Shipworms of the family Teredinidae were collected from driftwood along the coastal areas of Hokkaido between October 2020 and November 2021. Identification of species recorded a total of five species pervaded wooden debris: Teredo navalis Linnaeus, 1758, Lyrodus pedicellatus (Quatrefages, 1849), Bankia setacea (Tryon, 1863), Bankia bipennata (Turton, 1819), and Bankia carinata (Gray, 1827), the latter two were warm-water elements and considered a new record of species discovered from the temperate zone of Hokkaido waters. This suggests the possibility that ocean currents and suitable environmental conditions caused the settlement of these teredinids in driftwood along the vast coastal stretches of Hokkaido. Also, B. bipennata and B. carinata have been most likely distributed along the Sea of Japan and brought accidentally by typhoons from the Kuroshio region and Tsushima and Tsugaru currents to Hokkaido, respectively. Moreover, biogeographic patterns within Teredinidae from other coastal areas in the country and elsewhere were examined from the available literature.
Balanus rostratus is the largest species of barnacle in the coastal area surrounding Japan. It has not only been known as an edible barnacle in northern Honshu, but is also recognized as a fouling animal for the commercially important scallop Mizuhopecten yessoensis. This barnacle is a lesser-known marine resource in itself in Ofunato Bay, in which oyster and seaweed aquaculture is actively undertaken. The Bay has high primary productivity as the result of nutrient inputs from coastal waters, rivers and sewages. Under such environmental conditions, it is expected that this barnacle would grow faster and would be a new candidate for marine products grown locally. We aimed at elucidating its growth, feeding, and the seasonal appearance of its larvae for future cultivation. Individual barnacles grew 38–43 mm in basal diameter during the first 18 months after settlement and reached 47–50 mm after an additional 9 months. This growth surpassed those in Mutsu Bay and Okirai Bay with which we made a comparison. The results of stable isotopic ratio analysis indicated that these barnacles did not prey on zooplankton, but they might consume phytoplankton and particulate organic matter. They released nauplii in November to March and cyprid density reached about 120 ind./m3 in May. Clearly, this barnacle has a great capacity to be able to adapt to the nutrient-rich environment in Ofunato Bay.
The ingestion rates and somatic growth of Aurelia coerulea polyps fed Artemia nauplii or Oithona davisae were estimated. The ingestion rates of polyps fed O. davisae increased with increasing prey densities, and they were not saturated in all polyp size groups. Furthermore, the ingestion rates of polyps fed O. davisae were not attained to the level of the ones fed Artemia even if the highest density of O. davisae was supplied. The specific growth rates of polyps fed Artemia were also significantly higher than the ones fed O. davisae under all prey densities. The ingestion and growth rates of polyps fed Artemia will not be realistic to apply to the polyps settled in natural seawaters given the prey densities in ambient seawaters. In this study, it is appeared that A. coerulea polyps can utilize the most dominant copepods O. davisae as a food source, and the estimated ingestion and specific growth rates will be applied to the naturally settled A. coerulea polyps in ambient seawaters.
I studied an alien bivalve’s (Xenostrobus securis) distribution to understand its occurrence range better. I compared the bivalve’s horizontal seasonal change, vertical distribution, and population dynamics between periods of heavy eutrophication (1991–1992) vs. periods when water conditions were improved (2010–2011) in Dokai Bay, northern Kyushu, Japan.
The ascidian Styela plicata (Lesueur, 1823), which to date has been recorded from mid-temperate to tropical waters along the Japanese Pacific coast, from mid- and warm-temperate waters along the Sea of Japan coast, with northern limits in Tokyo Bay and Mutsu Bay, respectively, and from the mid-temperate Seto Inland Sea, was collected for the first time in 2019 from cool-temperate Ofunato Bay, Iwate Prefecture, further north of Tokyo Bay on the Pacific coast. Furthermore, hearsay evidence indicates that the ascidian has been observed on aquaculture equipment in Ofunato Bay since summer of 2017, following the 2016 introduction of the oyster Crassostrea nippona to the bay from Akita Prefecture for aquaculture. Long-term viability of the Ofunato Bay population of S. plicata now appears likely, indicating tolerance to winter water temperatures (to ca. 6°C), and a potential threat to local aquaculture.
The settlement of marine organisms on artificial surfaces cause a number of problems including increased fuel consumption of ship as a result of increased fluid resistance. To prevent biofouling on surfaces, tributyltin (TBT) compounds, the most effective biocide, had been used as an active ingredient in antifouling paints. However, TBT use in antifouling paints has been banned because it has toxic effects on marine organisms, and antifouling materials that are non-toxic and consume low amounts of energy have been demanded. Therefore, we focused on the relationship between the precise control of chemical surfaces and barnacle settlement towards the development of a non-toxic antifouling material. We found that few barnacles had settled on surfaces modified by a thiol compound having a terminal hydroxyl group in laboratory tests. In this paper, we verified the antifouling properties of the cross-linked PVA coating in both laboratory and field conditions. The results showed that the settlement rate increased with the amount of the cross-linking agent added, and the sample containing 10 wt％ of the cross-linking agent showed the lowest settlement rate in laboratory tests. Furthermore, the cross-linked PVA coating demonstrated antifouling activity for a period of at least 3 months under field conditions.
Study of the ascidian collection at the National Museum of Nature and Science, Tsukuba, revealed some Japanese specimens of the non-native ascidian, Ascidiella aspersa (Müller, 1776), collected in 2007 from both mid-temperate Oominato, Mutsu Bay, in the northernmost part of Honshû, and from warm-temperate Ago Bay, Kii Peninsula, middle Honshû. These specimens were collected one year earlier than the previous earliest Japanese record from cool-temperate Funka Bay, Hokkaido. Mutsu Bay has an international port, which can be assumed to be the invasion gateway for this ascidian from abroad. On the other hand, this ascidian may have arrived at Ago Bay by domestic transport because all of the bay’s ports are strictly for domestic use under governmental regulations. A comparison of the publicly available sequences for the 18S rRNA gene among this species and its allies suggested the possibility that it inhabited Korean waters as far back as the late 1990s, and it entered Japanese waters from Korea through an as yet unknown international port(s).
Submersible survey of biological communities are conducted using diving equipment and submersible instruments that are usually heavy and bulky. It also takes time to get permits to survey the inside of harbors and ports, and to prepare diving apparatus on site. Hence, it is desirable for intertidal ecologists to be able to conduct underwater surveys without the need for special diving skills and costly instruments. A portable videography apparatus has been devised for surveying biological communities on quay walls and to conduct observation at any time. It consists of a wearable underwater video camera, macrolens and collapsible kitchen shelf. Simultaneous species identification and quantitative analysis of organisms are possible with this apparatus which combines captured images from video and a measuring tape.
As there are few reports about the reproductive ecology of Fistulobalanus albicostatus which is a native species of Japan, reproduction of this species was investigated at the Suginoura quay of Miyajima, Hiroshima Prefecture, Seto Inland Sea from October 2013 to October 2014.
During the Fusetani Biofouling Project, isolation of natural products from benthic organisms was carried out in an at-tempt to develop nontoxic antifouling agents. In fact, more than 50 compounds showing antifouling activity against barnacle larvae have been obtained from marine invertebrates. 3-Isocyanotheonellin, isolated from a nudibranch species, exhibits potent antifouling activity against the larvae of the barnacle Balanus amphitrite (EC 50 0.13 µg/mL). However, its toxicity at high concentrations and structure–antifouling activity relationship have not yet been demonstrated. Herein, the structure– antifouling activity relationship studies conducted by synthesizing 3-isocyanotheonellin and its analogues are described. Based on these studies, various antifouling active isocyano compounds have been designed for developing environmentally friendly antifouling agents. In this review, the antifouling activity of isocyanides derived from citronellol and amino acids is mainly described. Most of these compounds showed potent antifouling activity without any significant toxicity against the cyprid larvae of the barnacle. These results suggested that isocyano compounds could be developed as environmentally friendly antifoulants in the near future. In addition, attempts to elucidate the mechanism underlying the expression of antifouling activity for the isocyano compounds are described.
