Ryusuke Kado

Fatty acids as antifoulants in a marine sponge

The antifouling factor against the blue mussel Mytilus edulis found in the organic extract of the marine sponge Phyllospongia papyracea collected in Kagoshima was purified by solvent partition, silica gel column chromatography and HPLC on Toyopearl HW‐40 and on ODS. The active substance was analyzed by gas chromatography after methylesterification and identified as a mixture of several free fatty acids containing C16: 0 (59.9%), C16: l (11.8%) and C18: l (13.8%) as the major components. Among the various authentic free fatty acids tested, C10: 0, C14: l, C16: 0, C16.1, C18: 2, C20: 4 and fatty acids from porcine liver (FAPL) showed antifouling activity against M. edulis. The stronger activity of fatty acid mixtures compared with the same amount of each used singly suggested a synergistic effect of fatty acids on antifouling activity. FAPL inhibited larval settlement in the barnacle Balanus amphitrite without killing the larvae.

Effect of water flow velocity on growth and morphology of cultured Undaria pinnatifida sporophytes (Laminariales, Phaeophyceae) in Okirai Bay on the Sanriku coast, Northeast Japan

Undaria pinnatifida sporophytes, originating from the same strain, were cultured at the commercial cultivation site exposed to wave action and the uncultivated site protected from water action of Okirai Bay, Northeast Japan, from January to April 2007; simultaneously, water flow velocity, water temperature, salinity, NO3 + NO2, and chlorophyll a were monitored to investigate the effect of water environment on their growth and morphology. Water temperature and salinity fluctuated within the optimal range for their growth whereas water flow velocity at the cultivation site was greatly fast compared with that at the uncultivated site. Successive chlorophyll a increases synchronized with NO3 + NO2 decreases were observed only at the uncultivated site for over a month; indicating developments of phytoplankton blooms and their nutrient consumption under the low-flow condition. Meanwhile, blade growth rate of cultured sporophytes was higher at the cultivation site than at the uncultivated site. Their thallus size expressed by six morphological characters (blade length, stipe length, blade wet weight, stipe wet weight, blade width, and undivided blade width) at the cultivation site became large in comparison with that at the uncultivated site. Their three morphological correlations (correlations between blade length and thallus length; blade wet weight and thallus wet weight; and undivided blade width and blade width) differed between the sites. They produced a thick and flat blade at the cultivation site but formed a thin and wrinkled blade at the uncultivated site. These results show the significant impact of water flow velocity on their growth and morphology.

Possible role of a taurine transporter in the deep‐sea mussel Bathymodiolus septemdierum in adaptation to hydrothermal vents

Various invertebrates inhabiting hydrothermal vents possess sulfur‐oxidizing bacteria in their tissues; however, the mechanisms by which toxic sulfides are delivered to these endosymbionts remain unknown. Recently, detoxification of sulfides using thiotaurine, a sulfur‐containing amino acid, has been suggested. In this study, we propose the involvement of a taurine transporter in sulfide detoxification in the deep‐sea mussel Bathymodiolus septemdierum by demonstrating: (i) the abundance of its mRNA in the gill; (ii) its activity under a wide range of salinities; (iii) its low Michaelis constant value in taurine transportation; and (iv) its affinity for thiotaurine and the thiotaurine precursor, hypotaurine.

Larval development of two Japanese megabalanine barnacles, Megabalanus volcano (Pilsbry) and Megabalanus rosa (Pilsbry) (Cirripedia, Balanidae), reared in the laboratory

Abstract Two species of megabalanid barnacles occur in Japan. The larval stages of Megabalanus volcano (Pilsbry) and M. rosa (Pilsbry) are described from larvae reared in the laboratory. The number of segments of the antennal exopod and the number of teeth on inner prong of the antennal gnathobase are introduced as important taxonomic characters, as a result of comparison of the larvae of M. volcano , M. rosa and 16 other barnacle species. The larvae of M. volcano and M. rosa can be easily distinguished from other cirripede nauplii around the coast of Japan by their distinctive dorsal shield spines and longer median lobe of the labrum. Morphological differences between the larval stages of the two species are minor, but species discrimination is possible in most stages. The larvae of M. volcano and M. rosa differ greatly from those of the Indian megabalanid M. tintinnabulum . The two megabalanids more closely resemble Austromegabalanus than Notomegabalanus algicola in the naupliar stages.

Formation and growth of filamentous thalli from isolated utricles with medullary filaments of Codium fragile spongy thalli

Abstract Formation and growth of filamentous thalli from isolated utricles with medullary filaments of Codium fragile (Suringar) Hariot was studied in the laboratory. Immediately after isolation of the utricles, their fusiform chloroplasts began to be transferred, leading to formation of the filamentous thalli after culture for 2–6 days. The utricles became attached to the substratum by elongation of those thalli developing immediately after the initiation of formation. Differences in medullary filament length extending from the isolated utricles had no effect on the formation of the filamentous thalli from the utricles, nor their ability to attach to the substratum. The filamentous thalli remained viable for 32 weeks. One primordium of spongy thallus surrounded by many filamentous thalli regenerated from the isolated utricles after 6 weeks of culture, and the primordium grew into young spongy thallus with four axes and filamentous thalli by 10 weeks. Furthermore, its separated axes grew into young spongy thalli by 6 weeks of separation. The filamentous thalli and utricles of the regenerated spongy thalli contain numerous fusiform chloroplasts. These results suggest that the protoplasm containing numerous chloroplasts plays an important role in vegetative reproduction of the isolated utricles and filamentous thalli.

Number and Duration of Zoeal Stages of the Hydrothermal Vent Crab Gandalfus yunohana from Laboratory Reared Specimens

Abstract The hydrothermal vent crab Gandalfus yunohana is found along the Izu-Ogasawara Arc in the north-western Pacific at depths from 420 to 1400 m. To study the larval developmental characteristics of this vent endemic species, we collected adult crabs from a depth of 445 m in May 2005 from the Kaikata Seamount (26°42.607′N, 141°04.457′E). These individuals were maintained at atmospheric pressure and temperature (15 and 18°C) for several months, until two females spawned and released larvae. Larvae were maintained at atmospheric pressure and at five different temperatures ranging from ∼18 to 30°C and fed Artemia sp. At ∼18°C, no larvae survived until the second zoeal stage. Some larvae reached the second or third zoeal stages when reared at ∼21°C. At 24-30°C, six individuals metamorphosed into the megalopal stage following a fifth or sixth zoeal stage 34-60 d after hatching. Megalopae swam actively, but they eventually died 58-104 d after hatching and showed no signs of moulting into the juvenile crab stage. Newly hatched first stage zoeae were phototactic, and we observed relatively high temperature requirements for larval survival and development. These facts suggest that zoeae may be distributed relatively high in the water column in warmer near-surface waters during their planktotrophic development. This is the first report of successful larval rearing of any species of bythograeid crabs. Our study establishes the conditions under which the megalopae moult to the first crab stage, laying the groundwork for future experiments.

Sterols from bivalves Calyptogena soyoae and Bathymodiolus septemdierum living in deep sea

From the two species of bivalves, Calyptogena soyoae around a cold seep and Bathymodiolus septemdierum near hydrothermal vents in the sea, sterols were isolated using high-pressure liquid chromatography analysis of the lipid fraction guided by characteristic 1H NMR signals of the sterol skeleton. The minor sterol composition of C. soyoae included 24-methylenecycloartanal, cycloeucalenol, and obutusifoliol, which are known phytosterols. From B. Septemdierum, lathosterol and cholesterol as main sterols together with more diverse sterols were obtained. The difference between these species and their sterol contents is most likely because of feeding modes and metabolism of nutrients from their habitat.

Morphology of Cyprid Attachment Organs Compared Across Disparate Barnacle Taxa: Does It Relate to Habitat?

This study used morphometric analyses to compare the structure of the third antennular segment, also called the attachment organ, in cyprid larvae from cirripede species representing a diverse set of taxonomic groups. The aim was to investigate the degree of morphological variation in view of the diversity of habitats, settlement substrata, and modes of life found in the Cirripedia. In all cyprids the third segment features a flat surface (the attachment disc) covered with small cuticular villi thought to function in adhesion. The parameters analyzed were the angle of this disc relative to the long axis of the antennule, its shape (outline), the density of cuticular villi, and the type of cuticular structure encircling the disc. The 10 species studied came from most major groups of cirripedes, and comprised shallow-water forms inhabiting hard bottoms (Capitulum mitella, Pollicipes pollicipes, Semibalanus balanoides, Austrominius modestus, Megabalanus rosa), sublittoral forms (Verruca stroemia, Scalpellum scalpellum), epibiotic forms settling on live, soft tissues (Balanus spongicola, Savignium crenatum), and a parasite (Peltogaster paguri). Significant structural variation was found among the species, but due to limited taxon sampling it was unclear whether the differences relate to ecological factors or phylogenetic affiliation. The disc perimeter is guarded by either a series of long and thin cuticular fringes overreaching the rim of the disc (= a velum) or a few low, but very broad cuticular flaps (= a skirt). The presence of a velum (in all rocky-shore species) or a skirt (all other species) around the attachment disc was the only parameter that was clearly correlated with habitat. The shape of the third antennular segment varied from a symmetrical bell shape with a distally facing attachment disc having a circular disc outline, to segments that were elongated in side view, with a very tilted ventral disc surface having an elliptical disc outline. The bell shape may be most common in forms from rocky shores, but in our test of morphometric parameters only Scalpellum scalpellum (sublittoral), Savignium crenatum (epibiotic in corals), and Peltogaster paguri (parasitic) had shapes that differed significantly from the other species. The density of villi on the attachment disc varied significantly, but also showed no clear-cut correlation with substratum or habitat. Attachment organ structure is clearly the most variable feature in cirripede cyprids. To evaluate the degree to which attachment organ structure is correlated with habitat, settlement substratum, and mode of life, future studies should employ a more refined statistical analysis on an enlarged dataset, with much increased taxon sampling and a more multifaceted definition of ecological variables.

Biochemical and immunohistochemical analyses of GnRH-like peptides in the nerve ganglion of the chiton, Acanthopleura japonica.

We examined whether a gonadotropin-releasing hormone (GnRH)-like peptide is present in the nerve ganglion of the chiton Acanthopleura japonica (Mollusca, Polyplacophora) using reverse-phase high performance liquid chromatography (rpHPLC) combined with time-resolved fluoroimmunoas-say (TR-FIA) analysis, and immunohistochemistry. An extract of the chiton head region showed a similar retention time to that of synthetic lamprey GnRH-II on rpHPLC combined with TR-FIA analysis using a rabbit polyclonal antibody raised against chicken GnRH-II (aCII6). Cell bodies immunostained with LRH13 (a mouse monoclonal antibody raised against the common amino acid sequence of vertebrate GnRH) were detected in the cerebrobuccal ring (CBR). Cell bodies immunostained with aCII6 were not only observed in the CBR but also in the lateral nerve cord (LCo). Fibers immunostained with LRH13 and aCII6 were widely distributed throughout the central nervous system in the CBR, subradular ganglion (SubRG), pedal nerve cord (PCo), pedal commissure (P/PCom), lateropedal commissure (L/PCom), and from the LCo to the suprarectal commissure (SupRecCom). The cell bodies and fibers immunostained with these two antisera were distinguishable by dual-label immunohistochemistry. These results suggest that multiple GnRH-like peptides are present in the nerve ganglion of the chiton Acanthopleura japonica.

First zoeal stage of the hydrothermal vent crab, Gandalfus yunohana (Decapoda, Brachyura, Bythograeidae)

[The first zoeal stage of Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000) is described and illustrated based on laboratory-hatched material. This is the first time that this has been accomplished for known species in the family Bythograeidae. Le premier stade zoe de Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000) est decrit et illustre a partir de materiel eclos en laboratoire. Ceci est une premiere pour une espece connue de la famille des Bythograeidae. , The first zoeal stage of Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000) is described and illustrated based on laboratory-hatched material. This is the first time that this has been accomplished for known species in the family Bythograeidae. Le premier stade zoe de Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000) est decrit et illustre a partir de materiel eclos en laboratoire. Ceci est une premiere pour une espece connue de la famille des Bythograeidae. ]