著者
福田 宏
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.56, pp.33-41, 2001-07-15 (Released:2009-08-07)
参考文献数
37
被引用文献数
2 or 0

The present status of the molluscs of the Suô-nada Sea coast is reported, and conservation of the species diversity there is discussed. This place is exceptional in modern Japan due to its extremely high biodiversity. Few people appreciate the rich biota in these tidal-flat ecosystems, and major destruction there has already begun. For the conservation of the biota of the Suô-nada Sea, it is essential to recognize the relationships between species and their microhabitats, because the habitats of most tidal-flat species are very restricted in space. Here I discuss some major problems in the conduct of environmental assessment studies in Japan, as illustrated by research into the expected impact on the molluscan fauna of the construction of the Kaminoseki Nuclear Power Plant on Nagashima Island. These problems include misidentifications, underestimation of faunal or ecological richness, failure of artificial plantings or mitigation, misleading treatment of the concept of conservation, and emphasis on protection of only a few species useful for human beings. I also discuss the role of amateur researchers in the conservation of tidal flats. Amateurs sometimes can provide new and precise information on the status of species, which is important when there have been recent rapid changes in environmental conditions. On the other hand, amateurs must understand that many species are endangered today and should not be overhunted only for private purposes.
著者
熊川 真二 中田 和義 川井 唯史
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.66, no.1, pp.26-32, 2011-10-15 (Released:2012-10-11)
参考文献数
20
被引用文献数
1 or 0

Official documents and archives suggest that the alien crayfish Pacifastacus leniusculus (Dana, 1852) was introduced into Japan from North America on five occasions from 1926 to 1930, and populations have survived in Hokkaido, Nagano, and Shiga Prefectures. The chemical conditions and biological environment of an established habitat near their original a release point in Akashina, Azumino City, Nagano Prefecture, were surveyed on four occasions in 1998 and 1999. Water quality (pH, DO, BOD) and WT were recorded seasonally at each of eight stations, and crayfish and other aquatic macro-organisms were collected. Some predatory fishes (Oncorhynchus mykiss, Anguilla japonica, and Lepomis macrochirus) that might actively eat juveniles of P. leniusculus were recorded. Individual density of P. leniusculus was relatively low compared to its other habitats in Japan. Only 52 crayfish were collected during this study, on 19 of 32 sampling occasions (eight sites, four times each). The shape of the acumen and the species composition of ectosymbiotic crayfish worms (Annelida: Clitellata: Branchiobdellidae) can be used as tools to trace the origin of introduced of P. leniusculus in Japan. The present crayfish from Nagano Prefecture have a relatively short acumen, different from those of specimens from Shiga and Hokkaido Prefectures. Furthermore, the crayfish worm Xironogiton victoriensis occurs only on crayfish from Akashina, Nagano Prefecture. The dates of introduction of P. leniusculus in Nagano (1926, 1929) also differ from those for Hokkaido (1930) and Shiga Prefecture (1926). These findings suggest that the regional population of P. leniusculus in Nagano has a different origin than those in Shiga and Hokkaido, having originated from crayfish that were introduced independently from North America.
著者
松尾 匡敏 首藤 宏幸 東 幹夫 近藤 寛 玉置 昭夫
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.62, pp.17-33, 2007-07-25 (Released:2010-02-05)
参考文献数
88
被引用文献数
1 or 0

In April, 1997, construction of a dike in the inner part of Ariake Sound to close off the innermost area of Isahaya Bay was completed. In June of both 1991 and 2002, benthic surveys were conducted using a Smith-McIntyre grab sampler at 88 stations over the entire sublittoral area of Ariake Sound. The structure of the gammaridean amphipod assemblage was compared between 1997 and 2002 with regard to any change in grain-size composition of the substrates and dissolved oxygen concentration of the bottom waters. No noticeable changes were observed in the distribution of the median particle diameter and silt-clay content, nor in the spatial arrangement of the sediment types of the substrates. Hypoxic water masses were observed in the bottom waters in 1997 in and around Isahaya Bay and in the southern part of Ariake Sound. Other studies also recorded hypoxic water masses in the former area in 1999 and 2001. For the amphipod assemblage, a total of 12, 434 individuals of 94 species belonging to 24 families was collected in 1997; the most dominant species was Photis longicaudata (family Isaeidae). In 2002, those values had changed to 37, 649 individuals, 89 species, and 27 families, with the most dominant species being Corophium sp. A (family Corophiidae). In both years, the amphipod assemblage was dominated by six families, including Isaeidae, Ampeliscidae, Corophiidae, Priscomilitaridae, Melitidae, and Aoridae, although the dominance order changed partially. The amphipod assemblage in both years inclusive was divided into eight groups using group-averaged clustering and non-metric multidimensional scaling. The group with the highest number of stations occupied the largest bottom area, composed of poorly-sorted medium to coarse sand along the longitudinal axis of Ariake Sound; the number of stations in this group increased from 41 in 1997 to 57 in 2002. Increase in individual density and expansion of distribution range of seven species of the superfamily Corophioidea (Corophiidae, Isaeidae, Priscomilitaridae), which occurred around the two hypoxic areas, contributed most to the range extension. For the above-mentioned six most dominant families, density of individuals and proportional composition of number of individuals in each of the two hypoxic areas and other, non-hypoxic areas were compared between the two years. In particular, both values remarkably increased for several members of the Corophiidae, including Corophium sp. A and C. crassicorne, in 2002; the exception was the value for density of individuals in the southern hypoxic area. The Shannon-Wiener species diversity index values were lower in 2002 for both the two hypoxic areas and the combined non-hypoxic areas, and for the three main groups of the amphipod assemblage.
著者
内田 紘臣
出版者
日本ベントス学会
雑誌
日本ベントス研究会連絡誌 (ISSN:1883888X)
巻号頁・発行日
vol.1983, no.24, pp.1-23, 1983-03-31 (Released:2010-02-05)
参考文献数
39
被引用文献数
1 or 0

Many species of polynoids have been famous for the "conrnensal" habit among Polychaeta. The author can count 274 species of cornmensal (or may be commensal) Polychaeta in 34 different families in literature, and 40% of them in polynoids. They are classified into three ranks. Rank A is for the Polychaetes almost always foufhd in commensal condition with hosts. Rank B is for the species not only frequently found in commensal but also in free living condition. Rank C is for the species almost free living, bur sometimes in commensal. The polychactes of strong tendency toward commensal life (A+B=t) are 154 species, and the species of the family Poiynoidae are half of them (72 species).Many groups of marine organisms are well known as involving of many commensal or parasitic species. But almost all the groups are classified as the differentiated or modified situation rather than the primitive one in each higher taxa. Polynoidae is said to one of the most primitive families in Polychaeta, and it is the largest family in Polychaeta. This is he most peculiar point of Polynoidae comparing with other commensal groups. But commensal condition of Polynoe dae is rather similar to that of the shrimps of the family Alpheidae.The setal modifications for comtneusal life in polynoids may be three characters. 1) Basal cusp in neurosetae, 2) Hook-shaped neurosetae to anterior parapodia, 3) short, stout neurosetae with reduced teeth on their free margin. Many genera known to contain commensal species, are applicable to some of three characters mentioned above, but some genera dissatisfy any of those. In opposition, two genera, weberia Horst 1915 and Paraholoepidella Pettibone 1965 never rerorded commensalism, satisfy the third character, therefore, these two genera my be commensas. Adaptive color patterns are also conspicuous in many species. Ventral lamellae aid unusual development of ventral cirri are also characteristic in some commensal species.Poiynoid comensals can be divided into two types, lodging type and clinging type. The former is for the species living in tubes or burrows of polychaetes, holothurians and other marine organisms. The latter is for the species clinging on the body surface of echinoderms, alcyonarians, etc. Polynoids of the subfamily Lepidonotinae prefer to lodging type, and that of the subfamily harmat;loinae to clinging type. Therefore, the range of host types are different between two subfamilies. The species in Lepidonotinae frequently prefer to sedentary polychaetes as theirr hosts, the other hand the species in Harmothoinae usually prefer to echinoderms and anthozoans.It seers reasonable that morphological and color adaptive changes for commensal life are necessary for the clingings rather than the lodgings. Therefore, Hamothoinae has more adaptive modifications in setal morphology or ventral structures than Lepidonotinae.Furthermore, the former has more genera consisted of only commensal species than the latter.
著者
中田 和義 永野 優季 大橋 慎平 河合 俊郎 大高 明史
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.69, no.2, pp.90-94, 2014-12-31 (Released:2016-02-06)
参考文献数
24

In Lake Akan, Hokkaido, northern Japan, the local population of the native and endangered Japanese crayfish Cambaroides japonicus (De Haan, 1841) is extinct, whereas the signal crayfish Pacifastacus leniusculus (Dana, 1852), an invasive species from North America, has become established and rapidly increased. This study provides information about specimens of C. japonicus preserved by Dr. Saburo Hatta from the lake in 1872. The six specimens (two males and four non-ovigerous females) are valuable evidence of C. japonicus formerly inhabiting Lake Akan. The body sizes of the specimens were 24.4–29.5 mm in carapace length and 55.7–67.4 mm in total length, and the estimated age of the largest specimen was ten years, indicating that Lake Akan of that time provided a suitable habitat. Twenty-two ectosymbiotic crayfish worms (Annelida, Clitellata, Branchiobdellida) were found attached to the specimens. Three branchiobdellidan species were identified: Cirrodrilus cirratus Pierantoni, 1905, C. inukaii (Yamaguchi, 1934) and C. megalodentatus (Yamaguchi, 1934). This is the first record of the latter two species from Lake Akan.
著者
益子 計夫
出版者
日本ベントス学会
雑誌
日本ベントス研究会誌 (ISSN:18838898)
巻号頁・発行日
vol.1990, no.38, pp.1-6, 1990-03-31 (Released:2009-08-07)
参考文献数
13

In the prawn Palaemon (Palaemon) paucidens DE HAAN which is widely distributed in inland fresh waters in Japan, affinity with environmental fresh and saline water was investigated for zoeal larvae. The larval survivorship was much better in diluted sea water (20∼60 % or 80 % concentrations of ordinary artificial sea water) than in fresh water under both conditions of starvation and feeding. Oxygen-consumption rate of newly hatched larvae (first-stage zoeae) was considerably greater in fresh water than in diluted or not diluted sea water, which is regarded to reflect the increment of energy cost for osmoregulation in freshwater medium. The cause of declined survivorship of P. paucidens larvae in fresh water was discussed in connection with their energy consumption and other physiological factors. Judging from larval physiological affinity with saline water, it is very likely that the infered evolutionary change of habitats from saline to fresh waters in this species has been accomplished without acquiring complete adaptation to external freshwater medium.
著者
岡本 直子 逸見 泰久
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.57, pp.75-78, 2002-06-27 (Released:2009-08-07)
参考文献数
8
被引用文献数
1 or 0

The reproductive strategy of the parasitic isopod Onisocryptus ovalis in the luminescent ostracod Vargula hilgendorfii was studied at a beach in Kumamoto Prefecture, Japan, and in the laboratory, mainly from April 2000 to May 2001. Onisocryptus ovalis is a protandrous hermaphroditic species and changes from a mobile male to an immobile female that loses most of its appendages and has a sack-like body. Male parasites O. ovalis invade female hosts V. hilgendorfii, eat the host eggs, change sex, produce eggs, and die after the eggs have hatched. Some parasites invade immature or male hosts, but move to female hosts immediately afterwards. The percentage of hosts parasitized by O. ovalis was low (0-18%) from summer to autumn, but increased greatly (28-91%) from winter to spring mainly because of a shortage of hosts. Usually, one or two male parasites were found in a host, and only one male of them changed sex. From winter to spring, however, up to 8 male parasites were found in a host and a maximum of five changed sex. The most adaptive parasitic strategy of O. ovalis seems to fertilize eggs as a male as many times as possible, and then to produce more eggs as the only female in a host, although these parameters are not available at present.
著者
大隅 大 弥益 輝文
出版者
日本ベントス学会
雑誌
日本ベントス学会誌 (ISSN:1345112X)
巻号頁・発行日
vol.55, pp.9-14, 2000-07-25 (Released:2009-08-07)
参考文献数
3
被引用文献数
1 or 0

Specimens of the nudibranch Gymnodoris nigricolor were found on the fins of three gobiid fish species, Amblyeleotris ogasawarensis, Ctenogobiops pomastictus, and C, feroculus, near Oujima and Sesoko Islands, Okinawa, in February and May, 1994. These gobiids inhabit the burrows of snapping shrimps. The nudibranchs could be found attached to any fin (caudal, dorsal, pectoral, anal, and pelvic fins) of these fish, and they appeared to feed on a portion of the fin membrane together with one or two of the adjacent fin rays. In the laboratory, G. nigricolor also attached to a free-living gobiid fish, Bathygobius cocosensis. Nudibranchs gathered in glass tubes that had been used as refuges by A. ogasawarensis and C. pomastictus. This suggests that the nudibranchs were attracted to substances that had originated from the fish and remained in the tubes. The nudibranchs did not always attach to the fins of test fish, and individuals that did so detached themselves 1-2 days later. Their association with the fish thus appears to be a predator-prey interaction. Spawning of Gymnodoris nigricolor was observed in a rearing tank. About 200-700 eggs of 0.15 mm in diameter were found in each egg mass. Embryos hatched 10-11 days after oviposition at 24°C.