Research Article |
Corresponding author: Michitaka Shimomura ( shimomura@kmnh.jp ) Academic editor: Niel Bruce
© 2015 Michitaka Shimomura, Tohru Naruse.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Shimomura M, Naruse T (2015) Two new species of Asellota (Crustacea, Isopoda) from coral reefs on Iriomote Island, Okinawa, Japan. ZooKeys 520: 27-40. https://doi.org/10.3897/zookeys.520.5943
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Pleurocope iriomotensis sp. n. and Prethura tuberculata sp. n. are described from Iriomote Island, Ryukyu Archipelago, southern Japan. These are the first records of Pleurocope from the Pacific and of Prethura from the Asian Pacific coast. Pleurocope iriomotensis differs from its congeners in having lateral spine-like processes on pereonite 4 and coxal plates of pereonite 7. Prethura tuberculata can be distinguished from its single congener in having a lateral short projection of protopod of pleopod 2.
Isopoda, Pleurocopidae, Pleurocope, Santiidae, Prethura, Japan
Iriomote Island (Fig.
The marine isopod fauna of the Ryukyus has been studied by several authors including the families Anthuridae Leach, 1814, Bopyridae Rafinesque, 1815, Cymothoidae Leach, 1818, and Gnathiidae Leach, 1814 (e.g.,
The shallow-water crustacean faunal survey of Amitori Bay, Iriomote Island in 2012 by SCUBA, yielded two species of asellote isopods of the families Pleurocopidae and Santiidae. Based on this material, two new species, Pleurocope iriomotensis sp. n. and Prethura tuberculata sp. n. are described and illustrated.
Collections of isopods were obtained by the Collaborative Research Program funded by the Ryukyu University in Iriomote Island in 2012. Pieces of coral rubble collected by hand near the coral reefs during SCUBA were washed in a bucket, and isopods were extracted by decanting the suspension through a sieve with a mesh size of 0.3 mm. All specimens obtained were fixed and preserved in 80% ethanol. Each individual was dissected and prepared for observation by a light microscope (Nikon E600). The total length as indicated in “Material examined” was measured from the tip of the head to the end of the pleotelson.
The type specimens are deposited in the Kitakyushu Museum of Natural History and Human History (KMNH).
Pleurocope Walker, 1901: 297;
Pleurocope dasyura Walker, 1901 (by original designation and monotypy).
P. dasyura Walker, 1901, Mediterranean; P. floridensis Hooker, 1985, Gulf of Mexico; P. wilsoni Kensley & Schotte, 2002, Thailand and Seychelles; P. iriomotensis sp. n., Iriomote Island, Ryukyu Islands (present study).
(modified from
The main changes in this new diagnosis are to accommodate the number of seta on maxillae.
Holotype. ♂ (0.9 mm), 24°20´N, 123°41´E, Amitori Bay, Okinawa, Japan, 19 July 2012, dead coral, 25 m, coll. TN (KMNH IvR 500,729).
Paratypes. 3♂♂ (0.5–0.9 mm), Amitori Bay, Okinawa, Japan, 19 July 2012, dead coral, 4 m, coll. MS (KMNH IvR 500,730–500,732).
Body (Fig.
Antennula (Fig.
Pleurocope iriomotensis sp. n. A–B, E–K holotype male C–D paratype male (KMNH IvR 500,732): A left antennula, dorsal B left antenna, ventral C left mandible, dorsal D right mandible, dorsal E left maxillula, ventral F left maxilla, ventral G left maxilliped, dorsal H left pereopod 1, medial; I left pereopod 2, medial J left pereopod 3, medial K left pereopod 4, medial. Scale bars: 100 μm.
Antenna (Fig.
Maxillula (Fig.
Maxilliped (Fig.
Pereopod 1 (Fig.
Pereopod 2 (Fig.
Pleurocope iriomotensis sp. n. A–G holotype male H paratype male (KMNH IvR 500,731): A left pereopod 5, medial B left pereopod 6, medial C left pereopod 7, lateral D pleopod 1, ventral E left pleopod 2, dorsal F left pleopod 2, ventral G left pleopod 3, dorsal H habitus, lateral. Scale bars: 100 μm.
Pleopod 1 (Fig.
Uropod (Fig.
Body (Fig.
Not known.
Pleurocope iriomotensis sp. n. can be identified by the following combination of characters: pereonite 1 lacking lateral spine-like processes; pereonites 2–4 and coxal plates of pereonites 5–7 each with lateral spine-like process; pleotelson twice as long longer as wide; flagellum of antenna consisting of 7 articles. Pereonite 1 without a spine-like process links the new species to Pleurocope floridensis Hooker, 1985, from the Gulf of Mexico and to P. dasyura Walker, 1901, from the Gulf of Naples, Italy. Pleurocope iriomotensis is distinguished from P. floridensis by the following characters (those of P. floridensis in parentheses): pereonite 4 and coxal plate of pereonite 7 with spine-like process (without spine-like process); eyestalks not reaching to second article of antennula (surpassing second article of antennula); fifth article of antennula with 1 aesthetasc (with 2 aesthetascs); ischium of pereopod 1 with dorsal projection (without dorsal projection); pleopod 1 apically with 3 pairs of short setae (apically with 5 pairs of short setae). Pleurocope dasyura differs from the new species in having pereonite 4 and coxal plate of pereonite 7 without spine-like processes, pereon with 6 long dorsal setae, antenna with long projection, and pleopod 1 apically with 4 pairs of short setae.
The species is named after the type locality.
1 | Lateral spine-like process on pereonite 4 and coxal plate of pereonite 7 absent | 2 |
– | Lateral spine-like process on pereonite 4 and coxal plate of pereonite 7 present | P. iriomotensis sp. n. |
2 | Lateral spine-like process on pereonite 1 absent; pleotelson twice longer than width | 3 |
– | Lateral spine-like process on pereonite 1 present; pleotelson twice as long as width | P. wilsoni |
3 | Lateral seta on pereonite 4 absent; dorsal short tooth of ischium of pereopod 1 absent | P. floridensis |
– | Lateral seta on pereonite 4 present; dorsal short tooth of ischium of pereopod 1 present | P. dasyura |
Prethura Kensley, 1982: 255; Wolff 1989: 181.
Prethura hutchingsae Kensley, 1982; by original designation and monotypy.
P. hutchingsae Kensley, 1982, Great Barrier Reef, Australia; P. tuberculata sp. n., Iriomote Island, Ryukyu Islands (present study).
(modified from Wolff 1989). Pleotelson subtriangular. Eyes well-developed, on short peduncles. Mandibular palp lacking. Coxal plates of pereonites 5 visible dorsally. Male pleopod 1 distally twisted, apically acute. Male pleopod 2 protopod enormously expanded. Uropods pedunculate, protopod enlarged, inserted ventrolaterally; medial ramus short. Female operculum pyriform.
The generic diagnosis is slightly modified from that of Wolff (1989). The significant change in this new diagnosis is to accommodate the presence of well-developed eyes on short peduncles.
Holotype. ♂ (0.9 mm), 24°20´N, 123°41´E, Amitori Bay, Okinawa, Japan, 19 July 2012, dead coral, 4 m, coll. MS (KMNH IvR 500,733).
Body (Fig.
Antennula (Fig.
Antenna (Fig.
Left mandible (Fig.
Prethura tuberculata sp. n. A–K holotype male: A left mandible, medial B right mandible, dorsal C left maxillula, dorsal D left maxilla, ventral E left maxilliped, dorsal F pleopod 1, ventral G right pleopod 2, ventral H endopod of right pleopod, dorsal I left pleopod 3, dorsal J left pleopod 4, ventral K pleotelson and uropods, ventral. Scale bar: 100 μm.
Maxillula (Fig.
Maxilliped (Fig.
Pleopod 1 (Fig.
Uropod (Figs
This new species differs from the only congener, P. hutchingsae Kensley, 1982, from the Great Barrier Reef, by the following characters (those of P. hutchingsae in parentheses): pleopod 1 lacking any setae (with setae); protopod of pleopod 2 with lateral projection (without projection); epipod of maxilliped with acute apex (blunt apex).
From the Latin “tuberculatus”, referring to the lateral projection of the protopod of pleopod 1.
This study was supported by the Collaborative Research Program funded by the Tropical Biosphere Research Center, University of the Ryukyus and the Ministry of Education, Science, Sports and Culture, Grant-in-Aid for Challenging Exploratory Research (No. 15K14596). We thank Dr J. Okuno (Coastal Branch of Natural History Museum and Institute, Chiba) and Ms. H. Noda (University of the Ryukyus) for supporting our field survey. Also, many thanks are given to Dr N. L. Bruce (Museum of Tropical Queensland, Townsville), Dr M. V. Malyutina (Institute of Marine Biology, Far Eastern Branch, Russian Academy of Sciences) and Dr J. Svavarsson (University of Iceland), for their valuable comments and suggestions on the manuscript.