Diadema setosum
(Leske, 1778)
Enter the name for this tabbed section: Description
This is the common "long spines" sea urchin. It is found in shallow water, typically between the surface down to 15 or even deeper. During the day it is often observed in large aggregation, particularly on soft substrates, or in small groups against block of corals or overhangs.
A taxonomic study based on genetics have shown that the two species found in Oman are separate from the other Diadema species of the Indo-Pacific (Lessios et al. 2001). Diadema setosum (clade b) is found all around the Arabian Peninsula, whereas clade a is found elsewhere in the Info pacific.
The species is characterized by long spines, often black, but sometimes lightly colored and a pronounced anal cone with a conspicuous red ring. Five bright spots mark each of the ambulacral grooves.
A taxonomic study based on genetics have shown that the two species found in Oman are separate from the other Diadema species of the Indo-Pacific (Lessios et al. 2001). Diadema setosum (clade b) is found all around the Arabian Peninsula, whereas clade a is found elsewhere in the Info pacific.
The species is characterized by long spines, often black, but sometimes lightly colored and a pronounced anal cone with a conspicuous red ring. Five bright spots mark each of the ambulacral grooves.
Enter the name for this tabbed section: Distribution
D. setosum is found nearly everywhere in Oman where corals are found. Their abundance though fluctuates widely from reef to reef. In shallow water, it is often found in large aggregations that disperse at night to feed but regroup at dawn, probably as a mean of group protection.
Largely dominant in northern Oman, it is often replaced in Dhofar by a similar species: D. paucispinum.
Largely dominant in northern Oman, it is often replaced in Dhofar by a similar species: D. paucispinum.
Enter the name for this tabbed section: Ecology and Biology
Like most sea urchin, Diadema setosum is herbivore and feeds preferentially on the turf algae that grow on hard surfaces underwater. Because of its constant grazing, it can also, progressively reduce the skeleton of corals.
Several species of fish find refuge and protection between the spines of Diadema spp.
The spines are composed on thousands of spirally arranged small ossicles and are very resistant longitudinally but very fragile laterally. They penetrate easily the skin of unfortunate or careless divers. Once in the skin, the muscle contraction and the pain break the spines into numerous fragments and release a venom and a pigment in the skin. The pain typically subsides after a few hours but removing the spines is nearly impossible. The body will progressively absorb the foreign spine fragments but this takes from a few days to a few months. Medical attention is needed if the spine penetrates and articulation or if the victim has an allergy to urchin tissue.
Several species of fish find refuge and protection between the spines of Diadema spp.
The spines are composed on thousands of spirally arranged small ossicles and are very resistant longitudinally but very fragile laterally. They penetrate easily the skin of unfortunate or careless divers. Once in the skin, the muscle contraction and the pain break the spines into numerous fragments and release a venom and a pigment in the skin. The pain typically subsides after a few hours but removing the spines is nearly impossible. The body will progressively absorb the foreign spine fragments but this takes from a few days to a few months. Medical attention is needed if the spine penetrates and articulation or if the victim has an allergy to urchin tissue.