Diadema savignyi ( Audouin 1809 )

Yiu, Sam King Fung & Mah, Christopher L., 2024, New Ecological Observations and Occurrence for Asteroidea and Echinoidea in Hong Kong, Zootaxa 5526 (1), pp. 1-69 : 14-15

Diadema savignyi ( Audouin 1809)

and Diadema setosum ( Leske 1778)

FIGURE 5A ( D. setosum ), 5B ( D. savignyi )

Comments

Diadema is intensively studied and many species are dealt with in much greater detail elsewhere (e.g. Muthiga & McClanahan 2020), and as such, are only included briefly here out of completeness. Chinese Diadema species were documented by Liao & Clark (1995). Both species are significant as subjects for understanding relationships between species across the tropical-Indo-Pacific region (e.g. Lessios 2000). Diadema setosum in particular has been the cause of coral bioerosion in Hong Kong ( Dumont et al. 2013; Qiu et al. 2014).

Both species are widely occurring throughout the Indo-Pacific. Diadema savignyi prefers exposed settings and is recorded from deeper depths (0–60 m) ( Fig. 5B ) compared to Diadema setosum which prefers sheltered sites at shallower depths, from 0–30 m ( Schultz 2015). In Hong Kong D. savignyi has been observed at Tung Ping Chau, Sung Kong and Wang Lan Island ( Fig. 5B ) at deeper depths,> 10.0 m in rocky habitats and but is more rarely seen. Liao & Clark (1995) reported Diadema savignyi as being very abundant at Hainan Island, such that the spines prevented steps between them. Diadema setosum has been observed at Sharp Island ( Fig. 5A ), and is more common in eastern waters.

Diadema savignvi is distinguished by a black anal cone and bold blue arch of iridophore pattern on the genital plates, whereas Diadema setosum bears white with an orange ring on its anal cone and blue spotted iridophore pattern ( Schultz 2015).

Occurrence/Distribution

Diadema savignyi

Hong Kong, 1–25 m

Outside Hong Kong, throughout the Indo-Pacific , except Pakistan and West India, Maldives and the Hawaiian Islands, 0–30 m.

Diadema setosum

Hong Kong, 1–30 m

Outside Hong Kong, southern China and throughout the Indo-Pacific. 0–60 m. (based on Liao & Clark 1995).

Figures

FIGURE 5. Diadema spp. A. D. setosum. B. D. savignyi. Photographer: Sam King Fung Yiu.