Comprehensive Description

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General Description

The body is cylindrical, and has a greatest length of 132 mm in alcohol. Fully expanded live specimens probably exceed 200 mm in length. The diameter is almost constant along the length of the body, approximately 5% of the total length. The mount and anus are terminal. The oral disc has 12 conspicuous tentacles that are supported by a well-developed calcareous ring. In a specimen 90 mm in length, the oral disc is 15 mm in diameter. The smooth dark-coloured body wall carries a few to very numerous wheel papillae in all interradii, which are whitish to greyish in colour. The wheel papillae contain numerous wheel ossicles, and range from circular to elongate oval, with an approximate average diameter of 1 mm. Some specimens have few such papillae, whilst in others a 20 mm long area of the mid-dorsal body may carry 35 papillae. The largest papillae surround the anus, often forming a ring of 5 papillae that are up to 2 mm in diameter. These terminal papillae superficially resemble the ‘anal teeth’ of non-apodid holothurians.

The colour of specimens in alcohol is mostly dark-purplish. Live specimens are coloured blue to bluish-grey, with the papillae conspicuous as white spots. The tentacles are lighter in colour than the rest of the body.

The 12 tentacles are equally spaced, with no ventral gap, and no bilateral symmetry in their arrangement. The tentacle stalks are cylindrical and terminate in a disc or pad that carries up to 20 discrete, finger-like digits, each approximately 1 – 1.5 mm long in a partially contracted state. In a contracted tentacle, the digits remain distinguishable as discrete structures. In situ photographs show that the digits are fully extended when the animal is actively feeding.

The calcareous ring is conspicuous, strong, and rigid. It is composed of 10 pieces, of which the left and right dorsal radial pieces are double (bipartite). The radial pieces are not perforated for the passage of the radial nerve. There are numerous polian vesicles of varying length, with usually more than 20 vesicles being present. There is a short, tightly coiled stone canal in the mid-dorsal interradius, which terminates at a conspicuous whitish madreporite that is attached to the body wall. The gonad is a short bunch of vesicles that extend 2-3 cm posteriorly in the dorsal area.

An average-sized wheel papilla from the mid-body contained almost 400 wheels of a typical chiridotid types, having six spokes and with an inner edge of the rim carrying numerous teeth. The wheels lie in the papillae with the toothed rim uppermost. At the centre of the inner surface of the wheel is a ‘star’ structure. Average diameter of the wheels is 175 um. The number of teeth on the rim ranges from 96 – 126, with the number teeth increasing in number as the wheels increase in diameter.

The tentacle stalks and terminal branches contain flattened rods that are very variable in size, 100-202 um in length, with slightly spinous ends and usually having a slightly widened central region. The rods are usually straight, sometimes branched and vary in length, with the average length being approximately 160 um.

(Pawson & Vance, 2004).


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