Eucidaris metularia ( Lamarck 1816 )

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 : 10-11

Eucidaris metularia ( Lamarck 1816)

FIGURE 2

The specimen observed was from 14m on Steep Island, on rocky substratum. This species is rarely seen in Hong Kong waters, with only a single sighting recorded in our survey. Eucidaris metularia is distinguished from the other cidarid urchin seen in Hong Kong by spine morphology which are blunt-tipped with banded coloration and spine length roughly equal in size to the test diameter in E. metularia versus Prionocidaris baculosa which has spines that are narrow to pointed, lack banding coloration and show spine length at least twice the test diameter with serrations along the spine surface. In terms of size. E. metularia horizontal test diameter is not known to exceed 30 mm whereas most adult Prionocidaris baculosa are generally larger than 30 mm in horizontal test diameter.

The colour in life is purplish-brown with the spines distinctly banded. It is widely distributed over the Indo-West Pacific region from Mozambique to the Hawaiian Island. A molecular phylogeny and biogeographic survey of Eucidaris spp. across its range, including E. metularia was published by Lessios et al. (1999). Eucidaris metularia has been reported from Xisha Island and the southern end of Hainan Island ( Liao & Clark 1995). This is the first occurrence in Hong Kong waters.

Feeding habits and other biology of Eucidaris metularia are poorly understood. Mortensen (1928) reported coralline algae, bryozoans, sponges and other “bottom material” from gut contents, but surprisingly little could be located. While not abundant in Hong Kong, other species of Eucidaris , such as Eucidaris thouarsii in the Galapagos have demonstrated ecological importance in coral reef settings ( Glynn et al. 1979) and there is likely significance for E. metularia among coral settings in Chinese habitats.

Occurrence/Distribution

Hong Kong, 14.0 m.

Outside Hong Kong. Mozambique and the Red Sea to the Fiji , Gilbert , and Hawaiian Islands and from south Japan to the north coast of Australia. 5–570m.

Figures

FIGURE 2. Eucidaris metularia. In situ image showing apical system and spines. Photographer: Josy Lai.