Diadema setosum (Leske, 1778)

Arachchige, Gayashan M., Jayakody, Sevvandi, Mooi, Rich & Kroh, Andreas, 2019, An annotated species list of regular echinoids from Sri Lanka with notes on some rarely seen temnopleurids, Zootaxa 4571 (1), pp. 35-57 : 39

Diadema setosum (Leske, 1778)

Material studied. WUSL/ER/208 (dry, denuded) from Polhena.

Literature records for Sri Lanka. Bell (1882, 1887), Sarasin & Sarasin (1887), Döderlein (1888), Herdman et al. (1904), Clark (1925), Price & Rowe (1996), Fernando (2006), Jayakody (2012), Gayashan & Jayakody (2012).

Distribution in Sri Lanka. Eastern and southern coasts of Sri Lanka.

Recorded depth range in Sri Lanka. 0.5– 3 m (present study), 0–62 m (previous records) .

Habitat. Coral reefs, rocky reef platforms.

Observed occurrence in this study. Southern coast (Hiriketiya, Nilwella, and Polhena) of Sri Lanka.

Remarks. Adults of this species differ from D. savignyi by having six to seven primary tubercles in one horizontal series in the interambulacra, a blue spot on each genital plate, and white spots along the interradii instead of lines. In addition, there is a prominent red ring around the anus at the tip of the inflated anal sac.

This species has been recorded consistently from the southern and eastern coasts of Sri Lanka since it was first mentioned as part of the Sri Lankan echinoid fauna ( Bell 1882). According to Lessios et al. (2001), D. setosum contains two mitochondrial lineages that split 3 to 5 million years ago and are now geographically separated. No specimens from Sri Lanka were included in the study by Lessios and co-workers, but species distribution modelling by Bronstein et al. (2017) predicts that the Sri Lankan representatives belong to D. setosum clade a. Genetic analyses are needed to confirm the prediction based on modelling.