Diadema palmeri Baker, 1967

Coppard, Simon Edward & Campbell, Andrew C., 2006, Taxonomic significance of test morphology in the echinoid genera Diadema Gray, 1825 and Echinothrix Peters, 1853 (Echinodermata), Zoosystema 28 (1), pp. 93-112 : 98-99

Diadema palmeri Baker, 1967

Specimens were collected from the Poor Knights Island and from Hen and Chickens Island, New Zealand. Mean test diameters measured 65 mm (h.d.) (SD ± 4.8 mm) by 35 mm (v.d.) (SD ± 2.6 mm) in adult specimens. Maximum test diameters of 78 mm (h.d.) by 44 mm (v.d.) were recorded from 20 specimens examined.

As first reported by Baker (1967), the test was spectacularly red with a striking pattern of iridophores ( Fig. 2J ). These occurred as brilliant blue or lilac lines radiating down each side of the naked median areas of the interambulacra, as spots on each interambulacral plate on the adradial edge of each column, and as ring around the periproct.

The ambulacra typically measured 20-25% of the interambulacra at the ambitus. Large naked areas occurred on the median areas of the interambulacra ( Fig. 2I ). Th ese were triangular and cream in colour, with a thin line of iridophores either side. A single, large, red spot accompanied by two to four smaller spots were typically seen in the centre of the naked median areas.

Th e apical system ( Fig. 1D ) measured 29-32% of the test’s horizontal diameter, was monocyclic, with all ocular plates insert. Th e genital plates ( Fig. 1D ) had between two and six tubercles on their inner edge, with corresponding spines found on living specimens. Strong arch-shaped depressions were found on the naked genital plates. Th ese formed the corners of the pentamerous apical ring. Th e genital pores were relatively small in relation to other species of the genus.

The periproct measured 16-18% (h.d.) and had a small anal cone that was slightly lighter in colour than the test, with white platelets present in the skin. A black anal ring was present around the opening, unique among species of Diadema .

Th e peristome measured 35-45% (h.d.) and was predominantly red in large adult specimens, paler in juveniles.

Figures

FIG. 2. — A-I, photographs of the median areas of the interambulacra, showing the variation in characters that occur: A, Diadema antillarum; B, D. mexicanum; C, D, D. savignyi; E, D. setosum; F, Echinothrix calamaris (brown colour morph); G, E. calamaris (white colour morph); H, E. diadema; I, D. palmeri; J, D. palmeri (whole specimen). Scale bars: A-I, 5 mm; J, 50 mm.

FIG. 1. — Drawings of the apical systems, showing species specific characters of the periproct and genital plates: A, Diadema antillarum; B, D. ascensionis; C, D. mexicanum; D, D. palmeri; E, D. paucispinum; F, D. savignyi; G, D. setosum; H, Echinothrix calamaris (brown colour morph); I, E. calamaris (white colour morph); J, E. diadema. Scale bars: 5 mm.