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1.
K. A. Pitt 《Marine Biology》2000,136(2):269-279
 The life history and settlement preferences of larvae of Catostylus mosaicus (Scyphozoa: Rhizostomeae) (Quoy and Gaimard, 1824) were investigated in New South Wales, Australia, over a 2 mo period beginning in November 1998. The life history consisted of an alternation between a sexual, medusoid stage and an asexual, polypoid stage, and was similar to that described for other rhizostomes. Planula larvae were brooded by the adults. Approximately 4 d after collection, larvae settled on a variety of substrata including wood, sandstone, shell, seagrass and glass, and metamorphosed into four-tentacled polyps. The number of tentacles increased and polyps strobilated when they had between 12 and 20 tentacles. Strobilation occurred within 15 d of settlement, but only polyps that settled on the concave surfaces of the shells strobilated. Both monodisk and polydisk strobilation was observed. Ephyrae were raised for one month and were observed developing oral arms. Polyps reproduced asexually via the formation of podocysts, by production of buds, and by partial fission. Received: 30 April 1999 / Accepted: 27 August 1999  相似文献   

2.
We present reports of sightings of living and stranded specimens of Rhizostoma luteum on the Atlantic coast of Morocco and along the south shore of the Iberian Peninsula in June–July 2012 and in January–February 2013. During summer 2012 and following the dominant currents, the jellyfish first appeared in the Gulf of Cadiz west of the Strait of Gibraltar. Subsequently, seven additional sightings were reported east of the Strait, in the Alboran Sea. In winter 2013, another event of stranded individuals of this species occurred in the Gulf of Cadiz. A phylogenetic analysis performed on the mitochondrial cytochrome c oxidase I (COI) gene sequence in specimens from both stranding events confirmed the morphological classification, ratifying that R. luteum differs from Rhizostoma octopus and Rhizostoma pulmo. This study records the presence of this species for the first time in 60 years.  相似文献   

3.
The life cycle of Lychnorhiza lucerna (Scyphozoa: Rhizostomeae) and the settlement preferences of its larvae were studied using laboratory-based rearing experiments. Mature medusae of L. lucerna were collected from the beach of the Río de la Plata estuary, Argentina. This species displayed the typical metagenetic, (i.e. medusoid and polypoid), life cycle reported for other rhizostomes. The fertilized eggs developed into motile and short lived planulae. The majority of planulae settled on the air-water interface (p < 0.001). Of those that settled on the settlement plates provided, no significant differences were observed between styrene slides, glass slides and shells of the bivalve Mactra isabelleana (p > 0.05). No planulae settled on stones. Several hours after planulae settled, they metamorphosed into sessile four-tentacled scyphistomae. Most scyphistomae attached onto the air-water interface. At 19–22°C, the scyphistomae grew up to 22 tentacles and reached 1,500 μm height. The scyphistomae increased their numbers by means of formation of podocysts from which new polyps emerged and strobilated. Strobilation occurred 46 days after settlement. Only polydisk strobilation was observed and each strobila always produced three ephyrae. After releasing ephyrae, strobilae returned to normal scyphistomae and were capable of repeating strobilation. A single founder polyp was estimated to produce up to 60 ephyrae over 4 months. Ephyrae developed into metephyrae 15 days after release at 19–22°C. In this paper we describe the morphological and some behavioural features of L. lucerna in the polypoid and early medusoid stages.  相似文献   

4.
The behaviour of the oral arms of Pelagia noctiluca (Forsskål) has been investigated in open sea predation and in predation induced both in the laboratory and the natural environment. Specimens were first studied in the field and then collected from coastal aggregations in the Gulf of Trieste, North Adriatic Sea, in December 1985 (Lat. 13°40 E, Long. 45°42 N) and in June 1986 (Lat. 13°39 E, Long. 45°43 N). The results of laboratory experiments and in situ observations, recorded on videotapes and photographs, show that the marginal tentacles are utilized to: (1) paralyze the prey; (2) contract and bend inward towards the nearest oral arm. Occasionally the tentacle does not contract and the prey is released; thus prey selection may occur. The oral arms are therefore involved in the: (1) transport of prey from the tentacle to the gastric cavity; (2) catching of motionless prey; (3) anchoring the medusa to the substratum. A similar feeding pattern can explain the survival of several specimens of P. noctiluca near the bottom during the winter of 1985/1986 in the Gulf of Trieste (North Adriatic Sea) in spite of the severe climatic conditions.  相似文献   

5.
Although complex behavior in marine zooplankton has been considered strong evidence of adaptation, ethological studies of marine zooplankton generally have not employed either the comparative approach or evolutionary perspective necessary to distinguish adaptation from any alternative. Consequently, the potential for intra-specific variation in the behavior of marine zooplankton has received insufficient attention and conclusions of adaptation remain poorly substantiated. Intra-specific comparison of patterns of migration and behavior for seven populations of golden jellyfish, Mastigias (Scyphozoa: Rhizostomeae), inhabiting isolated marine lakes and semi-enclosed lagoon coves in Palau document population specific differences in patterns of horizontal migration, vertical migration, pulse rate, swimming speed, and turning behavior. Evidence was found for symplesiomorphic behaviors, canalization, exaptation, adaptation, and probably once-deleterious traits. Behavioral evolution likely proceeded via, at least, relaxation of selection, trade-offs with morphology, and natural selection effected by predation. Behavioral patterns also may change with ontogeny. Geographic variation in the behavior of marine plankton therefore can be substantial and patterns of evolution complex. Behavioral evolution can rapidly generate coastal biodiversity. Thus, geographic variation in marine plankton is of potential interest to ethologists, evolutionary biologists, biogeographers, and conservation biologists.Electronic Supplementary Supplementary material is available in the online version of this article at Communicated by G.F. Humphrey, Sydney  相似文献   

6.
Bioluminescence is the production of visible light by a living organism. The light commonly appears as flashes from point sources (involving one or more cells, usually described as photocytes) or as a glandular secretion. A visible flash usually involves synchronous light emission from a group of cells or, if from a single-celled organism such as a dinoflagellate, from a group of organelles. The number of cells (or organelles) responding synchronously is the main determinant of the flash intensity. Bioluminescence is a common phenomenon in many deep-sea animals and is widespread among the Cnidaria. In this paper, we compare and contrast in situ and laboratory recordings of the bioluminescent responses of specimens of the deep-sea scyphozoans Atolla wyvillei, Atolla vanhoffeni, Atolla parva, Nausithoe rubra, Paraphyllina intermedia, Periphyllopsis braueri and Periphylla periphylla. Displays in all seven species consist of localised flashes and propagated waves of light in the surface epithelium. The first few single waves propagate at rates of up to 60 cm s-1 but subsequent ones in any sequence of stimuli gradually decrease in speed. After several single wave responses, a subsequent stimulus may elicit multiple waves that persist for several seconds. Following such a frenzy, the specimen becomes temporarily refractory to further stimuli, but if rested will recover its normal responses and may produce further frenzies. The dome area, situated above the coronal groove, of the genera Paraphyllina, Periphylla, and Nausithoe is covered with luminescent point sources. Such point sources are generally absent from the dome of species of Atolla. Captured specimens of A. parva also produce secretory bioluminescence, corroborating prior in situ observations of this ability. Secretory bioluminescence in P. periphylla takes the form of scintillating particles released from the lappet margins. We did not observe secretory displays in specimens of any other species in the laboratory, but one instance of apparent secretory luminescence was recorded in situ in a specimen of A. wyvillei.Communicated by J. P. Thorpe, Port Erin  相似文献   

7.
 The reproductive biology of the jellyfish Catostylus mosaicus (Quoy and Gaimard 1824) (Scyphozoa: Rhizostomeae) was investigated in New South Wales, Australia. Medusae were gonochoristic. There was a 1:1 ratio of male and female medusae and there was no evidence of sexual dimorphism. Oocytes arose from the gastrodermis and maintained contact with the gastrodermis, via trophocytes, throughout gametogenesis. Spermatogenesis occurred within follicles that arose from invagination of the gastrodermis. Detailed sampling of gonads over a period of 3.25 yr in Botany Bay, and over 2.5 yr in Lake Illawarra, indicated that gametogenesis occurred almost continuously during the year. Oocytes were smaller, or were absent from the ovaries during 3 of the 4 winters sampled at Botany Bay and during all 3 winter periods sampled at Lake Illawarra. Comparisons were made with other locations, although these were sampled less frequently. When medusae were present at a location, similar trends were observed. The size at which medusae matured varied, but during non-winter periods and at two locations, all medusae exceeding 130 mm diam were considered mature. Received: 6 January 2000 / Accepted: 3 July 2000  相似文献   

8.
The upside-down jellyfish Cassiopea is a globally distributed, semi-sessile, planktonically dispersed scyphomedusa. Cassiopea occurs in shallow, tropical inshore marine waters on sandy mudflats and is generally associated with mangrove-dominated habitats. Controversy over the taxonomy of upside-down jellyfishes precedes their introduction to the Hawaiian Islands during the Second World War, and persists today. Here we address the global phylogeography and molecular systematics of the three currently recognized species: Cassiopea andromeda, C. frondosa, and C. xamachana. Mitochondrial cytochrome c oxidase I (COI) sequences from Australia, Bermuda, Fiji, the Florida Keys, the Hawaiian Islands, Indonesia, Palau, Panama, Papua New Guinea, and the Red Sea were analyzed. Highly divergent COI haplotypes within the putative species C. andromeda (23.4% Kimura 2-parameter molecular divergence), and shared haplotypes among populations of two separate putative species, C. andromeda and C. xamachana from different ocean basins, suggest multiple anthropogenic introductions and systematic confusion. Two deeply divergent Oahu haplotypes (20.3%) from morphologically similar, geographically separate invasive populations indicate long-term (14–40 million years ago) reproductive isolation of phylogenetically distinct source populations and cryptic species. Data support at least two independent introductions to the Hawaiian Islands, one from the Indo-Pacific, another from the western Atlantic/Red Sea. Molecular phylogenetic results support six species: (1) C. frondosa, western Atlantic (2) C. andromeda, Red Sea/western Atlantic/Hawaiian Islands (3) C. ornata, Indonesia/Palau/Fiji (4) Cassiopea sp. 1, eastern Australia (5) Cassiopea sp. 2, Papua New Guinea and (6) Cassiopea sp. 3, Papua New Guinea/Hawaiian Islands.Communicated by P.W. Sammarco, Chauvin  相似文献   

9.
The author investigated the carotenoids in the jelly-fish Aurelia aurita (L.), from the Baltic Sea. By means of columnar and thin-layer chromatography, the following carotenoids were found to be present in that species: -carotene, echinenone isocryptoxanthin, canthaxanthin, lulein, zeaxanthin, astaxanthin and astacene.  相似文献   

10.
We studied the processes of gonadal maturation, spawning, fertilization and embryonic development of the giant jellyfish Nemopilema nomurai, which has been blooming in recent years in the Sea of Japan. Healthy medusae actively swimming offshore had immature gonads, but damaged and ashore-drifted animals had relatively mature gonads. The animals maintained in a small net on the nearshore to mimic the drifted condition showed induced gonadal maturation by the increase in oocyte diameter and darkness in the matrix. A similar maturation process also occurred in isolated pieces of ovary incubated at the same temperature. Fully grown oocytes that probably stopped at the prophase of the first meiosis reinitiated maturation divisions in response to light exposure, and massive spawnings occurred 80–100 min after the exposure. The spawned oocytes were first released within the subgenital sinus, then transported peripherally and finally shed into the gastrovascular cavity. Maturation and spawning in male gonads were similar to those of females except that the male spawning occurred within 30 min after the light exposure and always preceded the female spawning. Hence, it was suggested that fertilization might take place in the female gastrovascular cavity by the sperm that came in from surrounding seawater by animals’ pumping activities after dawn. Having mechanical damages might promote fertilization success of this species in the Sea of Japan.  相似文献   

11.
D. Zavodnik 《Marine Biology》1987,94(2):265-269
In the Adriatic Sea, the spatial distribution and aggregation aspects of swarning Pelagia noctiluca (Forskål, 1775) were studied by SCUBA divers from August 1984 to November 1985. Medusae were asually distributed in the upper 20- to 30-m layer. Dense aggregations caused by wind, currents and tidal phenomena occurred only in shallow coastal waters. Maximum population densities of swarms drifting freely near the shore were estimated at about 20 individuals per cubic meter, but when they had drifted ashore jellyfish could reach concentrations of 150 to 600 individuals in the same volume of sea water. Some peculiar forms of aggregations could be distinguished: couples, clusters, and surface and bottom aggregations. The effects of wind, currents and geomorphological features of the shore on passive aggregations of jellyfish are presented.  相似文献   

12.
The morphogenesis of ephyrae of Atorella vanhoeffeni Bigelow, 1909 (Werner, 1967) and of Nausithoe maculata Jarms, 1990 during strobilation is described. We found differences in the developmental pattern of marginal structures and structural changes of longitudinal muscle tubes in particular. During strobilation the polyp’s tetraradiate symmetry is passed to the ephyra of both taxa as a tetraradiate central symmetry that we consider a major plesiomorphic character. The present results also indicate divergent patterns of ephyra development during strobilation that lead to variable marginal symmetries of ephyrae and thus of medusae. Therefore, the marginal symmetry of medusae of N. maculata is octoradiate and of A. vanhoeffeni is hexaradiate. We conclude the latter is stated as derived pattern. These results lead us to maintain both families Nausithoidae and Atorellidae.  相似文献   

13.
Stages in the life cycle of the rhizostome jellyfish Rhizostoma octopus (L.) were reared in the laboratory from planula to young medusa and are described here. Fertilization of eggs was external, and planulae, 110–150 μm in length, appeared after 2 days. These settled and developed into the scyphistoma stage. Scyphistomae reached a maximum size of 2.3 mm, bore up to 24 tentacles, and had a large manubrium. Polyps reproduced asexually mainly by podocysts. Strobilation was induced by temperature change. Each strobila released up to five ephyrae that measured 2.7–5.8 mm in diameter at liberation. During transformation from newly released ephyra to young medusa, velar lappets appeared and increased in number, the manubrium developed eight branched oral arms with epaulettes, and a marginal gastric network arose. Only one cnidocyst type, the “a”-atrichous haploneme, was present in the planula. In addition to these haplonemes, heterotrichous microbasic euryteles were observed in polyps, ephyrae, and medusae. Statoliths, located in the rhopalia, had a characteristic compact shape. These sensory structures increased in number and size with the growth of ephyrae and medusae.  相似文献   

14.
Rhizostoma pulmo is one of the most abundant scyphomedusae along the Mediterranean coasts. To understand changes in the population densities of the medusa stage and its relationship with the benthic stage, we describe all developmental stages from the life cycle of R. pulmo, from the scyphistoma stage to young medusae reared in the laboratory. Mature scyphistomae showed a mean total body length of 1.7 mm and the average tentacle number was 16. Asexual reproduction occurred by lateral budding, podocyst and pedalocyst production. Each strobila released up to 8 ephyrae that had a mean total body diameter of 3.5 mm. Moreover, we also present data on the temporal and spatial distribution of the species in the Catalan Sea and the coastal lagoon on Mar Menor (NW Mediterranean) during the years 2007–2009. In the Catalan Sea, the presence of adult R. pulmo was recorded as extended along the whole coast, but most of the observation was concentrated in the central area; the highest abundances were recorded during the months of July and August. The highest number of observations was detected in 2008 in coincidence with the inter-annual variation observed in the Mar Menor lagoon.  相似文献   

15.
Some western Norwegian fjords host extraordinarily abundant and persistent populations of the mesopelagic, coronate scyphomedusa, Periphylla periphylla. In these environments, from late autumn to spring, the medusae undertake regular diel vertical migrations into surface waters. From unique observations obtained with a remotely operated vehicle (ROV), including observations made without artificial light, we observed that 90% of the medusae swam with their tentacles in aboral position. Stomach content analyses of surface-collected specimens revealed that the medusae ate mainly calanoid copepods, but ostracods and large euphausiids were also prominent components of their diets. The clearance rate potential of P. periphylla, assessed from in situ observations and stomach contents, was comparable to that of similar-sized, epipelagic gelatinous species. Our findings suggest that P. periphylla behave as active predators in surface waters.  相似文献   

16.
Scyphopolyps and scyphomedusae of Cassiopea andromeda Forskål (Cnidaria, Scyphozoa) containing dinoflagellate endosymbionts (zooxanthellae) were investigated for rates and pathways of carbon fixation. Photosynthesis by the algae, accounting for 80 and 15 mol C h-1 on a dry weight basis in medusae and polyps, respectively, by far exceeds dark incorporation of inorganic carbon by the intact association. Photosynthetic carbon fixation is operated via C3 pathway of carbon reduction. DCMU-treatment (1×10-6 M and 1×10-5 M) completely inhibits light-dependent carbon assimilation. Major photosynthates presumably involved in a metabolite flow from algal symbionts to animal tissue are glycerol and glucose. A total of 5–10% net algal photosynthate appears to be seleased in vivo to the host. This is probably less than the energy supply ultimately required for the nutrition of the polyps and medusae. The presence of zooxanthellae proved to be indispensable for strobilation in the scyphopolyps. However, photosynthesis by algal symbionts as well as photosynthate release is obviously not essential for the initiation of ephyrae as is shown by DCMU-treatment, culture in continous darkness, and aposymbiotic controls. It is therefore concluded that strobilation is supported, but not triggered by algal photosynthetic activity. The induction of strobilation thus seems to depend on a more complex system of regulation.  相似文献   

17.
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   

18.
Sabine Holst 《Marine Biology》2012,159(12):2707-2722
Jellyfish blooms or invasions could be detected in an early phase of development if the youngest medusa stages (ephyrae) and their early growth stages (post-ephyrae) were identifiable in plankton samples but a useful identification key for ephyrae in early growth stages is lacking for most species. In the present study, the identification characteristics of adult North Sea scyphomedusae (Aurelia aurita, Cyanea capillata, Cyanea lamarckii, Chrysaora hysoscella, Rhizostoma octopus) collected around the island of Helgoland (German Bight) in July?CAugust 2003 and 2004 are described. Planula larvae were measured and reared to polyps in the laboratory. The process of ephyrae development asexually produced by the polyps (strobilation) was photo-documented. Photographs of the ephyrae growth stages were combined with drawings of features useful for the species identification. The provided identification key allows discrimination among post-ephyrae from plankton samples, probably leading to conclusions on the development of jellyfish blooms and their causes.  相似文献   

19.
P.W. Frank 《Marine Biology》1975,31(2):181-192
At higher latitudes along the west coast of the USA the herbivorous intertidal snail Tegula funebralis (Adams, 1854) lives longer, grows more slowly, but attains a larger size than further south. To the north, age distributions are less predictable and often far from stationary. The differences, which have some generality, can be explained either by a primary temperature effect joined with increased hazards to planktonic larvae in the north, or else may result from a combination of interactions between intensity of predation, population density and food supply. Growth rates of transplanted individuals suggest a genetic basis for the latitudinal differences.  相似文献   

20.
Internal growth bands visible in cross-sections of the valves and hinge plates of Arctica islandica Linné are deposited annually, possibly in response to the reproductive cycle. Growth rate and longevity, inferred from the bands, are surprising: A. islandica grows very slowly and lives to an advanced age. Individuals with more than 90 bands are not uncommon; the maximum number of bands discovered so far is 149. On the basis of average size for Middle Atlantic Bight specimens, modal age is estimated to range from 65 to 105 years.  相似文献   

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