Toshiyuki Yamaguchi

First Hydrothermal Vent Communities from the Indian Ocean Discovered

Abstract Thriving chemosynthetic communities were located for the first time in the Indian Ocean between 2420 and 2450 m, on a volcanic knoll at the eastern crest of an axial valley, approximately 22 km north of the Rodriguez Triple Junction. The communities were distributed in a 40m by 80m field around the knoll. At least seven active vent sites, including black smoker complexes that were emitting superheated water at 360°C, were observed at the field. The faunal composition of the Indian Ocean hydrothermal vent communities had links to both Pacific and Atlantic vent assemblages. This discovery supports the hypothesis that there is significant communication between vent faunas in the Pacific and Atlantic Oceans via active ridges in the Indian Ocean.

The introduction to Japan of the Titan barnacle, Megabalanus coccopoma (Darwin, 1854) (Cirripedia: Balanomorpha) and the role of shipping in its translocation

The Titan Acorn barnacle, Megabalanus coccopoma, a native of the tropical eastern Pacific, has become established in the western Atlantic (Brazil and the northern Gulf of Mexico to the Carolinas), northwestern Europe and the western Indian Ocean (Mauritius), and therefore its dispersal capabilities are well known. This study reports its introduction to Japan and confirms its occurrence in Australia. In an attempt to determine the source of this introduction, phylogeographic techniques, involving cytochrome c oxidase I sequences of various widely separate populations of M. rosa and M. volcano, were utilized. No significant genetic differentiation or haplotype patterns between widely separated populations of each of the three species were found. Lack of such differentiation indicates recent geographical isolation and thus negates a null hypothesis predicting that the occurrence of one of more of these species in Australia was natural.

Occurrence and diversity of barnacles on international ships visiting Osaka Bay, Japan, and the risk of their introduction

Abstract The occurrence and diversity of barnacles attached to the hulls of two intercontinental bulk carriers were studied at the port in Osaka Bay, Japan, to assess the potential risk of introduction of exotic species to the inner part of the bay. Barnacles were sampled from the bulbous bows, near the midship draft marks, and around the propeller posts and rudders. Twenty-two species were found, with 14 of these not previously recorded in Osaka Bay, including four species not previously recorded elsewhere in Japan. From an assessment of environmental similarity between Osaka Bay and native ranges, of the 14 species, Elminius modestus and Amphibalanus variegatus were considered to have the highest risk of introduction to the inner part of the bay.

Expedition reveals changes in Lau Basin Hydrothermal System

TheValu Fa Ridge (VFR) in the southern Lau Basin—located behind the westward-dipping Tonga-Kerrnadec subduction zone—was one of the earliest targets to b e explored for hydrothermal activity in the southwestern Pacific Ocean (Figure l).In 1989, the French-German dive program NAUTILAU (Nautile-lan) discovered active hydrothermal fields venting high-temperature fluids with high acidity accompanied by massive ore deposits in this area [Fbuquet et al., 1993]. In September–October 2004, the SWEEP VENTS (Southwestern Edge of Pacific hydrothermal vents) expedition explored and sampled the hydrothermal systems of the VFR using the deep submergence research vehicle (DSRV) Shinkai 6500. The 2004 Shinkai dives focused on the geobiological and geochemical character of the deep-sea hydrothermal vent ecosystems of the Valu Fa Ridge and shed new light on these hydrothermal fields 15 years after their discovery These 2004 dives were the first to revisit this area, and have been followed by further dive programs and continued research.

Molecular investigations of the stalked barnacle Vulcanolepas osheai and the epibiotic bacteria from the Brothers Caldera, Kermadec Arc, New Zealand

The hydrothermal-vent barnacle Vulcanolepas osheai of the subfamily Neolepadinae is one of the most conspicuous organisms at the Brothers Caldera, south Kermadec Arc, New Zealand. Like a neolepad species found in the Lau Basin, V. osheai harbours filamentous bacteria on its elongated cirral setae. To define the phylogenetic affiliation of the epibiotic bacteria and the nutrition of the barnacle host, we conducted molecular phylogenetic and isotopic analyses. Analysis of 16S rRNA gene sequences of microbial communities on the cirral setae showed that among 91 bacterial sequences investigated, 2 8 sequences were related to the s-proteobacterial endosymbiont of Alviniconcha aff. hessleri; 11 sequences were related to the epibiont of the bresiliid shrimp Rimicaris exoculata. Fluorescence in situ hybridization showed that in contrary to results from the 16S rRNA gene-sequence library, approximately 80% of the filamentous bacteria hybridized with a probe targeting the sequences related to the epibiont of the bresiliid shrimp R. exoculata. The fatty-acid profiles of the filamentous bacteria and the host barnacle both contained high levels of monounsaturated C 16 and C 18 fatty acids, and the carbon isotopic compositions of the biomass and monounsaturated C 16 and C 18 fatty acids of both the bacteria and barnacle were nearly identical. This would suggest that the nutrition of the barnacle is highly dependent on bacteria thriving around the barnacle, including the epibiotic bacteria.

A new mangrove barnacle of the genus Fistulobalanus (Cirripedia: Amphibalaninae) from Sumbawa Island, Indonesia

The new mangrove barnacle, Fistulobalanus sumbawaensis sp. nov. from Sumbawa Island, Indonesia shares the common morphological characteristics with the subfamily Amphibalaninae in having a shell wall of six, porous compartmental plates; radii solid; alae not cleft; basis calcareous, tubiferous in single layer. This new species belongs to the genus Fistulobalanus mainly in having parietal tubes arranged in two or more rows; primary tubes with transverse septa; subsidiary tubes formed between the primary septum and outer lamina. In particular, the new species is similar to F. patelliformis in the shape of the shell, the transverse section of subsidiary tubes, the tergum and some characteristics of trophi and the cirri. However, this new species is easily distinguishable from all members of the genus Fistulobalanus in having no coloration or striations on the external surface of the shell, subsidiary tubes only appearing inside the ribbed part of the shell, and the scutum having a short adductor ridge.

Water Pumping in the Penduculate Barnacle Conchoderma Auritum

The cirral activity of the penduculate barnacle, Conchoderma auritum , was studied in a flow tank. The barnacles were exposed to different experimental water velocities and the response of the barnacles was recorded using a video system. In still and slow-moving water the barnacles show rhythmic cirral activity, the cirri extend and then withdraw into the mantle cavity. When water flow is accelerated the barnacles switch from rhythmic cirral activity to prolonged cirral extension, in which the cirri are extended in the water flow, facing the current. The water velocity at which barnacles switch from rhythmic activity to cirral extension depends on the size of the animal. During the rhythmic activity of Conchoderma water is pumped into the mantle through the ears. The prosoma serves as a piston which inhales the water into the capitulum and then ejects it at the apical end of the capitulum opening. This finding contradicts the generally accepted notion that the function of the ears of C. auritum is water ejection.