Tomomi Saito

Pair formation in Spongicola japonica (Crustacea : Stenopodidea : Spongicolidae), a shrimp associated with deep-sea hexactinellid sponges

The population structure of the deep-sea sponge-associated shrimp Spongicola japonica was investigated, and the mechanism of pair formation analysed from field samples. The composition pattern of shrimp in host sponges was divided into three patterns by sex and number as follows: solitary, a solitary inhabitant; sexually paired, a pair with a male and a female; grouped, multiple individuals excluding those designated as sexually paired. Juveniles usually remained grouped or solitary in a host cavity until the size at which gonadal maturity starts. Before forming sexual pairs, shrimp appear to have a free-living period outside the host, when the ovarian stages of females correspond to early to late vitellogenesis. Re-invasion is just before the first spawning, when females are in the ovarian stage of late vitellogenesis.

Active dispersal in loggerhead sea turtles (Caretta caretta) during the 'lost years'.

Highly migratory marine species can travel long distances and across entire ocean basins to reach foraging and breeding grounds, yet gaps persist in our knowledge of oceanic dispersal and habitat use. This is especially true for sea turtles, whose complex life history and lengthy pelagic stage present unique conservation challenges. Few studies have explored how these young at-sea turtles navigate their environment, but advancements in satellite technology and numerical models have shown that active and passive movements are used in relation to open ocean features. Here, we provide the first study, to the best of our knowledge, to simultaneously combine a high-resolution physical forcing ocean circulation model with long-term multi-year tracking data of young, trans-oceanic North Pacific loggerhead sea turtles during their ‘lost years’ at sea. From 2010 to 2014, we compare simulated trajectories of passive transport with empirical data of 1–3 year old turtles released off Japan (29.7–37.5 straight carapace length cm). After several years, the at-sea distribution of simulated current-driven trajectories significantly differed from that of the observed turtle tracks. These results underscore current theories on active dispersal by young oceanic-stage sea turtles and give further weight to hypotheses of juvenile foraging strategies for this species. Such information can also provide critical geographical information for spatially explicit conservation approaches to this endangered population.

Skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni , and host selection by the symbiotic shrimp Spongicola japonica (Crustacea: Decapoda: Spongicolidae)

Aspects of the skeletal growth of the deep-sea hexactinellid sponge Euplectella oweni Herklots and Marshall, and host size and type selection by the symbiotic shrimp Spongicola japonica Kubo were investigated using field-collected material. Two phases, flexible and stiff, were observed in the framework of the sponges. In the flexible sponges, the circular, longitudinal and oblique systems of the skeletal beams that constitute the principal framework were not fused to each other, and the parietal ledges running circularly, or sometimes obliquely, on the wall were not developed. The skeletal wall was fragile in texture, readily torn by any external force. The wall was much sturdier in the stiff sponges, in which the systems of the skeletal beams were coarse, fused to each other to make the principal framework tough in texture, and pareital ledges developed so as to reinforce the sponge wall. The flexible phase is mainly seen in smaller and younger sponges, while the stiff phase was seen in the larger (or dead) ones. Almost all the solitary and young pairs of shrimps were collected from flexible sponges.

Efficient establishment of primary fibroblast cultures from the hawksbill sea turtle (Eretmochelys imbricata)

The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered species at a risk of extinction. Preservation of the genomic and cellular information of endangered animals is important for future genetic and biological studies. Here, we report the efficient establishment of primary fibroblast cultures from skin tissue of the hawksbill sea turtle. We succeeded in establishing 19 primary cultures from 20 hawksbill sea turtle individuals (a success rate of 95%). These cells exhibited a fibroblast-like morphology and grew optimally at a temperature of 26°C, but experienced a loss of viability when cultured at 37°C. Chromosomal analysis using the primary cells derived here revealed that hawksbill sea turtles have a 2n = 56 karyotype. Furthermore, we showed that our primary cell cultures are free of several fish-related viruses, and this finding is important for preservation purposes. To our knowledge, this report is the first to describe primary cell cultures established from normal tissues of the hawksbill sea turtle. The results will contribute to the preservation of biodiversity, especially for the sea turtles that are critically endangered owing to human activities.

Direct development in the sponge-associated deep-sea shrimp Spongicola japonica (Decapoda: Spongicolidae)

An investigation of reproduction in the shrimp Spongicola japonica, associated with deep-sea sponges, revealed that juvenile shrimps hatch directly from eggs without intermediate planktonic stages. Gross morphology and behavior of the newly hatched juveniles are similar to those of adult shrimps. The intermolt period is relatively long, requiring approximately 70 days from hatching to the first molt, and a further 80 days to the second molt. In larval and juvenile development of the family Spongicolidae, the shallow-water genus Microprosthema has planktonic larvae, while S. japonica shows direct development. The relationship between the direct development in Spongicola and the distribution of the host sponge is discussed.

Larvae of the Deep-Sea Squat Lobsters, Agononida incerta (Henderson, 1888) and Munida striola Macpherson and Baba, 1993 with Notes on Larval Morphology of the Family (Crustacea: Anomura: Galatheidae)

Abstract There is little information on the larvae of squat lobsters of the family Galatheidae in spite of their abundance in mesopelagic and abyssal fauna. Larvae of two galatheid species, Agononida incerta (Henderson, 1888) and Munida striola Macpherson and Baba, 1993, are described and illustrated for the first time from the northwest Pacific region based on laboratory-hatched material. The zoeas of these two species are easily distinguished from each other by their size and the morphology of the antenna and maxillule. Previously-known zoeas of the family are compared and a provisional key for 6 galatheid genera is presented.

Cyclical Changes of Plasma Sex Steroids in Captive Breeding Loggerhead Turtles (Caretta caretta)

Abstract Loggerhead turtles (Caretta caretta) have been laying eggs in an indoor artificial beach since 1995, at the Port of Nagoya Public Aquarium (PNPA). Four individuals landed and laid eggs several times during the breeding period in 1996. Blood samples from these individuals were collected monthly throughout that year in order to investigate the changes in sex steroid hormones (testosterone, estradiol, and progesterone). In addition, detailed investigations were conducted daily during the breeding period on one particular individual that landed and laid eggs five times in 1998. Each steroid hormone changed periodically based on the laying cycle, and extraordinarily high levels of estradiol were noted even during the breeding period. In reports regarding the green turtle (Chelonia mydas), extremely different results were observed. Some of the obtained data suggest that progesterone induced ovulation. Data from a completely artificial environment such as the one at the PNPA provides elucidation of the reproductive physiology in these endangered species.

Development of external sexual characters in the deep-sea sponge-associated shrimp Spongicola japonica Kubo (Crustacea: Decapoda: Spongicolidae)

Development of external sexual characters in the deep-sea sponge-associated shrimp, Spongicola japonica Kubo is investigated. Sexual dimorphism is observed in the gonopore, pereopod 3, abdominal width, pleuron and pleopods, and the size difference between paired shrimps is apparent. The external appearance of the gonopore is the first evidence of sexual dimorphism, opening on the coxa of pereopod 3 of females, while on the coxa of pereopod 5 of males. In females a slower growth rate for the pereopod 3 chela length and a positive growth rate for the abdominal width is recognized when both sexes are compared. The morphological changes in abdominal appendages during the formative period of the brooding chamber are illustrated.

SPONGICOLOIDES IHEYAENSIS, A NEW SPECIES OF DEEP-SEA SPONGE-ASSOCIATED SHRIMP FROM THE IHEYA RIDGE, RYUKYU ISLANDS, SOUTHERN JAPAN (DECAPODA: STENOPODIDEA: SPONGICOLIDAE)

Abstract A new species of the deep-sea sponge-associated shrimp genus Spongicoloides Hansen, 1908, S. iheyaensis, is described and illustrated on the basis of 6 specimens (3 sexual pairs) collected from the North Knoll of the Iheya Ridge at depths of 988-1051 m, Ryukyu Islands, southern Japan. This is the fourth species of the genus known from the Pacific Ocean. The new species is similar to S. hawaiiensis from Hawaii and S. novaezelandiae from New Zealand, but is distinguished by the differences in spination of carapace, sixth pleonal somite, and third pereiopod. It is suggested that the egg number of the new species is greater than that of other congeneric species. Sexually dimorphic characters are discussed. A key to the Pacific species of Spongicoloides is provided.

Two new species of the stenopodidean shrimp genus Spongiocaris Bruce & Baba, 1973 (Crustacea: Decapoda: Spongicolidae) from the Indo-West Pacific

Two new species of the deep-water spongicolid genus Spongiocaris Bruce & Baba, 1973, are described and illustrated from two localities in the Indo-West Pacific. Spongiocaris panglao n. sp. is described on the basis of material from the Bohol Sea, the Philippines, at depths of 220-731 m. Spongiocaris tuerkayi n. sp. is described on the basis of material from Atlantis Bank in the southwestern Indian Ocean at depths of 743-1053 m. Among eight known congeners, both new species appear close to S. semiteres Bruce & Baba, 1973, differing in the rostral length and armature, shape of the carapace, telsonal armature, development of the grooming apparatus of the first pereopod and shape of the third pereopod chela. An identification key to the species currently assigned to Spongiocaris is presented.