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You are here:   OldClasses > 2012 > Holothuria atra |Emily Purton




Holothuria atra Jaeger




 Emily Purton (2012)







Fact Sheet



Physical Description


Life History & Behaviour

Anatomy & Physiology

Evolution & Systematics

Biogeographic Distribution

Conservation & Threats

References & Links

Physical Description

H. atra is a black sea cucumber with an elongate body that is characterised by two lines of spots that run along the oral-aboral axis (mouth towards anus).  The location of these spots on the dorsal side (the top) of the animal match the location of the two dorsal ambulacra (grooves running from the mouth to the anus) (Ruppert et al. 2004).  The size, spacing, and location of spots vary between individuals (Fig. 2).  Occasionally H.atra are found with a sand layer that appears to be peeling off, revealing their black epidermis (Fig. 3).

H. atra exists in two size classes that relate to the area of the reef they inhabit (see page: Ecology). The small morph is usually between 15 and 22 cm long, and the large morph grows up to 60cm long (Chao et al. 1993). Physical characteristic of the primary (oral-aboral) and secondary body axes (dorsal-ventral) of H. atra are addressed below (Fig. 4).

Figure 2: Variation in size, spacing and location of dorsal 'spots' of H. atra individuals, Heron Island reef flat, Great Barrier Reef


Figure 3: Sand layer 'peeling' off a H. atra individual.  Blue square denotes location of a remaining dorsal spot

Physical characteristic of the primary (oral-aboral) and secondary body axes (dorsal-ventral) of H.atra are addressed below (Fig. 4).


The oral tube feet are modified to form the buccal podia which extend from a calcareous ring around the mouth and allow the animal to process sediment (Fig. 4i).  H. atra typically has from 15-20 individual feeding tentacles (Ruppert et al. 2004).  


The anus is located at the opposite end of the animal to the mouth (Fig. 4ii).  Like the spots on the dorsal side, there is no sand present.  There is a high concentration of papillae surrounding the anus.  



Small triangular projections called papillae are present on the top and sides of the H. atra (Fig. 4iii).  These retract into the epidermis upon contact.    


Tube-feet, used for locomotion, are present on the underside of the animal (Fig. 4iv).  Unlike other species of sea cucumbers (for example the Sea Apple Pseudocolochirus violaceus), the tube-feet in H. atra are not arranged along the ventral ambulacra in three conspicuous, parallel lines.  The individual tube-feet of H. atra, and those belonging to other species of sea cucumbers in the same order as H. atra (Aspidochirotida), cover the entire underside of the animal (Ruppert et al. 2004).

Figure 4: Physical characteristics of the primary and secondary body axes of H. atra: i Feeding tentacles (oral); ii anus (aboral); iii papillae (dorsal); iv tube feet (ventral).   



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