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1.
The taxonomic status of the Montastraea annularis species complex is unclear. Much evidence has been accumulated to support the separation into 3 species, but the presence
of intermediate morphotypes and the apparent lack of effective reproductive barriers in some areas are yet unexplained. Several
authors have made a call for the introduction of new traits that can be used to resolve differences among closely related
coral species. We collected skeletal and tissue samples from corals within the M. annularis species complex (15 each of M. annularis, M. faveolata, and M. franksi) and 10 morphological intermediates from several reefs in the Florida Keys. Multivariate analysis of corallite skeletal measurements
supported the separation of the species complex into three taxa. We detected two main fluorescence emission peaks at 480 nm
(turquoise) and 515 nm (green) that were not distributed equally among the three species. Every M. annularis colony had a major turquoise fluorescence peak. Some had a weak green secondary fluorescence peak. Colonies of M. faveolata and M. franksi had either the green or turquoise fluorescence peak, but at significantly different frequencies. The intermediate morphotypes
proved to be highly heterogeneous with respect to both micromorphology and fluorescence, and their nature could not be fully
explained. We were not able to separate the three species using fluorescence characters alone, however this new trait does
increase our understanding of the taxonomic structure within the M. annularis species complex.
Received: 21 January 2000 / Accepted: 1 September 2000 相似文献
2.
The morphologically variable reef coral previously known as Montastraea annularis (Ellis and Solander, 1786) has recently been separated into three species based on differences in morphology, behavior, allele
frequencies and some life-history traits of Panamanian specimens. To further investigate the proposed reclassification and
its conformity to the biological species concept we conducted reciprocal intra- and inter- specific fertilization experiments
with gametes from each of the three species on Florida reefs. With one exception, self-fertilization rates were very low or
zero. Within-species crosses resulted in production of planulae, as did all inter-species (hybrid) crosses, but there was
much variation in fertilization success within each type of cross. In an experiment with separated gametes, hybrid crosses
between M. annularis and M. franksi produced more larvae than within-species crosses for each species. Hybridization crosses between M. faveolata and the other two species produced fewer larvae than did within- M. faveolata crosses in the experiment with separated gametes, but many larvae resulted when the hybridizations were performed by mixing
entire gamete bundles. Additional observations showed that M. franksi had 20% larger eggs and fewer eggs per gamete bundle than did the other two species and that it consistently spawned 1 to
1.5 h before the others, a potential temporal barrier to hybridization. These results indicate that there is no inherent pre-zygotic
barrier to cross-fertilization among the three morphological species, although post-zygotic survival and fertility remain
to be determined. The adherence of the proposed reclassification to the biological species concept requires further examination.
Received: 16 April 1997 / Accepted: 17 June 1997 相似文献
3.
Contrasting population genetic structures of sympatric, mass-spawning Caribbean corals 总被引:4,自引:0,他引:4
Coral reef conservation management policy often focuses on larval retention and recruitment of marine fish with scant data available on important, less motile reef-building species such as corals. To evaluate the concept of population connectivity in corals, we tested whether broadcast spawning reproduction per se confers the same degree of dispersal to two sister species, Montastraea annularis (Anthozoa: Scleractinia; Ellis and Solander 1786) and M. faveolata (Ellis and Solander 1786), both dominant taxa in reefs of the northern Caribbean. Genetic analyses of ten nuclear DNA loci (seven microsatellite and three single-copy RFLP) reveal strikingly different patterns of population genetic subdivision for these closely related, sympatric species, in spite of likely identical dispersal abilities. Strong population genetic structure typified the architecture of M. annularis, whereas M.
faveolata populations were principally genetically well mixed. A higher level of clonality was observed in M. annularis potentially because of a susceptibility to physical fragmentation. Clonality did not, however, significantly contribute to population genetic structure or low-level Hardy–Weinberg and linkage disequilibria observed in some populations. The lack of consistent association between reproductive mode and dispersal reinforces the perspective that population connectivity is not so much a function of predictable marine population source and sink relationships as is due to a more complex interface of oceanic currents interacting with and amplifying stochastic fluctuations in larval supply and settlement success. Our results support others promoting an overall ecosystem approach in marine protected area design.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users. 相似文献
4.
Reproductive effort in terms of fecundity and energy allocation was studied in Ophryotrocha labronica La Greca and Bacci, 1962 a small, semicontinuous iteroparous species. In O. labronica fecundity is more or less constant throughout life, and the total fecundity of the 64 couples examined in this experiment
only declined by 12% from the first to the last spawning. No linear relationship was found between fecundity and body size.␣The
energy content of germinal and somatic tissues was determined by differential scanning calorimeter. The␣reproductive effort
and a reproductive index based on the fifth spawning were evaluated to compare the␣patterns of energy allocation of a semicontinuous
iteroparous species with semelparous and annual iteroparous species. The reproductive index ranged from 0.20 to 0.77, with
an average of 0.480. The average reproductive effort was 0.840, ranging from 0.60 to 0.96. These figures highlight the enormous
amount of energy that O. labronica allocates to reproductive tissues.
Received: 23 July 1997 / Accepted: 20 October 1998 相似文献
5.
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
6.
Multi-year, seasonal genotypic surveys of coral-algal symbioses reveal prevalent stability or post-bleaching reversion 总被引:10,自引:0,他引:10
Daniel J. Thornhill Todd C. LaJeunesse Dustin W. Kemp William K. Fitt Gregory W. Schmidt 《Marine Biology》2006,148(4):711-722
This report documents the extent to which coral colonies show fluctuations in their associations with different endosymbiotic dinoflagellates. The genetic identity of Symbiodinium from six coral species [Acropora palmata (Lamarck), A. cervicornis (Lamarck), Siderastrea siderea (Ellis and Solander), Montastrea faveolata (Ellis and Solander), M. annularis (Ellis and Solander), and M. franksi (Gregory)] was examined seasonally over five years (1998 and 2000–2004) in the Bahamas and Florida Keys at shallow (1 to 4 m) fore-reef/patch reef sites and at deeper fore-reef (12–15 m) locations. Symbionts were identified genetically using denaturing gradient gel electrophoresis (DGGE) fingerprinting of the internal transcribed spacer region 2 (ITS2) of ribosomal RNA gene loci. Repetitive sampling from most labeled colonies from the Bahamas and the Florida Keys showed little to no change in their dominant symbiont. In contrast, certain colonies of M. annularis and M. franksi from the Florida Keys exhibited shifts in their associations attributed to recovery from the stresses of the 1997–1998 El Niño southern oscillation (ENSO) event. Over several years, a putatively stress-tolerant clade D type of Symbiodinium was progressively replaced in these colonies by symbionts typically found in M. annularis and M. franksi in Florida and at other Caribbean locations. Greater environmental fluctuations in Florida may explain the observed changes among some of the symbioses. Furthermore, symbiotic associations were more heterogeneous at shallow sites, relative to deep sites. The exposure to greater environmental variability near the surface may explain the higher symbiont diversity found within and between host colonies. 相似文献
7.
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
8.
The mussels Mytilus edulis L. and M. trossulus Gould are found sympatrically in most areas of Newfoundland, with a low frequency of hybrids. To assess the potential for
reproductive isolation, we sampled mussels from three sites in an eastern Newfoundland Bay from May–October 1996 to determine
if there were differences in the reproductive cycles of the two species and their natural hybrids. In mussels with sheil lengths
of 38–42 mm, males and females with mature gametes were dominant in June for M. edulis and hybrids, while M. trossulus showed a lower frequency of individuals with mature gametes. M. trossulus and hybrids spawned over a prolonged period (from late spring to early autumn) compared with most M. edulis individuals that spawned over a period of 2–3 weeks in July. This asynchrony in spawning activity between the two species
may partially explain the low frequency of hybrids found in previous studies of these mussel populations. Female and male
hybrids between M. edulis and M. trossulus showed normal gonad development, ripening and spawning, providing an opportunity for the introgression of genes between the
two species. M. trossulus had a higher reproductive output than M. edulis of similar shell length, while hybrids showed intermediate values of reproductive output. M. trossulus females produced smaller eggs than either M. edulis or hybrids. Differences in reproductive traits may partially explain the maintenance of the mussel hybrid zone in Newfoundland.
Published online: 13 August 2002 相似文献
9.
Two species of marine mussel, Mytilus edulis and M. galloprovincialis hybridize on the coasts of western Europe. Studies of hybrid mussel populations have shown that natural selection favors
M. galloprovincialis-like genotypes within this hybrid zone. Many hypotheses have been proposed to explain differential mortality in these populations.
This study tests two hypotheses addressing factors of mortality in a population, and describes yearly energy storage and reproductive
cycles of these two species and their hybrids. No evidence was found that the two taxa have different overall levels of reproductive
effort or parasite infestation. They do, however, have asynchronous spawning periods and divergent energy storage strategies.
In the year of this study, 1993, the M. edulis genotypic class spawned as a group in June and July. After spawning, they built up a high level of mantle energy-storage
tissues that are probably used for gametogenesis in the following winter and spring. The M. galloprovincialis genotypic group, however, spawned asynchronously, beginning in June and finishing by August, and did not build up high levels
of energy-storage tissues in summer. These results add a temporal component to the interpretation of selective forces acting
to shape this hybrid zone. Vulnerability of each species to mortality factors may differ because of their divergent reproductive
and energy-storage cycles.
Received: 15 January 1999 / Accepted: 26 July 2000 相似文献
10.
The sexual and asexual phases of the reproductive cycle of the sponge Mycalecontarenii (Martens, 1824) were studied from samples collected over a period of 2 years (June 1994 to May 1996) in a Mediterranean coastal
basin (Porto Cesareo, southwestern Apulia). The species is viviparous; year round it shows a discontinuous oocyte production.
No males were found, possibly owing to the very short period of spermatogenesis. M.␣contarenii produces asexual buds during autumn and winter, and this process seems to be related to changes in water temperature. Even
though, at present, we cannot evaluate the incidence of larval recruitment, we postulate that asexual reproduction in M.contarenii plays a crucial role in maintaining the sponge population.
Received: 8 July 1997 / Accepted: 5 November 1997 相似文献
11.
Influence of UV radiation on the survival of larvae from broadcast-spawning reef corals 总被引:2,自引:2,他引:0
Effects of ambient ultraviolet light on the survivorship of eggs and planulae larvae was investigated for three species of broadcast-spawning reef corals, Acropora palmata, Montastraea annularis, and M. franksi. Eggs and larvae from these corals contain high concentrations of lipids (60–70% by weight) and float in surface waters for 3–4 days following spawning. Larvae originating from colonies living at deeper sites on the reef exhibited significantly lower survivorship than conspecifics originating from parents in shallow water when experimentally exposed for up to 4 days to ambient surface levels of ultraviolet radiation (UVR). Concentrations of the UVR-protective compounds correlated positively with survival and matched concentrations found in parent colonies, implying that higher concentrations of ultraviolet B protective compounds are responsible for greater survival of eggs and larvae from shallow compared to deeper-dwelling parents. Ultraviolet B appears to be responsible for most of the observed differences in larval survivorship with ultraviolet A playing a minor or insignificant role. Data presented here indicate that coral recruits on Caribbean reefs and elsewhere may originate primarily from adult colonies dwelling in shallow water.Communicated by P.W. Sammarco, Chauvin 相似文献
12.
Sebastian J. Hennige Michael P. McGinley Andréa G. Grottoli Mark E. Warner 《Marine Biology》2011,158(11):2515-2526
It is speculated that differences in coral bleaching susceptibility may be influenced by the genotype of in hospite Symbiodinium and their differential responses to bleaching stressors. Photoinhibition of photosystem II (PSII), damage to the D1 (psbA)
PSII reaction centre protein and production of reactive oxygen species by in hospite Symbiodinium are likely precursors of coral bleaching. In order to assess whether photorepair rates of in hospite Symbiodinium underlie the bleaching susceptibility of their hosts, photoinhibition (net and gross), photoprotection and photorepair rates
were assessed in a bleaching-‘tolerant’ coral (P. astreoides) and a bleaching-‘sensitive’ coral (M. faveolata) using non-invasive fluorometric techniques and by blocking de novo synthesis of psbA. Previous studies using such techniques
have demonstrated that in vitro Symbiodinium types ‘sensitive’ to bleaching stressors had reduced rates of photorepair relative to ‘tolerant’ Symbiodinum types. Our measurements demonstrated that Symbiodinium in the more bleaching tolerant P. astreoides had higher photorepair rates than Symbiodinium in M. faveolata. Higher repair rates in P. astreoides resulted in lower net photoinhibition relative to M. faveolata, where both corals exhibited similar susceptibility to photodamage (gross photoinhibition). Photoprotective mechanisms were
observed in both corals; M. faveolata exhibited higher antennae-bed quenching than P. astreoides at low-light intensities, but at and above light-saturating intensities, which are different for each coral species, P. astreoides displayed more efficient non-photochemical quenching (Stern–Volmer quenching) of chlorophyll fluorescence than M. faveolata. Increased NPQ by P. astreoides at E/E
k ≥ 1 was not driven by antennae-bed quenching. The ability of in hospite Symbiodinium in P. astreoides to mitigate the effects of photoinhibition under high light conditions compared with Symbiodinium in M. faveolata, and their high repair capacity following photoinhibition, may be a key factor to consider in future bleaching studies and
may underlie the relative bleaching tolerance of P. astreoides compared to M. faveolata. 相似文献
13.
K. M. Swadling J. A. E. Gibson D. A. Ritz P. D. Nichols D. E. Hughes 《Marine Biology》1997,128(1):39-48
Chlorophyll a, primary productivity and grazing by copepods on phytoplankton were measured in the upper water column during the summer
of 1994/1995 at a coastal site near Davis Station, East Antarctica. Chlorophyll a was at a maximum in mid-December, then dropped markedly as the coastal fast ice melted and broke‐out. Phytoplankton biomass
increased again from mid‐ to late‐February. Copepods accounted for at least 65% of zooplankton biomass in the water column
before sea ice break‐out, whereas larval polychaetes and ctenophores dominated after ice break‐out. Oncaeacurvata was the numerically dominant species throughout the study. The highest grazing rate (8.7 mg C␣m−3␣d−1) was recorded on 21 December when O.␣curvata accounted for 64% of the total. Grazing had decreased markedly by 28 December (0.9 mg C m−3 d−1); again O. curvata accounted for over 50% of the total ingested. Copepod grazing increased after ice break-out until the last experiment on
20 February (⋍5 mg C␣m−3␣d−1). The main species responsible for grazing during this period were O. curvata, Oithonasimilis, Calanoidesacutus and unidentified copepod nauplii. It was estimated that copepods removed between 1 and 5% of primary productivity.
Received: 11 October 1996 / Accepted: 22 October 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.
Southern California's many large harbors form an important coastal ecosystem, yet they are also a␣major destination for thousands
of pleasure craft and cargo vessels that have often traveled great distances. Many groups of marine organisms, including ascidians,
have now been documented as undergoing range extensions as a consequence of rapid ship-transport between distant harbors phenomenon.
This has resulted in a rapid increase in the rate of introductions of non-indigenous species worldwide, yet these effects
of boat traffic remain largely unstudied in southern California. Ascidians are sessile marine filter-feeders, hermaphroditic,
and often self-fertilizing; many species are tolerant of a wide range of environmental conditions, can reach sexual maturity
in just a few weeks, and have a long breeding season. This paper documents the arrival of 14␣non-indigenous species in southern
California harbors␣during this century, 13 of which have persisted:␣four prior to the 1960s (Cionaintestinalis, Styelaclava, S.␣plicata, Botryllusschlosseri), another by 1972 (S.␣canopus, formerly S. partita), and 8 since 1983 [C.␣savignyi, Ascidia zara, Ascidia sp., Polyandrocarpa zorritensis, Symplegma brakenhielmi (formerly S. oceania, and S. reptans, Microcosmus squamiger, and Molgula␣manhattensis)]. We estimate the relative abundance and seasonal fluctuations of both non-indigenous and native ascidians in all harbors
in southern California from San Diego to Santa Barbara based upon the historical record, our 35 yr of field notes, and our
recent surveys carried out during fall 1994, spring and fall 1995, fall 1996 and spring 1997. Possible points of origin of
the exotics and predictions on further U.S. Pacific coast range-extensions are included. The concomitant decline in numbers
and species of native ascidians in the harbors of southern California during this century is also reviewed.
Received: 4 March 1997 / Accepted: 26 September 1997 相似文献
16.
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
17.
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
18.
Coral spawning in Western Australia (WA) occurs predominantly in the austral autumn in contrast to the Great Barrier Reef
(GBR) on Australia’s east coast where most spawning occurs in spring. Recent work, however, suggests a second spawning period
in northern WA with at least 16 Acropora spp spawning in spring or early summer. This discovery has initiated a re-examination of reproductive seasonality in northern
WA, particularly on inshore reefs adjacent to large development projects, such as the site of this study in Mermaid Sound,
in the Dampier Archipelago. Three locally abundant taxa, Porites spp, Pavona decussata and Turbinaria mesenterina were sampled monthly from September 2006 to May 2007 to determine sexuality, the mode of reproduction and the time of gamete
maturity. All three taxa were gonochoric broadcast spawners. Porites spp. colonies were mature in November and December, P. decussata in March and April. In contrast, most colonies of T. mesenterina contained mature gametes for up to 5 months beginning in November, suggesting either individuals are releasing gametes on
multiple occasions, or they retain mature gametes for more than 1 month. Field surveys to determine the reproductive status
of the remaining coral assemblage were conducted prior to the full moon in October 2006 and March 2007. Only four species
contained mature gametes in October 2006. In contrast, 55 species contained mature gametes in March 2007. We conclude that
the major spawning season of corals on shallow-inshore reefs in the Dampier Archipelago is autumn, although taxa that spawn
in spring and summer include Porites spp., Acropora spp. and possibly T. mesenterina that are numerically dominant at many of these sites. Consequently, management initiatives to limit the exposure of coral
spawn to stressors associated with coastal development may be required in up to five months per year. 相似文献
19.
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
20.
The purpose of this investigation was to establish reproductive phenology of the dioecious marine floridean red alga Polysiphonia lanosa (L.) Tandy. Specifically, the distribution and frequencies of male and female plants, timing of their sexual maturity, fecundity
and success of fertilization were investigated. The presence of cystocarps was taken as an indication of syngamy. Populations
of P. lanosa in the Bay of Fundy reproduce in spring, summer and autumn. Both male and female filaments were present in equal abundance
at all sampling locations, grew in close proximity, and occurred with equal abundance at all elevations above chart datum.
During the growing season most of the mature plants contained reproductive organs with apparently functional gametangia containing
gametes the structure and behavior of which conformed to those reported in the literature for other species of the genus.
Male and female plants of P. lanosa matured synchronously during late May to early July at all collecting sites. The ratio of spermatia to carpogonia calculated
for the sampled population was high, 3000–4800 spermatia:1 carpogonium. At the end of the growing season (late October) the
fertilization success was at its maximum of 50 to 90% and at its minimum in July at 24%. The three free-living life-history
phases (females, males and tetrasporophytes) were abundant and occurred with equal frequency, indicating that a complete life
cycle was common at the studied location.
Received: 10 December 1996 / Accepted: 16 January 1997 相似文献