Invertebrate · Echinoderms · Sea cucumber

Black Sea Cucumber

Holothuria atra Jaeger, 1833

syn. Halodeima atra, Holothuria (Halodeima) atra, Holothuria (Halodeima) atra amboinensis, Holothuria (Holothuria) atra, Holothuria (Microthele) affinis, Holothuria amboinensis +2 more

up to 60 cm0-20 mPoisonousLeast Concern

1766

A black sausage lying in the open on bright sand, up to 60 cm (24 in), usually with a coat of sand stuck to its back. The sand is deliberate. Black in shallow tropical water overheats, and the animal covers itself with sediment as shade, keeping bare only the parts it needs.

It is a sediment processor, and the scale is worth stating. It takes in sand at one end, strips the film of bacteria, algae and detritus off every grain, and passes the cleaned sand out at the other. A dense population turns over tons of the lagoon floor in a year, which is one reason sea cucumber fisheries change the places they empty out.

Some of them do not bother with sex. This species can reproduce by dividing: the body constricts across the middle and pulls itself into two, and each half regrows what it lacks. A population can be largely clones of a few individuals.

Handled or attacked, it releases a red fluid carrying holothurin - a saponin, toxic to small fish and thoroughly unwelcome in an eye. Harmless on skin. Wash your hands before touching your mask, and put the animal back the way you found it rather than upside down.

How to recognise it

smooth jet-black body, usually dusted with a coat of sand
no visible spines or papillae, unlike the knobbly species
often lying in the open in bright shallow water
releases a red fluid when handled
length up to 60 cm

Why it's threatened

Biological resource use

Intentional use: (subsistence/small scale) [harvest] · Intentional use: (large scale) [harvest]

In Kiribati, this species became part of a multispecies fishery after the depletion of the most valuable commercial species. This fishery is considered overexploited after a short exploitation period between 2000-2002 (Kinch et al. 2008). In Samoa, the beche-de-mer fishery consists in ca. 2% of this species; this fishery is now closed for exports and catches concentrate on supplying the domestic market. In Niue in 1990, sea cucumber stocks were not high enough to support a commercial venture, unless the fishery would target this low-valued species (Kinch et al. 2008).

In the Galápagos Islands (Ecuador), there is an illegal fishery for this species with no biological or ecological data for management (Toral-Granda 2008).

Although not one of the most important species (low value) for fishery purposes, it can be expected that this species may become more popular after the depletion or reduction of other species of higher commercial importance and value. As seen in Kiribati, after the decline of H. fuscogilva and T. ananas, in PNG after the decline of H. scabra, in Fiji after the decline of A. miliaris (Kinch et al. 2008), and in Thailand after the overexploitation of H. scabra (Choo 2008).

Many sea cucumbers are broadcast spawners, which can limit the fertilization success of a species in exploited populations.

Threat classification from the IUCN Red List.