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Rough Sea Cucumber

Rough Sea Cucumber

Australostichopus mollis

The rough sea cucumber also widely known as the soft sea cucumber, belongs to the family Stichopodidae, which are characterised by leaf-shaped tentacles, well developed respiratory trees  and pedicels on the body surface. Two gonads are present internally, one on each side of the body.  They are elongate animals with soft bodies, with small dark spinelets on bumps on a reddish-brown, black or grey background.  Similarly to sea stars and sea urchins (other members of the echinodermata class) they are radially symmetrical and they have tiny white tube feet, which are located on the undersurface only.  The rough sea cucumber has a head end that has a mouth surrounded by mucous-coated feeding tentacles, which are modified tube feet, and at the other end an anus.  This species grows to a maximum length of 20 centimetres.

Sea cucumbers play an important role in the ecosystem, by acting as the vacuum cleaners of the sea.  During the day they tend to be concealed in crevices and emerge at night to feed.  They are non-selective scavengers, and swallow large amounts of sand which pass through the gut and out the anus, removing small organic particles before excreting long strands of clean, recycled sand.  Members of this genus have two unique defensive strategies for when they are threatened, firstly they are capable of expelling their gut, otherwise known as respiratory trees.  This is in the form of many sticky, fine threads which the sea cucumber can regenerate.  Secondly when the animal becomes stressed, it virtually disintegrates, occasionally ‘melting’ beyond recovery.

The rough sea cucumber generally lives on hard substrates on the rocky reef, in sea grass meadows and on sand to depths of 140 metres.  The rough sea cucumber occurs abundantly throughout southern Australia, from the Houtman Abrolhos Islands, WA to central NSW and around Tasmania and New Zealand.

Other common names include:  Brown Sea Cucumber, Rori, and Common Sea Cucumber (NZ).

 

Occurrence at the Busselton Jetty: 

The rough sea cucumber is commonly observed from the underwater observatory.  They are often tucked into crevices created by the brackets and jetty piles one to two metres above the sea floor.  Evidence of their night scavenging is obvious on the cement ledges immediately outside the windows which are littered with strands of compacted sand.  They tend to remain in the one location for the duration of the day.

Image by: S. Teede