Sea-cucumber (Apsolidium densum)

Sea Cucumber (Apsolidium densum) underside view of foot, photo courtesy Leon Altoff
Sea-cucumber
Apsolidium densum
Kingdom: Animalia
Phylum: Echinodermata
Class: Holothuroidea
Order: Dendrochirotida
Family: Cucumariidae
Status
Australia: n.a.
Victoria: vulnerable (DSE 2009) pdf
FFG Act 1988 listed (DELWP 2016)

 

Sea Cucumbers are one of a group of marine invertebrates known as Echinoderms which also include Sea Urchins, Sand Dollars, Brittle Stars and Feather Stars. There are some 900 species of Sea Cucumber in the world with them being classed as a major component of the deep sea fauna. They also inhabit intertidal, seagrass and embayment habitats and can range in colour from black, white, brown or olive, and range in length from just over 3 centimetres to over one meter.  

Thirty one species of Sea Cucumber have been identified in Victoria but only one species,  Apsolidium densum  (O’Loughlin & O’Hara 1992), is recognised as being endemic to Victoria and taxonomically distinct. Despite intensive searches over a 10 year period along the entire coast line of Victoria only four specimens of Apsolidium densum  have been recorded from only two sites in Victoria, a Marine National parks at Flinders (Mushroom reef Marine Sanctuary) and also at Skenes Creek (approximately 10 kilometers North East of Apollo Bay) in Victoria’s South West (O’Hara & Barmby 2000).    

Sea Cucumber (Apsolidium densum) side profile, photo courtesy Leon Altoff

Some diagnostic features of the genus Apsolidium  include amongst other features, a stout body with a distinct sole, upturned anal and oral ends, 10 dendritic tentacles and 2 smaller ventral tentacles. Apsolidium densum grows to 40mm in length, 18mm wide and 12 mm high, it has a thick body wall, a sole narrower than the body wall and is mostly white with some grey flecking dorsally and on oral extension. A full description is provided by O’Loughlin & O’Hara (1992).

Habitat & ecology

The habitat and biology of Apsolidium densum is not fully understood, although unlike many species of Sea Cucumber that inhabit areas of fine sands and mud, it is thought that the Sea Cucumber Apsolidium densum is restricted to rocky, shallow and intertidal habitats (0-2 m) depth where it has been observed on algae covered surfaces and is unlikely to be found in any sub tidal surveys (O’Hara & Barmby 2000).

Sea Cucumbers in general need relatively clean water and species that are located in inter tidal areas are more tolerant to a rage of temperatures.

Unlike all other classes of echinoderms most Sea Cucumbers have male and female individuals with females known to carry small eggs (O’Loughlin & O’Hara 1992).  Most sea cucumbers discharge sex cells in to the surrounding water giving environmental cues and stimulation from other releases. Sea cucumbers are known for the ability to regenerate after being injured (Fenner 2016).

Mushroom Reef Marine Sanctuary

This area near Flinders supports the highly diverse inter tidal rocky reef communities. The Sanctuary comprises an extensive rock platform, which contains sheltered rock pools and coves which are protected by a shallow reef on the ocean side. At low tide, the sea level lowers to expose a large mushroom-shaped platform. The reef is formed from ancient basalt that over the years have weathered allowing a diverse range of marine life to be protected under the loose rocks or within the weathered cracks and crevices. The exposed ocean area of Mushroom Reef contains numerous sub tidal pools and boulders within inter tidal area (Parks Victoria 2006)

Skenes Creek 

Rocky, sandstone intertidal habitats present.

Decline and threats

Apsolidium densum is classified as rare due to there being only four specimens being collected from two sites. Only the Mushroom Reef Marine Park site provides protection, under the National Parks Act 1975, which forbids the collection of any material from with in the parks boundaries.

Due to limited knowledge of this species biology and ecology further studies are needed to assess potential impacts. It is believed however that this species is potentially threatened by degradation of rocky shore habitat by coastal development, or a reduction in water quality.

Of the 31 species of Sea Cucumber identified in Victoria, 5 species including Apsolidium densum have been identified being limited to a cool temperate environment. It is thought that impacts from global warming may pose a threat to cool temperate environments though a rise in sea surface temperatures and changed ocean currents,  with a rise of 1-2 degrees being significant enough to threaten the ecological viability of some species (O’Hara & Barmby 2000).

Apsolidium densum is not a commercially harvested species but may be prone to threats through marine aquarist collectors.

Conservation objectives

To ensure that Apsolidium densum is conserved for future generations by:

Suggested Actions

References

AFD (2016) Australian Faunal Directory, Species Apsolidium densum O'Loughlin & O'Hara, 1993;  [Accessed 29/12/2016] 

DSE (2009) Advisory List of Threatened Invertebrate Fauna in Victoria - 2009 - Department of Sustainability & Environment 2009 (now Department of Environment, Land, Water & Planning -Victoria).

DELWP (2016) Flora and Fauna Guarantee Act 1988 -Threatened List December 2016,  Department of Environment, Land, Water & Planning -Victoria.

Fenner, B. (2016) Sea Cucumber: Not A Pretty Picture http://www.wetwebmedia.com/seacukes.htm (sited 29 December 2016).

O’Loughlin, P.M. and O’Hara, T.D. (1992). New cucumariid holothurians (Echinodermata) from southern Australia, including two brooding and one fissiparous species. Memoirs of the Museum of Victoria 53: 227-266.

O’Hara, T. and Barmby, V. (2000). Victorian Marine Species of Conservation Concern: Molluscs, Echinoderms and Decapod Crustaceans. Parks, Flora and Fauna Division,

O’Loughlin, P.M. (2000) A Review of the Cucumariid Genus Psolidiella Mortensen (Echinodermata, Holothuroidea) Memoirs of Museum Victoria 58(1):25-37 (2000)

Parks Victoria, (2006) Mushroom Reef Marine Sanctuary  [sited 29/12/2016].

 

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