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1.
Reproductive success among clonal taxa is often portrayed as a simple function of clone size, but reproduction in Pseudoplexaura porosa (Houtuyn), a common Caribbean gorgonian, reflects a more complex relationship between size and gamete production. Tagged
colonies were sampled at two reefs in the San Blas Islands, Panama during the 1995 spawning season to determine the colony
size at first reproduction, size-dependent polyp fecundities, and whole colony gonad production, and to follow the gametogenic
cycle. Additional data were obtained during non-spawning months in 1984 and 1985. Of 120 colonies ranging in height from 20
to 250 cm, only colonies taller than 50 cm were reproductive. An average of 4.33 oocytes polyp−1, 560 to 800 μm in diameter, were released during monthly synchronous spawning events from June to September. Oocytes released
each month developed from a group of intermediate size oocytes present at the end of the preceding month. Almost all oocytes
>560 μm were released during each spawning event. Spermatogenesis was a shorter process than oogenesis. During each spawning
month, mature spermaries developed from a group of <125 μm spermaries. Virtually all spermaries >190 μm were released each
month, and most of the spermary volume in mature male polyps was generated anew each month of spawning. Among reproductive
colonies, polyp fecundity increased with colony height from 50 to 200 cm. Per capita fecundity of >200 cm tall female colonies
was lower than for 150 to 200 cm colonies, but whole colony fecundity of large colonies was greater due to the exponential
increase in the number of polyps that occurs with increasing colony height. In male colonies, both polyp and colony reproductive
output increased with colony height. The large amounts of sperm produced by large male colonies probably contributes to the
high rates of in situ fertilization observed in P. porosa. Differences in fecundity as a function of colony size and sex suggest differences in some combination of the cost of reproduction
and/or allocation of resources to reproduction.
Received: 9 September 1998 / Accepted: 7 June 1999 相似文献
2.
The majority of published accounts on scleractinian coral reproduction are from the tropical Pacific and Caribbean, with
very little information known about Red Sea species. This report examines variation in reproductive mode in 24 species of
hermatypic corals (belonging to seven families) in the Gulf of Eilat, Red Sea. Eighteen species are hermaphroditic broadcasters,
two are hermaphroditic brooders and three are gonochoric broadcasters. In the Pocilloporidae, the gonads project into the
body cavity, while in the other six families the gonads reside inside the mesenteries. The number of gonads per polyp in broadcasting
species follows family or genus lines. Fecundity (eggs per polyp) increases with polyp size. Brooding species usually exhibit
one or two gonads per polyp and each gonad contains only one to three oocytes. Oocyte size varies widely and does not relate
to mode of reproduction. The largest oocytes (diameter = 450 μm) occur in the brooding coral Alveopora daedalea and in broadcasting species of the genus Acropora (diameter = 420 μm). Gonad morphology and gonochorism versus hermaphroditism appear to be constrained phylogenetically at
the family or genus level. Lastly, this report compares the data presented for Red Sea scleractinian species with the data
available on scleractinian corals from other geographical regions.
Received: 2 February 1993 / Accepted: 9 March 1998 相似文献
3.
The reproductive biology of female Penaeus japonicus Bate was investigated in the Ariake Sea and Tachibana Bay (located outside the Ariake Sea), Japan from 1994 to 1996. Interannual,
seasonal, individual female body size and spatial influences on the incidence of spawning were examined. The proportion of
inseminated females, increased with increasing body size up to 170 mm body length (BL) and decreased thereafter. The minimum
size at maturity was similar between years; 130 to 140 mm BL. The minimum size of individuals with developing ovaries or spermatophores
differed from that of ripe females by 20 to 25 mm. Spawning occurred in the central part of the Ariake Sea and Tachibana Bay
but rarely in the inner part. P. japonicus had a clear reproductive cycle. Spawning started earlier and ended later, occurring from mid-May to mid-October, in the eastern
central part of and outside of the Ariake Sea compared with the western central part, where spawning occurred from mid-June
to mid-September. Spawning dynamics differed across seasons, body sizes and areas but not across years. The seasonal peak
in the proportion of ripe females varied with body size. In small individuals (130 to 169 mm BL), no peak was observed, whereas
in large individuals (>170 mm BL) the proportion of ripe individuals peaked in June. The proportion of ripe individuals increased
with increasing body size and was high outside the Ariake Sea. Factors causing the variation in spawning dynamics are discussed.
Received: 30 November 1998 / Accepted: 12 October 1999 相似文献
4.
Importance of cysts in the population dynamics of the red tide flagellate Heterosigma akashiwo (Raphidophyceae) 总被引:7,自引:0,他引:7
To elucidate roles of cysts in occurrences of Heterosigma akashiwo blooms, cyst dynamics were studied in northern Hiroshima Bay, the Seto Inland Sea of Japan, where H. akashiwo regularly forms red tide in June. Monthly measurements of seasonal changes in the densities of vegetative cells of H. akashiwo and their germinable cysts in surface sediments (top 1-cm layer) were made for 2 years at three stations. Vegetative cells
of H. akashiwo could be detected from April through December throughout the water column, and the existence of vegetative cells was confirmed
in surface waters even in winter after incubation of sampled seawater in culture medium. Germinable cysts, enumerated by the
extinction dilution method, existed in sediments in all seasons, even before and after the seasonal bloom. The effects of
incubation temperature on the germination of natural cysts of H. akashiwo in sediments were examined. Germination was not observed at 5 °C, was low at 10 °C, while it increased at 15 °C, and maintained
a high level to 25 °C. The bottom water temperature reached 15 °C (suitable for the germination of cysts) and the surface
about 18 °C or more (suitable for the growth of vegetative cells) 2 to 3 weeks before the blooms. The dark survival of H. akashiwo cysts was tested, and it was found that the cysts were viable for at least 650 d at 11 °C, and for 165 d at 25 °C, indicating
a significant role of cysts in the survival during winter and summer seasons. The cysts presumably also play an important
role in seeding primary populations into water columns when the bottom water reaches a suitable temperature (around 15 °C);
thereafter the populations develop with great annual regularity to bloom in June. These results suggest that initiation of
H. akashiwo red tides in the Seto Inland Sea could be triggered by bottom water temperature.
Received: 3 July 1998 / Accepted: 12 January 1999 相似文献
5.
The mode of reproduction in Pocillopora verrucosa Ellis and Solander, 1786 varies between geographically isolated regions. This scleractinian coral is common along the KwaZulu-Natal
coast, and its reproductive mode and period of reproduction were assessed using histological preparations. The study was undertaken
from 1992 to 1994 and showed that P. verrucosa is a simultaneous hermaphrodite and broadcast spawner in KwaZulu-Natal. Gametogenesis occurs from October to January, with
the gametes maturing simultaneously so that spawning can be synchronised at new moon in January (mid-summer). Zooxanthellae
are present in the mature oocytes.
Received: 10 September 1997 / Accepted: 6 July 1998 相似文献
6.
Sexuality and cyst formation of the spring-bloom dinoflagellate Scrippsiella hangoei in the coastal northern Baltic Sea 总被引:3,自引:0,他引:3
The temporal sequence and the magnitude of the sexual reproduction and subsequent cyst deposition of the common spring-bloom
dinoflagellate Scrippsiella hangoei (Schiller) Larsen was studied during spring 1996 on the SW coast of Finland, Baltic Sea. The abundances of the different
size of fractions of S. hangoei (14 to 18 μm, 18 to 22 μm and >22 μm) were monitored in the water column, and the deposition of resting cysts was measured
using moored sediment traps. Cyst sedimentation rates were measured throughout the seasonal cycle in order to estimate cyst
resuspension rates for the quantitative assessment of the fraction of population undergoing encystment. The onset of sexual
reproduction, indicated by a significant increase of the small cells (14 to 18 μm) representing gametes, occurred in a nutrient
replete environment well before the exponential growth phase and peak abundances of vegetative cells. Gamete formation was
followed by high abundances of large cells (>22 μm) representing planozygotes, and subsequent sedimentation of resting cysts.
Approximately 60% of the asexually growing bloom population was estimated to form planozygotes, suggesting that encystment
was an important factor in bloom termination and possibly plays a role in the regulation of the magnitude of the bloom. Finally
encystment accounted for 40% of the entire S. hangoei population, resulting in a considerable loss of the bloom population and an input of the vernal phytoplankton biomass to
the benthos.
Received: 11 December 1998 / Accepted: 8 April 1999 相似文献
7.
Use of the fluorochrome calcein as an in situ growth marker in the brown mussel Perna perna 总被引:2,自引:0,他引:2
This study assesses the potential of the fluorochrome calcein for use as a growth marker in bivalve shell growth studies.
Calcein solutions were administered in situ to the brown mussel Perna perna (Linneaus), both by injection and immersion, and the effect of calcein concentrations on fluorescent mark deposition and mussel
mortality was investigated in the laboratory. Field investigations showed that, 1 month after administration, calcein injection
(125 mg l−l) into the mantle cavity produced superior results to the immersion treatments (150 and 500 mg l−l). Both methods resulted in fluorescent mark incorporation at the growing edge, but during immersion general calcein deposition
associated with endolith activity resulted in fluorescence that made identification of a distinct datum point difficult. In
contrast, the injection method produced clearly defined growth marks, which were easily distinguished from autofluorescence
and persisted without visible degradation for a minimum of 9 months. Shell growth rates estimated using the fluorescent mark
as a datum point were similar to those from earlier studies using different methods. Laboratory investigations revealed that
at␣calcein concentrations of 80 mg l−l and above, 100% of juvenile (20 to 30 mm) and adult mussels (60 to 70 mm) retained a visible growth mark, while at concentrations
>160 mg l−l all marks were bright and clearly defined. No mussel mortality was exhibited at any time, even at calcein concentrations
of 640 mg l−l, eight times higher than those required for mark deposition. These results suggest that, compared to traditional methods
of bivalve growth determination, the use of fluorochromes presents a relatively inexpensive, non-invasive and rapid alternative.
When using calcein as a growth marker, problems associated with some other fluorochromes (e.g. inconsistent mark incorporation,
high post-treatment mortality) were not exhibited.
Received: 14 July 1998 / Accepted: 23 October 1998 相似文献
8.
Sexual reproduction of the scyphomedusa Aurelia aurita in relation to temperature and variable food supply 总被引:1,自引:0,他引:1
The effects of food availability and temperature on sexual maturation and female reproductive output of the scyphomedusa
Aurelia aurita was examined in two populations from the contrasting environments of Southampton Water and Horsea Lake, England. Trends in
oogenesis and subsequent reproductive output differed markedly between the two populations. In Southampton Water, the onset
of sexual maturation occurred earliest in the larger medusae, but eventually all females became ripe, the smallest being 45 mm
bell diameter (BD). The decrease in minimum size at maturity was correlated with increasing temperature. In A. aurita from Horsea Lake, size at maturity varied on a seasonal basis, with the smallest ripe female being only 19 to 20 mm BD. There
were spring and autumn periods of sexual maturation in this population. During the autumn period, it is likely that food limitation
was playing a more critical role in determining medusa size, with decreasing temperature indirectly affecting A. aurita by limiting primary and secondary production. In similar-sized ripe medusae, fecundity was greater in Southampton Water,
but the planula larvae produced were significantly smaller than those in Horsea Lake. It is suggested that in Horsea Lake,
the quality of the larvae are greater in terms of biochemical content to ensure survival of the few gametes produced (i.e.
K-strategy). Comparison of the reproductive effort of the two A. aurita populations revealed that medusae from Southampton Water, which experience greater food availability, are able to direct
more energy to reproduction than Horsea Lake medusae. In the latter, A. aurita medusae appear to partition the available food resources into either somatic growth (and therefore increased future fecundity)
when food is abundant, or reproductive growth when food is scarce.
Received: 24 June 1997 / Accepted: 23 March 1998 相似文献
9.
The gold-eye rockfish Sebastes thompsoni lives in association with drifting seaweed during the early developmental period. Early life history traits of the gold-eye
rockfish were studied by means of otolith analysis of larvae and juveniles associated and unassociated with drifting seaweed
in the waters off southern Sanriku, Tohoku, northern Japan, from 1993 to 1995.␣Daily growth increments and the existence of
an extrusion check were confirmed by both a series of tetracycline marking experiments and an analysis of the relation between
the number of increments and the number of days after extrusion. Larvae and juveniles associated with drifting seaweed occurred
from late May to late July, with a peak in late June, showing the same seasonal fluctuation in abundance as drifting seaweed.
Larvae seemed to associate with drifting seaweed after aggregation to surface slick areas. Body size at the commencement and
the end of the seaweed-associated period was estimated at 18 and 50 mm total length, respectively. Growth rates were low until
the beginning of the association with seaweed; thereafter they became high but declined towards the end of seaweed-associated
life. Larvae and juveniles born later grew faster than those born earlier. This tendency was detected both before and during
the association with drifting seaweed. Although the season of abundant drifting seaweed was about 2␣months shorter, and occurred
2 months later, than the extrusion season of the gold-eye rockfish from early February to early June, this seemed to be compensated
by the growth variation dependent on birth month. Early life history traits of the gold-eye rockfish are discussed in relation
to the successful utilization of drifting seaweed.
Received: 3 August 1997 / Accepted: 24 March 1998 相似文献
10.
The reproductive cycle of the Antarctic articulate brachiopod Liothyrella uva (Broderip, 1833) is described from monthly samples collected between September 1985 and July 1987 from a population at Signy
Island, Antarctica. Spermatogenesis and oogenesis are described for the first time in this species. Surface dried-tissue masses
for a standard individual (41 mm shell length) were calculated for the digestive diverticula, gut, lophophore and gonad from
monthly dissections of 15 brachiopods. Seasonal patterns, with summer peaks, were observed in the digestive diverticula and
gut. The lophophore and gonad masses did not exhibit seasonal trends. Females showed a sharp decrease in proportion of large
oocytes between October and November in 1986, suggesting spawning during this period. There was no similar decrease during
the same period in 1985. Mean percent spermatozoa measurements revealed a large increase in November 1985 and a rapid decline
in December 1985. This suggested a large spawning event for males in 1985 which was not repeated the following year. These
data indicate large inter-annual differences in reproductive activity as well as differences between males and females. They
also suggest the possibility of sperm storage by females. Brood characteristics were also highly variable. The smallest brooding
female was 31.5 mm in length. Some females brooded more than one developmental stage simultaneously, and variation in brood
size (numbers of embryos or larvae held in the lophophore) and brood composition between individuals was high. All samples
collected throughout the 2 yr period contained some females with broods. The data suggest that the reproductive strategy of
L. uva is highly plastic, and that there may be three reproductive periodicities on seasonal, annual and inter-annual time scales.
Received: 16 May 1997 / Accepted: 2 March 1998 相似文献
11.
Metallothionein-like proteins (MTLs) have been measured by differential pulse polarography every two months during a period
of two and half years in the marine bivalve Macoma balthica from two locations of the Western Scheldt Estuary. The MTL concentrations (0.85 to 7.81 mg g−1 dry wt) are comparable to most values found for other marine invertebrates. These concentrations vary significantly with
the seasons (higher in winter, lower in summer), which is mainly due to body weight fluctuations. Strong correlations exist
between MTL and metal levels. Upon short-term exposure to a mixture of Cd, Cu and Zn, there are on average significant MTL
increases, but important seasonal variations have been observed: in winter, the clams are more sensitive to metals, uptake
more Cd and Cu and induce more MTL than during the warmer months.
Received: 16 May 1997 / Accepted: 6 June 1997 相似文献
12.
Effects of food type and ration on reproductive maturation and growth of the sea urchin Strongylocentrotus droebachiensis 总被引:1,自引:0,他引:1
We investigated the effects of food quality and quantity on reproductive maturation and growth of juveniles of Strongylocentrotus droebachiensis (Müller) in a 22 month laboratory experiment in which we fed sea urchins four diets: (1) kelp (Laminaria spp.) for 6 d wk−1 and mussel (Mytilus spp.) flesh for 1 d wk−1 (KM); (2) kelp for 7 d wk−1 (high ration, KH); (3) kelp for 1 d wk−1 (low ration, KL) and (4) no food other than encrusting coralline algae (NF). At their first and second opportunity for reproduction,
all sea urchins in the KM and KH treatments, and most in the KL treatment were reproductively mature, whereas all sea urchins
in the NF treatment remained immature. Gonad index differed significantly among all fed treatments at first and second reproduction,
and was highest in the KM and lowest in the KL treatment. Gonad index was similar in both sexes at first reproduction, but
it was higher in females than in males at second reproduction. Diet had little or no effect on the relative abundance of spermatocytes,
spermatozoa, or nutritive phagocytes in testes at first and second reproduction. In ovaries, nutritive phagocytes were significantly
more abundant in females in the KM and KH treatments than in the KL treatment at first reproduction, and significantly more
abundant in unfed (NF) than fed (KM, KH, KL) females at second reproduction. Mean oocyte size was similar in all fed females
at first reproduction, but significantly larger in fed than unfed females at second reproduction. Mean ovum size was similar
in all fed females in both reproductive periods. Increase in test diameter was greatest in the KM treatment and smallest in
the KL treatment; sea urchins in the NF treatment decreased slightly in size. Survival was 95 to 100% in all fed sea urchins
but significantly lower in unfed ones. The feeding rate on kelp was significantly greater in the KL than the KM and KH treatments.
In the KM treatment, the feeding rate on kelp increased significantly over a 6 d period after mussel flesh was provided. Our
results demonstrate that a diet of high food quality and quantity accelerates reproductive maturation and growth rate, and
enhances gonad production and survival in juvenile and young adult S. droebachiensis. These findings contribute to our understanding of the reproductive ecology of S. droebachiensis in habitats with differing food supplies (e.g., kelp beds and barrens). Our results also can be used to improve aquacultural
practices for sea urchins.
Received: 3 June 1998 / Accepted: 2 February 1999 相似文献
13.
Life cycle of the copepod Calanus hyperboreus in the Greenland Sea 总被引:11,自引:0,他引:11
H.-J. Hirche 《Marine Biology》1997,128(4):607-618
The seasonal ontogenetic migration of the Arctic copepod Calanus hyperboreus was described from surface-to-bottom hauls in the central Greenland Sea Gyre (GSG) and in the Westspitsbergen Current (WSC).
All stages except females spent the winter below 500 m in the GSG and below 1000 m in the WSC. Seasonal ascent begins in April,
and descent in July. For the C.␣hyperboreus population an active downward transport of 8.1 g m−2 dry weight during 8 months of overwintering was estimated, similar to flux rates of particulate matter in sediment traps.
Seasonal distribution of biomass was determined from weight measurements of single stages. Annual means varied from 4.0 to
9.2 g m−2 in two different years in the GSG and were 1.1 in 1 year in the WSC. The life cycle in the Greenland Sea was reconstructed
from field data on stage composition, vertical distribution, reproduction, and moult cycle phase from tooth development of
CV. Laboratory experiments were conducted on the moulting of CIV and CV in fall. A 3-year (males) and 3- to 4-year (females)
life cycle is proposed for the GSG and 2 to 3 years for the WSC. However, the small number of young larvae and the incomplete
spring ascent by older copepodites observed in the WSC cast doubt on the reproductive success in the WSC. A suite of physiological
strategies and adaptations performed by the developmental stages support survival of this species in harsh environments.
Received: 25 January 1997 / Accepted: 11 February 1997 相似文献
14.
The origin of the deep-sea benthic fauna is poorly understood and represents an enormous gap in our understanding of basic
evolutionary phenomena. One obstacle to studying evolutionary patterns in the deep sea has been the technical difficulty of
measuring genetic variation in species that are typically minute, rare, and must be recovered from extreme depths. We used
molecular genetic techniques to quantify variation in the 16S rRNA mitochondrial gene within and among populations of the
common protobranch bivalve Deminucula atacellana (Schenck, 1939). We analyzed 89 individuals from nine samples collected in the 1960s along a depth gradient from 1100 to
3800 m in the western North Atlantic. Genetic variability within populations is much lower than between populations, and peak
haplotype numbers occur near the center of its depth distribution. Continental slope (<2500 m) and rise (>2500 m) populations
were genetically distinct despite the lack of any obvious topographic or oceanographic features that would impede gene flow.
These findings indicate that the deep-sea macrofauna can have strong population structure over small (134 km) spatial scales,
similar to that observed in shallow-water and terrestrial organisms. This surprisingly high biodiversity at the genetic level
affords the potential for adaptation and evolutionary diversification, the ultimate historical causes of high species diversity
in the deep-sea benthos.
Received: 24 July 1997 / Accepted: 26 January 1998 相似文献
15.
The current contribution deals with the reproductive biology of a genus endemic to Brazil –Mussismilia Ortmann, 1890 – including all three species of the genus: M. braziliensis (Verrill, 1868), M. hartti (Verrill, 1868), and M. hispida (Verrill, 1902), which occur sympatrically in the studied area, the Abrolhos Reef Complex, Brazil. Sexuality patterns, modes
of reproduction, synchrony and spawning periods are reported, and were determined by histological examination of material.
All three species started to develop female and male gametes over different periods in the same breeding season. The three
species are probably broadcast spawners, since no embryos or planulae were observed in any species at any given time of the
year. Each reproductive cycle lasted approximately 11 months. Oogenesis and spermatogenesis started in different periods,
with spermaries appearing in approximately the eighth month of ovary development and lasting about 3 months. Reproductive
cycles were annual. Spawning probably occurred in consecutive months in each species. In M. braziliensis, spawning presumably happened between March and the middle of May in 1996 and 1997. Evidence suggested that spawning events
of M. hispida took place between the end of April and mid-June. M. hartti may have spawned between September and November. The data presented here suggested that all studied species have at least
one exclusive spawning period, asynchronically with the others. A possible exception may be the simultaneous (or close) spawnings
of M. braziliensis and M. hispida in May. It is suggested that asynchrony in spawning periods among species may reduce the chance of hybridization, gamete
waste and the competition for settlement surfaces. The occurrence of extended spawning periods for each species may also reduce
the risks of reproductive failure, due to temporary adverse conditions.
Received: 8 December 1998 / Accepted: 15 July 1999 相似文献
16.
M. Thiel 《Marine Biology》1998,132(2):209-221
The suspension-feeding amphipod Dyopedos monacanthus (Metzger, 1875) is a common epibenthic amphipod that lives on self-constructed “mud whips” (built from filamentous algae,
detritus and sediment particles) in estuaries of the northern North Atlantic Ocean. The population biology of D. monacanthus at a shallow subtidal site in the Damariscotta River Estuary (Maine, USA) was examined between July 1995 and July 1997. The
resident population at the study site was dominated by adult females during most months of the year. High percentages of subadults
were found in late summer/early fall. Often, between 10 and 20% of the adult females were paired with males, and the percentage
of ovigerous females varied between 40 and 100%, indicating continuous reproduction. The percentage of parental females varied
between 40 and 80% during most months, but dropped to levels below 20% during summer/early fall. The average size of amphipods
on their own mud whips was ∼4 mm during the summer/early fall, after which it increased continuously to >7.0 mm in March or
April, and then dropped again. In March and April, the average number of eggs and juveniles female−1 was ∼100 eggs and 55 juveniles, while during the summer/early fall the average number of eggs female−1 was <20 and that of juveniles female−1 was <10. Many juveniles grew to large sizes (>1.4 mm) on their mothers' whips in winter/early spring but not in the summer/fall.
The average number of amphipods at the study site was low in late summer/early fall (<50 individuals m−2), increased steadily during the winter, and reached peak densities of >3000 individuals m−2 in April 1996 (>1600 individuals m−2 in May 1997), after which densities decreased again. The decrease of the D.␣monacanthus population at the study site coincided with a strong increase of amphipods found pelagic in the water column. This behavioural
shift occurred when temperatures increased and benthic predators became more abundant and active on shallow soft-bottoms,
suggesting that D. monacanthus at the study site is strongly affected by predation. The effects are direct (by predation on amphipods) and indirect (by
reducing duration of extended parental care and enhancing pelagic movements). Both extended parental care and pelagic movements
are important behavioural traits of D.␣monacanthus (and other marine amphipods), and significantly affect its population dynamics.
Received: 18 January 1998 / Accepted: 27 May 1998 相似文献
17.
Frederico P. Brandini Eduardo T. da Silva Franciane M. Pellizzari Alessandra L. O. Fonseca Luciano F. Fernandes 《Marine Biology》2001,138(1):163-171
Production rates, chlorophyll concentrations and general composition of periphytic diatom communities growing on glass slides
were studied in relation to environmental parameters during one seasonal cycle in the Bay of Paranaguá, southern Brazil. Slides
were routinely submersed at 1, 2 and 3 m depth and recovered weekly for microscopic examinations, analyses of chlorophyll,
cell counts and in situ photosynthetic incubations using the Winkler titration method. Water samples were also collected at
surface and bottom layers for determinations of temperature, salinity, nutrients and chlorophyll in the water. The periphytic
community was mainly formed by epipelic and epipsammic species, dominated by Navicula phyllepta, Cylindrotheca closterium, Navicula spp. and Amphora sp. Weekly chlorophyll a and cell accumulations on slides varied from <1–32 mg m−2 and up to 31 × 108 cells m−2, respectively. Photosynthetic rates varied from <1 to 35 mg oxygen mg chlorophyll a
−1 h−1, with higher values in summer. Daily production varied from 5 to 3,600 mg oxygen m−2 day−1 (<0.01–1.4 g carbon m−2 day−1). Multiple regression analysis revealed that vertical differences in light conditions and grazing pressure jointly affected
the influence of temperature on the seasonal patterns of cell densities and chlorophyll concentrations according to depth.
Received: 27 April 2000 / Accepted: 16 August 2000 相似文献
18.
New information on the brooding reproduction of Amphiura carchara, and previous studies of several deep-sea congeners, contradict the prevailing notion that direct development is exceptional
among deep-sea echinoderms. Over 500 specimens of A. carchara from 2,850 to 4,100-m depths off the coast of California, USA, were studied. The species was found to be gonochoric, although
most brooding species of ophiuroids are hermaphroditic. Females each brooded up to 72 embryos at a time, with up to 10 in
a single bursa. The embryos of individual adults were often at different stages of development, but those brooded in a single
bursa tended to be at the same stage. Thus, the species has characteristics that breach the distinctions between sequential
and simultaneous brooding exhibited by shallow-water ophiuroids. The embryos developed from yolky eggs that are large for
an ophiuroid, with the mean largest oocytes 0.45 mm, and ranging to 1.28 mm in diameter. Almost all late-stage embryos were
positioned with their mouth and arms pressed against the wall of the bursa, possibly to facilitate the uptake of nutrients
from the parent. Thus, A. carchara may be matrotrophic. The largest embryos examined had a rudimentary disk skeleton, and arms with four joints and a terminal
plate. Emerging juveniles probably differ in disk diameter. The species appears to brood year round, although differences
in gonad size, the incidence of brooding, and the relative numbers of early developmental stages in summer and winter samples
indicated that there are seasonal trends in reproduction.
Received: 14 February 2000 / Accepted: 3 July 2000 相似文献
19.
In situ egg production of the egg-carrying calanoid copepod Pseudodiaptomus marinus was investigated in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan, at 3- to 5-d intervals for a year. This
species reproduced throughout the year, and the adults showed a large abundance peak in June/July and a small peak in September/October.
Females usually outnumbered males, comprising 61.4% of the annual mean. The composition of ovigerous females varied from 7.9
to 100%, with an annual mean of 55.7%. Adult prosome length was consistently large throughout winter and spring, and decreased
with increasing temperature in summer and fall. Egg diameter varied from 98 to 121 μm, and was negatively correlated to temperature.
The seasonal variation in clutch size (range: 15.1 to 38.2 eggs) was bicyclical, with peaks in May and December. The egg production
rate of breeding females was low in January to March (mean: 2.3 eggs female−1 d−1), while it was constantly high from mid-May to early October (mean: 12.1 eggs female−1 d−1). The specific egg production rate for the breeding females was highly correlated to temperature; it increased linearly from
0.03 d−1 at 9 °C to 0.27 d−1 at 26 °C. Compared to other co-occurring copepods, the reproductive rate of P. marinus was lowest, which is one of the reasons why this species never dominates in this inlet.
Received: 11 November 1996 / Accepted: 7 December 1996 相似文献
20.
Parker's seminal work brought attention to the possibility of postmating sexual selection by non-random fertilization success.
Mechanisms for these processes are still only partly understood and there is clearly a need for more studies of intraspecific
variation in sperm precedence. Here, we report results from an experimental study of the variation in fertilization success
between males of the water strider Gerris lacustris. Genital morphology, male body size, and copulation duration were examined as possible correlates of paternity. The significance
of guarding duration was also analysed. Only male genital morphology was correlated to fertilization success. This is one
of the first studies showing a relationship between male genital traits and fertilization success, supporting the view that
sexual selection may be responsible for the rapid and divergent evolution of genital structures in animals with internal fertilization.
The fertilization success of last males varied considerably after double matings with a short mating interval (10 min). Last-male
priority ranged from 0 to 100% and usually one of the males involved fertilized almost all the eggs. After double matings
with a short mating interval, the proportion of eggs fertilized by the last male averaged 0.68 and was greater than 0.5. In
contrast, the average fertilization success was biased towards the first male when the matings were more spread out over time
(24 h). These results do not support earlier suggestions of a widespread last-male sperm priority in water striders.
Received: 28 July 1998 / Received in revised form: 15 March 1999 / Accepted: 28 March 1999 相似文献