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1.
Recruitment patterns of marine invertebrates are affected both by settlement and early post-settlement events. This study
examined the settlement and recruitment patterns of echinoderms at three sites in the rocky subtidal zone of Bocabec Cove,
Bay of Fundy, Canada using artificial turf collectors and quadrats on the natural substrate. Potential predators were quantified
at two of the sites along transects and in 1-m 2 quadrats. Both potential predators and competitors were quantified in 0.0625-m 2 quadrats. Settlement varied across sites (1.5–3 km apart) and two years of sampling (2004, 2005). The site of most potential
settlement differed for the three groups of echinoderms: sea urchins ( Strongylocentrotus droebachiensis), sea stars ( Asterias spp.) and sea cucumber ( Psolus fabricii). Settlement densities on the artificial turf collectors tended to be greater than the densities of settlers on the natural
substrate. On the natural substrate, the only significant difference between densities of juveniles over time was that newly
settled sea stars were found in July and were not found the following October. Large lobsters and carnivorous worms were potential
predators with densities that varied between sites. Potential competitors that differed in abundance between sites were herbivorous
gastropods and conspecifics for sea urchins; and carnivorous worms for sea stars. This study suggests that patterns of recruitment
are either set up by patterns of settlement or by events during the first few weeks/months on the benthic substrate for these
echinoderms. 相似文献
2.
Acroporid corals are the main reef-building corals that provide three-dimensional habitats for other reef organisms, but are
decreasing on many reefs worldwide due to natural and anthropogenic disturbances. In this study, temporal patterns of larval
settlement and survivorship of two broadcast-spawning acroporid coral species, Acropora muricata and A. valida, were examined through laboratory rearing experiments to better understand the potential for larval dispersal of this important
coral group. Many larvae were attached (but not metamorphosed) to settlement tiles on the first examination 3–4 days after
spawning (AS). The first permanent larval settlement (i.e. metamorphosed and permanently settled juvenile polyps) occurred
at 5–6 days AS, and most larval settlement (85–97% of total) occurred within 9–10 days AS. Larval survivorship decreased substantially
to around 50% by the first week of the experiment and to approximately 10% by the second to third week. The rates of larval
attachment, settlement, and the initial drop in survivorship of larvae suggest that effective dispersal of some acroporid
species may largely be completed within the first few weeks AS. 相似文献
3.
We present the first study of the effects of ocean acidification on settlement of benthic invertebrates and microfauna. Artificial
collectors were placed for 1 month along pH gradients at CO 2 vents off Ischia (Tyrrhenian Sea, Italy). Seventy-nine taxa were identified from six main taxonomic groups (foraminiferans,
nematodes, polychaetes, molluscs, crustaceans and chaetognaths). Calcareous foraminiferans, serpulid polychaetes, gastropods
and bivalves showed highly significant reductions in recruitment to the collectors as pCO 2 rose from normal (336–341 ppm, pH 8.09–8.15) to high levels (886–5,148 ppm) causing acidified conditions near the vents (pH
7.08–7.79). Only the syllid polychaete Syllis prolifera had higher abundances at the most acidified station, although a wide range of polychaetes and small crustaceans was able
to settle and survive under these conditions. A few taxa ( Amphiglena mediterranea, Leptochelia dubia, Caprella acanthifera) were particularly abundant at stations acidified by intermediate amounts of CO 2 (pH 7.41–7.99). These results show that increased levels of CO 2 can profoundly affect the settlement of a wide range of benthic organisms. 相似文献
4.
Settlement into the benthic habitat may be an important process in regulating sea urchin abundance, which potentially modifies the structure of benthic communities. Strong settlement events may increase sea urchin abundance beyond a certain threshold, leading to the formation of coralline barrens (overgrazed communities with a dominance of encrusting coralline algae). To understand the role of settlement in regulating sea urchin populations we first need to determine settlement variability. Temporal variation in settlement of the sea urchin Paracentrotus lividus was monitored at three sites in the Medes Islands, NW Mediterranean, during three settlement seasons (March 1998 through October 2000). Spatial variation in settlement was studied in 1999 at 50 sites along a gradient of exposures to waves and currents, inside and outside the archipelago, and separated by distances from tens to thousands of meters. Bathymetric distribution of settlement was also studied in 2000 at six sites at 5, 10, 15 and 20 m depths. Settlement of P. lividus occurred in a single annual peak within 3 weeks in May–June. Differences in settlement between years were more than two orders of magnitude. Spatial variability was found at all scales investigated, showing strong patchiness at the smallest spatial scales (tens of meters). Sea urchins settled preferentially at depths between 5 and 10 m. Substratum type, level of protection, and adult population densities were not significant in determining settlement. However, settlement was found to be related to the degree of exposure to waves and currents, indicating that physical processes are very important at the spatial scales investigated. This greatly variable settlement is a necessary, although not sufficient, condition to create gradients of adult P. lividus abundance. Further studies should be designed to investigate the interaction between settlement strength and post-settlement mortality.Communicated by O. Kinne, Oldendorf/Luhe 相似文献
5.
The nature of heat coma was examined in the edible periwinkle Littorina littorea (L.). Duration of acclimation did not influence heat-coma temperature at 12 °C, although other acclimation temperatures were
important in influencing thermal tolerance, with positive shifts in coma temperature observed in response to elevated temperatures.
Previous thermal history also influenced heat-coma temperatures. Individuals subjected to repeat heat-coma events on a daily
basis showed significant declines ( P < 0.05) in coma-temperature; in contrast individuals exposed to repeat heat-coma events on a weekly basis showed no decline
in thermal tolerance. Size-effects occurred at selected sites, where decreased heat-coma temperatures were recorded in large
individuals.
Received: 16 August 1999 / Accepted: 13 June 2000 相似文献
6.
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
7.
Spatio-temporal variability in settlement and recruitment, high mortality during the first life-history stages, and selection
may determine the genetic structure of cohorts of long-lived marine invertebrates at small scales. We conducted a spatial
and temporal analysis of the common Mediterranean Sea urchin Paracentrotus
lividus to determine the genetic structure of cohorts at different scales. In Tossa de Mar (NW Mediterranean), recruitment was followed
over 5 consecutive springs (2006–2010). In spring 2008, recruits and two-year-old individuals were collected at 6 locations
along East and South Iberian coasts separated from 200 to over 1,100 km. All cohorts presented a high genetic diversity based
on a fragment of mtCOI. Our results showed a marked genetic homogeneity in the temporal monitoring and a low degree of spatial
structure in 2006. In 2008, coupled with an abnormality in the usual circulation patterns in the area, the genetic structure
of the southern populations studied changed markedly, with arrival of many private haplotypes. This fact highlights the importance
of point events in renewing the genetic makeup of populations, which can only be detected through analysis of the cohort structure
coupling temporal and spatial perspectives. 相似文献
8.
Late larvae of the serranid coral trout Plectropomus leopardus (Lacepède), captured in light traps, were released during the day both in open water and adjacent to two reefs, and their
behaviour was observed by divers at Lizard Island, northern Great Barrier Reef. Coral trout larvae ( n = 110) were present in light-trap catches from 18 November to 3 December 1997, including new moon (30 November). The swimming
speed of larvae in open water or when swimming away from reefs was significantly greater (mean 17.9 cm s −1) than the speed of larvae swimming towards or over reefs (mean 7.2 cm s −1). Near reefs, larvae swam at average depths of 2.7 to 4.2 m, avoiding 0 to 2 m. In open water, swimming depth varied with
location: larvae >1 km east of Lizard Island swam steeply downward to >20 m in 2 to 4 min; larvae >1 km west oscillated between
2.6 and 13 m; larvae 100 to 200 m east of Lizard Island oscillated between 0.8 and 15 m. Nearly all larvae swam directionally
in open water and near reefs. In open water, the average swimming direction of all larvae was towards the island, and 80%
(4 of 5) swam directionally ( p < 0.05, Rayleigh's test). Larvae swam directionally over the reef while looking for settlement sites. The frequency of behaviours
by larvae differed between two reefs of different exposure and morphology. Depending on site, 26 to 32% of larvae released
adjacent to reefs swam to open water: of these, some initially swam towards or over the reef before swimming offshore. In
some cases, offshore-swimming seemed to be due to the presence of predators, but usually no obvious cause was observed. Depending
on the reef, 49 to 64% of the larvae settled. Non-predatory reef residents aggressively approached 19% of settlers. Between
5 and 17% of the larvae were eaten while approaching the reef or attempting to settle, primarily by lizardfishes but also
by wrasses, groupers and snappers. A higher percentage of larvae settled in the second week of our study than in the first.
Average time to settlement was short (138 s ± 33 SE), but some larvae took up to 15 min to settle. Average settlement depth
was 7.5 to 9.9 m, and differed between locations. No settlement took place on reef flats or at depths <4.2 m. Larvae did not
appear to be selective about settlement substrate, but settled most frequently on live and dead hard coral. Late-stage larvae
of coral trout are capable swimmers with considerable control over speed, depth and direction. Habitat selection, avoidance
of predators and settlement seem to rely on vision.
Received: 7 July 1998 / Accepted: 26 January 1999 相似文献
9.
Thermal environment is often regarded as a key determinant of distribution limits in marine invertebrates and hence may represent one of the most important barriers to invasion by non-indigenous species. For the first time in the subarctic northwestern Atlantic, we investigated variation in the timing and magnitude of settlement, recruitment, and colony cover of the recently (early 2000s) introduced bryozoan Membranipora membranacea on the kelp Saccharina longicruris and how this variation relates to changes in sea temperature (thermal histories) across eight sites spanning a 450-km latitudinal range between southwestern Newfoundland and southeastern Labrador, Canada. We show that (1) up to 61 % of the variation in settlement, recruitment, and colony cover was explained by sea temperature alone, with highest and lowest abundances at warmest and coldest sites, respectively; (2) between-site differences in rates of sea cooling explained 85 % of the variation in settler abundance; (3) varying the temporal window over which data were aggregated increased the explanatory power of sea temperature to as much as 98 % for settlement and recruitment, and 86 % for colony cover; (4) exposure to waves and surface area of colonies improved relationships between sea temperature and settlement and recruitment by up to 11 %; and (5) recruit abundance was a strong predictor of colony cover, explaining as much as 89 % of the variation. Consistently low abundances of settlers and recruits at the northern tip of Newfoundland and southern tip of Labrador suggest that M. membranacea is nearing its northern distribution limit in the northwestern Atlantic. Our findings extend knowledge of population dynamics of M. membranacea in the northwestern Atlantic, while highlighting the complexity of the interactions between physical and biological factors and processes that affect population dynamics in invertebrates with planktonic larvae in predominantly cold marine habitats. 相似文献
10.
To understand how extraction of different energy sources impacts water resources requires assessment of how water chemistry has changed in comparison with the background values of pristine streams. With such understanding, we can develop better water quality standards and ecological interpretations. However, determination of pristine background chemistry is difficult in areas with heavy human impact. To learn to do this, we compiled a master dataset of sulfate and barium concentrations ([SO4], [Ba]) in Pennsylvania (PA, USA) streams from publically available sources. These elements were chosen because they can represent contamination related to oil/gas and coal, respectively. We applied changepoint analysis (i.e., likelihood ratio test) to identify pristine streams, which we defined as streams with a low variability in concentrations as measured over years. From these pristine streams, we estimated the baseline concentrations for major bedrock types in PA. Overall, we found that 48,471 data values are available for [SO4] from 1904 to 2014 and 3243 data for [Ba] from 1963 to 2014. Statewide [SO4] baseline was estimated to be 15.8 ± 9.6 mg/L, but values range from 12.4 to 26.7 mg/L for different bedrock types. The statewide [Ba] baseline is 27.7 ± 10.6 µg/L and values range from 25.8 to 38.7 µg/L. Results show that most increases in [SO4] from the baseline occurred in areas with intensive coal mining activities, confirming previous studies. Sulfate inputs from acid rain were also documented. Slight increases in [Ba] since 2007 and higher [Ba] in areas with higher densities of gas wells when compared to other areas could document impacts from shale gas development, the prevalence of basin brines, or decreases in acid rain and its coupled effects on [Ba] related to barite solubility. The largest impacts on PA stream [Ba] and [SO4] are related to releases from coal mining or burning rather than oil and gas development. 相似文献
11.
We used DNA microsatellites to investigate temporal and spatial patterns of local genetic differentiation and relatedness
in a solitary mammal, the dusky-footed woodrat ( Neotoma fuscipes). Patterns of genetic variation were measured relative to spatial clusters, or neighborhoods, of woodrats. We detected significant genetic differentiation among woodrat neighborhoods in two populations spanning multiple
habitat types and densities. Estimates of θ
ST
among neighborhoods ranged 0.034–0.075 and were comparable to levels reported in social mammals. Genetic differentiation
at such a local scale is noteworthy because it occurred in the absence of any physical barriers to gene flow, suggesting that
the patterns observed are linked to the nonrandom patterns of mating and dispersal that characterize woodrat social structure.
Genetic differentiation and relatedness among neighborhoods were even higher when only resident females were analyzed. These
results are consistent with a pattern of female philopatry and male-biased dispersal in woodrats. Geographic distance and
relatedness were inversely correlated in adult females at intermediate densities, but not at low densities. Nonetheless, matrilineal
genetic structure was apparent even at low woodrat densities based on estimates of θ
ST
among neighborhoods of resident females that were significantly greater than zero and consistently greater than estimates
including all individuals. In summary, this study demonstrates a matrilineal genetic structure in dusky-footed woodrats. In
addition, our results support the idea that intermediate densities may be better at facilitating the formation of spatial
kin clusters than either extreme.
An erratum to this article can be found at 相似文献
12.
Limited gene flow via the restricted dispersal of larvae and gametes is expected to result in the genetic differentiation
of populations of clonal invertebrates on small spatial scales. However, occasional dispersal events over greater distances
may generate sufficient gene flow to maintain genetic homogeneity. We applied a spatial autocorrelation approach that does
not require a priori definitions of subdivision boundaries to examine genetic differentiation within a continuous population
of the colonial ascidian Botryllus schlosseri (Pallas) at two allozyme and five polychromatism loci. Colonies were sampled in July 1992, on a 12 by 18 m grid superimposed
on a shallow subtidal (1 to 3 m) population in the Damariscotta River estuary in Maine, USA. Low but significant levels of
positive autocorrelation were detected over very small spatial scales (<5 m), with negative autocorrelation occurring on larger
scales (>8 m). This pattern indicates significant genetic differentiation over distances of 8 to 21 m, and is consistent with
genetic drift and inbreeding creating small scale genetic structure.
Received: 18 October 1999 / Accepted: 11 July 2000 相似文献
13.
In situ measurements of seagrass photosynthesis in relation to inorganic carbon (Ci) availability, increased pH and an inhibitor
of extracellular carbonic anhydrase were made using an underwater pulse amplitude modulated (PAM) fluorometer. By combining
the instrument with a specially designed Perspex chamber, we were able to alter the water surrounding a leaf without removing
it from the growing plant. Responses to Ci within the chamber showed that subtidal plants of the seagrasses Cymodocea serrulata and Halophila ovalis had photosynthetic rates that were limited by the ambient Ci concentration depending on the irradiance that was available
during short-term photosynthesis–irradiance trials. Relative electron transport rates (RETRs) at light saturation (up to 500 μ
mol photons m −2 s −1) increased by 66–100% when the Ci concentration was increased from ca. 2.2 to 6.2 mM. On the other hand, intertidal plants
of the same species exhibited a much lesser limitation of photosynthesis by Ci at any irradiance (up to 1500 μ mol photons
m −2 s −1). Both species were able to use HCO −
3 efficiently, and there was stronger evidence for direct uptake of HCO −
3 rather than extracellular dehydration of HCO −
3 to CO 2 prior to Ci uptake. Subtidally, H. ovalis and C. serrulata grew to 10 and 12 m, respectively, where ambient irradiances were approximately 16 and 11% of those at the surface. Maximum
RETRs (at light saturation) were lower for these deep-growing plants than for the intertidally growing ones. For both species,
the onset of light saturation of photosynthesis ( E
k) occurred at approximately 100 μ mol photons m −2 s −1 for the deep water populations, which was four and two times lower than for the shallow populations of C. serrulata and H. ovalis, respectively. This, and the differences in maximal photosynthetic rates ( RETR
max), reflects an acclimation of the deep-growing populations to the lower light environment. The results presented here show
that photosynthesis, as measured in situ, was limited by the availability of Ci for the deeper growing plants in Zanzibar,
while the intertidally growing plants photosynthesised at close to Ci saturation. The latter result is contrary to previous
conclusions regarding Ci limitations for these intertidal plants, and, in general, our findings highlight the need for performing
similar experiments in situ rather than under laboratory conditions.
Received: 4 April 2000 / Accepted: 31 August 2000 相似文献
14.
We tested the hypothesis that regional differences in oceanic productivity have led to the evolution of predictable patterns
of regional variation in life-history traits of pelagic larvae of tropical reef fishes. To do so we compared larval traits
(egg and hatchling size, larval growth rate and duration, and size at settlement) among closely related reef fishes from the
Atlantic and Pacific coasts of the Isthmus of Panama. This comparison provides a control for phylogenetic effects because
those regions shared a common fauna prior to the rise of the Isthmus ˜3.5 million years ago, subsequent to which each fauna
evolved independently under a very different productivity regime. We measured larval traits of 12 benthic-spawning damselfishes
(Pomacentridae: Abudefduf, Chromis and Stegastes) and 13 pelagic-spawning wrasses (Labridae: Bodianus, Halichoeres and Thalassoma). These included members of each genus on each side of the Isthmus and four sets of transisthmian sister species of pomacentrids.
Among the pomacentrids we found consistent transisthmian differences in hatchling size, but not in other larval traits. Essentially
the reverse pattern occurred among the labrids – larval growth and duration differed consistently among congeners in the two
regions, but without consistent differences in hatchling size or size at settlement. Neither relationship is predicted by
the regional-productivity hypothesis. Most of the differences were quite small. Stronger phylogenetic effects on larval traits
(inter- and intrageneric variation within regions) occur in both families and evidently overwhelm any effect of regional variation
in productivity. Reassessment of data that takes into account such phylogenetic effects questions previous conclusions about
the existence of regional differences in larval traits among damselfishes in the West Pacific and the Caribbean.
Received: 19 January 2000 / Accepted: 26 September 2000 相似文献
15.
Laboratory and field experiments were used to determine whether high (≃100 mg l −1), low (≃50 mg l −1) and control (≃0 mg l −1) levels of suspended sediment affected fertilisation, larval survival, and larval settlement in the scleractinian coral Acropora digitifera (Dana, 1846). Both high- and low-sediment treatments significantly decreased fertilisation, but post-fertilisation embryonic
development was not inhibited by suspended sediments. Larval survival and larval settlement were significantly reduced in
high- and low-sediment treatments. No difference was found between high- and low-sediment treatments in any of the three post-spawning
processes investigated, suggesting that they are susceptible to sediment concentrations which are not exceptionally high even
under natural conditions (>50 mg l −1). The introduction of an additional stress in the form of high levels of suspended sediments coupled with naturally high
variability in recruitment may have a considerable effect on the successful supply and settlement of coral larvae to a reef.
Given that many coral communities are open reproductive systems, the consequences of disturbance events are not likely to
be restricted to the impact area. Recruitment to a population may be reduced significantly in the presence of high levels
of suspended sediments because of effects on larval survival and settlement. Recruitment of larvae to adjacent populations
may also be affected due to a decreased fertilisation success and potential increases in mortality of larvae passing through
the affected site.
Received: 13 August 1998 / Accepted: 22 July 1999 相似文献
16.
Naticid gastropod predators leave characteristic boreholes in the shells of their bivalve prey that allow the evaluation of
spatial differences in occurrence and intensity of predation. This approach, extensively used in paleobiological research,
was used to compare spatial variation in predation by moonsnails ( Euspira heros Say) on initial recruits of the Atlantic surfclam ( Spisula solidissima Dillwyn). A four-year sampling at two 12-m deep stations on either flank of Beach Haven Ridge on the inner continental shelf
detected temporal and spatial differences in surfclam densities following a large settlement pulse in early July. Between-station
density differences were large during the first peak in surfclam density, but decreased in August-September, when densities
at both stations also decreased. Surfclam seasonal peaks were followed by peaks in density of articulated shells (recent mortality
due to non-crustacean predators and/or intrinsic mortality) and surfclams with boreholes (mortality due to naticids). The
proportion of surfclams with boreholes was consistently higher (more than twice, on average) at the station where the highest
densities of surfclams were also detected. These spatial differences are interpreted as differences in predation intensity
resulting from a corresponding higher abundance of moonsnails at the same station. Although naticid predation is not the primary
source of surfclam mortality, it consistently contributes to the reduction of spatial differences in density initially created
by dissimilar levels of larval surfclam settlement. 相似文献
17.
Batches of hundreds of freshly collected megalopae of the shore crab Carcinus maenas (L.) showed persistent circatidal rhythms of moulting to the juvenile crab stage when maintained in constant laboratory conditions.
Peaks of moulting occurred around expected times of high tides, with few megalopae moulting at other times. In larvae collected
offshore, the highest tidally-timed peak of metamorphosis occurred during the second to fifth expected times of high tide,
and metamorphosis of 50% of each batch took about 22 h or longer. In contrast, in larvae collected at the water's edge, 70%
metamorphosed during the first expected episode of high tide, within 6 to 8 h after collection. However, although inshore
megalopae moulted before offshore ones, the tidal timing of moulting remained unaltered whether megalopae were collected at
neaps or springs, from the water's edge or farther offshore, in the presence or absence of natural substratum, and under various
light–dark and salinity regimes. Metamorphosis of C. maenas megalopae around the times of high tides may enhance settlement into the upper intertidal zone. Early juveniles of the crab
apparently prefer that zone as they are most abundant there and, unlike adults, do not undertake up-and-down-shore migration
with tides. The present finding demonstrates, for the first time, endogenous physiological timing of circatidal periodicity
in the metamorphic moult of crab megalopae, suggesting that endogenous factors, as well as exogenous ones should be taken
into account in considering the process of settlement by crab megalopae.
Received: 21 February 1996 / Accepted: 27 November 1996 相似文献
18.
Using the number of segments of pleopod rami as a marker of instar number, the population structure (instar composition)
of the mesopelagic gammarid amphipod Cyphocaris challengeri was investigated by monthly samplings from May 1997 to April 1999 at a station off southwest Hokkaido, Japan. Laboratory-rearing
experiments were also conducted to establish the relationship between the number of segments of pleopod rami and instar number,
and to estimate the growth pattern of this gammarid based on the intermolt period and molt-increment data. Stratified sampling
in the field (0 to 200 and 200 to 400 m depth strata) showed this species occurred mainly at 200 to 400 m depth during the
day. Instar analysis indicated that C. challengeri has 12 instars in females and 11 instars in males. Based on observations of secondary sexual characters, Instars 1 to 6 were
designated juveniles (Instars 1 to 3 occurred in the marsupia of gravid females); in males, 7 to 9 were immature and 10 and
11 were mature, while in females 7 and 8 were immature and 9 to 12 were mature. Off southwest Hokkaido, Instar 4 (just released
from a female's marsupium) was found throughout the year, with a peak abundance occurring in April to July of each year. A
sequential development of Instar 4 to 9 (youngest adult instar) through the year was observed. Generation length (i.e. the
time required to grow from Instar 4 to 10) was estimated from a laboratory-obtained growth curve to be 216 to 584 d at the
in situ temperature range (2 to 5 °C), which is consistent with observations on field populations. Specimens older than Instar
9 were rare in the field and could not be used in laboratory-rearing experiments, so longevity could not be estimated. Eggs
were oval and measured 0.6 mm (large diameter). Brood size ranged from 20 to 65. Comparing the present results with those
of epipelagic hyperiid amphipods, the nearly identical growth rates together with the production of fewer but larger eggs
seen in C. challengeri appear to reflect to the typical life mode of deep-living pelagic crustaceans.
Received: 14 February 2000 / Accepted: 6 July 2000 相似文献
19.
Reproduction and recruitment in high-latitude coral populations in Japan have been little studied. A comprehensive study of the reproduction and early life history was conducted on nine common scleractinian coral species in Amakusa, southwestern Japan (32°N) from 2001 to 2003 including; (1) fecundity (the proportion of colonies with mature eggs), (2) timing and synchrony of spawning, (3) initial larval settlement pattern, (4) recruitment, (5) post-settlement mortality. The fecundity was high (76.7–100%) in six of seven species examined in 2002 and 2003. Annual spawning of the seven species occurred from mid July to August in 2001–2003, when seawater temperature was at the annual maximum. Spawning was highly synchronised among conspecific colonies and species in 2002 and 2003, with five species spawning five to nine nights after the full moon and another two spawning around the new moon. Temporal patterns of larval settlement of three spawning species during the first 10 days after spawning were similar to those of other spawning species from low latitudes. The number of scleractinian recruits on settlement plates, deployed from July to October (the major recruitment period at the study site), was low (2 recruits/m 2) for the three consecutive years. Post-settlement mortality of 1–1.5 month old spat of five species ranged between 88 and 100% over 3–10 months in the field, similar to the values reported for both high and low latitude species (>94–99%). Among the key stages examined, the low recruitment rate may be the most important step in limiting successful reproduction and recruitment of these high-latitude scleractinian populations. The low recruitment rate may be attributable to (1) the reduced influx of larval supply from other coral populations, which are smaller and more isolated at high-latitudes and (2) the longer precompetent larval phase of broadcast-spawning corals which results in an increased chance of larvae being dispersed away from parent populations. 相似文献
20.
The reproductive biology of the jellyfish Catostylus mosaicus (Quoy and Gaimard 1824) (Scyphozoa: Rhizostomeae) was investigated in New South Wales, Australia. Medusae were gonochoristic.
There was a 1:1 ratio of male and female medusae and there was no evidence of sexual dimorphism. Oocytes arose from the gastrodermis
and maintained contact with the gastrodermis, via trophocytes, throughout gametogenesis. Spermatogenesis occurred within follicles
that arose from invagination of the gastrodermis. Detailed sampling of gonads over a period of 3.25 yr in Botany Bay, and
over 2.5 yr in Lake Illawarra, indicated that gametogenesis occurred almost continuously during the year. Oocytes were smaller,
or were absent from the ovaries during 3 of the 4 winters sampled at Botany Bay and during all 3 winter periods sampled at
Lake Illawarra. Comparisons were made with other locations, although these were sampled less frequently. When medusae were
present at a location, similar trends were observed. The size at which medusae matured varied, but during non-winter periods
and at two locations, all medusae exceeding 130 mm diam were considered mature.
Received: 6 January 2000 / Accepted: 3 July 2000 相似文献
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