研究者詳細 - 土井　航

論文 - 土井　航

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Jinno M., Doi W., Mizutani A., Kohno H. . Population dynamics and growth of the soldier crab Mictyris guinotae: comparison between the river mouth and upper reach habitats . Journal of Natural History60 ( 21-24 ) 1197 - 1209 2026年5月査読

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Natural History

We compared population dynamics and growth of soldier crab Mictyris guinotae in the Urauchi River (Ryukyu Islands) using monthly or bimonthly sampling at two sites located 300 m (river mouth) and 3000 m (upper reach) upstream from the mouth over 18 months. Abundance and growth differed between the downstream core habitat and the upstream peripheral habitat. Megalopae and early juveniles were more abundant at the river mouth, whereas individuals at the upper reach grew faster and attained larger maximum body size. However, mean size-at-age estimates at the upper reach were limited to approximately 2.10–2.26 years, whereas corresponding estimates at the river mouth extended to 2.91–3.09 years. Therefore, differences in longevity between sites could not be evaluated using the present dataset. Von Bertalanffy growth models quantified site differences, with higher growth coefficients at the upper reach for both sexes. Males attained larger sizes than females at both sites. Between-site temperature differences were minimal, suggesting that other factors (e.g. population density, food availability, or salinity gradients) may contribute to the observed growth patterns. Maximum carapace length at the upper reach exceeded all previously reported values for this species across its geographic range. These results demonstrate pronounced intraspecific variation in life-history traits along a downstream–upstream estuarine gradient within a single river. Although this observational study does not test mechanisms, it generates hypotheses about potential drivers and highlights the importance of sampling both downstream and upstream sites when evaluating estuarine benthic populations.

DOI： 10.1080/00222933.2026.2658196

Scopus

水野有朝・土井航 . 鹿児島県黒島におけるヤマトヌマエビとコツノテナガエビ（十脚目：コエビ下目）の記録 . Nature of Kagoshima52 227 - 229 2026年3月

Doi W., Vazquez-Archdale M. . Life history of the Japan-endemic crab, Pseudopinnixa carinata (Ortmann, 1894) (Decapoda: Brachyura: Varunidae) . Journal of Crustacean Biology46 ( 1 ) 2026年3月査読国際誌

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Crustacean Biology

Pseudopinnixa carinata (Ortmann, 1894) (Decapoda) is a small-size brachyuran endemic to Japan and placed within, or near, Varunidae. It inhabits primarily sandy intertidal flats in sheltered inner bays. We aimed to elucidate the life history and habitat use of this species on a tidal flat at Nishio City, Aichi Prefecture, central Japan. Burrowing individuals were collected monthly from sediment cores (10 cm diameter × 25 cm high) extracted from the sand flat between January and December 2016. The presence of burrows and biological traces did not significantly affect the number of individuals collected and the possibility of the sediment sample containing crabs. This species lives freely, excavating only shallowly into the sand rather than constructing its own burrows. Differences in monthly frequencies between the upper and lower intertidal zones showed that the species appears to vacate the upper intertidal zone in summer and shift its distributional core into the subtidal zone. Recruits with a carapace width (CW) of less than 3 mm were collected during April and May, resulting in a bimodal CW frequency distribution. Ovigerous females were observed only in October and November, and in each of these months their CWs fell within the largest size classes among females collected concurrently.

DOI： 10.1093/jcbiol/ruag006

Scopus

岩崎敬二, 逸見泰久, 木村妙子, 佐藤慎一, 中山聖子, 風呂田利夫, 阿部博和, 大谷道夫, 柏尾翔, 加戸隆介, 小玉将史, 斉藤英俊, 土井航, 西川輝昭, 平野弥生, 山口寿之, 良永知義 . 日本の海産外来種：2002–2003年と2022–2023年のアンケートの結果から . 日本ベントス学会誌80 ( 1 ) 62 - 136 2025年12月査読

Md Alomgir HOSSEEN, Wataru DOI, Kazuhiro SHIOZAKIand Jun OHTOMI . Recruitment, growth pattern and longevity of jack-knife shrimp Haliporoides sibogae (Solenoceridae) in Kagoshima Bay, southern Japan . Aquaculture Science73 ( 1 ) 15 - 28 2025年4月査読

土井航 . 種子島におけるアシハラガニとコメツキガニの記録 . Nature of Kagoshima51 281 - 285 2025年3月

Kobayashi G., Doi W., Yamamoto T. . Genetic homogeneity in soldier crab Mictyris guinotae populations across their geographic distribution in the Ryukyu Islands, Japan . Marine Biology Research21 ( 1 ) 38 - 46 2025年査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Marine Biology Research

The Japanese Archipelago comprises a chain of islands; therefore, gaps between islands can represent potential dispersal barriers for coastal species, especially those inhabiting tidal flats. This study investigates the population genetic structure of the soldier crab Mictyris guinotae (Brachyura: Thoracotremata: Mictyridae) using mitochondrial COI gene sequences. Specimens were collected from Tanegashima Island and five Ryukyu Islands, covering the species’ known geographic distribution. Although the Mantel test identified a moderate trend (r2 = 0.41, P < 0.01) for isolation by distance, all populations exhibited high haplotype and nucleotide diversities, with neither analysis of molecular variance nor ΦST detecting genetic differences among populations. Notably, the northernmost population (Tanegashima Island), approximately 260 km from the nearest known geographic distribution on Amami-Oshima Island, shared haplotypes with other populations, although the number of specimens from Tanegashima Island is only four due to its small population size. This absence of genetic differences among populations of M. guinotae differs from other intertidal organisms in the region examined in previous studies. Mismatch distributions suggest contrasting demographic history in M. guinotae and the sand bubbler crab Scopimera ryukyuensis, which has been revealed to show population genetic structuring despite its similar geographic distribution to M. guinotae. The present study provides another case of genetic diversity among intertidal organisms in the Ryukyu Islands.

DOI： 10.1080/17451000.2024.2423169

Scopus

Hosseen M.A., Doi W., Shiozaki K., Ohtomi J. . Recruitment, growth pattern and longevity of jack‑knife shrimp Haliporoides sibogae (Solenoceridae) in Kagoshima Bay, southern Japan . Aquaculture Science73 ( 1 ) 15 - 28 2025年

記述言語：日本語出版者・発行元：Aquaculture Science

Haliporoides sibogae is widely distributed on the continental shelves and slopes of the western Pacific Ocean. Recruitment, growth patterns, and longevity were examined in Kagoshima Bay, a semi-enclosed deep-water bay in southern Japan, using a time series of length-frequency distributions from January 1995 to December 2022. Carapace length ranged from 8.6 to 29.5 mm in males and 7.7 to 33.6 mm in females. Regular recruitment occurred during April and June, with modal sizes of approximately 11 mm carapace length for both sexes. In addition, irregular recruitment occurred between December and February in some years. Genetic variability analysis revealed that both recruitment types originated from the same population. Growth patterns were expressed using Pauly and Gaschütz’s growth function for both sexes. The growth rates were lower between December and January, coinciding with the spawning season of this species. Growth functions showed that females had a significantly higher asymptotic length and lower growth rate than males. The longevity was estimated to be around 2 years for both sexes.

DOI： 10.11233/aquaculturesci.73.15

Scopus

Jinno M., Doi W., Mizutani A., Kohno H. . Intraspecific Variation in Reproductive Aspects of Female Soldier Crabs, Mictyris guinotae, Between the River Mouth and Upper Reach Habitats . Marine Ecology 2024年12月査読

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Marine Ecology

The soldier crab, Mictyris guinotae, is a dominant intertidal crustacean associated with sand flats in the vicinity of the Urauchi River estuary on Iriomote Island, Japan. We compared various aspects of its reproductive biology at two sites (the river mouth and upper reach) on exposed bare sand flats 300 m and 3000 m upstream from the mouth. Bimonthly sampling was conducted between November 2010 and April 2011. The abundance of female crabs was higher at the mouth of the river. Female individuals had significantly larger body sizes (approximately 1.5 times larger carapace length) in the upper reaches. Despite the low presence of ovigerous females in the upper reach site, their larger body size led to the release of a substantial number of larvae per individual, although fewer larvae were produced per day than by females at the river mouth. The breeding period, as inferred from the occurrence of ovigerous females, persisted from December to March. At the upper reach site, the duration was slightly shorter, with an earlier peak. Variations in larval release timing may compensate for fluctuations in recruitment success.

DOI： 10.1111/maec.12850

Scopus

Hossen M.A., Doi W., Ohtomi J. . Ovarian maturation, size at sexual maturity, and spawning season of jack-knife shrimp Haliporoides sibogae (Decapoda: Solenoceridae) in Kagoshima Bay, southern Japan . Fisheries Science90 ( 5 ) 733 - 743 2024年6月査読

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Fisheries Science

Jack-knife shrimp Haliporoides sibogae is a target species for boat seine fishery in the waters off south-western Kyushu, Japan. Reproduction, including ovarian maturation, size at sexual maturity, and spawning season of this species were studied using females collected from Kagoshima Bay, southern Japan. The present study also explored an alternative maturity index by conducting a microscopic examination of oocytes. Histological analysis of the ovaries validated six oocyte developmental stages. Ovarian development was asynchronous, indicating multiple spawning throughout a reproductive season. On the basis of the developmental stage of the most advanced oocytes, ovarian maturity was categorized into three stages: immature, maturing and mature. Females containing oocytes exhibiting cortical crypts were defined as mature. The gonadosomatic index (GSI) significantly increased as ovarian maturation progressed, and all females with a GSI of ≥ 6% were determined to be mature. The minimum size at sexual maturity was estimated to be 24.0 mm in carapace length. The spawning season extended from November to May, with February being the peak. Moreover, microscopically, the oocytes with spherical bodies on the periphery all had cortical crypts. Therefore, observation of oocytes using a microscope was considered an effective method to easily identify mature females.

DOI： 10.1007/s12562-024-01798-7

Scopus

その他リンク： https://link.springer.com/article/10.1007/s12562-024-01798-7/fulltext.html

Doi W., Nohara K., Inoue H., Kohno H. . Genetic structure and diversity of the island-endemic freshwater prawn Macrobrachium shokitai Fujino & Baba, 1973 (Decapoda: Caridea: Palaemonidae) on Iriomote Island, Ryukyu Archipelago, southern Japan . Journal of Crustacean Biology44 ( 2 ) 2024年6月査読

担当区分：筆頭著者,　責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of Crustacean Biology

Iriomote Island is a small continental island hosting approximately 40 rivers characterized by short, steep-gradient streams and small waterfalls. WeexaminedthepopulationgeneticstructureanddiversityofthefreshwaterprawnMacrobrachiumshokitaiFujino&Baba,1973(Palaemonidae) using the mitochondrial cytochrome c oxidase subunit I (COI) gene sequence. Specimens were collected from 19 sites along ten rivers on the island, covering the known geographic distribution of the species. Haplotype and nucleotide diversities were very low within each river on the island. Nearly all haplotypes were exclusive to a given river, confirming distinct population structures among rivers at a small geographical scale. Slight genetic differentiation was discerned between the upper and lower sites of waterfalls in only the Yuchin River. Phylogenetic tree reconstruction, haplotype network, and principle coordinate analysis classified five clades roughly correspond to geographical groups in the western, southern, central, and northern regions of the island. Extreme caution should therefore be taken when translocating individuals to other rivers to avoid introducing genetic disturbance, even during conservation and mitigation efforts.

DOI： 10.1093/jcbiol/ruae031

Scopus

Nawer F., Doi W., Ohtomi J. . Recruitment and growth patterns of the portunid crab Charybdis bimaculata in Kagoshima Bay, southern Japan . Fisheries Science89 ( 2 ) 223 - 232 2023年査読

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Fisheries Science

We studied the recruitment and growth patterns of the portunid crab Charybdis bimaculata in deep water for the first time. The study area, Kagoshima Bay, is a semi-enclosed, deep-water bay characterized by steep slopes, with unique caldera walls where C. bimaculata is one of the dominant decapods and acquiring commercial importance. The monthly length-frequency method was used from a total of 8265 individuals collected over a three study periods—1990s, 2010s, and 2020s—at the central basin (174–229 m depth) and one study period 1990s at the channel area (122–136 m depth). Carapace width ranged from 9.5 to 42.7 mm in males, and 9.5 to 35.0 mm in females. The overall sex ratio significantly deviated from 1:1 favoring females. Recruitment was estimated to occur between September to November in this bay. Recruitment seemed to be synchronized with the peak spawning season with a time lag of 2–4 months. Growth was appositely delineated by the von Bertalanffy growth function for both sexes. The growth equations revealed that males had lower K values and higher asymptotic sizes than females. Spatial and temporal comparison in growth parameters between the same sexes found no statistical differences except in one case.

DOI： 10.1007/s12562-022-01661-7

Scopus

その他リンク： https://link.springer.com/article/10.1007/s12562-022-01661-7/fulltext.html

Size at sexual maturity of male Lucensosergia lucens (Decapoda: Sergestidae) in Suruga Bay, Japan . Crustacean Research51 ( 0 ) 1 - 10 2022年12月査読

Mating and burrow plugging behavior of Cardisoma carnifex on the Iriomote-jima Island in Japan . Crustacean Research51 ( 0 ) 137 - 145 2022年12月査読

土井航, 鈴木伸洋 . 駿河湾におけるハマスナホリガニHippa truncatifronsの成長と繁殖 . 水生動物2022 ( 0 ) AA2022-11 - 11 2022年6月査読

Doi W., Inoue H., Kohno H. . Aspects of distribution, growth, and reproduction of the fluvial prawn, Macrobrachium shokitai, in a subtropical river on Iriomote Island, Japan . Plankton and Benthos Research17 ( 2 ) 192 - 200 2022年5月査読

担当区分：筆頭著者,　責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：日本プランクトン学会、日本ベントス学会

This study investigates the distribution, growth, and reproduction of the fluvial, regional, and vulnerable species, Macrobrachium shokitai, on Iriomote Island in southwestern Japan. Prawns were captured at seven stations along a small, 4.0-km-long river, among ca. 40 rivers on the island. Animals were collected monthly during 2019 and abundance, carapace length (CL), sex, and the presence or absence of eggs attached to pleopods were documented. Prawns were primarily collected at stations >2.7 km above the river mouth at >270 m elevation. Stable, dense populations were observed above the waterfall. The sex ratio was significantly female-biased between January and August. Later in the year the ratio was 1: 1. A bimodal CL distribution was recorded; with the emergence of larger individuals in some months. Lifespan appeared to be >1 year. Recruits, including several juvenile instars, were found between August and December. Ovigerous females were encountered from April to October but were more abundant from June to August. The phenology and duration of the breeding season were consistent with generic characteristics of the genus throughout subtropical and temperate East Asia.

DOI： 10.3800/pbr.17.192

Scopus

CiNii Research

橋本慎太郎, 新海龍ノ介, 土井航 . 鹿児島県本土と屋久島におけるスナガニ属（短尾下目：スナガニ科）の分布 . Nature of Kagoshima49 31 - 34 2022年5月

Nawer F., Doi W., Ohtomi J. . Oocyte and embryonic development, size at sexual maturity, and spawning season of Charybdis bimaculata . Fisheries Science88 ( 4 ) 449 - 459 2022年5月査読

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Fisheries Science

This study describes the first thorough investigation of oocyte and embryonic development as well as histologically confirmed size at sexual maturity of female Charybdis bimaculata. A total of 1211 females were collected from the central part of Kagoshima Bay, southern Japan, from October 2018 to January 2020. Six sequential oocyte developmental stages were confirmed by histological examination. C. bimaculata exhibited asynchronous-type ovarian development. Therefore, ovarian maturity status (immature, maturing, and mature) was determined from the most advanced oocyte found in the ovary. Females having oocytes evidencing either germinal vesicle breakdown or migratory nucleus were defined as mature. Mature females ranged from 19.0 to 30.6 mm in carapace width. The size at sexual maturity was estimated to be 21.8 mm in carapace width based on the 50% maturity size. The spawning season was determined from May to November when mature females occurred. Microscopic observation confirmed four sequential embryonic developmental stages. The majority of females with final-stage embryos had mature ovaries signifying continuity of reproduction. Asynchronous-type ovary, continuous reproduction, and consecutive broods suggest multiple spawning in a single spawning season. The incubation period was estimated to be under 1 month for C. bimaculata.

DOI： 10.1007/s12562-022-01601-5

Web of Science

Scopus

土井航, 森田進, 武藤文人 . 駿河湾奥部の礫浜海岸におけるマメアカイソガニの成長と繁殖 . 日本ベントス学会誌76 ( 0 ) 31 - 38 2021年12月

Jinno M., Doi W., Mizutani A., Kohno H. . Influence of salinity on the horizontal distribution of soldier crab Mictyris guinotae in a subtropical river in Japan . Marine Biology Research17 ( 7-8 ) 707 - 722 2021年11月査読

担当区分：責任著者記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：Marine Biology Research

The horizontal distribution of Mictyris guinotae was studied in relation to gradients of salinity and sediment characteristics in sandy flats between 0 and 8.2 km from the mouth of a subtropical river. Lower salinity tolerance was also tested at seven salinity levels (0, 2, 4, 8, 12, 24 and 32) by a survival experiment for 14 days. Environmental clines were found in salinity but not in sediment characteristics. The upper limit of the occurrence of crab was 5.07 km upstream where seawater could reach during the spring flood tide. The densities of age-0 crabs tended to be higher at lower stations (0–0.65 km upstream), suggesting more recruits settle near the river mouth. Carapace length was significantly larger in the upper section (2.50–5.07 km upstream) in which salinity fluctuated or remained low (<10) for longer periods. It is unlikely that low salinity has a negative effect on post-larval growth. In contrast, body size was smaller in the lower section, possibly due to the effect of density. Some individuals died at the end of the experiment at salinity ≤12. The upper limit of appearance was explained by the salinity of riverine water and low salinity tolerance of the crab.

DOI： 10.1080/17451000.2021.2013502

Scopus

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