Abstract: The bopyrid isopod Athelges takanoshimensis Ishii, 1914 was originally described in 1914 using specimens from Japan and has since been reported from Far Eastern Russia, Korea, China, Taiwan, Philippines, Singapore, Indonesia, and Papua New Guinea. Japan is located at the northernmost limit of the distribution of the species. This review lists all known host species from these countries and shows all collection localities on maps of Japan and East Asia. Two families of hermit crabs, Paguridae and Diogenidae, serve as hosts for A. takanoshimensis. In subarctic and temperate waters, pagurids are major hosts, but their importance decreases in subtropical waters. Diogenids are infested in subtropical and tropical waters, but the known hosts from the latter waters are only diogenids. Infested hosts are usually found in the intertidal zone but there is a record of the species collected as deep as 508–680 m. Prevalence of infestation is usually less than 10% and differs between host species. The previous work of A. takanoshimensis focused largely on its taxonomy, and we need further research to understand various aspects of the biology (e.g., host utilization, seasonal and annual change in occurrence, growth and reproduction, impact on a host) of the species.
The cheliped waving frequency (number of waves per min) of individual male Ilyoplax pusilla (Brachyura, Dotillidae) during the reproductive season was investigated in terms of body size, temperature and season at two sites where the density at one site was ca. 3 times higher than that at the other site. The waving frequency in the high-density site was ca. 1.5 times higher than in the low-density site. The males waved more intensely in the middle reproductive season, but the seasonal change in the waving frequency was not strongly related with the air temperature. There was also no clear association between the body size and the waving frequency, which is contrast with the positive association so far known for several ocypodoid species including I. pusilla. Among body size, site (high or low density), temperature and research period, site (i.e. the population density) was the most important factor to predict the waving frequency.
Tachaea chinensis (Isopoda: Corallanidae) is an ectoparasitic isopod that is sporadically reported from East Asia. Freshwater prawns and shrimps are characteristic hosts. Two specimens of unidentified crustacean collected at Lake Kasumigaura in 1915 were identified as T. chinensis. The specimens were originally kept at the Center for Ecological Research, Kyoto University and are now maintained at the Kyoto University Museum. To the best of my knowledge, these two specimens represent the oldest example of T. chinensis in Japan. The specimens are assumed to have been collected by N. Annandale. Other specimens collected at the same time were entrusted to W.M. Tattersall and reported in 1921. The specimens, collected over 100 years ago, are important in understanding biodiversity and environmental changes.
Five brachyuran species, Ebaliopsis erosa (A. Milne-Edwards, 1873), Aulacolambrus hoplonotus (Adams & White, 1849), Certolambrus pugilator (A. Milne-Edwards, 1873), Thalamita bouvieri Nobili, 1906, and Paramedaeus octogesimus Ng & Clark, 2002, were reported on the basis of specimens obtained from Chichijima Island, Ogasawara Islands, south Japan. This report includes the first specimen-based record of Paramedaeus octogesimus in Japanese waters.
Six specimens of Thamneus rostratus Bovallius, 1887 (Amphipoda: Hyperiidea) including a shining with iridescent glitter mature female attaching under surface of the umbrella of a warm water medusa, Pelagia noctiluca (Forsskål, 1775) (Cnidaria: Scyphozoa) were found from a shore coast in Jogashima, southern end of the Miura peninsula, Pacific coast of central Japan. The morphological features of the present specimens were in close agreement with the descriptions of Thamneus rostratus (or as Euthamneus rostratus) in previous literatures. This hyperiid have widely distributed, known from records in tropical and temperate regions of the world’s oceans, but it is relatively uncommon. This finding represents the first record of T. rostratus from Japanese water.
The varunid crab Cyclograpsus pumilio Hangai and Fukui, 2009 is mainly distributed in central-western Honshu, Shikoku and northern Kyushu in Japan. Three males and 9 females of C. pumilio were collected from the Boso Peninsula of Chiba Prefecture in eastern Honshu and the Satsuma Peninsula of Kagoshima Prefecture in southern Kyushu, Japan. In the both sites, C. pumilio were found under gravels deposited in the upper intertidal zone. This is the first record of C. pumilio from the both prefectures, representing its easternmost and southernmost records.
The ectoparasitic isopod Holophryxus fusiformis Shiino, 1937 was found attached to the dorsal part of a male shrimp Sergia laminata (Burkenroad, 1940) carapace in Suruga Bay of Japan. We report that S. laminata is a new host decapod for this rare parasite. Observation of a live specimen indicated that H. fusiformis was similar in color to that of the host shrimp, which may be a form of camouflage from predators in the bathypelagic layer. Females of this parasitic isopod have been recorded from three species of pelagic shrimps viz., S. laminata, Lucensosergia lucens (Hansen, 1922) and Prehensilosergia prehensilis (Spence Bate, 1881) and are newly revealed to change the body colors depending on those of the hosts.
Pseudohelice subquadrata (Dana, 1851) known to be widely distributed in the tropical Indo-West Pacific, is rarely recorded from central Japan. One specimen was collected from Ogamogawa River on southeast area of Izu Peninsula, central Japan, October 2019. The specimen was adult male, represent the third northmost record for the species from around Sagami Bay and its first record from Izu Peninsula, Shizuoka Prefecture.
Females of the lernaeopodid copepod Tracheliastes sachalinensis Markevich, 1936 were collected from the fins of big-scaled redfin, Pseudaspius hakonensis (Günther, 1877) (Cypriniformes: Leuciscidae) in a stream at the Nagano Prefectural Fisheries Experimental Station, Azumino, Nagano Prefecture, central Japan. In this country, the copepod was previously reported only from Hokkaido, and the present collection represents the first record of T. sachalinensis from Honshu, the main island of Japan. The females of the species are briefly described. Prevalence was 24.0% in 50 fish examined and the number of copepods per infected host ranged from 1–3 (mean intensity, 1.3). The anal fin was most frequently infected.
A mantis shrimp species of the family Nannosquillidae, Pullosquilla pardus (Moosa, 1991), is reported from the Ogasawara and Ryukyu Islands. This report represents the first record of P. pardus from the Japanese waters. The record from Anijima, Ogasawara Islands, expands the distributional range of the species to the north.