Polyp and medusa of Dipurena bicircella n. sp. (Hydrozoa: Corynidae) from Northern California

The polyp and medusa of Dipurena bicircella n. sp., a metagenic hydrozoan from Northern California, USA, is described. The arrangement of capitate tentacles of the polyp, in two alternating cycles or circlets, is unique to the genus Dipurena as well as to the family Corynidae. Medusae released in the laboratory attained sexual maturity in 2 weeks. The adult medusa can be distinguished from other medusae of the genus by means of 2 gonad rings, a slight terminal nematocyst cluster on each tentacle, and a relatively small size (about 2 mm in bell height). The polyp was not found in association with sponges, as is the case with some of the other polyps of the genus Dipurena. The medusa is not yet known from the plankton.     

Mating behaviour and reproductive cycle of Archaster typicus (Echinodermata: Asteroidea)

This study examines the reproductive cycle, the mechanism of male-on-female pairing behavior and the spawning behavior of Archaster typicus Müller et Troschel. Field studies were conducted in the intertidal zone of the sand beaches at Penghu, Taiwan (23 32N; 119 33E) at ebb-tide in 1984 and 1985. The pairing behavior of A. typicus is a reproductive behavior which leads to simultaneous spawning, increasing the probability of fertilization. As the breeding season approaches, sea stars, especially males, display increased mobility. Because only males tend to mount another individual and because males can detect the sex of another individual by contact with the side of their arms, a male-on-female pair is formed when a male encounters a female. Eighty-five percent of the sea stars observed were paired during the pairing season. Spawning by a paired female is closely followed by spawning of its paired male; male spawning, however, does not induce spawning in its paired female. During spawning, the male turns slightly so that its arms overlap the arched arms of the female. The gonad volume of males is much less than that of females. This may result from the high efficiency of fertilization in this species, which does not require a large amount of gametes to be released, or from the higher energetic demands made on the males.     

Population dynamics of Eudendrium racemosum (Cnidaria, Hydrozoa) from the North Adriatic Sea

Benthic suspension feeders in shallow waters develop in relation to the food availability and the variation of physical parameters giving rise to complex communities that act as a control factor on the plankton biomass. The aim of the work is to establish the role of the hydrozoan Eudendrium racemosum in the energy transfer from the plankton to the benthos in marine food chains of the North Adriatic Sea. This study highlighted that the hydroid biomass changed over time in relation to temperature and irradiance, and the highest abundance was observed during summer with about 400,000 polyps m⁻² (about 19 g C m⁻²). The population suffered an evident summer decrease in relation to a peak of abundance of its predator, the nudibranch Cratena peregrina, whose adult specimens were able to eat up to 500 polyps day⁻¹ and reached an abundance of 10 individuals m⁻². The gut content analysis revealed that the hydroid diet was based on larvae of other benthic animals, especially bivalves and that the amount of ingested preys changed during the year with a peak in summer when it was estimated an average predation rate of 13.7 mg C m⁻² day⁻¹. In July, bivalves represented over 60 % of the captured items and about 18 mg C m⁻² day⁻¹. Values of biomass of E. racemosum are the highest ever recorded in the Mediterranean Sea, probably supported by the eutrophic conditions of the North Adriatic Sea. Moreover, our data suggest that settling bivalves provide the greater part of the energetic demand of E. racemosum.     

Halistaura bruuni sp. nov. (Leptomedusae,Mitrocomidae) with notes on its distribution and ecology

A new hydromedusa collected in 1963 in the Bay of Bengal during the International Indian Ocean Expedition by the RV Anton Bruun is here described as Halistaura bruuni sp. nov. Some environmental data are given. The new species is characterized by a number of open marginal vesicles approximately equal to that of the tentacles, oval gonads on the distal half of the radial canals, and by the presence of nematocyst depots in the tentacle bulbs.Publ. No. 273 of the Instituto Oceanográfico da U. S. P.     

The annual reproductive cycle of the holothurian Aslia lefevrei (Dendrochirota: Echinodermata)

The dendrochirote holothurian Aslia lefevrei (Barrois) is locally and densely aggregated (>70 individuals m^-2) in Galway Bay, on the west coast of Ireland. It has a discrete, relatively short breeding period from the end of February to the beginning of April, with peak activity in March. The sexes are separate and the single gonad, consisting of numerous tubules (100 to 800), lies in the anterior coelom. Both gonad index values and histological observations indicate that gametogenesis resumes in June/July after a brief post-spawned resting period. Little oocyte growth and sperm production occurs over the warm summer months when the holothurian is actively feeding. Gonad index values, however, increase rapidly during this period and reach high values by early winter without concomitant increases in maturity indices. This is subsequently followed by slight reductions in the gonad indices, before reaching peak values in February. It is suggested that this is probably due to the initial build-up and subsequent assimilation of storage products in the gonad, the development of gametogenic products and the frequent assimilation thereafter of unwanted ova. Spawning generally takes between 5 and 60 min, with the entire contents of the gonad rarely being shed in a single release. During this process, the holothurian raises its anterior end and, with the extended tentacles close together, emits a stream of gametes from the genital pore in the mid-dorsal line. Laboratory experiments and general observations indicate that increased temperature and low light levels may influence spawning behaviour.Contribution No. 248 to the School of Marine Sciences, University College Galway, Ireland     

Foraging, prey capture, and gut contents of the mesopelagic narcomedusa Solmissus spp. (Cnidaria: Hydrozoa)

Narcomedusae are the most common group of medusae in the mesopelagic depths of Monterey Bay, California. Numerous capture events of various prey taxa were recorded in situ and analyzed using the Monterey Bay Aquarium Research Institute's remotely operated vehicle "Ventana". In situ video analysis of the stomach contents of 82 Solmissus incisa and S. marshalli revealed 88 identifiable prey items. Most (88%) were gelatinous animals. Of these gelatinous prey, 60.3% were ctenophores, 20.5% were cnidarians, 12.8% were salps, 3.8% were chaetognaths, and 2.6% were polychaetes. Euphausiids accounted for 11.4% of the diet, but they were probably captured adventitiously, as the gut contents of ctenophore prey. The tentacle-first foraging behavior of the narcomedusae is an effective way to capture large, comparatively fast-moving prey, because the fluid disturbance caused by swimming is decoupled from the area of prey capture. This behavior contrasts with the prevailing models of feeding behavior in medusae. Stealth predation may be the dominant mode of capturing prey by medusae in the mesopelagic depths of the oceans.     

Pluri-annual study of the reproduction of two Mediterranean Oscarella species (Porifera, Homoscleromorpha): cycle, sex-ratio, reproductive effort and phenology

This study presents the phenology of two common Mediterranean sponges belonging to the genus Oscarella (Porifera, Homoscleromorpha). Oscarella tuberculata and Oscarella lobularis are two sibling species, dwellers of shallow benthic communities which tend to have distinct ecological behavior, respectively, euryecious and rather stenoecious. The comparative study of their reproductive cycle showed that both Oscarella species have a seasonal reproductive cycle with a successive phase duration differing from one species to another. In both species, there is a continuous oogenesis, with new oocytes appearing in spring, whereas the spermatogenesis generally starts later with the early warming of the sea. The embryonic development and the larval release are restricted to the warmest months of the year. We also observed a shift in the period of gametogenesis and larval emission depending on species and differences in their sensitivity to changes in thermal regime. It appears that an increase in seawater temperature can affect sex determination, with mainly a shift toward males in both species. Their reproductive efforts are variable in time, and can be in some cases influenced by the temperature regime. This is especially the case of O. lobularis which seems to be the most thermosensitive, its phenology responding significantly to changes in thermal regime, whereas O. tuberculata seems to be less sensitive and/or reactive. By detecting phenological changes among sponges, this study demonstrated the relevance of such monitoring to assess the possible biological response to climate change.     

The reproductive cycle of Asterina stellifera (Möbius) (Echinodermata: Asteroidea) in the Cabo Frio region, southeastern Brazil

Reproduction of Asterina stellifera was studied in two populations from the Cabo Frio region, southeastern Brazil. One was located in an intertidal seagrass flat at Japonês Island (1994–1995); the second was on a sublittoral rocky shore at Pontal beaches (1999–2000). Reproductive cycle was studied at monthly intervals by organ indices and histological examinations of gonads. Although these two populations were studied in different habitats and at different times, the periodicity of the annual reproductive cycle was very similar for the two populations. The highest gonad index (GI) values were found in August/September (late winter), followed by a drop in GI values, indicating spawning. The GI and pyloric caeca index (PCI) tended to have an inverse relationship in both populations, but it was only statistically significant in the rocky-shore population. Gametogenesis in the two populations was described and roughly confirmed the reproductive cycles determined by GIs. Published online: 9 August 2002     

Population dynamics and reproductive cycle of Pholoë minuta (Polychaeta: Sigalionidae) in Galway Bay

Pholoë minuta (Fabricius) is a prominent member of the Amphiura filiformis (O.F. Müller) subcommunity in Galway Bay, Ireland. The aim of the present investigation was to study the population dynamics and reproductive cycle of P. minuta in this area. Monthly sampling over a 2 yr period (November 1978–October 1980), at a permanent station (18 m) with a fine sand substrate, revealed a mean density of 96 individuals per 0.1 m². The width of the fifth elytron was correlated with total body length and was used as a basis for analysing population structure. Four distinct year classes were evident and estimates of recruitment levels and growth rates were calculated. P. minuta is polytelic and reproduces for the first time when approaching 3 yr of age. Spawning occurred in March—April and appeared to be associated with a seasonal low in bottom-water temperature.     

Interannual variation in the reproductive cycle and biochemical composition of the cockle Cerastoderma edule from Mundaca Estuary (Biscay,North Spain)

Seasonal determinants of body weight, biochemical composition and reproductive condition in the cockle Cerastoderma edule L. from the Mundaca Estuary, Spain, were performed from December 1983 to July 1985. Interannual differences in timing of gametogenesis and spawning between 1984 and 1985 were correlated with temporal variations in the cycles of storage and utilisation of carbohydrate reserves. Young individuals exhibited larger annual fluctuations in soft-body weight, displaying higher growth rates in spring and greater diminishment of energy reserves during autumn and winter than older individuals. Carbohydrate content displayed a similar tendency, levels being lower in young individuals throughout the year.     

Annual reproductive cycle, spatial distribution, abundance, and size structure of Oreaster reticulatus (Echinodermata: Asteroidea) in Bocas del Toro, Panama

The structure, distribution, and population abundance of Oreaster reticulatus (Linnaeus, 1758) in 47,157 ha of shallow-water habitat in the archipelago of Bocas del Toro, Panama, were assessed from May to October 2000. The reproductive cycle of the sea star was studied in Isla Solarte, from February 2000 to February 2001. In total, 4,818 sea stars were recorded with a mean density of 149.7 ind. ha^-1, and a population of over 7 million was estimated for the archipelago. O. reticulatus was absent in ca. 50% of the evaluated areas, possibly due to high runoff and sedimentation; highest density was observed in an intermediate-runoff regime (255 ind. ha^-1). About 45% of the population was found in substrata dominated by seagrass (Thalassia testudinum) and coarse, calcareous sand, 51% occurred in habitats where coral reef patches were mixed with seagrass, and 4% exclusively on coral reefs. The average size, based on the major radius, was 9.5 cm (3-21 cm), with a population structure composed of ca. 83% juveniles and 17% adults. The average reproductive size, measured as major radius, was 15 cm, and the minimum was 7 cm. Both males and females with a maximum stage (IV) of gonad development were observed throughout the year. The gonad index showed three peaks of maximum reproductive activity, which is not comparable to studies from other localities. The reproductive cycle did not seem to be related to water temperature, which ranged from 27°C to 30°C, but may respond more closely to changes in local rainfall. This relationship was not statistically significant based on this 1-year study. These data provide a useful baseline for management of local populations in the face of an increasing harvest for the aquarium trade and as souvenirs.     

Somatic condition of the fish, Notopterus notopterus (Pallas) during different phases of the reproductive cycle

The study on the mathematical relationship between length and weight of fishes has considerable importance in fishery research especially for the study of fish population dynamics and patterns of growth in fish stocks. This aspect is useful in rationally managing the population of fishes, and is an index of relative robustness of the fish). Variations from expected weight or length of an individual fish or group of fish indicate the general well being and state of gonadal development. The condition of fish can be influenced by the onset of maturity. The results indicate that the overall condition of the female and male fish seems to get improved towards the approach of maturing and mature stages of the gonads during pre-spawning phases. The reduction in the condition factor (K) and somatic condition factor (Ks) during spawning phase may be because of the fish becoming exhausted due to spawning activity. Although improvement in the condition of the fish was observed on the approach of breeding period, the overall condition seems to be better in the aquatic body from which the fish was collected.     

Effects of stage of colony cycle,context, and intercolony distance on conspecific tolerance by paper wasps (Polistes fuscatus)

Summary We observed in the field how resident females of the social wasp, Polistes fuscatus, treated female nestmates, non-nestmate first cousins, and unrelated non-nestmates. Behavioral observations were made 1, 3, 4, 6, 7, 8, and 11 weeks after the emergence of a colony's first workers. Resident females were highly tolerant of female nestmates but highly intolerant of unrelated non-nestmates throughout the post-worker-emergence phase of the colony cycle. First cousins were treated either highly tolerantly or highly intolerantly, although most cousins ( 63%) were treated highly intolerantly. The treatment of cousins suggests that they are treated either tolerantly (like nestmates) or intolerantly (like unrelated non-nestmates) depending on whether they fall above or below an acceptance threshold, respectively. Resident females did not significantly change their tolerance nestmates, first cousins, and unrelated females between different observation periods. However, all conspecifics were generally treated the most intolerantly 11 weeks post-worker-emergence, a time in the colony cycle when combs no longer contain brood. This decreased tolerance and its associated variance patterns late in the colony cycle are consistent with a more restrictive acceptance threshold. The optimal level of the acceptance threshold appears to be a compromise between the fitness consequences of accepting unrelated non-nestmates and rejecting one's nestmates. In a laboratory study, resident females were equally tolerant of female nestmates on and off the comb but significantly less tolerant of unrelated females on the comb than off the comb. Thus, females can modify their tolerance rapidly in different recognition contexts. In a second laboratory study, resident females were equally intolerant of unrelated females, regardless of whether they were from colonies 50 m or 50 km distant.Offprint requests to: G.J. Gamboa     

The effect of depth on the reproductive cycle ofBrissopsis lyrifera (Echinoidea,Echinodermata) in the Gulf of Lions,Mediterranean Sea

A sample of 227Brissopsis lyrifera were collected in the Gulf of Lions in the Mediterranean Sea between 60 and 1000 m depth over a 21/2-yr period (June 1983 to November 1985). Males and females were sexually mature at the end of summer. After a period of gonadal inactivity during winter, gametogenesis resumed at the beginning of spiring. The cycle was synchronous over the entire bathymetric range studied. Variations in environmental conditions may be one factor inducing gametogenesis.     

Observations on the biochemical changes in gonads and other organs of Uca annulipes,Portunus pelagicus and Metapenaeus affinis (Decapoda: Crustacea) during the reproductive cycle

The fluctuations in biochemical constituents such as water, nitrogen, non-protein nitrogen, protein, lipid and glycogen in gonad, muscle and hepatopancreas have been followed in 3 decapod crustaceans, Uca annulipes (Latreille), Portunus pelagicus (Linnaeus) and Metapenaeus affinis (Milne-Edwards). The water and ash content of the entire body show no systematic fluctuation in relation to the annual reproductive cycle. The water content of the ovary diminishes as it matures. In the ovary of these crustaceans, the lipid fluctuated greatly in relation to the reproductive cycle. The maturing ovary contains more lipid than an immature or spent ovary per unit tissue weight. The changes in the biochemical constituents in the testis are not so pronounced as in the ovary, since the testicular cycle is often drawn-out and almost continuous in these crustaceans. There is an inverse relationship between water content and lipid content of the hepatopancreas; the greater the fat content, the lesser the water content. The hepatopancreas in these crustaceans is apparently a storage organ and contains much lipid and glycogen. At the height of the breeding season, when gonad production is intense, there is an indication of the mobilisation of at least a part of the lipid from hepatopancreas to gonad.Dissertation for the award of a Doctorate Degree of the Kerala University.Formerly the Marine Biological Laboratory.     

Seasonal changes in biochemical composition of body walls,gonads and pyloric caeca in two populations ofSclerasterias mollis (Echinodermata: Asteroidea) during the annual reproductive cycle

Seasonal changes in biochemical composition of tissues are compared in a shallow inshore and deeper offshore population of the seastarSclerasterias mollis (Hutton, 1872) on the Otago shelf, New Zealand, from 1985 to 1986. The biochemical composition of the body wall, gonads and pyloric caeca of the two populations did not differ greatly, even though reproductive output and nutrient storage of reserves were consistently higher in the offshore population. The biochemical composition of the ovaries and testes differed. High levels of carbohydrate and lipid were maintained in the ovaries from the commencement of vitellogenesis until spawning occurred. The testes had higher ash levels during spermatogenesis. During the annual reproductive cycle, an inverse relationship in the carbohydrate levels between the ovary and the pyloric caeca suggests nutrient transfer from the pyloric caeca to the gonads during gametogenesis. Annual changes in biochemical composition indicate that the body wall is also used for nutrient storage.