Triangle crab | |
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Genus: | Eurynolambrus
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Species: | E. australis
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Binomial name | |
Eurynolambrus australis H. Milne Edwards & Lucas, 1841
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Eurynolambrus australis, commonly known as the triangle crab, and by its Māori name riangi, is a small species of crab that is widespread throughout New Zealand.[1][2]
E. australis is commonly found among stones and under rocks in the lower and sub tidal region of the intertidal zone where it can reach depths of up to 80 m.[1][3][4] It is often found in rock pools with coralline turf.[1]
Adults are between 50 – 65 mm in size with a broad triangle-shaped carapace that extends over the leg base. This can be white, pink or bright red in colour with white, grey-brown, and yellow markings.[1][3] Legs are short and flat with irregular crests. Their colour can be mottled with orange, dark red and white. They fold neatly underneath the carapace. Chelipeds have a rough and pitted surface and curve inwards. They are purple in colour with a white inner surface. The antennules are usually a pale yellow colour. The eyestalks are red.[2]
The triangle crab is a scavenger feeder.[5] It feeds mostly on coralline alga, which is thought to cause the bright red pigmentation on its shell.[1] It also feeds on red and green algae, as well as amphipods, isopods and decapods.[4]
It is a cryptic species that defends itself from predation with camouflage. Some divers and amateur observers suggest it is more active at night and may be nocturnal.[6][7]