A Starfish of the Genus Asterodiscus new to New Zealand
[Read before the Auckland Institute, November 18, 1936; received by the Editor, December 1, 1936; issued separately, June, 1937.]
During October, 1934, Mr. N. Kokich presented to the Auckland Museum a brilliantly coloured asteroid which he obtained from the fishing launch “Dalmacia” in 29 fathoms 1 ½ miles west of Sail Rock, Hen and Chickens Islands. This specimen proved to be Asterodiscus truncatus Coleman, genus and species new to New Zealand; the holotype being from deep water off the coast of New South Wales. The New Zealand example differs from the holotype in having broader, shorter rays and more widely spaced abactinal tubercles. However, Mr. Arthur A. Livingstone, of the Australian Museum, Sydney, who has seen hundreds of examples of this species during trawling opera|tions off the New South Wales coast, assures me that the holotype is unfortunately not typical of the species as it shows extreme variation in the crowding of the abactinal tubercles.
Mr. Livingstone mentions also that the spines of the adambulacral armature range from two to four to a plate, according to position on ray and age of specimen, and that the colour-pattern of the New Zealand specimen fits Australian examples exactly.
The brilliant colouration of this species has earned for it the name of “fire-brick star” among the New South Wales trawler men. A New South Wales specimen kindly sent on loan by Mr. Livingstone is almost identical with the sole New Zealand example.
Description of the New Zealand specimen:—
Asterodiscus truncatus Coleman.
1911. Mem. Aust. Mus., 4, p. 14, pp. 697–701, pl. 83.
Rays 5. R— 120 mm.; r— 56 mm. R— 2 14r. Breadth of ray at base 67 mm. Disc large and inflated. Rays broad, fairly long, tapering to a blunt extremity; slightly unequal as to length and breadth. Abactinal surface covered with numerous large tubercles which are circular, flat-topped and slightly constricted towards their base of attachment. The largest of these tubercles is 5.5 mm. in diameter. Each tubercle stands on a prominence of the test, and the larger ones are confined to the disc and medium sections of the rays. Scattered among the tubercles are large spherical granules which vary in size but are mostly about 1 mm. in diameter. Marginal plates not conspicuous. Corresponding to superomarginals are three ossicles omitting large plate at extremity of ray which is 9 mm. across. Each ossicle is circular and convex, about 4 mm. in diameter
and encircled by a ring of small oblong granules. Inferomarginal plates 10, each encircled with small irregular granules. Actinal area paved with fairly regular rows of acron-shaped tubercles, each surrounded by a row of large irregular granules. Adambulacral armature composed of furrow series of four subcylindrical blunt-pointed spines and a transverse series of two stout square-sided spines, the outer one smaller and often triagulate. Mouth-plates with a furrow series of seven or eight spines similiar to those of the adambulacrals. Pincer-shaped pedicellariae occur plentifully on the actinal interradial areas and on the abactinal surface. Madereporite conspicuous, situated about one sixth distance from centre to margin, on the interradial line.
Colour: ground colour of abactinal surface chrome, heavily blotched with vermilion; larger tubercles and superomarginal plates mauve to dull purple: ground colour of actinal surface chrome with vermilion abactinal patches encroaching slightly at the margins: larger tubercles mauve, ambulacral regions pale grey to mauve.
Specimen in the Auckland Museum.
Only four species of Asterodiscus are known:—elegans Gray 1847, tuberculosus Fisher, helonotus Fisher 1913 and truncatus Coleman 1911.