Histocidaris purpurata (Thomson, 1872)

Filander, Zoleka, Samyn, Yves & Griffiths, Charles, 2019, Four notable additions to the South African echinoid fauna (Echinodermata, Echinoidea), ZooKeys 831, pp. 71-80 : 72

Histocidaris purpurata (Thomson, 1872) Fig. 1A, B

Poriocidaris purpurata : Mortensen 1928: 104-107, pl. I, fig. 6, pl. III, figs 3-5 [distribution and synonymy].

Histocidaris purpurata : Clark 1925: 38; Schultz 2011: 872-973, figs.1465-1468; Atkinson et al. 2018: 441.

Identification.

Test medium sized (test diameter = 28 mm); round and robust. Marginal series with regular and small tubercles. Interambulacra with distinctively large, crenulate primary tubercles. Areoles slightly deepened. Apical system covered with tubercles, ocular plates exsert. Periproct raised, with plates decreasing in size inwards. Primary spines cylindrical, tapering gently. Oral spines broad, flattened, slightly curved, with serrated edges. Secondary spines flattened, narrowing towards blunt point. Primary spines brown to purplish violet, with white shaft. Secondary spines light brown. Denuded test white.

Material examined.

SAMC.A090123: one specimen collected by an otter trawl through the South African Observation and Environmental Network/Department of Agriculture and Fisheries long-term offshore invertebrate programme in May 2016 on board the Compass Challenger, depth 570 m. Whole specimen preserved in 70 % ethanol.

Habitat.

Muddy habitat.

Global distribution.

Previously known only from the Atlantic, Ireland to Canary Islands, and the Caribbean, at 750-1084 m depth ( Mortensen 1928; Schultz 2011).

South African distribution.

South-east coast of South Africa, off Mossel Bay (35.079°S, 23.603°E).

Remarks.

Although Döderlein (1906) previously reported this species in the Indian Ocean (at the Sombrero Channel, Nicobar Islands, at 805 m), Mortensen (1932) disregarded this record on the basis that the specimen was too small and that no adults of this species had been previously collected in the region. The current record therefore represents the first reliable report of this species from the Indian Ocean.

Only one other species, Histocidaris elegans (A. Agassiz, 1879), belonging to this genus has previously been reported in South African waters and this remains a dubious record, as it lacks locality data ( Mortensen 1932; Filander and Griffiths 2017). Nonetheless, H. purpurata differs from H. elegans both in its distinctive coloration and shape of the primary spines. Histocidaris purpurata has a distinctively purple and brown coloration, with thick, cylindrical, and pointed primary spines; whereas H. elegans is light brown in colour, with thinner and blunt primary spines.