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1.
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
2.
The annual epidemic spawning period of a Scottish population of Arenicola marina (L.) has been recorded over a period of 13 yr. This population spawns between mid-October and mid-November in a discrete
spawning event over a period of 4 to 5 d. Endocrine manipulation experiments showed that spawning is induced in females only
if sufficient titres of PMH (prostomial maturation hormone) are present in the prostomia. These levels are attained during
the 2 to 3 wk prior to the natural spawning date. The East Sands, St. Andrews population always spawns during periods of spring
tides regardless of tidal amplitude or whether they are full- or new-moon tides. Meteorological data, including sea-temperature
data were collected for each year, and correlation of the environmental data with spawning time was attempted. Correlation
of spawning times with weather patterns showed that mean daily air pressures were significantly higher during the spawning
period than from September to November as a whole. Evidence also suggests that a reduction in sea temperature is required
prior to spawning. A significant moderate negative correlation was found between May to July air temperatures and spawning
date, suggesting that higher May to July temperatures may induce early spawning. Daily rainfall and wind speed were also lower
during the spawning period, but not significantly so. These results indicate that air pressure (or changes therein) may act
as a final spawning cue, and the advantages of this are discussed in relation to fertilization success. A model of the interplay
between environmental parameters and the endocrine mechanisms controlling the induction of spawning is proposed. Higher than
average summer temperatures may advance gametogenesis to bring the population into a state of maturity (full-size oocytes,
well-developed sperm morulae), and may also advance spawning time. Once the population has completed gametogenesis, a drop
in sea temperature is then required to trigger an increase in endocrine titres within the prostomium, without which spawning
cannot be induced by prostomial injection. The population spawns on spring tides; however a lack of clement weather coinciding
with the spring tide will result in population-wide spawning being aborted, as in 1996. Clement weather (high pressure, low
rainfall and wind speed) in conjunction with spring tides permits spawning to proceed to completion.
Received: 21 June 1999 / Accepted: 25 January 2000 相似文献
3.
Early development of the Antarctic sea urchin Sterechinus neumayeri was examined under two differ-ent culture regimes: one to simulate development near-bottom (“demersal development”) and the
other to simulate the development of embryos in the water column (“pelagic development”). When embryos of both treatments
reached the hatching blastula stage at 5 d post-fertilization (−1.5 °C), the blastulae that had undergone demersal development
evidenced significant differences (by ANOVA or suitable non-parametric comparison) in the following: a thicker blastoderm
layer (12%, P < 0.001), higher ash-free dry weights (19%, P < 0.01), lower mass-specific respiration rates (50%, P < 0.001), higher incorporation rates of 35S-methionine into protein (23%, P < 0.003), and a differential pattern of protein synthesis. When embryos developed demersally, they remained in the jelly-coat
material released with the eggs at spawning. Quantitative isolation of this jelly-coat material in S. neumayeri demonstrated that it contained a significant amount of organic matter, 115 ng ash-free dry mass per egg, equivalent to 17%
of the egg's initial organic mass. Uptake of external nutrients during embryogenesis may be a significant component of the
physiological energetics of this polar invertebrate by allowing the utilization of jelly-coat material released by a female
during spawning.
Received: 21 April 1999 / Accepted: 5 June 2000 相似文献
4.
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
5.
A mass synchronous spawning of the sea urchin Evechinus chloroticus (Valenciennes) was observed in situ in Doubtful Sound, a large New Zealand fiord. Spawning occurred between 17:30 hrs and
18:30 hrs on 27 January 1994 and coincided with a full moon, spring tides and a period of decreasing sea temperatures. During
spawning, the sea urchins formed a dense spawning aggregation of both sexes, with >90% of the urchins observed spawning at
the time. Spawned gametes clouded the water column, and some were eaten by small labrid fish species. The spawning, which
may have been as widespread as 40 km, marked a 42 to 50% decrease in gonad indices and resulted in a widespread, dense cohort
of E. chloroticus larvae within the fiord.
Received: 25 September 1997 / Accepted: 6 March 1998 相似文献
6.
The spawning patterns of two penaeid prawns, Metapenaeus endeavouri (Schmitt) and M. ensis (De Haan), were examined from data collected at 45 stations between March 1986 and March 1992. An index of population fecundity
based on the abundance, proportion and fecundity of sexually mature females was used as a measure of spawning output of the
prawn stock. The population fecundity index for M. ensis was higher than that for M. endeavouri. The monthly population fecundity index for M. endeavouri varied markedly among years, while that for M. ensis was consistent among years. Spawning of M. endeavouri occurred year-round, while that of M. ensis was concentrated mainly in spring (September to November). For M. endeavouri, a minor spawning, derived from a relatively small number of summer spawners, occurred in the 20 to 30 m offshore waters
in summer. In early summer (after May), the major spawning group consisted of large females from the winter-spawning cohort,
and the spawning area shifted to depths of 30 to 60 m. In winter (July), the major spawning, derived from the winter-spawning
cohort, occurred at depths of 20 to 40 m. For M. ensis, the major spawning, derived from the spring-spawning cohort, was observed in depths <50 m and was concentrated particularly
in inshore waters (<20 m) in spring. In autumn, the spawning output was mainly from the autumn-spawning cohort, which comprised
but a small number of individuals. In winter, the major spawning group again consisted of the large females from the spring-spawning
cohort, and spawning increased in the oceanic waters (>50 m). These results suggest that mature female M. endeavouri and M. ensis move offshore (>40 m) by May and July, respectively, and return to shallow waters (<35 m) in July and November, respectively.
The monthly reproduction patterns of both species in the “effective spawning” area showed that the major spawning season for
M. endeavouri is August to October and that for M. ensis is September to December.
Received: 19 February 1999 / Accepted: 18 June 2000 相似文献
7.
The reproductive biology of the alfonsino Beryx splendens was studied by histological examinations, gonadosomatic index and macroscopic scales of maturation of a large sample of gonads.
Alfonsino is a gonochoric species. The size-frequency distribution of the sex ratio was bimodal and considered to be due to
size dimorphism. In New Caledonia, the breeding period of this species occurs during the southern summer, with a peak in December
to January. The spawning stage is attained at a minimum fork length of 28 cm for females and 33 cm for males. The size at
which 50% of the population attain sexual maturity (FL50) is 33.2 cm for females and 34.5 cm for males. Maximum potential fecundity is estimated to lie between 270 000 to 675 000
eggs for fish between 34 and 40 cm in fork length. It was possible to differentiate vegetative zones, in which juvenile alfonsino
grow until they reach maturity, from reproductive zones (fishing grounds) which are inhabited by mature individuals. The larvae
and juveniles could be carried from the reproductive zone to the vegetative zone by currents in an oceanic eddy system.
Received: 26 April 1996 / Accepted: 20 September 1996 相似文献
8.
Between June 1994 and September 1996, a mark–recapture study was conducted in the Hinchinbrook Channel area of tropical northeastern
Australia to investigate the movements of the sparid fish Acanthopagrus berda. A total of 962 A. berda were tagged, 922 within a single estuary system, Deluge Inlet. No movements among estuaries were detected. Of the fish tagged
in Deluge Inlet, 12.9% were recaptured. Two movement regimes were detected: local movements (mostly <500 m) during non-spawning
times, and longer migrations (up to 3.12 km) during spawning seasons, to and from a spawning site at the estuary mouth. Although
there appeared to be a major spawning aggregation in the mouth of Deluge Inlet, ripe female A. berda were present in upstream sites, indicating that spawning probably occurs there also. This contrasts to the situation in South
Africa, where A. berda is reported to spawn only close to estuary mouths. Differences such as this highlight our limited knowledge of variations
in the reproductive biology of widespread species such as A. berda.
Received: 25 November 1997 / Accepted: 10 September 1998 相似文献
9.
The northern Pacific asteroid Asterias amurensis (Lütken) has been recently introduced to Tasmania and is now well-established in east and southeast Tasmania. This sea star
is conspicuous throughout the Derwent River estuary and is particularly abundant in the Hobart port area. Reproduction of
two populations of A. amurensis at Sullivans Cove and at Sandy Bay was investigated from August 1993 to October 1994 by gonadal histology and measurement
of the gonad index (GI). An intense period of vitellogenic and spermatogenic growth started in April, with the breeding condition
reached by June. In 1994, peak GI was recorded at Sullivans Cove in July and at Sandy Bay in August. Although these data indicated
that the Sullivans Cove population spawned before the Sandy Bay population, histological examination revealed that major spawning
activity occurred in both populations from July onwards. In the early part of the breeding season, gametogenesis proceeded
in parallel with spawning, with released gametes being replaced by continual gametogenesis. Maintenance of a higher GI during
the early part of the breeding season at Sandy Bay was due to prolonged gametogenic replacement at this site. Spawning continued
to October 1994, resulting in a sharp decline in the GI. The cyclic expansion and regression of the genital haemal sinus coincident
with germinal proliferation and growth, respectively, support the contention that haemal fluid provides nutrients for gametogenesis.
In Tasmania, A. amurensis experiences temperature and photoperiod regimes similar to those experienced by endemic populations of this species in the
north Pacific. Comparison of reproduction of A. amurensis in Japan and Tasmania at similar latitudes shows that gametogenesis of the northern and southern populations is 6 mo out
of phase. This phase shift provides evidence for photoperiodic regulation of gametogenesis in A. amurensis. The similar trend in sea-temperature regimes associated with the stages of gametogenesis in northern and southern populations
suggests that temperature also plays a modulatory role. Based on the periodicity of reproduction and the ontogeny of A. amurensis, the planktotrophic larvae of this species would be expected to be in the plankton for several months from the end of winter
through summer. Considering the highly fecund, dispersive life-history of A. amurensis, the southeast Tasmanian populations have considerable potential to serve as a seed source for establishment of new populations
of this asteroid elsewhere in Tasmania and in mainland Australia.
Received: 18 October 1996 / Accepted: 22 October 1996 相似文献
10.
M. D. Herrero-Pérezrul H. Reyes Bonilla F. García-Domínguez C. E. Cintra-Buenrostro 《Marine Biology》1999,135(3):521-532
The reproduction and growth of Isostichopus fuscus (Ludwig, 1875) at Isla Espíritu Santo, Baja California Sur, México from July 1992 to September 1993 and from August 1996
to July 1997 were analyzed. The reproductive cycle was monitored by using histological analysis. Five gonadal stages were
described according to cell types present in the gonad; undetermined, gametogenesis, maturity, spawning and post-spawning.
This holothurian reproduces annually during summer (July to September), when sea surface temperature reaches 27 °C. The gonad
index is related to the gonadal stages. The first sexual maturity for I. fuscus was calculated at 367 g (4 to 5 years old) according to the von Bertalanffy equation, and nearly all the specimens at Isla
Espíritu Santo were 5 to 7 years old (including some individuals over 35 years old). Data of the length–weight relationship
showed that I. fuscus grows allometrically at the studied site (b = 1.83). The mortality rate was relatively high (M = 0.51), indicating that in a typical cohort, 40% of the recruits does not survive the first year, and less than 20% reaches
maturity.
Received: 15 July 1998 / Accepted: 19 August 1999 相似文献
11.
Sexual reproduction of the reef-building coral Montastreacavernosa was studied in the Santa Marta area, Caribbean coast of Colombia, from October 1990 to October 1991. The area is subjected
to a seasonal upwelling–outwelling regime. From microscopical analysis of tissue sections sampled each lunar month around
the full moon, it was confirmed that this is a gonochoric, broadcasting species, with a single gametogenic cycle per year,
and a 1:1 sex ratio. Oogenesis began a few weeks after spawning, and extended for 11 mo. The onset of spermatogenesis occurred
just before the full moon of June, later than at other localities where sea-water temperatures during the first half of the
year are not as low. The amount of reproductive tissue strongly increased in both sexes after July, in association with an
increase in sea-water temperature and a decrease in photoperiod. The gonad index of fully mature female colonies was about
four times lower than at other localities, perhaps due to the stressful seasonal regime. The male gonad index was lower than
that of the female, indicating sex-related differences in the rates of biomass allocation to reproduction. As in other Caribbean
localities, spawning occurred after the full moons of August and September. However, there was some evidence of a third spawning
episode after the full moon of October, possibly associated with a delay in the occurrence of maximum sea-water temperatures
in near-equatorial localities compared to higher latitudes. The probability of cross-fertilization in this species with a
gonochoric breeding system and a broadcasting mode of reproduction is favored by its balanced sex ratio, its usually high
within-reef zone abundance, and by localized and repeated spawning episodes, synchronized by lunar phase.
Received: 19 April 1996 / Accepted: 24 September 1996 相似文献
12.
E. Mutlu 《Marine Biology》2001,138(2):329-339
The distribution of moon jellyfish (Aurelia aurita Linnaeus, 1758) in the Black Sea was determined from plankton samples collected above the anoxic zone (maximum depth 200 m)
in the summer, winter and spring during 1991–1995. Distribution was patchy. Average biomass ranged from 98 to 380 g m−2, and abundance varied from 2 to 14 individuals m−2. Biomass and abundance peaked in late spring and summer. The distribution was correlated with hydrographic features in the
Black Sea, with higher concentrations occurring at the peripheries of anticyclonic eddies. Centers of the two main cyclonic
gyres generally had a low biomass of A. aurita. From July 1992 to March 1995, the populations were largely concentrated in offshore regions. A. aurita were confined to the upper part of the mixed layer. Smaller A. aurita (≤1 cm) were present in early spring (March), and individuals reached maximum size in the summer. Release of the epyhrae
occurred in spring on the northwestern shelf of the sea when the seawater temperature was 11–12 °C. Microscopic analysis of
stomach contents showed that copepods and mollusks form their main diet.
Received: 3 September 2000 / Accepted: 29 September 2000 相似文献
13.
Previous studies have shown that large numbers of ciliated and nonciliated epithelial cells (diam.: 6 to 15 μm) are released
by adult sea scallops, Placopecten magellanicus (Gmelin), during summer months in Newfoundland when water temperatures are at a maximum and gonads are well developed. Such
exfoliation of cells could be a response to stresses associated with elevated water temperatures and/or spawning activity.
In the present study an electronic particle counter/sizer was used to further investigate the factors that influence exfoliation
of epithelial cells by juvenile and adult scallops throughout the year. We observed release of epithelial cells from juveniles,
and from adults collected in months when gametogenic activity was minimal, indicating that exfoliation does not occur as a
result of reproductive activity alone. SEM analysis revealed little difference in surface characteristics of the gills, mantle
and gonad between scallops that had released cells and those that had not, suggesting that exfoliation of small numbers of
cells may be a consequence of cellular turnover and normal physiological function. Adult scallops were monitored in a second
experiment to determine the effects of raising water temperatures from 8.5 to 14.7 and to 21.0 °C on the frequency (proportion)
and rate of cellular exfoliation. Only at the highest experimental temperature (21.0 °C) were exfoliation rates significantly
higher than rates recorded at 8.5 or 14.7 °C. SEM analyses revealed some damage to gill, mantle and gonad tissues when scallops
were exposed to 14.7 and then to 21.0 °C for a total of 8 d.
Received: 21 August 1996 / Accepted: 13 September 1996 相似文献
14.
The gonads of Serranus cabrilla (Linnaeus, 1758) from the Canary Islands were studied between September 1992 and July 1993. Macroscopic classification of
the maturity stages was compared with histolog ical classification of gonad characteristics, and the effect␣of the classification
method on the determination of the spawning season and size at maturity was investigated. Analysis of gonad organization and
development confirmed that this species is synchronously hermaphroditic. Ovarian-tissue development is asynchronous, and testicular
tissue consists of continuous spermatogonia. Six stages of oogenesis and five of spermatogenesis are described, based on differences
in staining and in size and on differences in the nucleus and cytoplasm structure as viewed through a light microscope. Two
types of atretic degeneration of eggs are also described. Agreement between macroscopic and histological staging was low,
although both methods provided similar results in spawning-season determination and size at maturity. The spawning season
of S. cabrilla is from February to July, with a peak in May. Fish size at first maturity (size at which 50% of all fish sampled are in relevant
maturity stage) is 152 mm standard length (SL), and size at mass maturity (size at which 95% of all fish sampled are in relevant
maturity stage) is 167 mm SL.
Received: 21 May 1996 / Accepted: 9 August 1996 相似文献
15.
Samples of southern bluefin tuna, Thunnus maccoyii (Castelnau), taken from off the coasts of South Africa, Western Australia, South Australia and Tasmania from 1992 to 1994
were analysed for six polymorphic allozyme loci (ADA
*, GDA
*, GPI-A
*, MPI
*, PGDH
* and PGM-1
*, n = 595 to 733 per locus) and for mitochondrial DNA variants revealed by three restriction enzymes (Bam HI, Bcl I and Eco RI) detecting polymorphic cut sites (n = 555). No significant spatial heterogeneity was detected. There were no sex-related differences in allele or mtDNA haplotype
frequencies. Juveniles (30 to 35 cm and 46 to 54 cm) from what are thought to be two temporally-separated spawning peaks showed
no significant genetic differentiation. There were also no significant differences in allele or haplotype frequencies between
fish smaller than 70 cm and those larger than 70 cm. These data are consistent with the null hypothesis of a single unit stock
of southern bluefin tuna, with a single spawning area. This is located to the south of Java and off the north-west coast of
Australia.
Received: 28 August 1996 / Accepted: 30 September 1996 相似文献
16.
Experiments were performed to determine how ultraviolet radiation (UVR) in the environmentally relevant range affects development
of the sea urchin Strongylocentrotus droebachiensis (Müller) and whether mycosporine-like amino acids (MAAs), present in the early life stages, reduce UV-induced damage. Eggs,
embryos, and larvae contained five MAAs having absorption maxima ranging from 320 to 334 nm. Eggs contained principally shinorine
and porphyra-334, which absorb maximally at 334 nm and half-maximally at 312 and 348 nm, spanning much of the environmental
range of biologically effective UVR. Concentrations of MAAs remained constant in unirradiated embryos through the gastrula
stage, but decreased significantly in two-armed pluteus larvae. Daily exposure to combined photosynthetically active radiation
(PAR, 400–700 nm) and UVR did not affect the concentration of MAAs in these embryos up to the two-armed pluteus stage. Prism
larvae of sea urchins and the sand dollar Echinarachnius parma (Lamarck) did not accumulate shinorine from the surrounding seawater. Daily exposure of embryos to UVA (320–400 nm) and UVB
(295–320 nm) radiation in the presence of PAR induced delays and abnormalities during development, and removing UVB eliminated
this effect. Abnormalities in embryos included thickening of the blastoderm wall, filling of the blastocoel by abnormal cells,
exogastrulation, and formation of abnormal spicules. The percentage of embryos that developed normally was lower in batches
of embryos exposed to PAR + UVA + UVB, except in embryos from urchins maintained on MAA-rich diets. In all cases, the percentage
of PAR + UVA + UVB-exposed embryos that developed normally was positively related to the concentration of MAAs in eggs from
which the embryos developed. Thus, the MAAs found in S. droebachiensis embryos protect them against UVB-induced abnormalities during their development to at least the four-armed pluteus larval
stage.
Received: 8 May 2000 / Accepted: 29 September 2000 相似文献
17.
A method was developed for measurement of active oxygen production in embryonic stages of the brown seaweed Fucus spiralis, using the label CM-DCFH-DA. Active oxygen species convert the label into the green fluorescent CM-DCF (exc/em 488/530 nm)
that is detected via confocal laserscan microscopy and quantitative image analysis. Loading of the label did not harm the
embryos; loading efficiency was age-independent, and the esterases needed for conversion to CM-DCFH were not inhibited by
the effective UV dose (2 W m−2) applied in the experiments. After correction for daily variation of the laser power, and calibration with DCF standard solutions,
this automated analysis of confocal images rendered active oxygen concentrations in fucoid embryos (μM DCF). An experiment
was designed for the assessment of active oxygen production following irradiance stress in the light-sensitive embryos. Dim-light-acclimated,
1-, 2- and 4-day-old embryos were transferred for 60 min to defined high-light conditions (4π-irradiance 300 μmol photons
m−2 s−1), optionally without UV radiation, including UVA, or including UVA plus UVB. PSII yield measurements (PAM fluorometer) were
carried out in order to assess the degree of photoinhibition under these light conditions. The imposed light stress initially
caused a rapid decrease of the PSII yields (ΦP). With increasing embryo age, minimum ΦP values attained under light stress remained higher. Consequently, electron transport rates (ETR) would increase with embryo
age, i.e., with the development of their photosynthetic apparatus. Active oxygen production increased with ETR, and when UVB
was included, relatively greater amounts of active oxygen were produced. A slow, second-phase decrease of ΦP under light stress that was proportional to active oxygen production indicated that some photooxidative damage was caused,
in particular during UVB exposure. Recovery from light stress was a rapid process in the absence of UVB; in such cases ΦP was almost restored to the initial values within 60 min. The relative state of recovery of ΦP was correlated with both the effective UV dose and active oxygen production rate (DCF). Recovery was slowest in embryos exposed
for 60 min to an experimental UVB dose, which was representative of a situation at low tide, on a sunny day. The results suggest
that active oxygen may cause an in situ inhibition of growth of the earliest life stages of F. spiralis.
Received: 26 January 2000 / Accepted: 4 September 2000 相似文献
18.
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
19.
At the beginning of their offshore migration, hatchling sea turtles orient directly into oceanic waves as they swim away
from land. Recent experiments have demonstrated that hatchlings swimming underwater can determine the propagation direction
of waves by monitoring the circular movements they experience as waves pass above. During July and August 1993, we studied
how loggerhead sea turtle hatchlings (Caretta caretta L.) from the east coast of Florida, USA, responded to a range of wave parameters. We constructed a wave simulator to reproduce
in air the circular movements that normally occur beneath small ocean waves. Hatchlings suspended in air and subjected to
these orbital movements attempted to orient into simulated waves when periods and amplitudes were similar to those found near
the Florida coast. Orbital movements with longer periods (greater than 10 s), however, failed to elicit responses. The results
demonstrate that hatchling loggerheads can distinguish between waves with different periods and amplitudes, and that Florida
hatchlings respond most strongly to orbital movements closely resembling those of waves that occur near their natal beach.
Received: 28 May 1996 / Accepted: 17 September 1996 相似文献
20.
A. L. Moran 《Marine Biology》1997,128(1):107-114
An understanding of spawning and larval development can be fundamental to interpreting the abundance, distribution, and population
structure of marine invertebrate taxa. Tegula funebralis (A. Adams, 1855), the black turban snail, has been the focus of numerous ecological studies on the Pacific coast of North
America. To date, there are only conflicting and anecdotal reports of spawning, and there is no information on larval or juvenile
development for this conspicuous and abundant species. On 19 September 1995, two individuals of T. funebralis were observed free-spawning gametes into seawater in tanks at the Oregon Institute of Marine Biology. Embryos and larvae
were subsequently reared to metamorphosis and beyond. Development was pelagic and similar to development described for other
trochids, and larvae were observed not to feed at any stage. Larvae began to metamorphose at 5.7 to 6.7 d and settled at 260
μm shell length. Juveniles grew ≃ 10 μm in shell length per day and appeared to feed on detritus. Juveniles lacked some adult
diagnostic shell characters, including two columellar nodes and a closed umbilicus. In the field, small (<3 mm) juveniles
occurred in the adult habitat on all sampling dates between October and March. Small juveniles were found only under rocks
and were most abundant under rocks partially buried in coarse sand, suggesting that juveniles may utilize a specific microhabitat
within the adult T. funebralis habitat.
Received: 7 October 1996 / Accepted: 17 October 1996 相似文献