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The Holothurian Fauna of Cook Strait, New Zealand

Subfamily Thyonidiinae

Subfamily Thyonidiinae

Diagnosis: Calcareous ring without posterior processes. The individual pieces of the ring are undivided.

Heding and Panning (1954) listed 13 genera in this subfamily. A new genus was described from Cook Strait by the writer (Pawson, 1962), thus increasing the number of genera to 14.

Neocucumella Pawson, 1962

Diagnosis: Tentacles 20 (outer ring with five pairs of larger tentacles, interradial; inner ring with five pairs of smaller tentacles, radial). Tubefeet confined to the radii, arranged in double rows. Radial pieces of the calcareous ring each with a deep median anterior notch. Interradials rounded anteriorly. Calcareous deposits numerous two-pillared tables, with symmetrical circular or elliptical bases, 0.05mm in average length, perforated by four large and four small (alternating) holes.

Neocucumella bicolumnata (Dendy and Hindle) Plate III. figs. 1–3
  • Pseudocucumis bicolumnatus Dendy and Hindle, 1907, p. 106, Pl. 11, fig. 6, Pl. 12, figs. 13–14; Joshua and Creed, 1915, p. 19; Engel, 1933, p. 36.
  • Mensamaria bicolumnata Clark, 1946, p. 406; Dawbin, 1950, p. 38.
  • Neocucumella bicolumnata Pawson, 1962, p. 65, figs. 1–2.
  • Non: Amphicyclus thomsoni (Hutton).
page 23

Material Examined: VUZ 64, off Point Howard Wharf, 5 fathoms, blue mud, 1 specimen.

Diagnosis: Shape fusiform. Colour light brown. Tubefeet dark brown. Tentacles reddish-brown.

Description: The single specimen is 30mm in total length, and the body is attenuated posteriorly to form a more or less distinct "tail" region. The anterior end narrows as an introvert which carries the crown of 20 tentacles. The body wall is quite thin but opaque, and there is some transverse wrinkling near the posterior end.

Colour in alcohol light brown. The tubefeet are dark brown and the tentacles are dark reddish-brown. The tubefeet are confined to the five ambulacra, where they are arranged in double rows. There are no tubefeet on the introvert. Near the extreme posterior end of the body they are more scattered, and the double row arrangement is lost.

Two rings of richly branched tentacles surround the mouth. The outer ring has five pairs of large tentacles 4—5mm in length, lying in an interradial position, while the inner ring has five pairs of small tentacles, 1mm in length, radially placed. The mid-dorsal pair of larger tentacles are smaller than the other outer ring tentacles.

The calcareous ring is composed of ten simple pieces. Each radial piece is approximately rectangular in shape and has a wide and deep posterior notch and a pronounced median anterior notch. There are no anterior processes on the radials. Interradials are Y-shaped, with the tail of the "Y" directed anteriorly. This anterior projection is bluntly rounded. Length of each radial piece 2.0mm; length of each interradial piece 1.0mm.

The internal anatomy has been described by Dendy and Hindle (1907).

Calcareous deposits of three types were found:

1. Tables: The skin contains very large numbers of tables, closely aggregated together. In general the table disc is oval in shape, and has eight perforations, four large (approximately 0.013mm diameter) and four small (approximately 0.007mm diameter). Average table length is 0.05mm, breadth 0.03mm (Plate III, fig. 1). Departures from this basic pattern are so rare that only three tables of unusual shape were found (Pl. III, fig. 3). At its centre the disc of each table carries two short pillars, which are joined at the top by a single crossbar. Average height of pillars is 0.02mm.

2. Tentacle deposits: The digits of the tentacles contain large numbers of rod-like deposits (Pl. III, fig. 2). The extremities of the rods are expanded and carry a number of perforations (up to 20 in each rod). Average length of the tentacle rods is 0.06mm. No unperforated rods were found.

3. Tubefoot deposits: The tubefeet carry well developed endplates in their sucking discs.

Distribution: The type specimen was recorded from "off Dunedin" (Dendy and Hindle, 1907). Joshua and Creed (1915) recorded a specimen from Australia, probably collected near Adelaide. The new record, Wellington Harbour, enlarges the distribution area of the species, but N. bicolumnata is still a rare species.

Discussion: Dendy and Hindle (1907) described an S-shaped intestine, feebly developed respiratory trees, a single Polian vesicle, and gonads consisting of two bunches of very long filaments in their specimen of this species..

The systematic historv of N. bicolumnata has already been outlined (Pawson. 1962).