''Austruca perplexa'' is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

of fiddler crab. It is found from the

Ryukyu Islands The , also known as the or the , are a chain of Japanese islands that stretch southwest from Kyushu to Taiwan: the Ōsumi, Tokara, Amami, Okinawa, and Sakishima Islands (further divided into the Miyako and Yaeyama Islands), with Yona ...

, Japan to

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, throughout the

Malay Archipelago The Malay Archipelago (Indonesian/ Malay: , tgl, Kapuluang Malay) is the archipelago between mainland Indochina and Australia. It has also been called the " Malay world," " Nusantara", "East Indies", Indo-Australian Archipelago, Spices Arch ...

, along eastern Australian coasts from

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

New South Wales ) , nickname = , image_map = New South Wales in Australia.svg , map_caption = Location of New South Wales in AustraliaCoordinates: , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , es ...

, and in various

Pacific islands Collectively called the Pacific Islands, the islands in the Pacific Ocean are further categorized into three major island groups: Melanesia, Micronesia, and Polynesia. Depending on the context, the term ''Pacific Islands'' may refer to one of ...

, including Fiji,

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and

Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; bi, Ripablik blong Vanuatu), is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of no ...

. ''Austruca perplexa'' was formerly in the genus '' Uca'', but in 2016 it was placed in the genus ''

Austruca ''Austruca'' is a genus of indo-west Pacific fiddler crabs in the family Ocypodidae The Ocypodidae are a family of semiterrestrial crabs that includes the ghost crabs and fiddler crabs. They are found on tropical and temperate shorelines arou ...

'', a former subgenus of ''Uca''. As in other fiddler crabs, the male has a greatly enlarged claw, which is used for signalling. The higher the claw is waved by the male, the greater his chance of attracting a female; the size of the claw is therefore subject to

sexual selection Sexual selection is a mode of natural selection in which members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (in ...

. ''Austruca perplexa'' is usually found on sandy substrates near river mouths or on sheltered beaches in the mid-intertidal zone, usually near mangroves.

References

Ocypodoidea Crustaceans described in 1837 Taxa named by Henri Milne-Edwards {{crab-stub