Hot lips spider crab covered by debris
Hot lips spider crab with hydroids.
Photos Adriaan Johnson
The "hot lips" mouthparts.
Hot lips spider crab covered by a sponge
Hot lips covered by more debris.
Hot lips spider crab covered by a sponge
Cape long-legged spider crab
Cape long-legged spider crab
Photos Guido Zsilavecz
Two species of spider crab can be found regularly in Cape Town waters: the hot lips and Cape long-legged spider crabs. Both are most often seen when perched on a sea fan, especially the palmate seafan Leptogorgia palma, as they are quite conspicuous then. They may be found elsewhere too - on reefs, for example, but are usually so well camouflaged as to be nearly invisible.
Hot lips spider crab. The exact species is not known but it may be a member of the genus Achaeopsis or Inachus. The name is derived from its bright orange-red mouthparts. If these are not visible, which given its small body size if often the case, look for the red spots on the chelipeds (nippers or pincers). Overall it is also stockier, and less "spidery" when compared to the long-legged species. It also tends to cover itself with a greater variety of "stuff" - sponges, hydroids, bryozoans and maybe even ascidians. The cover they have does not always seem particularly suitable for where the crab is sitting; for example, white debris when on a bright red seafan is rather obvious, but I think the aim is not necessarily to look like the background, but rather to look less like a crab. Growing hydroids would be useful though, as then the crab will have a sting sharper than a habanero chilli, due to the hydoids' stinging cells. Away from sea fans, on reefs, the crabs are definitely hard to spot.
Hot lips spider crabs can be found in waters further offshore - from the seaward side of A-Frame or Castle Rocks, for example, to deep reefs offshore.
Cape long-legged spider crab Macropodia falcifera. With its long, slender legs and elongated rostrum (the bit sticking out between the eyes), this crab can be distinguished readily from the hot lips one. If is also generally less overgrown, but naturally covered by short, spiky hairs. It prefers deeper, calmer waters, and is rarely, if ever, found close inshore. While it also likes sea fans, it too can be found on reefs. It is less common than the hot lips species, but often several may be seen on a single sea fan.
Descriptive Catalogue of South African Decapod Crustacea (Crabs and Shrimps), KH Barnard, 1972
Crustacea Guide of the World, H. Debelius, 2001
Two Oceans, A guide to the marine life of Southern Africa, GM Branch, CL Griffiths, ML Branch and LE Beckley, 1994.