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1.
The present study addresses the effect of maternal diet on hatching success and condition of embryos and larvae of Antarctic
krill Euphausia superba. Lipid and fatty acid content and composition were determined in field and laboratory samples. Developmental stages analyzed
in embryos included: multiple-cell, gastrula, and limb-bud stages. Larval stages analyzed included: nauplius I, nauplius II,
and metanauplius. Laboratory-reared embryos were spawned by gravid females incubated under three feeding groups: (1) phytoplankton
mixture, (2) phytoplankton mixture and minced clam, and (3) phytoplankton mixture, minced clam, and commercial larval food.
Hatching success was highest in group 3 (100%), lowest in group 1 (0%), and highly variable in field samples (0–48%). Lipid
decreased slightly in embryos during embryonic development, while large decreases in lipid were found during nauplius development.
High levels of 18:2(n-6), 20:4(n-6), and 22:6(n-3) observed with group 3 samples coincided with high hatching success in krill
embryos. The ratio of 22:6(n-3)/20:5(n-3) also correlated to hatching success of embryos. The fatty acid profile of embryos
in group 3 was similar to that of the field-collected embryos, reflecting the contribution of the commercial larval food in
the maternal diet. In our study, the maternal diet was found to influence the fatty acid composition of embryos and in turn
affects the hatching success of krill. Specific polyunsaturated fatty acids appeared to play important roles in embryogenesis
in krill. 相似文献
2.
Teegavarapu R. Rao 《Marine Biology》1974,24(2):155-162
Effects of salinity on embryonic development and survival were determined for eggs and larvae of the California killifish Fundulus parvipinnis Girard. Incubation salinities over the range of 5 to 14 S produced the shortest incubation period, maximum yolk-conversion efficiency, largest larval size at hatching, and maximum viable hatch. Various morphometric measurements of the newly-hatched larvae were influenced significantly by incubation salinity. Fertilization salinity also effected certain development criteria; in general, lower fertilization salinities resulted in shorter incubation periods and larger larvae at hatching. A salinity range of 5 to 14 S is anggested as a physiological optimum, and the known freshwater affinity of the species suggests that an eventual freshwater colonization by the California killifish is possible.Based on a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, University of California, Irvine. 相似文献
3.
Summary. Recent studies indicate that amphibian eggs are capable of hatching plasticity in response to chemical cues released by predators
feeding on conspecific eggs or larvae. However, information is scarce on the relative importance of predator and conspecific
cues in such a process. In particular, no attempt has been made to compare the effects of embryonic exposures to chemical
cues indicative of a predation risk for eggs and larvae, although both life stages can co-occur in natural habitats. In this
context, common frog embryos (Rana temporaria) were raised until hatching in the presence of crushed conspecific extracts from eggs and tadpoles to assess their respective
influences on some hatching and larval traits. While a significant delay in hatching time was observed in embryos exposed
to chemical cues from tadpole extract, this life-history shift appeared unaffected by embryonic exposure to egg extract. Hatchlings
derived from eggs incubated in the presence of both conspecific extracts showed a significantly greater weight than unexposed
controls. However, such an effect was no longer apparent 15, 30 and 50 days after hatching, suggesting that embryonic exposure
to chemical cues from damaged conspecific eggs and tadpoles has no influence on larval growth. Lastly, morphological measurements
performed on hatchlings and older tadpoles (15, 30 and 50 days old) revealed no significant effect of embryonic treatments
on the shape of body and tail. 相似文献
4.
The importance of salinity experienced during embryonic development and initial larval biomass on larval growth was studied
in the South American estuarine crab Chasmagnathus granulata. Ovigerous females were maintained at three salinities (15, 20, and 32‰) from egg laying to hatching of zoea l. Larvae from
all treatments were reared under constant conditions of photoperiod (12∶12), temperature (18°C), and salinity (first instar
at 20‰, subsequent instars at 32‰). Biomass was measured as dry weight, carbon, and nitrogen content per individual at egg
laying, hatching of zoea l, premoult zoea l, and zoea 4, and in 8-day-old megalopa. From hatching to premoult zoea 4, biomass
was higher for larvae from prehatching salinities of 15 and 32‰. There was a significant positive correlation between biomass
at hatching and at premoult zoea l and zoea 4. Accumulated biomass during zoeal stages tended to be higher for larvae from
broods with higher biomass at hatching, although this trend was not always significant. Zoea 4 either directly metamorphosed
to megalopa or moulted to zoea 5, following, respectively, a short or long developmental pathway. The proportion of zoea 4
that followed the long pathway was negatively correlated with biomass of zoeal stages. Biomass at hatching was correlated
with biomass of megalopae developed through the short pathway, although it was not correlated with the accumulated biomass
at this stage. Megalopae developed through the long pathway (i.e. metamorphosed from zoeae 5) had higher biomass than those
from the short pathway. The present results suggest that prehatching salinity and initial egg and larval biomass can be very
important for larval growth.
Published online: 9 August 2002 相似文献
5.
Female mud crabs, Rhithropanopeus harrisii, carrying newly extruded eggs, were collected from the Petaluma River (San Francisco Bay Estuarine System, California, USA) in summer 1985, and exposed to factorial combinations of temperature (20°, 25° or 30°C) and salinity (2, 5, 15, 25, or 32%.). Upon hatching, dry weights of 12 to 15 h-old zoeae were determined. Subgroups of the remaining zoeae were transferred from hatching salinities to the salinities listed above and raised until metamorphosis to megalopa. Low salinities reduced zoeal dry weights by as much as 25%. Temperature played a secondary role in reduction of hatching weight of zoeae. Survival of larvae through zoeal development was best when hatching and rearing salinities were the same; in this case, overall survival increased with temperature. Both duration of zoeal development and megalopal dry weights were strongly influenced by temperature and rearing salinity, with only a small contribution from hatching salinity. The influence of hatching salinity was most obvious at extremes of the range tested. These studies indicate that physical conditions during embryogenesis profoundly influence subsequent larval development. Interpretation of experimental approaches to study ecophysiological adaptations of larval stages should not neglect the role of physical conditions during embryogenesis. 相似文献
6.
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
7.
Toby Mitchell Lesley A. Alton Craig R. White Craig E. Franklin 《Conservation biology》2012,26(6):1112-1120
Global increases in ultraviolet‐B radiation (UVBR) associated with stratospheric ozone depletion are potentially contributing to the decline of numerous amphibian species around the world. Exposure to UVBR alone reduces survival and induces a range of sublethal effects in embryonic and larval amphibians. When additional environmental stressors are present, UVBR can have compounding negative effects. Thus, examination of the effects of UVBR in the absence of other stressors may substantially underestimate its potential to affect amphibians in natural habitats. We examined the independent and interactive effects of increased UVBR and high conspecific density would have embryonic and larval striped marsh frogs (Limnodynastes peronii). We exposed individuals to a factorial combination of low and high UVBR levels and low, medium, and high densities of striped marsh frog tadpoles. The response variables were time to hatching, hatching success, posthatch survival, burst‐swimming performance of tadpoles (maximum instantaneous swim speed following an escape response), and size and morphology of tadpoles. Consistent with results of previous studies, we found that exposure to UVBR alone increased the time to hatching of embryos and reduced the burst‐swimming performance and size of tadpoles. Similarly, increasing conspecific density increased the time to hatching of embryos and reduced the size of tadpoles, but had no effect on burst‐swimming performance. The negative effect of UVBR on tadpole size was not apparent at high densities of tadpoles. This result suggests that tadpoles living at higher densities may invest relatively less energy in growth and thus have more energy to repair UVBR‐induced damage. Lower densities of conspecifics increased the negative effects of UVBR on developing amphibians. Thus, low‐density populations, which may include declining populations, may be particularly susceptible to the detrimental effects of increased UVBR and thus may be driven toward extinction faster than might be expected on the basis of results from single‐factor studies. Relaciones entre la Densidad Conespecífica y los Efectos de la Radiación Ultravioleta‐B sobre el Tamaño de Renacuajos de Limnodynastes peronei 相似文献
8.
Combined effects of temperature and salinity on embryos and larvae of the northern bay scallop Argopecten irradians irradians 总被引:1,自引:0,他引:1
The combined effects of temperature and salinity on embryonic development and on larval survival and growth to setting size of the northerm bay scallop Argopecten irradians irradians (Lamarck) were studied in the laboratory. A 6x6 complete factorial design was used; temperatures ranged from 10° to 35°C, at 5C° intervals, and salinities ranged from 10 to 35S, at 5S intervals. Response-surface contour diagrams were generated to provide estimates of conditions for optimal responses. Normal development of embryos occurred over a very narrow range of temperature and salinity. Survival of larvae occurred over a wider range of temperature and salinity than did embryonic development or growth of larvae. Satisfactory growth (>70% of the maximum observed value) occurred only at high temperature-high salinity conditions; optimal conditions for survival occurred at similar salinities, but at slightly lower temperatures. Temperatures of 35°C or greater and/or salinities of 10S or less were lethal for all life stages studied. Both salinity and temperature exerted significant effects on development and survival, but temperature was clearly the dominant factor influencing growth. It is suggested that northern bay scallop embryos and larvae be reared at their respective optimal temperature-salinity levels so as to increase efficiency of aquaculture operations.This paper is adapted from a thesis submitted to the College of Fisheries, University of Washington, in partial fulfillment of the requirements for the MS degree. This study was conducted at the NMFS Laboratory in Milford, Connecticut, USA 相似文献
9.
Renae J. Brodie Richard Styles Stephen Borgianini Jenice Godley Khayree Butler 《Marine Biology》2007,152(6):1283-1291
Dense populations of the fiddler crab Uca minax (Le Conte 1855) are common along tidally influenced freshwater rivers and streams >50 km from the sea. Adults do not migrate
from inland sites to release larvae, but instead release them directly into an environment where the zoeae cannot survive.
Laboratory salinity tolerance experiments were used to determine how long larvae from the inland-most population of U. minax along the Pee Dee River, South Carolina, USA can survive zero salinity compared to larvae from a brackish water population
(salinity 5) near the mouth of Winyah Bay in the same estuary. Larvae from the brackish water population were also exposed
to a salinity of 5 and their survival tracked. These experiments were conducted from May to August 2004 and 2005. To determine
if inland larvae suffered significant mortality in transit due to salinity stress, current profiles were measured in the field
and used to model the time taken by a larva using ebb-tide transport to travel to permissive salinities. The laboratory tolerance
experiments showed that larvae from the inland freshwater population had LT50’s of 4–5 days at 0 salinity, which were significantly
longer than those of the brackish water zoeae (2–3 days). Zoeae from the brackish water population survived for at least one
larval molt at a salinity of 5 with LT 50’s of ∼12 days. Estimated travel times to reach permissive salinities from the inland-most
population based on current profiles were 3–5 days for larvae using night-time only ebb-tide transport and 1.5–2.5 days for
those using ebb-tide transport both day and night. Previously published field data indicate that U. minax larvae do use both day- and night-time ebb-tide transport, and are found in high densities in the water column during the
day. These results lead to the conclusion that U. minax stage I zoeae do not undergo significant salinity-induced mortality during their 50+ km trip to the sea. 相似文献
10.
Size regulation in larvae of the crustacean Balanus eburneus (Cirripedia: Thoracica) 总被引:1,自引:0,他引:1
We tested the hypothesis that larval size in the acorn barnacle Balanus eburneus Gould (Cirripedia Thoracica) varies in relation to food availability. In March–November 1980, and March–July 1981, larvae were obtained from adult Balanus eburneus collected in the Newport River, North Carolina, USA. Carapace length and width of larvae reared at three different food concentrations were measured. Mean naupliar instar size was independent of food concentration. Mean size of the cypris instar increased with increasing food level. Greater cypris size could be attributed to increased food reserves in the preceding naupliar stage, and was coinciden with inmarked increase in metamorphic success. Variation in instar size remained constant or declined during naupliar development, but increased sharply at the molt to the cyprid. Naupliar size regulation involved: (1) conservation of a molt increment specific for each naupliar-naupliar molt, (2) an inverse relationship between premolt size and the molt increment during the first five naupliar instars, and (3) an increase in the precision of the molt increment at the molt to the sixth naupliar instar. Experimental evidence implies that size regulation in Balanus eburneus limits variation about a fixed final naupliar size (e.g. volume). Measurement of naupliar size, accumulated energy reserves, survival and development time, and cypris metamorphic success indicated that naupliar cuticular growth is the most conservative feature of larval development. The data suggest that maximum naupliar size is limited by escalating metabolic costs during development, while minimum naupliar size is limited by size-related feeding effectiveness. 相似文献
11.
Laboratory experiments on ovigerous females of northern shrimp (Pandalus borealis) were used to assess the effects of temperature and food ration on female condition during incubation and examine how combined effects of temperature and female condition influenced egg survival, embryonic development, and larval characteristics. Ovigerous females were maintained at 2°C, 5°C, and 8°C and fed on a low (three times/week; 2–2.7% W/W) or high ration (five times/week at satiation). The increase in temperature accelerated the developmental time of the eggs but their survival at 8°C was reduced. Conversion efficiency of yolk reserves in developing embryos was significantly reduced at elevated temperatures and larvae hatching at 2°C and 5°C were significantly larger and heavier than those hatching at 8°C. The experimental design did not result in any effect of food ration on the energetic condition of females or on egg characteristics and their biochemical composition. However, lower energy reserves were observed for females held at 8°C. 相似文献
12.
Cod (Gadus morhua L.) eggs may develop and hatch within temperatures of −1.5 to 12 °C, but little is known about the effects of very low temperatures
on larval characteristics. Eggs of the Northeast Arctic cod (Gadus morhua) were incubated at 1, 5 or 8 °C from Day 1 after fertilisation until hatching, and transferred to 5 °C after hatching. Histological
samples of the axial musculature were taken at hatching and 5 d after hatching, and the data on muscle cellularity from these
samples were related to survival and hatching, size, developmental data and viability of the yolk sac larvae. All larvae hatched
at the same developmental stage. Incubation of eggs at 1 °C produced shorter larvae with a larger yolk sac and more, small
deep fibres at hatching than larvae from eggs incubated at 5 or 8 °C. The larval size difference was still present 5 d after
hatching, a time at which the larvae from 1 °C-incubated eggs were less developed and less resistant to an acute viability
stress test (65 ppt salinity). Although there were no differences between temperature groups in number and size of muscle
fibres 5 d after hatching, the deep fibres of the 1 °C-group contained less myofibrils than the two other groups. The phenotype
of the larvae at hatching was thus affected within these incubation temperatures. Although all groups were transferred to
the same temperature after hatching, the lowest egg incubation temperature (1 °C) still had a negative effect 5 d after hatching,
as these larvae were both smaller, less resistant to stress and had less functional muscles at the time of first feeding.
Our conclusion is therefore that 1 °C is close to, or below, the lower thermal tolerance limit for normal functional development
of Northeast Arctic cod. The results are discussed in relation to larval viability and recruitment of this species in the
wild.
Received: 4 February 1998 / Accepted: 10 July 1998 相似文献
13.
Effects of 0.01, 0.1 and 1.0 ppm methoprene (Altosid®: ZR-515), a juvenile hormone (JH) mimic which shows high activity against some economically important insect pests, especially Diptera, were tested on larvae of the mud-crab Rhithropanopeus harrisii (Gould) (Brachyura: Xanthidae) from hatching to the first crab stage under optimum and stress conditions of a number of salinities and cyclic temperatures. There was a significant reduction in survival of zoeal larvae with increasing concentrations of methoprene in nearly all combinations of salinity and temperature. On the average there was 9% less survival in the 0.01 ppm concentration of methoprene than in the control, and in the 0.1 ppm concentration the survival was further reduced by another 16%. At 1.0 ppm methoprene no larvae survived beyond the first zoeal stage under optimum conditions or under stressful combinations of salinity and temperature. Except at 0.2 ppm in 27.5% S, survival of the megalopa was not significantly reduced in 0.01 or 0.1 ppm methoprene in any salinity or temperature, although the percentage of abnormal megalopa increased under stress conditions. The first zoeal stage was the most sensitive of the larval stages to methoprene as well as to salinity and temperature stress. The duration of zoeal development was significantly lengthened with an increase in concentration of methoprene under nearly all conditions of salinity and temperature. The JH mimic had, however, no significant effect on the duration of megalopa development. A significant synergism between methoprene, salinity and temperature was not observed. It can be concluded from the results that methoprene does not inhibit metamophosis of R. harrisii larvae at the 0.1 ppm level or lower. Reduction in survival of zoeal stages and increased duration of zoeal development with increasing concentrations of methoprene are presumably related to stress. 相似文献
14.
以泥鳅的胚胎及仔鱼为试验材料,选择胚胎发育的4个不同时期(囊胚期、原肠胚中期、神经胚期、尾芽期)及仔鱼期为处理开始的时间点,探讨了离子液体[C8mim]Cl的毒性作用。结果表明,随着[C8mim]Cl浓度增加,泥鳅胚胎的孵化率下降,畸形率上升,具有明显的剂量-效应关系,67~150 mg·L-1的[C8mim]Cl对泥鳅胚胎均表现出明显的致畸毒性效应;随着[C8mim]Cl浓度增加,泥鳅仔鱼死亡率上升,而100~225 mg·L-1的[C8mim]Cl对泥鳅仔鱼具有明显的致畸、致死作用。其中,[C8mim]Cl对孵出期泥鳅仔鱼的24 h、48 h的半致死浓度分别为97.95和86.77 mg·L-1;而[C8mim]Cl对孵出后3 d泥鳅仔鱼的24 h、48 h的半致死浓度分别为73.77和40.98 mg·L-1。由上可知,在一定的剂量内,[C8mim]Cl对泥鳅胚胎及仔鱼的发育有明显的致畸、致死作用,这为离子液体[C8mim]Cl的合理使用提供了理论依据。 相似文献
15.
The current model for larval release in subtidal crustaceans suggests that hatching time is controlled by the embryos, which
release a pheromone that stimulates the parent female to undergo behaviors that synchronize larval release. Alternatively,
hatching could be controlled by the females. Ovigerous spiny lobsters Panulirus argus (Latreille) exhibit stereotypic behaviors during larval release, including rapid abdominal extensions and pleopod-pumping
activity. Ovigerous P. argus were collected from coral reefs in the Florida Keys, USA during the summers of 2005 and 2006. Pleopod-pumping activity was
quantified to determine if a female’s pumping activity correlates with the developmental state of the embryos. The role of
pheromones released by developing and hatching embryos in controlling pumping behaviors was tested by measuring the pumping
response of ovigerous lobsters to (1) hatch water, (2) homogenized embryo water, (3) embryo-conditioned water (unhatched late-stage
embryos soaked for 20 h), and (4) water containing homogenized post-hatch embryo cases. Bioassays were conducted under constant
conditions (dim-red light) in the laboratory at random times during the day to control for any possible rhythm in pumping
activity. Spontaneous pleopod-pumping activity increased significantly with increasing embryo development. Upon exposure to
hatch water, ovigerous lobsters with late-stage embryos displayed increased pleopod pumping with increased treatment concentration.
Water individually conditioned with homogenized late-stage embryos, intact late-stage embryos, and homogenized post-hatch
embryo cases all induced larval release behaviors in females with late-stage embryos. Ovigerous females with early-stage embryos
did not respond to water conditioned with homogenized early- or late-stage embryos. These results suggest that active substances
are released by embryos at the time of hatching and induce the stereotypical pumping behaviors of the female that synchronizes
larval release. The results support the model that larval release in subtidal crustaceans is controlled by pheromones released
from hatching embryos. 相似文献
16.
Hatching, the life history switch point between embryonic and larval or subadult stages, has traditionally been regarded as a fixed event in an organism’s development. This notion has been challenged by reports of environmentally cued hatching in recent years, which show embryos improve fitness by hatching in response to mortality risks. Here, we present evidence of accelerated hatching due to predation at two points during embryonic development in Chiromantis hansenae. Young embryos (0 day old) exposed to simulated predation hatched earlier compared to undisturbed clutches. Old embryos (4 days old) subjected to direct katydid predation had more immediate responses, hatching <1 h after predation on average. Hatching time was not correlated with female frog size, egg attendance time, or other predator cues. Results confirm predator-cued hatching in a new family of amphibians and support hatching plasticity being a widespread and potentially ancestral condition. We suggest mechanisms and ecological basis of cue transmission and response in C. hansenae and point out potential further research. 相似文献
17.
Binbin Shao 《Behavioral ecology and sociobiology》1997,41(6):399-406
The reproductive success of male parental pumpkinseeds, Lepomisgibbosus, was studied in relation to the use of their nests by spawning golden shiners, Notemigonuscrysoleucas. The brood size of pumpkinseeds with and without golden shiner's young was compared in a field population. Mean egg and larval
numbers of pumpkinseeds did not differ between broods with and without shiners, suggesting that shiners had no net effect
on the fitness of host pumpkinseeds. In the laboratory, however, hatching success of pumpkinseed embryos was significantly
lower with shiners than without. This difference was attributable to fungal infection. Against this fitness loss, the presence
of shiner larvae reduced predation on pumpkinseed larvae in laboratory experiments. Thus, two counteracting mechanisms are
proposed to account for no observed net effect on the host: (1) increased fungal infection on pumpkinseed embryos and (2)
decreased predation on pumpkinseed young.
Received: 10 January 1997 / Accepted after revision: 9 August 1997 相似文献
18.
The ivory tree coral Oculina varicosa (Leseur, 1820) is an ahermatypic branching scleractinian that colonizes limestone ledges at depths of 6–100 m along the Atlantic coast of Florida. This paper describes the development of embryos and larvae from shallow-water O. varicosa, collected at 6–8 m depth in July 1999 off Fort Pierce, Florida (27°32.542 N; 79°58.732 W). The effect of temperature on embryogenesis, larval survival, and larval swimming speed were examined in the laboratory. Ontogenetic changes in geotaxis and phototaxis were also investigated. Embryos developed via spiral cleavage from small (100 µm), negatively buoyant eggs. Ciliated larvae developed after 6–9 h at 25°C. Embryogenesis ceased at 10°C, was inhibited at 17°C, and progressed normally at 25°C and 30°C. Larval survival, however, was high across the full range of experimental temperatures (11–31°C), although mortality increased in the warmest treatments (26°C and 31°C). Larval swimming speed was highest at 25°C, and lower at the temperature extremes (5°C and 35°C). An ontogenetic change in geotaxis was observed; newly ciliated larvae swam to the water surface and remained there for approximately 18 h, after which they swam briefly throughout the water column, then became demersal. Early larvae showed no response to light stimulation, but at 14 and 23 days larvae appeared to exhibit negatively phototactic behavior. Although low temperatures inhibited the development of O. varicosa embryos, the larvae survived temperature extremes for extended periods of time. Ontogenetic changes in larval behavior may ensure that competent larvae are close to the benthos to facilitate settlement. Previous experiments on survival, swimming speeds, and observations on behavior of O. varicosa larvae from deep-water adults indicate that there is no difference between larvae of the deep and shallow populations.Communicated by J.P. Grassle, New Brunswick 相似文献
19.
Early development was examined, under various salinities, for two sympatric nereidid polychaetes, Hediste japonica and H. diadroma, which participated in a simultaneous reproductive swarming in an estuary of the Omuta-gawa River in Ariake Sea, Japan. The
eggs of both species were isotonic to the medium of 27.5–30 psu salinity. The egg diameter in the isotonic salinity was 180–205 μm
in H. japonica, and 130–160 μm in H. diadroma. Successful development of most embryos was observed in a salinity range of 22.5–30 psu in both species, while successful
fertilization occurred in wider ranges of salinity, i.e., 10–34 psu in H. japonica and 10 to 30 psu in H. diadroma. In both species, free-swimming larval life started from the indistinct hatching of trochophores out of a jelly layer capsule.
The lecithotrophic development appeared to run to the 4-setiger nectochaetes in H. japonica, while to 3-setiger nectochaetes in H. diadroma, resulting in a shorter pelagic larval life in H. japonica. In a comparison of larval morphology among Hediste species, we found a definite negative correlation between the prostomium width, which represents the larval size and depends
on egg size, and relative length of chaetae to the prostomium width: the relative length of chaetae was the longest in H. diadroma (with the smallest egg size and long pelagic life), intermediate in H. japonica (intermediate egg size, short pelagic life), and the shortest in H. atoka (largest egg size, no true pelagic life). We also examined the possibility of hybridization between H. japonica and H. diadroma through cross-insemination experiments. The gametes of the two species were reciprocally compatible, and viable hybrid offspring
were produced by the laboratory crosses. The hybrid larvae expressed intermediate phenotypes, but with a greater maternal
influence in characteristics such as the relative length of chaetae and the lecithotrophic larval duration. 相似文献
20.
Semi-lunar spawning in the intertidal zone has been observed in many teleost species. Because the eggs of these species are
placed at elevations reached only by the highest tides, the timing of hatching is critical to survival. To quantify and clarify
the relationship between development rate, hatching, and survival we developed a computer model that simulated the reproductive
strategy in one such species, Fundulus heteroclitus (Linnaeus). We determined expected hatching success for F. heteroclitus embryos as a function of development rate by simulating spawning, embryo development, and hatching of F. heteroclitus embryos in Delaware Bay. Our simulation analysis included manipulation of several model parameters. The results indicated
that there is balancing selection acting on development rate in this species. In particular, false hatching cues (rainfall)
increased mortality among embryos with very fast and very slow development rates. The simulation results did not appear susceptible
to manipulation of the sensitivity of embryos to false hatching cues. The timing of spawning relative to the spring tides
determines which development rate is optimal in terms of average hatching success. Including a constant daily mortality rate
in our simulations, as a simple model of predation and/or disease, shifted the optimized development rates to faster values.
These results may be applicable to other fish species with similar reproductive strategies.
Received: 2 September 1996 / Accepted: 17 September 1996 相似文献