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1.
Eggs and larvae of the Senegal sole, Solea senegalensis Kaup, were reared from fertilization until the end of metamorphosis, which occurs by Day 17 after hatching at 19.5 °C. Changes
in energy content and biomass quality were studied in terms of dry weight and of carbon, nitrogen and energy content. S. senegalensis spawned eggs of about 1 mm diameter which hatched 38 h after fertilization. Average dry weight of individual eggs was 46 μg,
the chorion accounting for about 18% of total dry weight. Gross energy of recently fertilized sole eggs was approximately
1 J egg−1. From fertilization to hatching, eggs lost 8% of their total energy (chorion not included). After hatching, larvae lost 14%
of their initial energy until the start of feeding which occurred about 48 h afterwards. The principal components catabolized
during embryogenesis were carbon-rich compounds that decreased by 26%, while nitrogen-rich compounds decreased by only 10%
and were practically unaltered from hatching to the start of feeding. Feeding larvae displayed constant growth during the
period studied (specific growth rate on a dry weight basis was 0.26 d−1). The relative proportion of carbon and nitrogen content revealed an accumulation of high energy compounds in the days before
metamorphosis. By Day 14, the energy content reached values similar to those of recently hatched embryos, but decreased again
during metamorphosis.
Received: 10 June 1998 / Accepted: 28 January 1999 相似文献
2.
Free amino acids and energy metabolism in eggs and larvae of seabass, Lates calcarifer 总被引:3,自引:0,他引:3
Contents of free amino acids (FAA), protein and ammonium ions together with rates of ammonia excretion and oxygen consumption
were measured in order to study the role of FAA as an energy substrate in developing eggs and larvae of seabass (Lates calcarifer) maintained in seawater (30 ppt) at 28 °C without feeding. Initially eggs contained 25.3 nmol ind−1 of FAA of which 21.5 nmol was rapidly utilised by the developing eggs and larvae during the period up to 40 h post spawning
(PS) when nearly all the yolk had been resorbed. During the same period, a net increase in protein content of 1.7 μg ind−1 was observed, indicating that the major part of the amino acids lost from the free pool had been polymerised into body proteins.
Assuming that the balance of the FAA after protein synthesis was used entirely for energy metabolism, FAA appeared to be an
important energy substrate during the embryonic stages (2 to 16 h PS); after hatching, the contribution of FAA to energy metabolism
was less significant. From 50 h PS until the end of the study period at 100 h PS, amino acids derived from somatic protein
were used for energy metabolism. For the overall period from just after spawning up to 100 h PS, the data indicate that ca.
14% of the total aerobic energy metabolism was derived from amino acid catabolism.
Received: 26 September 1997 / Accepted: 1 April 1998 相似文献
3.
It has been hypothesized that marine fish larvae in the advanced stages of starvation would show increased density (ρ = mass
volume−1) from water loss due to osmoregulation failure. Changes in larval buoyancy are currently attributed to swim bladder regulation
and protein synthesis or catabolism. Osmoregulation-related changes in density is an alternative mechanism, the importance
of which remains untested in the laboratory and the influence of which on vertical distributions is unknown. We provide evidence
that loss of osmotic control is a plausible mechanism for increased density of larval cod (Gadus morhua L.). Furthermore, our results show that this mechanism is not restricted to larvae in the advanced stages of starvation.
“Relative” larval densities are estimated using a modified density gradient. We use a gravimetric method to separate the effects
of nutrition from osmoregulation failure. We assessed the importance of sampling strata on estimates of larval density. Proportional
sampling within three depth strata (stratified sample) produced the least biased method for determining the “average” density
of a population of larvae in laboratory culture. Larvae sampled from the bottom third of the culture tank were significantly
more dense then those sampled from the surface. This was true for larvae of all ages. The average change in density from hatching
till death from starvation for larvae sampled in the surface stratum was nominal (Δρ = 5.0 × 10−4 g cm−3), while the change for those sampled from the bottom stratum was large (Δρ = 3.8 × 10−3 g cm−3). These large density differences suggest that larvae sampled from the bottom stratum were either osmotically stressed or
were facultatively changing their density via regulatory pathways. Preliminary observations suggest that vitality is lower
amongst those larvae which are sampled near the bottom. The small change in average density of larvae sampled from the surface
stratum was due to starvation. The density differences we observed between “osmotically stressed” and “starving” larvae could
readily have been misconstrued as differences in feeding and growth experienced by individual larvae. The potential bias of
increased density from osmoregulation failure must be considered as a factor in experimental designs developed to assess the
effect of fed and starved treatments on buoyancy for larvae of all ages. The simple bioassay we describe may prove useful
both as a means of assessing larval condition and as a mechanism for evaluating factors affecting larval vertical distributions
in the field.
Received: 13 January 1997 / Accepted: 3 February 1997 相似文献
4.
The relationship between somatic growth and incremental growth of otoliths of Pacific saury, Cololabis saira (Brevoort), larvae under different temperature conditions was studied in the laboratory for three age groups (0 to 9, 10
to 20 and 20 to 30 d posthatch). Larvae were incubated from hatching to 9 d at 24, 20, and 16 °C. Further, larvae initially
reared at an ambient temperature of 21.7 °C were transferred to experimental temperatures of 22, 18, and 14 °C on Day 10 and
reared to Day 20 and similarly from Day 20 and reared to Day 30 posthatch. Growth trajectories of larvae sampled at the end
of the three experiments were back-calculated using the biological intercept method and compared to the measured values 0
and 5 d after the start of each experiment. Back-calculated knob length at the different temperatures indicated no significant
difference to the measured knob lengths except for the cases at 20 °C from hatching to 9-d-old larvae and at 14 °C from 20-
to 30-d-old larvae. The close correlation between somatic and otolith growth shown in this study indicated the feasibility
of estimating the growth history of Pacific saury larvae using otolith readings.
Received: 14 April 1999 / Accepted: 27 October 1999 相似文献
5.
P. J. Krug 《Marine Biology》1998,132(3):483-494
A San Diego population of the opisthobranch mollusc Alderia modesta (Lovén, 1844) exhibits poecilogony, the presence of two development modes within a single species. In spring, half of the
adults spawned masses containing ∼300 eggs with a mean diameter of 68 μm. After 3 d, these egg masses hatched planktotrophic
veligers with a maximum shell dimension of 116 μm. The remaining adults spawned masses containing ∼30 eggs with a mean diameter
of 105 μm. These egg masses hatched after 5 to 6 d, releasing lecithotrophic larvae with a maximum shell dimension of 186 μm.
About 1% of field-collected adults produced mixed clutches containing a continuum of larval sizes, spanning the size extremes
of planktotrophy and lecithotrophy and hatching larvae with a mean maximum shell dimension of 152 μm. Adults producing planktotrophic
and lecithotrophic larvae were interfertile, and no hybrid breakdown was observed through the F3 generation. When starved,
adults which previously produced only lecithotrophic larvae switched to producing planktotrophic larvae or mixed clutches
with both planktotrophic and lecithotrophic larvae. Sequence-polymorphisms from a portion of the mitochondrial cytochrome
c oxidase I gene support the conclusion that the two reproductive morphs represent a single species. Most of the lecithotrophic
larvae and a small percentage of the larvae from mixed clutches were metamorphically competent within 3 d of hatching. A. modesta is the only molluscan species as yet known to have both planktotrophic and pelagic lecithotrophic development within a single
natural population.
Received: 14 August 1997 / Accepted: 11 April 1998 相似文献
6.
Copepod resting eggs are abundant in the seabed of many bays and estuaries where they provide a potential source of recruits
for growth of planktonic populations. In the northeastern Gulf of Mexico the copepod Centropages hamatus (Lillejeborg) occurs in the water column only during the late fall, winter and early spring. The species produces subitaneous
and diapause eggs, and both egg types have been found in the seabed. We determined the longevity of these two egg types to
ascertain their potential for contributing to the growth of the planktonic population and for sustaining a persistent egg
bank. Eggs were collected from females and incubated in the laboratory under temperature and oxygen conditions chosen to simulate
field conditions. The diapause eggs were also exposed to sulfide. The total hatching success of subitaneous eggs in two experiments
declined from highs of 78 and 97% to zero after 60 and 90 d of exposure to anoxia. The total hatching success of diapause
eggs that were exposed to anoxia for 90 d however was typically greater than 80%. Some diapause eggs hatched after being incubated
under anoxia for 437 d. Diapause eggs survived longer at ambient field temperatures when incubated under anoxia (437 d) compared
to normoxia (118 d). Exposure to sulfide did not result in greater mortality of diapause eggs compared to anoxia alone. Diapause
eggs that were incubated at ambient field temperatures did not hatch when exposed to normoxia until the temperature dropped
to <20 °C. The results of this study suggest that C.␣hamatus sustain a short-term reserve of subitaneous eggs in the seabed that provides recruits for the current year's population.
The greater longevity of diapause eggs suggests that they sustain the seasonal reappearance of the species year after year
in the northeastern Gulf of Mexico. However, the contribution of diapause eggs of C. hamatus from the Gulf of Mexico to a persistent egg bank is questionable since hatching ceased after 437 d.
Received: 30 July 1997 / Accepted: 18 January 1998 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.
Benjamin J. Laurel Louise A. Copeman Thomas P. Hurst Christopher C. Parrish 《Marine Biology》2010,157(8):1713-1724
The lipid/fatty acid composition of marine fish eggs and larvae is linked with buoyancy regulation, but our understanding
of such processes is largely restricted to species with pelagic eggs. In this study, we examined developmental changes in
the lipid/fatty acids of eggs and embryos of Pacific cod (Gadus macrocephalus), a species that spawns demersal eggs along coastal shelf edges, but as larvae must make a rapid transition to the upper
reaches of the water column. Adult Pacific cod were collected in the Gulf of Alaska during the spawning season and eggs of
two females were artificially fertilized with sperm from three males for each female. The eggs were subsequently reared in
the laboratory to determine (1) how lipids/fatty acids were catabolized during egg and larval development, and (2) whether
lipid/fatty acid catabolism had measurable effects on egg/embryo density. Eggs incubated at 4°C began hatching after 3-weeks
and continued to hatch over a 10-day period, during which there was a distinct shift in lipid classes (phospholipids (PL),
triacyglycerols (TAG), and sterols (ST)) and essential fatty acids (EFAs: 22:6n-3 (DHA), 20:5n-3 (EPA), and 20:4n-6 (AA)).
In the egg stage, total lipid content steadily decreased during the first 60% of development, but just prior to hatch we observed
an unexpected 2–3-fold lipid increase (~6–9 μg individual−1) and a significant drop in egg density. The increase in lipids was largely driven by PL, with evidence of long-chained fatty
acid synthesis. Late-hatching larvae had progressively decreasing lipid and fatty acid reserves, suggesting a shift from lipogenesis
to lipid catabolism with continued larval development. Egg density measures suggest that lipid/fatty acid composition is linked
to buoyancy regulation as larvae shift from a demersal to a pelagic existence following hatch. The biochemical pathway by
which Pacific cod are apparently able to synthesize EFAs is unknown, therefore representing a remarkable finding meriting
further investigation. 相似文献
9.
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
10.
The functional response of the aspects of reproductive success of a southwestern Baltic population of Acartia tonsa (Copepoda: Calanoida) was quantified in the laboratory using wide ranges in temperatures and salinities. Specifically, daily
egg production (EP, # female−1 day−1) was determined for 4 or 5 days at 18 different temperatures between 5 and 34°C and the time course and success of hatching
were evaluated at 10 different temperatures between 5 and 23°C. The effect of salinity (0 to 34 psu) on egg hatching success
was also examined. The highest mean rates of EP were observed between 22 and 23°C (46.8–50.9 eggs female−1 day−1). When studied at 18 psu, hatching success of eggs increased with increasing temperature and was highest (92.2%) at 23°C.
No hatching was observed for eggs incubated at low temperatures (≤12°C) that were produced by females acclimated to temperatures
≤10°C indicating a possible thermal threshold between 10.0 and 13.0°C below which only the production of diapause (or low
quality) eggs exists in this population. When tested at 18°C, the hatching success of eggs incubated at 15 different salinities
increased asymptotically with increasing salinity and was maximal (81.4–84.5%) between 17 and 25 psu. The high reproductive
success observed over wide ranges in temperatures and salinities in this Baltic population demonstrates one of the mechanisms
responsible for the cosmopolitan distribution of this species within productive, estuarine and marine habitats. 相似文献
11.
Food limitation is likely to be a source of mortality for fish larvae in the first few weeks after hatching. In the laboratory,
we analyzed all aspects of foraging in cod larvae (Gadus morhua Linnaeus) from 5 to 20 d post-hatching using protozoa (Balanion sp.) and copepod nauplii (Pseudodiaptomus sp.) as prey. A camera acquisition system with two orthogonal cameras and a digital image analysis program was used to observe
patterns of foraging. Digitization provided three-dimensional speeds, distances, and angles for each foraging event, and determined
prey and fish larval head and tail positions. Larval cod swimming speeds, perception distances, angles, and volumes increased
with larval fish size. Larval cod swam in a series of short intense bursts interspersed with slower gliding sequences. In
94% of all foraging events prey items were perceived during glides. Larval cod foraging has three possible outcomes: unsuccessful
attacks, aborted attacks, and successful attacks. The percentage of successful attacks increased with fish size. In all larval
fish size classes, successful attacks had smaller attack distances and faster attack speeds than unsuccessful attacks. Among
prey items slowly swimming protozoans were the preferred food of first-feeding cod larvae; larger larvae had higher swimming
speeds and captured larger, faster copepod nauplii. Protozoans may be an important prey item for first-feeding larvae providing
essential resources for growth to a size at which copepod nauplii are captured.
Received: 20 April 1999 / Accepted: 12 January 2000 相似文献
12.
Growth trajectories of individual larvae of Japanese sardine, Sardinops melanostictus, caught in the coastal waters off western Japan were back-calculated from the first feeding stage up to date of capture (approximate
size of 20 to 35 mm total length; TL) based on individually determined allometric relationships between otolith daily ring
radii and fish total lengths. The larvae in January-, February-, and March-hatched cohorts in the coastal waters grew faster
and more uniformly than those in the oceanic waters offshore of the Kuroshio current. Growth trajectories of the three hatch-month
cohorts were similar and could be expressed by the Gompertz model. The inflection points of the growth curves were reached
at 9 to 11 d after hatching, when larvae were 10.8 to 11.8 mm TL. Maximum growth rates at these points were 0.80 to 0.85 mm
d−1. Growth rates gradually declined after the inflection points, and larval TLs converged into the infinite length of 29 to
32 mm, the sizes at which metamorphosis from larvae to juveniles is initiated. This asymptotic growth pattern in the larval
stage resulted in the narrow ranges in TLs in spite of the wide range of ages of the larvae caught by boat seiners in the
coastal waters. Slow growth and therefore long duration of the metamorphosing stage could be influential in determining the
cumulative total mortality in the early life stages of the Japanese sardine.
Received: 14 July 1996 / Accepted: 20 August 1996 相似文献
13.
J. H. M. Kouwenberg H. I. Browman J. J. Cullen R. F. Davis J.-F. St-Pierre J. A. Runge 《Marine Biology》1999,134(2):269-284
In the Gulf of St. Lawrence, Canada, productivity-determining biophysical interactions occur in the upper 0 to 30 m of the
water column. The eggs and larvae of several commercially important marine invertebrates and fishes (e.g. Gadus morhua L.) are found in this layer. Measurements of the diffuse attenuation coefficients for ultraviolet-B radiation (280 to 320 nm,
UV-B) at various locations in this geographic region indicated maximum 10% depths (the depth to which 10% of the surface energy
penetrates at a given wavelength) of 3 to 4 m at a wavelength of 310 nm. This represents a significant percentage of the summer
mixed-layer water column: organisms residing in this layer are exposed to UV-B radiation. Laboratory experiments using a Xenon-arc-lamp
based solar simulator revealed that cod embryos exposed to UV-B exhibited high wavelength-dependent mortality. The strongest
effects occurred under exposures to wavelengths below 312 nm. This susceptibility was also dependent upon developmental stage;
mortality was particularly high during gastrulation. At the shorter wavelengths (<305 nm) UV-B-induced mortality was strongly
dose-dependent, and not significantly influenced by dose-rate. The biological weighting function (BWF) derived for UV-B-induced
mortality in cod eggs is similar to that reported for naked DNA – suggesting that the mortality is a direct result of DNA
damage. There was no evidence of a detrimental effect of ultraviolet-A radiation (320 to 400 nm). Calculations based upon
the BWF indicate that, under current noon surface irradiance, 50% of cod eggs located at or very near (within 10 cm) the ocean
surface will be dead after 42 h of exposure. Under solar spectral irradiance simulating a 20% decrease in ozone layer thickness,
this time drops to 32 h. These are first-order estimates based upon surface irradiance taken at a time of day during which
the values would be maximal. Nonetheless, they illustrate the relative changes in UV-B impacts that will result from ozone
layer depletions expected over the coming decades. It is also important to point out that variability in cloud cover, water
quality, and vertical distribution and displacement of cod eggs and larvae within the mixed layer, can all have a greater
effect on the flux of UV-B radiation to which fish eggs are exposed than will ozone layer depletion at these latitudes.
Received: 2 March 1998 / Accepted: 18 December 1998 相似文献
14.
The pattern of settlement over time of three broadcast spawning coral species (Cyphastrea serailia, Acanthastrea lordhowensis, and Goniastrea australensis) from the Solitary Islands (30°00′S; 153°20′E) was studied in 1995 and 1996 in order to determine the maximum length of time
these larvae could remain in the water column and still retain the ability to settle and metamorphose. Larvae were maintained
in aquaria and the number which had settled on biologically-conditioned tile pairs was monitored every 5 to 10 d. While the
majority of larvae settled quickly after becoming competent, some larvae survived and settled for extended periods after spawning.
Competency periods ranged from 26 d for C. serailia to 56 d for G. australensis and 78 d for A. lordhowensis. These data greatly extend the known competency periods for larvae of broadcast-spawning corals and indicate the potential
for transport of broadcast-spawned coral larvae over large distances. Medium to long-distance larval dispersal of the species
studied provides a mechanism for their widespread distribution in subtropical regions, on reefs which are often widely spaced
and relatively isolated.
Received: 27 May 1997 / Accepted: 27 November 1997 相似文献
15.
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
16.
B. A. Kerrigan 《Marine Biology》1997,127(3):395-402
The effects of food availability, female size, and social interactions on the quality of Pomacentrus amboinensis larvae at hatching were examined using two field-based experiments. In Experiment 1, food availability and female size significantly
influenced size, eye diameter and levels of yolk reserves of larvae at hatching. Small females (47 to 52 mm standard length,
SL) whose diets were not supplemented, produced the longest larvae (3.0 ± 0.01 mm total length, TL) with the least yolk reserves
(50.1 ± 1.04 μm2). Irrespective of female size, those that received additional food produced larvae with the largest yolk-sacs (large females:
87.60 ± 1.53 μm2; small females: 80.14 ± 1.24 μm2). In Experiment 2, interactions with conspecifics had a greater affect on the somatic development of larvae at hatching than
food availability. Increased social interactions resulted in larvae that were ⋍3% longer, with 2% greater head depth, than
larvae from females that spawned in isolation on the experimental reefs. Fed females produced larvae with ⋍20% more yolk than
larvae from females whose diets were not supplemented. All three factors (food availability, female size, and intensity of
social interactions) tested within these experiments vary spatially and temporally among reefs. There is the potential, therefore,
for larvae at the onset of the planktonic stage to vary in quality, level of development, and probability of survival.
Received: 12 August 1996 / Accepted: 26 August 1996 相似文献
17.
In spring 2004 and 2005 we performed two sets of experiments with Baltic sprat (Sprattus sprattus balticus Schneider) eggs and larvae from the Bornholm Basin simulating ten different temperature scenarios. The goal of the present
study was to analyse and parameterise temperature effects on the duration of developmental stages, on the timing of important
ontogenetic transitions, growth during the yolk sac phase as well as on the survival success of eggs and early larval stages.
Egg development and hatching showed exponential temperature dependence. No hatching was observed above 14.7°C and hatching
success was significantly reduced below 3.4°C. Time to eye pigmentation, as a proxy for mouth gape opening, decreased with
increasing temperatures from 17 days post hatch at 3.4°C to 7 days at 13°C whereas the larval yolk sac phase was shortened
from 20 to 10 days at 3.8 and 10°C respectively. Maximum survival duration of non-fed larvae was 25 days at 6.8°C. Comparing
the experimental results of Baltic sprat with existing information on sprat from the English Channel and North Sea differences
were detected in egg development rate, thermal adaptation and in yolk sac depletion rate (YSDR). Sprat eggs from the English
Channel showed significantly faster development and the potential to develop at temperatures higher than 14.7°C. North Sea
sprat larvae were found to have a lower YSDR compared to larvae from the Baltic Sea. In light of the predictions for global
warming, Baltic sprat stocks could experience improved conditions for egg development and survival. 相似文献
18.
We performed an intensive year-round sampling with the aim of studying the abundance of sponge larvae in four Mediterranean
benthic communities: photophilic algae, sciaphilous algae, semi-obscure (i.e. low light-intensity) caves and sandy bottoms.
We record here for the first time, a larval bloom of Cliona viridis (Schmidt 1862), the most common excavating sponge in the Mediterranean, which took place simultaneously in several rocky
communities of the Blanes sub-littoral (NE Spain), and discuss the role of restricted larval dispersal in the distribution
of adult sponges. In the communities studied, C. viridis larvae bloomed synchronously once, in June. Spawning and consequent embryo development presumably occurred in May, when water
temperature was 16 °C. The free larva is a small, evenly ciliated, weakly swimming parenchymella with low dispersal capabilities.
The number of larvae m−3 and sponge abundance (as percent cover and biomass) were significantly higher in the community of sciaphilous algae than
in the other communities studied. Because of limited larval dispersal, larval and adult abundance in the communities were
positively correlated. Larvae developed into juvenile sponges 10 to 15 d after settlement. Settlers displayed distinctive
features: a peripheral cuticle, vacuolar etching-like cells at the sponge base, absence of oscular chimneys, and the presence
of zooxanthellae, which were presumably transmitted during oocyte maturation.
Received: 24 January 2000 / Accepted: 4 July 2000 相似文献
19.
P. Munk 《Marine Biology》1995,122(2):205-212
Fish larvae meet diverse environmental conditions at sea, and larval growth and chance of survival depend on a flexible response to environmental variability. The present study focuses on the flexibility of the foraging behaviour of larval cod in a series of laboratory experiments on larval search activity, prey selectivity, and hunger in a variable prey environment. Gadus morhua eggs were collected in March 1992 and 1993 from the Kattegat area, Denmark, fertilised and incubated in the laboratory. After hatching, the larvae were transferred to rearing tanks of 172 litres. The behaviour of larvae (6 to 7 mm long) was observed visually, and prey attacks, swimming activity and gut contents were registered across a range of 1 to 120 copepod nauplii l-1. When prey density decreased, larvae increased their swimming activity, increased their responsiveness to prey (distance of reaction) and decreased their prey size selectivity. Behavioural response was to a large degree determined by the level of hunger, represented by the number of newly ingested prey in the gut. The findings show that cod larvae have a flexible response to changes in feeding conditions and imply that larvae can grow and survive even in the lower range of (mean) prey densities measured at sea. 相似文献
20.
The content of free amino acids (FAA) in the cod (Gadus morhua L.) egg is about 200 nmol at spawning, decreasing by about 100 nmol/egg during the egg stage and about 75 nmol/larva during the yolksac larval stage. Together, alanine, leucine, serine, isoleucine, lysine, and valine account for about 75% of the decrease. Ammonium accumulates gradually during the egg stage and is quickly excreted after hatching. The body protein content is maintained during the egg and yolksac larval stages. The measured oxygen uptake of the cod embryo during the egg and yolksac larval stages accounts for about 85% of the oxygen necessary to catabolize the FAA disappearing during this period. Ammonia excretion of the cod embryo, as taken from literature data, is similar to the expected ammonia production from catabolism of the FAA. Our data suggest that FAA are a major substrate for aerobic energy production in cod eggs and yolksac larvae. The implication of this finding for the production of a favourable first-feed for cod and other cultivated marine fish larvae, and for the selection of high quality eggs of marine fishes, is stressed. 相似文献