light and temperature enhanced the internal O2 cycling within hypersaline cyanobacterial mats.
Received: 30 November 1999 / Accepted: 11 April 2000 相似文献
17.
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
18.
This study investigates the reproductive periodicity and reproductive output of the seagrass Zostera novazelandica on two intertidal reefs. Peak numbers of flowering shoots occurred during March (late summer) of two years at both sites
and no flowering shoots occurred during the winter months of July to September. There were greater numbers of flowering shoots
in seagrass patches in the low intertidal zone (up to an average of 55 per 0.1 m2) compared to the middle (up to 20 per 0.1 m2) and upper (up to 9 per 0.1 m2) zones, and about three times greater reproductive output in patches associated with tidepools compared to those not bordering
tidepools. The average number of inflorescences per shoot was 3.1 (±0.25) at one site vs 1.2 (±0.08) at the other, and showed
a progressive decrease from the lower shore to the upper shore. Patches associated with tidepools had twice the number of
inflorescences per shoot (2.8 ± 0.24) than patches not bordering tidepools (1.5 ± 0.16). The number of flowering shoots was
highly correlated with leaf width, leaf length, and ramet density, while the leaf-area index decreased from the lower shore
to the upper shore. The reproductive effort of plants, as measured by the percent biomass invested in flowering shoots during
peak reproduction, was significantly different between sites, tidepool associations, and shore level. For all the variables
measured, there was considerable spatial variation, with significant interaction terms between most factors investigated.
In laboratory experiments, more inflorescences were produced at light intensities of 30 and 300 μE m−2 s−1 than at 100 μE m−2 s−1. At a salinity of 17‰, 1.5 × the number of flowers was produced than at 33‰, while none was formed at 70‰. Plants cultured
at 5 °C had about three times the number of inflorescences than those at 15 °C, while none was formed at 25 °C.
Received: 25 June 1997 / Accepted: 24 September 1997 相似文献
19.
Survival, developmental and consumption rate (Artemia nauplii ingested per day) as well as predation efficiency (ingested per available Artemia nauplii) were studied during the larval development of the shallow-water burrowing thalassinid Callianassa tyrrhena (Petagna, 1792), which exhibits an abbreviated type of development with only two zoeal stages and a megalopa. The larvae,
hatched from berried females from S. Euboikos Bay (Aegean Sea, Greece), were reared at 10 temperature–food density combinations
(19 and 24 °C; 0, 2, 4, 8 and 16 Artemia nauplii d−1). Enhanced starvation resistance was evident: 92 and 58% of starved zoeas I molted to zoea II, while metamorphosis to megalopa
was achieved by 76 and 42% of the hatched zoeas at 19 and 24 °C, respectively. The duration of both zoeal stages was affected
by temperature, food density and their interaction. Nevertheless, starvation showed different effects at the two temperatures:
compared to the fed shrimp, the starved zoeae exhibited accelerated development at 19 °C (8.4 d) but delayed metamorphosis
at 24 °C (5.9 d). On the other hand, both zoeal stages were able to consume food at an increased rate as food density and
temperature increased. Predation efficiency also increased with temperature, but never exceeded 0.6. Facultative lecithotrophy,
more pronounced during the first zoeal stage of C.tyrrhena, can be regarded as an adaptation of a species whose larvae can respond physiologically to the different temperature–food
density combinations encountered in the wide geographical range of their natural habitat.
Received: 28 February 1998 / Accepted: 21 October 1998 相似文献
20.
To assess the effects of both temperature and food ration on gonad growth and oogenesis of the green sea urchin, Strongylocentrotus droebachiensis (O.F. Müller), individuals collected December 1996 (winter experiment) and June 1997 (summer experiment) were maintained
for 3 months in one of four experimental treatments: (1) 3 °C and fed ad libitum (high ration), (2) 3 °C and fed one-seventh of the maximum ration (low ration), and (3) 12 °C and fed the high ration; (4) 12 °C and fed
the low ration. All individuals were fed an artificial diet and exposed to only 1 h of light every day. At the end of both
experiments, mean gonad indices of sea urchins fed the high ration had increased significantly (11–24% and 6–19% in the winter
and summer experiments, respectively), while the gonad indices of individuals fed the low ration did not change. At the high
ration (both experiments), the increase in gonad index of sea urchins occurred primarily as the result of a significant increase
in the mass of nutritive phagocytes, as revealed by histological analyses. Primary oocytes were significantly larger in individuals
held at 3 °C than at 12 °C throughout the winter experiment, regardless of food ration; during the summer experiment, primary
oocytes were significantly larger in individuals receiving the high ration, regardless of the temperature at which they were
held. These results suggest that: (1) food availability is the most important factor regulating energy storage and the relative
size of gonads throughout the year, (2) temperature affects the rate of growth and maturation of primary oocytes during the
later stages of oogenesis, and (3) once gametogenesis has been initiated, mature ova will be produced, even under conditions
of low food availability. Conditions of high food availability in summer and low temperature in winter would thus favor reproductive
output in sea urchin populations.
Received: 1 March 2000 / Accepted: 4 October 2000 相似文献