The organisms attaching to cathodically protected mild steel and to control plates lacking catholic protection were investigated at two locations, Shinagawa and Funabashi, in the innermost coastal area of Tokyo Bay, which has shown progressive recent improvement in water quality. The results are compared to those of studies at Numazu in Suruga Bay. At Numazu, the quantity of attached organisms on cathodically protected plates was greater than that on control plate, but there was no clear difference between the two types of plate at the two locations in Tokyo Bay. The quantity of attached organisms at the latter two sites was about 10% of that found in Suruga Bay, and fewer than 50% of the Suruga Bay species were present. Typical attaching animals included Balanus eburneus and Mitylus sp. at Shinagawa and Caulibugula ciliata and B. improvisus at Funabashi. Of algal species, a small amount of green algae and Colpomenia sp. was observed at Shinagawa, while none was observed at Funabashi. Compared to Suruga Bay, the water quality of Shinagawa and Funabashi was marked by low pH and Cl^- while resistivity was high. In addition, the extent of corrosion of the mild steel was about 1.5 times greater than that at Numazu, which may partly explain the lower quantity of attached organisms at the Tokyo Bay sites.

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There are 13 species of coral-inhabiting megatrematine barnacles of which five or possibly six are extinct. Despite a meager geological record dating from the early Pliocene, it appears, based on their distribution megatrematines are far older than indicated by their fossil record, likely originating early in the Miocene if not the Oligocene. Nonetheless, in apparently maintaining a conservative morphology, especially in their opercular plates, they never attained the diversity of forms such as found in the coral-inhabiting pyrgomatines. However, we propose new taxa herein including Memagreta n. gen. for M. pandorae n. sp., Megatrema youngi n. sp. and Pyrgomina djanae n. sp. The extinct species Pyrgoma elargatum Seguenza and P. sulcatum Philippi are considered valid species and herein assigned to Pyrgomina. Adna Sowerby is reinstituted as a valid genus. The tribe Pyrgominini is proposed for Pyrgomina and Adna and the tribe Megatrematini for Megatrema and Memagreta.

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At least 18 species of introduced marine sessile animal, including two newly discovered ones, the barnacle Balanus glandula and the ascidian Polyandrocarpa zorritensis, are known from Japanese waters. These include Polychaeta (2 species), Bryozoa (2), Gastropoda (1), Bivalvia (4), Cirripedia (6), and Ascidiacea (3). Dispersal routes and vectors of some of these species, and distributions of all the species in Japan, are reviewed based on the literature and original data. Dispersal routes have varies among species. In the case of sessile animals, fouling of ship hull accounts for introductions of foreign species arriving in Japanese waters; ballast water may be more important for dispersal within Japan. Introductions appear to have conspicuously increased during the two decades of the 1960s and 1970s, but fewer introductions have been reported in the last 20 years. The increase was probably because of the expansion ocean-going shipping coming to Japan, deterioration of water quality, and large-scale loss of natural coastline. The reason for the subsequent decrease are unclear, but likely causes for the change in the number of recorded introduced species are discussed.

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Chemical cues from conspecifics are believed to induce settlement of cypris larvae in barnacles, and a settlement-inducing protein complex, SIPC, is thought to be one of the key substances for gregarious settlement in Balanus amphitrite. In the present study, we examined effects of adult extracts including SIPC and nature of substrata on larval settlement in B. amphitrite and Megabalanus rosa by multiwell plate assay and membrane filter assay. Especially in M. rosa, settlement rates of the cypris larvae after larval culture in the presence of antibiotics are higher than those in the absence of antibiotics. Larval settlement in both species was induced by conspecific adult extracts in both assays using multiwell plates and mixed cellulose ester type membrane filters (CE). However, no cypris larvae settled on cellulose acetate type membrane filters (CA), which are inactive for protein adsorption. The results of assays using five different types of membrane filter showed that capacity for protein adsorption in substrata seems to affect larval settlement. On the other hand, the settlement pattern of M. rosa cyprids in a choice assay using CE was different from that of B. amphitrite; B. amphitrite cyprids settled exclusively on the adult extract-adsorbed region, while M. rosa cyprids settled on the unadsorbed region as well as the adsorbed region. These results indicate that settlement-inducing proteins and nature of substrata are important factors in larval settlement of barnacles, and that settlement patterns are species-specific.

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Investigation of the molecular mechanism underlying the fouling of marine mussels is an interdisciplinary endeavor encompassing the fields of biochemistry, polymer chemistry, and biological chemistry. In this review, recent progress in the research on the adhesive proteins secreted by mussel species is summarized. The present subject includes: (i) material performance of mussel byssus, (ii) recent advances in biochemistry and molecular biology of byssus precursor proteins, (iii) cross-linking reactions and adhesion mechanisms of mussel adhesive protein, (iv) surface chemical properties of mussel adhesives, (v) antifouling strategy based on the surface chemical properties of the substrata, and (vi) conclusions and perspectives.

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Mechanisms of larval settlement in the marine hydroid Tubularia mesembryanthemum have been investigated. Actinula larvae demonstrated two forms of attachment behavior: temporary attachment by atrichous isorhiza (AI) nematocyst discharge from the tentacle tips, and permanent settlement by cement secretion from the basal protrusion. During settlement, the larvae discharged numerous AIs by rubbing the tentacle tips on the substrata surfaces, and the other types of nematocytes synchronously migrated to the tentacle tips. Thus, the nematocyst composition of the tentacles radically changed after larval settlement in parallel with the functional change (from attachment to feeding and defense) of the tentacles. AI discharge was induced by tactile stimuli as well as high K⁺; a simultaneous transitory surge of [Ca²⁺]_i was observed in the tentacle tips. This was inhibited by≤0.9mM[Ca²⁺] and by 10-50μM[Gd³⁺]. Actinula settlement was induced by direct contact of larval tentacles to microbial films, particularly films of the benthic diatom Cocconeis sp. The inducing activity of biofilms was inhibited by treatment with HIO₄ and lectins, especially LCA, thus indicating the involvement of polysaccharides in the activity. GLWamide peptides, which are peptidic neurotransmitters, were found to induce actinula settlement, and the occurrence of GLWamidepositive neurons was confirmed in ontogenetic stages varying from competent larvae to juvenile polyps. These results suggest that an influx of extemal Ca²⁺via mechano-sensitive (stretch-activated) cationic channel activation and LCA-binding sugar-chains may play important roles in larval mechano-/chemoreception, and that GLWamide peptides may control larval morphogenesis as the internal signals. AI nematocytes are likely to act as sensors and effectors of actinular settlement

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Recent studies of Aurelia aurita polyps using settling plates are reviewed. In particular, population dynamics of polyps under natural conditions were investigated by observing of the continuous changes in the number of polyps on settling plates in Tokyo Bay for one year. The rapid decrease in the survivorship of newly settled polyps was considered to be the result of the invasion and growth of other benthic organisms such as Mytilus galloprovincialis. The decrease of such competition in autumn enabled the polyps to survive and increase their abundance by budding. We suggest that most liberated ephyrae originate from the polyps that settled in autumn, and the presence of ripe medusae with planula larvae in autumn should contribute to a mass occurrence of meduse in the following year.

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