Coenobita purpureus(EN)

Image©tonycoenobita

Common name

Purple Land Hermit Crab, Okinawan or Ryūkyūan Blueberry.

Size

Shield length can reach 24mm.

Distribution

Originally, it is a native species in Japan(Oita Prefecture, Miyazaki Prefecture, Kagoshima Prefecture, Okinawa Prefecture, Ryukyu Islands, Ogasawara Islands etc). Recently they are also found in Taiwan.

Habitat 

Live near forests or sandy beach, hiding under grass or rocks during daytime.

Larval stages

Four to Five zoeal stages.

Characteristics

Adult
Body colour from light blue to dark purple. Most of them are purple blue, purple, but body colour of some individuals is white. 

Shield strongly swollen just behind front, dorsal surface with granules on anterior, posterior and lateral portions.

Eyestalks
Eyestalks are compressed in shape. Eyestalks are white or light yellow with a yellow brown ring around the eye. 

Generally juvenile do not have black band on the lower surfaces of the eyestalks, but some adult has light brown band on this portion.

Antenna
Antennal acicles are fused with the second segment of peduncle. Flagellum of antennule (1st antennal) are red.

The bottom part of antenna are white.

Cheliped
Left cheliped is bigger than right cheliped. There is series of 4-5 ridges (////) on upper outer surface of palm of left cheliped.

Upper margins of both cheliped with brush of setae.

Yellow brown to red purple marks near dactylus and fixed finger of left cheliped.

Walking legs
Outer surface of propodus of left 3rd walking leg not flat, slightly swollen in midline.

Yellow brown marks on joints of walking legs, longitudinal yellow brown streak on surface of walking legs on some individuals.

Outer surface of propodus of left 3rd walking leg separated from dorsal surface by a well-marked longitudinal crest(B).

Abdomen
The abdomen is short.

Male coxae of 5th legs
Coxae of 5th legs of both sides produced ventrally, unequal and right coxa produced into an elongate tube, usually longer then left one, its tube turning to the left and curved ventrally.

Juvenile
Body colour is cream or light yellow, others are similar to adult.

Remark

1. It is quite difficult to identify the species of Coenobita purpureus and Coenobita rugosus for some small individuals or white colour adult individuals, but for most individuals it was possible to determine by means of the existence of a black band on the lower surfaces of the eyestalks, outer surface of propodus of 3rd walking leg and male coxae of 5th legs.

2. Coenobita lila was treated as Coenobita purpureus before.

Gallery

Reference links

  • coenobita.e-monsite.com
  • coenobitaspecies.com
  • 台灣生物多樣性資訊入口網
  • 東京都環境局

Reference articles

  • Chia-Hsuan Hsu & Keryea Soong., 2017. Has the Land Hermit Crab Coenobita purpureus settled in Taiwan ?
  • Chia-Hsuan Hsu., Yi-Bei Liang., Jheng-Jhang Li., Chi-Chang Liu., 2019. Ecological information of land hermit crabs (Crustacea: Decapoda: Anomura: Coenobitidae) and new record in Dongsha Atoll National Park, Taiwan
  • Hung-Li Yuan, 2008. Morphological and Molecular Evidence for a Stepwise Terrestrial Evolution and Species Delimitation on the Coenobita Phylogeny
  • McLaughlin P. A., Komai T., Lemaitre R., Rahayu D. L., 2010. Annotated checklist of anomuran decapod crustaceans of the world (exclusive of the Kiwaoidea and families Chirostylidae and Galatheidae of the Galatheoidea) Part I. Lithodoidea, Lomisoidea and Paguroidea
  • Nakasone Y., 1988. Land hermit crabs from the Ryukyus, Japan, with a Description of a New Species from the Philippines (Crustacea, Decapoda, Coenobitidae)
  • Nakasone Y., 1988. Larval Stages of Coenobita purpureus Stimpson and C. cavipes Stimpson Reared in the Laboratory and Survival Rates and Growth Factors of Three Land Hermit Crab Larvae (Crustacea: Anomura): Taxonomy
  • Nakasone Y., 2001. Reproductive Biology of Three Land Hennit Crabs (Decapoda: Anomura: Coenobitidae) in Okinawa, Japan
  • 有馬啓人, 2014. ヤドカリ (ネイチャーウォッチングガイドブック), 誠文堂新光
  • 朝倉彰, 2004. ヤドカリ類の分類学,最近の話題 - オカヤドカリ科 (Asakura A., 2004. Recent topics on taxonomy of hermit crabs from Japanese waters – family Coenobitidae
  • 岩本敏, 2003. 週刊 日本の天然記念物 動物編 オカヤドカリ 42, 小学館
  • 三浦知之, 2011. 宮崎県におけるオカヤドカリ類の生息状況 (Miura T., 2011. Land hermit crabs recorded from Miyazaki Prefecture, Japan)
  • 仲宗根幸男, 1987. 「あまん」オカヤドカリ生息実態調査報告, 沖縄教育委員
  • 大澤正幸, 藤田喜久, 2016. 宮古諸島伊良部島・下地島から得られた口脚目および十脚目 (アナエビ下目, アナジャコ下目, 異尾下目) 甲殻類 (Osawa M., Fujita Y., 2016. Stomatopods and decapods of Axiidea, Gebiidea and Anomura (Crustacea: Malacostraca) from Irabu-jima and Shimojijima Islands, Miyako Group, southern Ryukyus, Japan)
  • 豊田幸詞, 関慎太郎, 2014. 日本の淡水性エビ.カニ: 日本産淡水性・汽水性甲殻類102種(ネイチャーウォッチングガイドブック), 誠文堂新光社

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