Akajima Marine Science Laboratory

Okinawa, Japan

Akajima Marine Science Laboratory

Okinawa, Japan
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Kaneko T.,1 9 5 202 Komaicho | Omori M.,Akajima Marine Science Laboratory
Bulletin of the Plankton Society of Japan | Year: 2012

Reproductive features of Sergia lucens of the 1993 and 1995 year-classes were investigated during the spawning season from June to November, 1994 and 1996. Mean carapace length of the 1995 year-class was smaller than the 1993 year-class, presumably due to lower temperature in the environment. The relationship between fecundity and egg size was correlated with low fecundity and large eggs in the early spawning period and with high fecundity and small eggs during the highest spawning period. The fecundity however lowered when the carapace length exceeded 12.0 mm during the late spawning period. Total fecundity of one individual during its lifetime was estimated to be 12000-13500. The fact that shrimp size and fecundity varies among year-classes is invaluable information for management and conservation from the fishery resources point of view. © 2012 Plankton Society of Japan.

Suzuki K.,1 1 Oppamahoncho | Nakada C.,Akajima Marine Science Laboratory | Omori M.,Akajima Marine Science Laboratory
Bulletin of the Plankton Society of Japan | Year: 2012

This study concerns the reproductive biology of the commercially important sergestid shrimp Sergia lucens in Suruga Bay, Japan. It includes observations on oocyte development, copulation and the number of spawnings of an individual female during the spawning season. Histological sections of the ovary revealed 10 developmental stages of gametogenesis. In the ovary there were always oocytes of different developmental stages. Spermatozoa are retained in the female's sperm receptacle after spawning. They are also found in the thelycum of immature females, suggesting that the shrimp copulate several times, since the females are not fully matured. Based on the data from the monthly occurrences of eggs in Suruga Bay from 1981 to 1989 and from laboratory spawning experiments in July, August and September in 1992 and 1993, it was estimated that one female spawns 7-8 times between May and November at an average interval of 19 days. © The Plankton Society of Japan 2012.

Nakamura R.,Fisheries Infrastructure Development Center | Ando W.,Fisheries Infrastructure Development Center | Yamamoto H.,ECOH Corporation | Kitano M.,ECOH Corporation | And 4 more authors.
Marine Ecology Progress Series | Year: 2011

We attempted to develop practical methods for coral reef rehabilitation, by means of the production of juveniles obtained from sexual reproduction, for a remote island where recruitment is limited. Adult corals (broodstocks) of Acropora tenuis were transported 1100 km from Okinotorishima, Japan's southernmost island in the Pacific, to a hatchery in Okinawa and maintained in land tanks. Eggs were obtained from captive spawning and the resulting larvae and juvenile corals were cultured under laboratory conditions. The present methodology enabled high survivorship and led to the successful mass production of coral juveniles. A total of 564 substrates with ∼ 63 000 juvenile corals at the age of 10 mo were transported to the native reef. They were then transplanted in 3 experimental treatments, in order to evaluate effectiveness of protection by cages and/or hiding the juveniles under other substrates. Additionally, the effects of orientation on coral growth were tested by attaching the juveniles face down. The cages effectively protected the corals from predation and nibbling by fishes. The unshaded, upward facing corals in the cages steadily increased their coverage nearly 4-fold in ∼ 2 yr. © 2011 Inter-Research.

Yasuda N.,Japan National Research Institute of Fisheries And Environment of Inland Sea | Ogasawara K.,Okinawa Environmental Research and Technology Center | Kajiwara K.,Miyakojima City Office | Ueno M.,Yaeyama Fishermens Association Ishigaki | And 6 more authors.
Plankton and Benthos Research | Year: 2010

Chronic outbreaks of the coral eating crown-of-thorns starfish (Acanthaster planci) have devastated coral communities throughout the Ryukyu Islands in the past four decades. Since A. planci has high fecundity and long larval duration, knowledge of reproductive timing and larval dispersal are keys to understanding mechanisms of successive recruitment and consequent outbreaks of adults. As the first step to acquiring this knowledge, we monitored water temperature and peak spawning periods using gonad observation. A total of 379 A. planci specimens were collected from May to September in 2004 at five latitudinally different locales in the Ryukyu Islands. Peak spawning, at which starfish gonads rapidly shrunk in size, was first observed in late May in Ishigaki Island, the southernmost sampling site. Then spawning time was progressively delayed with increasing latitude, ie. from mid to late June in Miyako Is., late June to mid July in Kerama Is., late July in Okinawa Is. and Amami Ohshima Is. When we started the survey in May, some A. planci had already started spawning, though not at Amami Ohshima. The peak spawning time in every locality coincided with the time when the water temperature exceeded 28°C. Accordingly, we can predict the approximate peak for spawning by monitoring water temperatures throughout the Ryukyu Islands. The information will be useful for: (1) numerical simulations predicting larval dispersal pathways by particle tracking through provision of the input parameter for the timing of larval release, (2) selecting times for larval sampling in the field in empirical early life history studies. © The Japanese Association of Benthology.

Kitamura M.,University of Tokyo | Kitamura M.,Japan Agency for Marine - Earth Science and Technology | Omori M.,Akajima Marine Science Laboratory
Plankton and Benthos Research | Year: 2010

Based on sampling of specimens and field observations on jellyfish fisheries in Malaysia, Indonesia, and Myanmar, six trade types of edible jellyfish were identified and the proper scientific names were applied to them with synopses of their taxonomy. An identification key for the Suborder Daktyliophorae, allowing identification of edible species, is provided. Jellyfish fishing activities at various locations in Southeast Asia are reported. © The Plankton Society of Japan.

Isomura N.,Okinawa National College of Technology | Iwao K.,Akajima Marine Science Laboratory | Morita M.,University of Ryukyus | Fukami H.,University of Miyazaki
Coral Reefs | Year: 2016

The role of hybridization through multi-specific synchronous spawning in the evolution of reef-building corals has been discussed since the 1990s, particularly for the genus Acropora. However, F1 hybrids have been reported as common in only one case in the Caribbean, with no evidence of mechanisms that would allow continuous reproduction of the hybrids. In this study, we report for the first time the fecundity of two F1 hybrid colonies produced experimentally from two Indo-Pacific species, A. intermedia and A. florida. These F1 hybrids spawned at the same time as the parental corals. Backcrossing and F1 hybrid crossing were successful in both directions. Furthermore, more than 90% self-fertilization was achieved in an F1 hybrid, although it was negligible in the parental corals. While it is possible that the F1 hybrid was a chimera, these results suggest that some products of interspecific hybridization may persist as the offspring of self-fertilizing F1 hybrids. © 2016 Springer-Verlag Berlin Heidelberg

Kuanui P.,Chulalongkorn University | Chavanich S.,Chulalongkorn University | Viyakarn V.,Chulalongkorn University | Park H.S.,Korea Advanced Institute of Science and Technology | Omori M.,Akajima Marine Science Laboratory
Tropical Zoology | Year: 2016

This study examined the capture rates and prey digestion of three corals species in two genera (Acropora and Pocillopora) found dominantly in Thailand and the Federated States of Micronesia using Artemia salina nauplii as a food source. In addition, feeding during day and night times of corals was investigated. Results showed that all three coral species, namely, Acropora millepora, Acropora nobilis, and Pocillopora damicornis captured and consumed A. salina nauplii under both light and dark conditions. The capture rates of the three species ranged between 0.44 and 2.39 individuals/polyp/12 h. The results also showed complete digestions of A. salina nauplii by A. millepora and A. nobilis after 2 h, whereas P. damicornis took 2.5 h to complete the prey digestion. Even though feeding corals with Artemia is not a novel implication since this is widely used, the results of optimum daily feeding frequency of corals by Artemia may be applied for optimum corals growth and survival in captivity or aquarium. © 2016 Istituto per lo Studio degli Ecosistemi of the Consiglio Nazionale delle Ricerche, Firenze.

Kuanui P.,Chulalongkorn University | Chavanich S.,Chulalongkorn University | Viyakarn V.,Chulalongkorn University | Omori M.,Akajima Marine Science Laboratory | Lin C.,National Dong Hwa University
Ocean Science Journal | Year: 2015

This study investigated the effects of temperature and salinity on growth, survival, and photosynthetic efficiency of three coral species, namely, Pocillopora damicornis, Acropora millepora and Platygyra sinensis of different ages (6 and 18 months old). The experimental corals were cultivated via sexual propagation. Colonies were exposed to 5 different temperatures (18, 23, 28, 33, and 38°C) and 5 different salinities (22, 27, 32, 37, and 42 psu). Results showed that temperature significantly affected photosynthetic efficiency (Fv/Fm) (p < 0.05) compared to salinity. The maximum quantum yield of corals decreased ranging from 5% to 100% when these corals were exposed to different temperatures and salinities. Temperature also significantly affected coral growth and survival. However, corals exposed to changes in salinity showed higher survivorship than those exposed to changes in temperature. Results in this study also showed that corals of different ages and of different species did not display the same physiological responses to changes in environmental conditions. Thus, the ability of corals to tolerate salinity and temperature stresses depends on several factors. © 2015, Korea Ocean Research & Development Institute (KORDI) and the Korean Society of Oceanography (KSO) and Springer Science+Business Media Dordrecht.

Isomura N.,Okinawa National College of Technology | Iwao K.,Akajima Marine Science Laboratory | Fukami H.,University of Miyazaki
PLoS ONE | Year: 2013

Natural hybridization of corals in the Indo-Pacific has been considered rather rare. However, field studies have observed many corals with intermediate interspecific or unusual morphologies. Given that the existence of F1 hybrids with intermediate interspecific morphologies has been proven in the Caribbean, hybrids may also inhabit the Indo-Pacific and occur more frequently than expected. In this study, we focused on two morphologically different species, Acropora florida and A. intermedia, and performed crossing experiments at Akajima Island, Japan. Results showed that these species could hybridize in both directions via eggs and sperm, but that fertilization rates significantly differed according to which species provided eggs. These results are similar to those reported from the Caribbean. Although all embryos developed normally to the planular larval stage, the developmental processes of some hybrid embryos were delayed by approximately 1 h compared with conspecific embryos, suggesting that fertilization occurred 1 h later in interspecific crosses than in intraspecific crosses. More successful hybridization could occur under conditions with low numbers of conspecific colonies. Additionally, a comparison of survival rates between hybrid and intraspecific larvae revealed that intra- and interspecific larvae produced from eggs of A. florida survived for significantly longer than those produced from eggs of A. intermedia. Considering these data, under specific conditions, hybrids can be expected to be produced and survive in nature in the Pacific. Furthermore, we identified one colony with intermediate morphology between A. florida and A. intermedia in the field. This colony was fertilized only by eggs of A. florida, with high fertilization rates, suggesting that this colony would be a hybrid of these two species and might be backcrossed. © 2013 Isomura et al.

PubMed | University of Miyazaki, Akajima Marine Science Laboratory, Okinawa National College of Technology and University of Ryukyus
Type: Journal Article | Journal: Biology letters | Year: 2016

Multi-specific synchronous spawning risks both sperm limitation, which reduces fertilization success, and hybridization with other species. If available sperm of conspecifics are limited, hybridization with heterospecific sperm could be an alternative. Some species of the reef-building coral Acropora produce hybrid offspring in vitro, and therefore hybridization between such species does sometimes occur in nature. Here, we report that the interbreeding species Acropora florida and A. intermedia preferentially bred with conspecifics at optimal gamete concentrations (10(6) cells ml(-1)), but when sperm concentration was low (10(4) cells ml(-1)), A florida eggs displayed an increased incidence of fertilization by sperm of A intermedia However, A intermedia eggs never crossed with heterospecific sperm, regardless of gamete concentrations. It appears that A florida eggs conditionally hybridize with heterospecific sperm; in nature, this would allow A florida to cross with later-spawning species such as A intermedia These results indicate that hybridization between some Acropora species could occur in nature according to the number of available sperm, and the choice of heterospecific sperm for fertilization could be one of the fertilization strategies in the sperm-limited condition.

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