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Reproductive cycle, asexual reproduction, and population dynamics of the fissiparous brittle star, Ophiactis savignyi, which inhabits the exhalant passages of the sponge Haliclona sp. were examined monthly from February 1991 to January 1992 at Wanlitung, southern Taiwan (22°N; 120°E). Mature gametes were found from March to December, but release was mainly in May and June. Sexual recruits were found from May to December, with the highest frequency (14.1% of population) in June. Sexual recruits composed 2.4% of the 1-yr sample. Sex ratio of male to female was 24:1. Fission occurred throughout the year, although the frequency of recently split individuals was lower from January to June (6 to 31%), and higher from July to December (42 to 52%). The occurrence of fission was highest after spawning. Regenerating individuals composed 48.2% of the 1-yr sample. Population density fluctuated greatly during summer due to recruitment by fission and mortality or dispersal due to the stressful environmental conditions. Both sexual and asexual reproduction of O. savignyi were successful at this site. 相似文献
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A. B. Josefson 《Marine Biology》1995,124(3):435-442
Quantitative data on size structure of the ophiuroid Amphiura filiformis (O.F. Müller) from 35 benthic stations in the Kattegat sampled twice with a 143 d interval, June and October 1991, were used to estimate somatic growth. The material was objectively divided into cohorts, and cohorts, from the two occasions were paired to give estimates of growth. The growth constant, K, in the Von Bertalanffy equation, was estimated from a Ford-Walford plot to 0.54 yr-1. Results were in agreement with previous estimates from a few single sites, and suggest that the main part of dise growth occurs within the first 5 to 7 yr of living. Size specific growth in oral width was density independent despite high densities of A. filiformis (>3000 ind m-2) and high total benthic biomass (up to 1000 g wet wt m-2) in some areas. Growth was uncorrelated with plant pigment concentrations in the sediment and showed weak positive correlation with sediment carbon and nitrogen, as well as water depth. Growth was higher in fine sediments. This is the first attempt to estimate growth in this important species over a large area and to relate growth in the field to environmental factors. 相似文献
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Reproduction in Amphiura filiformis (Echinodermata: Ophiuroidea): Seasonality in gonad development 总被引:1,自引:0,他引:1
T. Bowner 《Marine Biology》1982,69(3):281-290
The burrowing ophiuroid Amphiura filiformis (O. F. Müller) (Echinodermata: Ophiuroidea) colonises an extensive area and is a numerically dominant member of the macrofauna in Galway Bay on the west coast of Ireland. There, it has a discrete, relatively short annual breeding period, from June to September, with peak activity in the month of August. The breeding period approximates in timing those of other European populations. The oocytes of a particular year are laid down in the autumn of the previous year; they begin to develop in spring, with the period of fastest growth in May/June. Gonad growth corresponds quite closely to the annual rise in water temperature, with spawning taking place during the warmest months of the year. The species is polytelic, and it is suggested that the long-lived Galway Bay individuals may breed every year for several years. The relationship between spawning and population dynamics is discussed in the light of current, available literature concerning A. filiformis from other parts of Europe. The role of so-called ultimate factors in the process of ophiuroid maturation and spawning is discussed. 相似文献
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Masami Obuchi Yoshihisa Fujita Yoshikatsu Nakano Tsuyoshi Uehara Tatsuo Motokawa 《Marine Biology》2010,157(6):1191-1201
Reproduction and larval/post-larval development of the one of the smallest known comatulid Dorometra sesokonis were studied on the coral reefs of Sesoko-jima Island, Okinawa, Japan. Breeding individuals were found every month from May 2003 to April 2004 indicating continuous reproduction. Individuals possessed both mature ovaries and testes, and were therefore characterized as simultaneous hermaphrodites. This species was observed to be an external brooder in which the embryos developed on the surface of parental genital pinnules until the doliolaria larval stage, and subsequently released doliolariae settled on substrata within 4 days after hatching. Larvae then metamorphosed into the post-larval cystidean stage, which lasted for more than a month. The reproductive features of this species are unique among crinoids, and, together with juvenile morphological features observed in adults, can be interpreted as adaptations to their cryptic habitat, which is subject to frequent natural disturbances. 相似文献
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Flat fishes, such as the dab Limanda limanda, commonly prey on arms of Amphiura filiformis. We demonstrate in flume experiments that A. filiformis showed a more or less simultaneous response to an up-stream predation by dab on conspecifics: the arms, which are stretched
up into the water column when filter feeding, responded by bending down to the sediment surface, and some arms submerged,
at least partly, into the sediment. We interpret this as an alarm response. A similar, but significantly weaker response in
A. filiformis was also recorded when dab ate Amphiura chiajei. Homogenates of the two Amphiura species and arm pinching – to simulate partial predation – elicited a similar response in A. filiformis, the arms bent to the sediment surface. In contrast, however, the behavioural response of the arms to the homogenates was
to protrude further out of the sediment and sweep the surface vigorously. We interpret this as a feeding behaviour. Response
to arm pinching was less clear. The ecological consequences and origin of alarm signal response in A. filiformis are discussed.
Received: 8 February 1999 / Accepted: 16 July 1999 相似文献
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The infaunal ophiuroid Amphiura chiajei Forbes is a dominant member of the A. chiajei community in Killary Harbour, a fjord-like inlet on the west coast of Ireland. High density populations (700 individuals/ m2) occur in sediments with a silt/clay content of 80 to 90% and organic carbon levels of 5 to 7%. A study of the population dynamics of this species was carried out from November 1985 to October 1988. At the outset, the population consisted of approximately equal numbers of adults and juveniles. By October 1988, the percentage of adults had increased to 95%, with little or no change in the mean annual dersities. However, there was some degree of variability between the mean monthly densities. Such variability may have been due to very low bottom temperatures, resulting in mortality among the older members of the population. Observations suggest that in Killary Harbour the species may attain an age of 10 yr, with an early annual growth rate of 0.5 mm (oral width). Annual recruitment was variable and low, due presumably to intraspecific competition with the adults; recruitment success may be very closely linked to adult mortality. The Killary Harbour findings are considered in the light of what is currently known of similar amphiurid populations in different geographical locations. 相似文献
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D. H. Patent 《Marine Biology》1970,6(3):262-267
The changes in morphology of Gorgonocephalus caryi embryos over the 8 1/2 day period of their survival are described. Fertilized eggs are 220 in diameter. Division is equal and holoblastic, and the blastula stage is reached within 24 h. Gastrulation begins at about 40 h. At 68 h, the anterior end of the embryo begins to elongate. The embryos are pear-shaped at 72 h. At about 84 h the anterior end begins to bend towards one side. By 98 h the entire embryo has flattened perpendicular to the anterior-posterior axis, and the embryo is a flattened, trilobed structure. At 4 1/2 days the anterior tip twists around to lie with its axis in a plane perpendicular to the other 2 lobes. They, meanwhile, shift in position so that the resulting embryo resembles an umbrella which is flat on top and has a curved handle. Meanwhile, the hydrocoel forms as an out-pouching from the archenteron in the anterior lobe. The general coelom develops by schizocoely. Between 5 and 5 1/2 days, the anterior lobe coelesces with the flattened area as it becomes pentagonal. By 5 1/2 days, many embryos are starshaped. At 6 1/2 days the mouth begins to form. By 8 days the embryos were dying, and none lived beyond 10 1/2 days. At no time did cilia or other locomotory structures develop. The development of G. caryi does not resemble that of any other ophiuroid studied. There is not trace of a pluteus, and it is postulated that the pluteus evolved after the Phrynophiurida and the Ophiurida were differentiated. 相似文献
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Reproductive biology of the common antarctic crinoid Promachocrinus kerguelensis (Echinodermata: Crinoidea) 总被引:2,自引:0,他引:2
Histological examinations of the gonads of Promachocrinus kerguelensis Carpenter, 1888 collected in November 1984 from McMurdo Sound, Antarctica, revealed ripe ovaries containing three distinct size classes of oocytes: 20 to 90, 91 to 150 and 151 to 180 m diameter as well as ova. Testes were ripe, and filled with mature sperms. There was marked inter-pinnule and inter-individual synchrony of gametogenesis and spawning is probably synchronous, at least within the sub-population sampled. The number of eggs per pinnule is allometrically related to body size. Body weight and arm length are positively correlated with total egg number. Annual fecundity was estimated to be 29 000 eggs (full-grown oocytes and ova) for a crinoid weighing 53.6 g wet weight with an arm length of 16.3 cm. The eggs float. Female genital pinnules contain more lipid and energy than male pinnules. Reproductive output and effort (23.4 to 65.2 kJ and 26 to 38%, respectively) increase with body size and are similar to values reported for other echinoderms with lecithotrophic larvae. The greatest overall energetic contribution is represented by the arms and genital pinnules. Spawning in P. kerguelensis probably occurs in November and December within McMurdo Sound. If development is slow, as in all other antarctic echinoderms studied to date, then settlement most likely occurs 2 to 3 mo later, after the short summer period of high phytoplankton productivity. High fecundity, a pelagic mode of reproduction, and the high probability of a slow rate of development may contribute to the wide geographic distribution of this common antarctic crinoid. 相似文献
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Arm tissues from species of brittlestars from the British Isles and North America were examined by light and electron microscopy for the presence of sub-cuticular bacteria (SCB) which were recorded in 17 of the 19 species studied. Three major groups of SCB could be distinguished on the basis of their morphology. The bacterial morphology was not correlated with the host ecology but did appear to be related to the phylogeny of the hosts. Ophiuroids of the same genera had morphologically similar SCB and this was also generally true of species from the same family. This indicates the possibility of co-evolution between the SCB and their hosts. Estimates of SCB load were made for 9 of the species by direct counting and by quantifying the amount of bacterial endotoxin present in the host tissues. SCB numbers varied interspecifically from 3.7×108 to 4.6×109 SCB per gram of ash-free brittlestar arm tissue. Endotoxin values ranged from 5.97 to 285 g g–1 ash-free arm tissue. Calculations suggest that SCB form at least 0.1 to 1% of the total biomass of the arm tissues. There was considerable intraspecific variation in SCB load. The possible role and significance of SCB is discussed. 相似文献
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The Boreo-Mediterranean amphiurid Amphiura filiformis (O. F. Müller) occurs in high densities within Galway Bay. This burrowing species consistently shows signs of recent regeneration (of both arms and disc “cap”) at the above locality. Specimens were collected by SCUBA in March, April and May 1980, May 1981, and April 1982. Biomass assays have revealed that individuals with up to 50% (mean ca. 25%) of their entire body weight consisting of regenerated tissue are not uncommon. The occurrence of arm breakage and regrowth was found to be more frequent in the proximal (basal) and mid-arm regions than in the exposed arm tip portions. Roughly 3% of the population were found to be in the process of regenerating the disc “cap” or covering. Preliminary results from gut analyses of potential predators at the sampling station indicate that young flatfish (plaice and dab) actively “crop” the arms of A. filiformis. Records from north western Europe of this species occurring in the diets of fish and invertebrates are considered. In this long-lived species, the continual necessity to regenerate is deemed to be a major drain on bodily resources. 相似文献
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The post-larval skeletal plate ontogeny of the ophiuroids Ophiura ophiura (Linnaeus) and Acrocnida brachiata (Montagu) from the recently metamorphosed 0.3 mm disc diameter size to a juvenile size of 2.0 mm disc diameter has been examined using scanning electron microscopy. Post-larval development of O. albida Forbes is briefly described for sizes between 1.0 and 2.0 mm disc diameter. Early post-larval development in the 0.2 to 1.0 mm discsize range involves considerable morphogenetic change and necessitates the use of a developmental series in the identification of newly settled ophiuroids. Comparison of these ophiuroids with other closely related species reveals that the post-larvae are readily distinguishable at even the smallest sizes by their transient post-larval morphologies. Abbreviated larval development in A. brachiata is suggested from the egg size and post-larval form. The ophiuroid post-larvae were collected from the shallow sublittoral of Oxwich Bay, Bristol Channel, UK, during the years 1980 to 1982. 相似文献
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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
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At 33 salinity a tissue stump formed 2 to 3 d after autotomy and developing ossicles were present by the fourth day inOphiothrix angulata (Say). Regeneration proceeded rapidly from the sixth day until the thirteenth day, when the rate decreased greatly. The length of the regenerated arm and the number of ossicles formed did not vary over a salinity range of 28 to 38 S, but were significantly less at 23 S. The number of ossicles regenerated increased linearly (y=1.9 x-7.7;r=0.9089) with the calcium concentrations ranging from 3.8 to 9.5 mM. No ossicle formation occurred at 3.8 mM calcium concentration. Rate of net uptake of calcium-45 into the ossicles of intact individuals in salinities of 28 and 33 was significantly greater than that in 23 and 38 S. However, net uptake rate of calcium into the soft tissues of the arms was significantly higher at 18S than at the lower two salinities. 相似文献
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Two laboratory experiments were conducted on Ophiocoma echinata (Lamarck, 1816) collected from Missouri Key, Florida, USA, to ascertain the effects of arm regeneration on energy storage and gonad production. In each experiment individuals were divided into non-regenerating (all arms intact) and regenerating (three arms autotomized) groups and maintained together in a re-circulating seawater system for 2 mo. In Experiment 1, individuals were fed once a week, and in Experiment 2 once every 2 wk. The amount of food energy required for maintenance was estimated to be 0.172 kJ d−1. The lower feeding level (Experiment 2) was below maintenance ration and both groups lost material relative to an initial group. At the higher feeding level (Experiment 1), regeneration of three arms resulted in less storage of organic material, mainly lipid in the stomach, and less gonad production. Thus, regeneration may reduce energy reserves and reproductive output. Received: 23 April 1998 / Accepted: 11 January 1999 相似文献
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R. L. Turner 《Marine Biology》1974,24(3):273-277
Juveniles of the burrowing amphiurid Ophiophragmus filograneus from Tampa Bay, Florida (USA) exhibit a growth pattern unreported in the ophiuroid literature. Two nonadjacent arms grow at a greater rate than the other three arms. This phenomenon might be a developmental adaptation to avoid salinity and temperature fluctuations in surface waters of the shallow-water environment which O. filograneus inhabits. It is proposed that concentration of growth into 2 of the 5 arms permits earlier descent of the disc into the substratum with continued ability to feed on the surface with the arm tips. Larger specimens show a gradual equalization of arm lengths. Changes in growth rates and cropping of the longer arms by breakage and predation might account for such eventual equalization. 相似文献
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Clibanarius longitarsus (De Haan), a hermit crab, feeds by means of both micro- and macrofeeding. Microfeeding is of two types: filter feeding and deposit feeding. In macrofeeding, the animal depends mainly on green algae, barnacles and some worms, etc. In filter feeding, the hermit crab uses its paired antennules for trapping microorganisms drawn into the water current created by the second and third maxillipeds; the antennae do not play any role in filter feeding. In deposit feeding, the hermit crab uses its chelae as well as pereiopods for toughing and obtaining detritus food material. In macrofeeding, the organism employs sharp chelae to collect small pieces of muscle from barnacles and then transfer them to the inner mouth parts. In algal feeding, the chelae as well as maxillipeds help in collecting and moving food material towards the mouth. In this investigation functional organisation ofC. longitarsus mouth parts was studied in detail with reference to the various feeding mechanisms, in specimens collected from the intertidal region of Bheemunipatnam, Andra Pradesh, India, in 1988 and 1989. 相似文献
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This study documents the annual reproductive cycle of the Temnopleurid echinoid Holopneustes purpurascens near Sydney. H. purpurascens reached sexual maturity between 11 and 26 mm diameter and was gonochoristic. The sequence of oogenesis was similar to previously described echinoids. However, the proportion of eggs at each stage showed no temporal pattern in abundance, suggesting that vitellogenesis is continuous throughout the year. Spermatogenesis was also similar to other echinoids and showed a significant increase in the proportion of partially spawned testes in spring, followed by a similar increase in the proportion of partially spawned testes in late spring and summer. Gonad indices showed a peak in weight from late winter to mid-spring (9.10ǃ.47 for females; 6.28ǂ.43 for males; mean-SE), then a decline for both sexes. Although spawning was variable over time, there was a peak in the proportion of spawning from late winter to early summer that correlated with the observed peaks in gonad indices and gametogenic cycles. The demographic implications of this reproductive pattern are that new recruits can enter the population through synchronous spawning during the breeding period, and smaller haphazard spawning events at other times of the year. 相似文献