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1.
Brooding, embryonic and larval development, and the influence of environmental and biological factors in tidepool habitats
were studied in the sea star, Anasterias minuta, at various sites along ~220 km of the Patagonian coast. This species has a benthic, lecithotrophic development that includes
eight distinct developmental stages. A larval organ, the connection cord, is developed from a small preoral lobe at early
stages of development and becomes larger and thinner at advanced stages. Fecundity and average egg size increased with female
body size. The regression of log egg number to log sea-star size and weight at different sites had a slope significantly less
than 3.0, resulting in negative allometry and indicating that brood capacity was limited in large females. Development was
generally synchronous among sites, but varied within each brood at advanced stages, with more developed brooded larvae located
at the periphery of the brood mass. Brooding was synchronous among various populations at different years and spatial scales,
and extended over a period of 8 months. The highest proportion of brooding females occurred during May and June (austral winter).
Juveniles were released mainly during September. The likelihood of finding brooding sea stars decreased with increasing sea
water temperature, tidal height, and wave exposure, and increased with increasing body size. Both body size of brooding females
and brooding rate were higher in the infralittoral fringe than at midlittoral levels. A revision of the current model of brooding
behavior and development among forcipulate sea stars is given. 相似文献
2.
Ingrid Ahnesjö 《Behavioral ecology and sociobiology》1996,38(3):167-172
Embryo success was studied in the paternally brooding pipefish Syngnathus typhle. During brooding, which lasts about a month, males provide embryos in their brood pouch with nutrients and oxygen via a placenta-like
structure. Egg size depends on female size. In aquaria, males were mated with differently sized females to give the following
treatments: M, mixed-egg-size broods of approximately half large and half small eggs; L, single-egg-size broods of large eggs;
S, single-egg-size broods of small eggs; and F, field mated males. All males were kept in aquaria for a full brooding period.
For each egg-size category, the number of newborn was compared with the number of eggs the male initially fertilized in his
brood pouch. Within mixed-egg-size broods, a higher proportion of large eggs survived and large eggs resulted in heavier newborn
than small eggs. Indeed, small eggs from a mixed-egg-size brood had significantly lower relative success (proportion of embryos
surviving to birth) than those from a brood entirely composed of small eggs. The implication is that embryos compete for resources
within the brood pouch, and that competitive success depends on egg size. Given that females produce eggs corresponding in
size to their body size, and that females are known to compete indirectly for access to mates (i.e., the sex-roles are reversed),
this intrabrood competition could be seen as an extension of female-female competition, but alternative explanations are discussed.
Received: 28 April 1995/Accepted after revision: 28 October 1995 相似文献
3.
Reproductive biology in two species of deep-sea squids 总被引:2,自引:0,他引:2
Deep-sea squids, Moroteuthis ingens and Gonatus antarcticus, were collected in the slope waters off the Falkland Islands and their reproductive systems preserved and investigated onshore.
Changes in oocyte length-frequencies at maturation and spawning, and their fecundity were studied. These squids, as well as
many other species, are characterised by a synchronous oocyte growth and ovulation. Oviducts are not used for ripe egg accumulation
and consequently the universal scale of Lipinski (1979) cannot be applied to assign female maturity. M. ingens spawns near the bottom; its fecundity is 168–297 thousand eggs. Maximum egg size is 1.8–2.7 mm. G. antarcticus spawns midwater; its fecundity is 10–25 thousand eggs. Egg size is 3.2–3.3 mm. In M. ingens spawning takes place in the austral autumn and winter, in G. antarcticus—in austral winter. Our data and the literature data show that the so-called “synchronous ovulation” probably occurs in all
deepwater squids. This pattern is very rare among fish, but is quite common among benthic octopods that brood their egg masses. 相似文献
4.
Male limitation of female reproductive success in a pipefish: effects of body-size differences 总被引:2,自引:0,他引:2
Summary In the pipefish Syngnathus typhle, a species with exclusive male parental care, males limit female reproductive success because of their limited brood pouch space and long pregnancy. Sexual size dimorphism is absent in these 1-year-old animals but increases with age so that older females are larger than similarly aged males. Because fecundity is related to size in both sexes and increases more rapidly with body size in females than in males, the difference in growth increases female fecundity more, relative to male fecundity, as the fish get older. We therefore predicted that male limitation of female reproductive success is even more severe when all age classes are considered. To measure a female's maximum reproductive rate, she was provided with three males. Small 1-year-old females produced as many eggs, or produced eggs at the same rate, as a male of similar size could care for. Small females filled on average 1.06 males within the time span of one male pregnancy and actually produced on average 10 eggs fewer than needed to fill a similarly sized male. Large 2-year-old females, in contrast, produced on average a surplus of 149 eggs and filled 2.7 similarly sized males within the course of one pregnancy. The difference between females of the two size classes was highly significant. Males prefer to mate with larger females if given a choice. In nature sex ratios are equal, and males limit female reproductive success in the whole population. Therefore, small females are more severely constrained by mate availability than are larger females because males choose to mate with larger females.
Offprint requests to: A Berglund 相似文献
5.
Nicholas D. Higgs Adam J. Reed Rachel Hooke David J. Honey Olaf Heilmayer Sven Thatje 《Marine Biology》2009,156(5):1073-1081
We present information on the reproductive biology, population structure, and growth of the brooding Antarctic bivalve Adacnarca nitens Pelseneer 1903, from the Ross Sea, Antarctica. Individuals ranging from 0.85 to 6.00 mm were found attached to a hydrozoan colony. This
species shows low fecundity and large egg size, common to other brooding species. The minimum size at which oogenesis was
detected was 2.3 mm and the minimum size at which brooding was evident was 3.9 mm. Embryos of a full range of developmental
stages were brooded simultaneously in females. The population showed a log–normal distribution and results suggest non-periodic
reproduction with continuous embryonic development. The reproductive traits of A. nitens are discussed in the context of circum-Antarctic species distribution and limitations to dispersal in brooding benthic invertebrates. 相似文献
6.
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
7.
Long-distance dispersal of a subantarctic brooding bivalve (Gaimardia trapesina) by kelp-rafting 总被引:4,自引:0,他引:4
The probability of successful dispersal by sessile benthic invertebrates is thought to strongly influence their geographic distribution and population genetics. Generally, species with long-lived planktonic larvae are expected to exhibit wider distribution patterns than those species which brood their young, due to their presumably greater potential for dispersal. In some cases, however, brooding species exhibit broad distributions and show evidence of genetic exchange with geographically distant populations. One potential factor that has been invoked as an expianation is dispersal by floating and rafting of adults and egg masses. Several studies have shown that it is possible for sessile adults to disperse on the order of several to many thousand kilometers by rafting on debris in ocean currents. With very few exceptions, however, direct evidence of rafting in the open ocean has been lacking. We present evidence of long-distance (1300 to 2000 km) dispersal of a brooding pelecypod,Gaimardia trapesina (Lamarck, 1819), in the Southern Ocean in the vicinity of Cape Horn, the Falkland Islands, and the antarctic island South Georgia (54°S; 37°W). Data on survival and fecundity rates ofG. trapesina and the prevalence of kelp rafts collected during the austral winter of 1993 indicate that dispersal by rafting can occur over ecologically relevant time scales and could potentially serve as a significant means of genetic exchange between populations. 相似文献
8.
The reproduction of Crepidula fornicata was studied in the Bay of Brest in order to characterise the first step of the reproductive cycle of this invasive species. The survey was carried out from 2000 to 2003 and different parameters were measured, namely, the percentage of the different sexual stages, the straight length of the shell and the percentage of brooding females using a survey of the embryonic development and the fecundity. The juvenile frequency increases generally from mid-June or mid-August, depending on the year. In 2001 and 2003, a first peak was observed as early as May, but it was followed by a rapid disappearance of the individuals. The sex-ratio female/male increased from 0.22 to 0.46 between 2001 and 2003. The sex change between intermediates and females took place mainly in summer and was well marked in 2001 and 2003. The survey of the embryonic development in the egg capsules brooded by the females provided an annual phenology of the laying and hatching processes. The laying period extends from February to September with three to four major periods of egg-laying per year and corresponding hatching periods about 1 month later. Each female lays two to four times per year on average. The first egg-laying concerned fewer females than subsequent ones, except in 2003, and exhibited a higher fecundity. The annual mean of the number of eggs for each stage was not significantly different, thus indicating no significant mortality rate during embryonic development. For the C. fornicata population in the Bay of Brest, several reproductive characteristics tend to highlight its invasive capacity: (1) a long reproductive period, (2) reproduction in a ‘multi-trials’ process equivalent to a spreading out of the risks and (3) a relatively high fecundity. 相似文献
9.
Maturity,fecundity, and reproductive cycle of the spotted ratfish, <Emphasis Type="Italic">Hydrolagus colliei</Emphasis> 总被引:1,自引:1,他引:0
Lewis A. K. Barnett Ryan L. Earley David A. Ebert Gregor M. Cailliet 《Marine Biology》2009,156(3):301-316
Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratfish, Hydrolagus colliei (Lay and Bennett, 1839), off the coast of California, Oregon, and Washington. Maximum body size and size at median maturity
were greater for females than males. Skeletal muscle concentrations of the steroid hormones testosterone (T) and estradiol
(E2) predicted similar, but slightly smaller sizes at maturity than the morphological criterion. Stage of maturity for males
was estimated identically using internal organs or external secondary sexual characters, thus allowing non-lethal maturity
assessments. Size at median maturity was greater north of Point Conception for females, and north of Cape Mendocino for males.
Peak parturition occurred from May to October, with increased concentrations of E2 in skeletal muscle of females correlating with ovarian recrudescence during November to February. No significant seasonal
trends in female T were apparent, but mean female 11-ketotestosterone (11KT) was 300% greater in April than any other month
during the parturition season. There was a marginal evidence for increased number and size of ova with maternal size. Extrapolation
of the hypothesized 6 to 8-month egg-laying season to observed mean parturition rates of captive specimens yielded an estimated
annual fecundity of 19.5–28.9 egg cases. Differences in fecundity among higher taxonomic classifications of chondrichthyans
were detected with chimaeriform fishes more fecund than lamniform, myliobatiform, squaliform, and rhinobatiform fishes, and
less fecund than rajiform fishes.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
10.
In Portuguese waters, thornback ray Raja clavata spawns mainly between May and January, although females and males in spawning condition are found throughout the year. The
maturation process can be divided into three main phases by using information on gonad weight, oviducal gland and uterus width
in females and on gonad weight, clasper length and sperm duct width in males. Females attain length-at-first-maturity at 784 mm
and males at 676 mm, at ages of 7.5 and 5.8 years, respectively. In females larger than length-at-first-maturity, a resting
stage was identified characterized by low gonadosomatic index and well-developed oviducal glands and uteri. These results
along with the low proportion of adult females that are effectively reproducing per month demonstrated that the thornback
ray cannot be considered a continuous spawner as described in other studies. Fecundity was determinate with about 35 eggs
released per batch. During the spawning season, a total of four batch episodes occur indicating that the total fecundity was
approximately 136 eggs per female. Regional differences may exist in the reproductive strategy of the species, namely on the
duration of the spawning season, length-at-first-maturity, and fecundity, which can be related to a more intense fishing pressure
in northern European waters. 相似文献
11.
Changes in size, morphology, and biochemical composition in adults and embryos of a brooding sea star, Neosmilaster georgianus (Sladen), were studied in a population adjacent to Anvers Island, Antarctic Peninsula (64°46′S; 64°04′W) during the austral
spring, 1991. Five morphological stages of development were designated in 24 broods, and for each the weight and biochemical
composition of the brooding adults and their embryos were determined. Between Stage 1 and 2, the dry weight (dw) and organic weight (ow) of the embryo did not change. From Stage 2 to 3, the dw and ow increased significantly by 10%. Stage 2 and 3 embryos were in clusters of a few (2 to 10) to as many as 40 individuals. In
the smaller clusters, individual embryos were attached by tissue cords to another, sometimes atrophied, brood member. In the
larger clusters, they were attached to a central mass of tissue containing remnants of embryos. We interpret these interactions
as a form of cannibalism which may account for the weight gains between Stage 2 and 3. During Stages 4 and 5, as juvenile
form was approached, the dw and ash weight of the young increased significantly and the ow decreased significantly. The calculated energy content for the juvenile (Stage 5) was not significantly different from the
energy content of the earliest undifferentiated stage (Stage 1), an indication that most of the organic matter in the egg
is the primary contribution to the large juvenile. In brooding females, pyloric caeca indices declined by 52% from Stage 1
to Stage 5 and pyloric energy stores declined by 63% due to proportionately equivalent declines in protein and lipid. The
ovary index was low and increased only slightly during brood protection, while the size of the largest oocytes remained approximately
23% that of ova. Energy stores in the pyloric caeca of brooding N. georgianus thus become depleted over a long period of incubation during which the adults apparently starve. This may delay oocyte development
and ultimately limit the frequency of individual reproduction.
Received: 15 September 1998 / Accepted: 9 March 1999 相似文献
12.
C. S. Gallardo 《Marine Biology》1993,115(4):595-603
A population of the small clam Kingiella chilenica Soot Ryen 1959 was studied from March 1986 to December 1988 in an intertidal flat at Queule River, in the south of Chile. The life cycle and life history pattern of the bivalve were established contrasting population structure and dynamics to its reproductive habits. Individuals are gonochoristic and semelparous, presenting a typical annual life cycle. The species is a sequential brooder whose embryos undergo direct development. After the brooding season (summer through autumn), the adults disappear gradually (autumn through winter). Recruited juveniles overwinter during a relatively long period, undergoing rapid growth during the spring to attain the adult stage during the summer. The number of brooded embryos increases in proportion to adult length cubed. Life history traits of this bivalve are compared to those reported for other small brooder clams. Some basic tendencies become apparent when traits for semelparous versus iteroparous species are contrasted. As in other semelparous sequential brooders (Transennella tantilla, Gaimardia bahamondei), the relationship between brood size and shell length obseved in K. chilenica does not fit the allometry hypothesis for marine brooding invertebrtes that allometric constraints on the brooding space limit the fecundity of larger individuals. Also contrary to theoretical predictions, small body size does not limit the diversity of a clam's developmental patterns. Possible explanations for this finding are discussed. 相似文献
13.
Accurate fecundity estimates are central to population modelling of reproductive status and egg production in a fishery. Southern
rock lobster (Jasus edwardsii) fisheries are managed with the consideration of performance measures based on the level of current egg production relative
to the unfished stock. Egg production is a function of the size at the onset of maturity, the size structure of the stock,
and the fecundity at length of lobsters. Fecundity at length of the Tasmania stock of J. edwardsii has not been reported previously and was estimated from seven sites around Tasmania. Data were analysed by classical linear
regression and also generalised linear models (GLM) with gamma and Poisson distributions. GLM with a gamma distribution produced
the best fit and did not require a correction factor to generate a model on the linear scale. Individual fecundity ranged
from 43,918 to 660,156 and could be predicted from carapace length according to the equation F = −1.707 + 2.969 (log length). The coefficient of length approximated three, implying the fecundity at length relationship
is cuboidal. Despite the spatial heterogeneity in reproductive parameters in this fishery, the inclusion of spatial information
and egg development stage into the analysis only explained an additional 1% of the variance in fecundity. Thus, it appears
valid to apply the relationship across the fishery without spatial separation. 相似文献
14.
Timothy C. Sparkes 《Behavioral ecology and sociobiology》1996,39(6):411-417
In field surveys, laboratory observations and field-based assays of behavior, I examined the effects of size-dependent predation
risk on the interaction between size at reproductive maturity and maternal care behavior in the stream-dwelling isopod, Lirceus fontinalis. L. fontinalis exhibit population-specific sizes at reproductive maturity which result in population differences in predation risk during
the adult phase. Females from streams containing salamander larvae (that prefer small prey) mature at large sizes and then
become relatively safe from predation. Females from streams containing fish (that consume all size classes of prey equally)
mature at small sizes and remain at risk. I tested whether these differences in expected survival were reflected in the behavior
of females during the maternal phase (i.e., the period during which females exhibit maternal care). Female L. fontinalis carry developing juveniles inside a brood pouch. I simulated predatory attacks on gravid female L. fontinalis from the different population types and found that female behavior correlated with population differences in risk. When “attacked”,
females from streams with predatory fish (that experience high risk to adult females) released juveniles from the brood pouch,
whereas females from populations with predatory salamander larvae (that pose relatively little risk to adult females) did
not release juveniles. I discuss the results with reference to the joint evolution of behavioral and life history traits.
Received: 6 March 1996 /Accepted after revision: 12 August 1996 相似文献
15.
The bathyal West Antarctic Peninsula (WAP) shelf experiences intense seasonal variability in primary production, with summer phytoplankton blooms yielding intense pulse of phytodetritus to shelf sediments. Echinoderms form a conspicuous proportion of the deposit-feeding megabenthos on the shelf and of these Amphipneustes lorioli was the most abundant irregular echinoid. To explore the reproductive response of A. lorioli to this seasonal production cycle, A. Lorioli was sampled at one location on the WAP shelf during four separate cruises between March 2000 and March 2001. Reproductive patterns were determined by histological analyses of gonad tissue, and elemental (CHN) analyses were used to estimate the nutritional and energetic status of the body tissues. Histological analysis of the brooding echinoid A. lorioli suggested a quasi-continuous gametogenic pattern in both the ovaries and the testes. Biochemical analysis of the gonads and the gut tissues were consistent with a continuous gametogenic cycle, showing no significant changes in the biochemical composition of the tissues among seasons. Size-frequency distributions of the embryo and juvenile echinoids within the adults’ brood pouches revealed a synchronous recruitment of embryos and juveniles in specific cohorts between different adult specimens. Whilst this occurrence of different cohorts of the developing brood may be an adaptation to limited brood space, there may also be an external factor influencing the synchrony between adult individuals. Nonetheless, a continuous gametogenic cycle and the lack of seasonal variation in the biochemical composition of gonad and gut tissues suggest that this deposit-feeding irregular urchin is exploiting a persistent sediment food bank in WAP shelf sediments throughout much of the year. 相似文献
16.
Life history and reproductive strategies influence population dynamics at the inter- and intra-specific level. Environmental
conditions suitable for gonad development and spawning, the reproductive range, may be a smaller portion of the broader species
distribution. The only known breeding population of veined rapa whelks (Rapana venosa) in North America is in Chesapeake Bay, USA. There is considerable interest in the potential reproductive range of this non-indigenous
species given the rapa whelk’s negative impacts on commercial shellfish species in both its native and introduced ranges.
Weight-specific reproductive output is described for wild caught Chesapeake Bay rapa whelks maintained in flow-through mesocosms
for 2 years. Measured reproductive output within and between egg capsule deposition seasons (years) in relation to water temperature,
salinity, daylength, and female size is used to describe the rapa whelk’s reproductive range. Egg capsule production is influenced
by seasonal and absolute water temperatures as well as seasonal daylength cycles. Egg capsule deposition by Chesapeake Bay
rapa whelks begins at water temperatures of approximately 18°C and continues for 11–15 weeks. Forty to 70% of female whelks
deposited egg capsules in most weeks during this season, producing 150–200 egg capsules female−1 week−1. Water temperatures >28°C caused reduced egg capsule production relative to temperatures of 20–25°C. Egg capsule production
was positively related to seasonal changes in daylength, and two peaks of egg capsule deposition were observed in the 2001
and 2002 deposition seasons. The combination of declining daylength and higher water temperatures in late summer was associated
with the cessation of egg capsule deposition. A lower average weight specific reproductive output in 130–145 mm SL rapa whelks
(average 12 ± 1%) than in 90–106 mm SL rapa whelks (average 22 ± 1% of body weight) may reflect a life history that balances
the physiological costs of maintaining a large body mass with the production of many planktonic larvae from multiple clutches
of egg capsules per breeding season over a 10–15-year lifespan. Estimates of the cumulative day-degree requirements corresponding
to the annual initiation of egg capsule deposition were 238 and 236 for 2001 and 2002, respectively. Reproductive output and
day-degree requirements for Chesapeake Bay rapa whelks were similar to values calculated from previous studies of native muricids
(Eupleura caudata and Urosalpinx cinerea). A latitudinal range of 30–41° (N and S) is predicted as the realized reproductive range for rapa whelk populations on the
basis of the day-degree requirements for native whelks and reproductively active invasive rapa whelk populations.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
17.
Interval between reproductive events is an important factor for iteroparous animals because it determines the number of clutches
throughout life. This study examined whether female size, clutch size, shell size and prenuptial molting affected the clutch
interval in the hermit crab Pagurus nigrivittatus. Precopulatory guarding pairs of P. nigrivittatus were sampled in the field and kept in the laboratory until the female extruded eggs. The clutch interval of each female was
assessed as one of two types of relatively “short” and “long” intervals by checking whether the guarded female had eggs and/or
egg cases from the preceding brood or not when the guarding pair was collected. The clutch interval was longer in females
with prenuptial molting than those without molting and these females usually grew larger at the prenuptial molt. This suggests
that female P. nigrivittatus with a long interval might allocate energy into growth at the expense of the number of clutches during the current reproductive
season. The allocation to growth is theoretically predicted to decrease with female size. Gastropod shell size is also known
to affect the reproductive activity in hermit crabs. However, female size did not significantly affect the clutch interval
in P. nigrivittatus, and the effect of gastropod shell size on clutch interval was not consistent with previous empirical studies. These results
may be caused by differences in the gastropod species of shell occupied by the females of P. nigrivittatus. 相似文献
18.
The gonad index, GI, is widely used as a measure of changes in reproductive state. There are, however, problems with its use
because it is based on the implicit assumption of an isometric relationship between gonad size and some measure of total size.
If, for example, gonad weight and total weight are used, the exponent for an allometric relationship usually is ignored and
hence assumed to be 1.0. It is further assumed that this exponent is fixed for all states of the reproductive cycle and that
gonads begin to develop at size = 0. Data for the purple sea urchin Strongylocentrotus purpuratus at Gregory Point, Oregon, USA, gathered over a period of 31 months showed that these assumptions cannot be supported. The
relationship is better modeled with a function that (1) takes into account size of initial gonad production and (2) allows
allometric exponents that vary with site or season. Thus, a better approach is to use a wide range of sizes to estimate size
when gonads begin to develop and then, with this correction, ANCOVA to test for differences of gonad size among samples. Gonad
changes at Gregory Point were estimated using fixed sizes of 5 cm diameter and 60 g total weight. Publishing means for X and Y, the standard error of the estimate, R
2, and slope for each regression are shown to be sufficient to compare our results with results across studies. 相似文献
19.
This study reports the first multi-year observations on the reproductive patterns for an Antarctic predator/scavenger, Odontaster validus (Koehler 1912). Seastars were collected monthly from a shallow site (15–20 m depth) near the British Antarctic Survey (BAS) Rothera Research
Station (Adelaide Island, 67°34′S 68°08′W) from July 1997 to January 2001. Reproductive condition, oocyte size frequencies
and spermatogenesis were examined in at least ten seastars each month using histological and image analysis techniques. Gonad
indices (GI) and pyloric caeca indices (PI) were also examined in the same samples. Female and male GIs varied seasonally,
in parallel with a reduction in the proportion of large oocytes and mature sperm in the gonad in August to mid-October following
winter spawning. Despite there being remarkable consistency in the timing of spawning from year to year, differences in the
reproductive condition of individuals were apparent. Patterns in the digestive tissues also varied with season, peaking in
December and reaching a minimum in February in two of the three study years. This weaker annual pattern may partly reflect
the varied diet of this predator/scavenger species, which is not directly dependant on the timing and magnitude of the annual
phytoplankton bloom. Pooled oocyte size distributions and residual analysis suggested that oogenesis progressed over 18–24 months,
with the largest of the two size classes (maximum diameter = 183 μm) being spawned annually. This pattern of oocyte growth
and spawning was previously reported in the early 1960s for an O. validus population from McMurdo Sound, which lies south of Rothera by 10° latitude. The extremely catholic diet of this predator/scavenger
suggests the reproductive patterns of the seastar will be less susceptible to changes in food supply compared to polar suspension
feeders or deposit feeders.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
Daniel S. Townsend 《Behavioral ecology and sociobiology》1986,19(3):187-195
Summary Parental care is practiced exclusively by males of the Puerto Rican frog, Eleutherodactylus coqui. Males brood clutches of direct-developing eggs in non-aquatic nest sites and defend eggs against cannibalistic nest intruders. Here, I report on energetic and mating costs incurred by males that provide parental care, and suggest how these proximate costs affect male fitness and the evolution of male parental care in this species. Energetic costs are small for brooding males in comparison to non-brooding, calling males. Brooding males had a higher frequency of empty stomachs and lost small, but significant, fractions of their initial body mass during parental care. Abdominal fat bodies of brooding males during the middle third of parental care were significantly smaller than those of calling males; those of males brooding eggs in earlier or later stages were not different. The mating cost of parental care is greater. Most brooding males cease calling during parental care. However, gravid females are available (i.e., known to mate) on most nights during the principal breeding season; hence non-calling males miss potential opportunities to mate. A mating cost was estimated by calculating nightly mating probabilities for calling males in a plot where nightly calling male densities and daily oviposition schedules were known. On average, a male exhibiting normal calling behavior would be expected to obtain a new mate once every 35.7 days. Hence a brooding male that ceased calling for a 20-day parental care period would miss, on average, 0.56 additional mates. Males that were more successful than average in attracting mates could miss up to 1.63 matings. A marginal value model (Fig. 1) is used to analyze the net effect on male fitness of parental care benefits and costs in E. coqui (Fig. 3). The model indicates that males garner the highest reproductive success by providing care from oviposition through hatching. There is no stage during the pre-hatching period at which a desertion strategy would yield higher reproductive success. In fact, the model suggests that males should provide full parental care even in the face of much higher mating costs than currently obtain in the system. 相似文献