Pentaceraster sibogae Döderlein 1916

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 : 59-61

Pentaceraster sibogae Döderlein 1916

FIGURE 42C–D , 43A–F

Comments

This species was identified based on descriptions summarized by Liao & Clark (1995) and Döderlein (1936). Diagnostic characters used include the presence of large carinal spines and abactinal-lateral spines on both the disk and arm, as well as spines present on all of the superomarginal spines. This species varies widely however, demonstrating a broad range of body shape with highly variable R/r ratios demonstrating more elongate versus more triangular arms in some individuals as well as a variably thick to arched disk as well as a large number of color patterns ranging from disk and arms with light blue to red to spines with dark red to yellow or white respectively. The interradial arcs in some individuals ranged from weakly curved to straight to more acute. No oral side characters, such as furrow spines or subambulacrals, were observed. The high degree of variation suggests further work into the possibility of cryptic taxa across this widely occurring species. Figures 43C and 43D show Hong Kong specimens with variable arm number, six and four respectively.

This represents the first occurrence of this species in Hong Kong.

Occurrence/Distribution

Hong Kong, 10– 20 m.

Outside Hong Kong. Southern China, Hainan Island , Borneo Bank and Indonesia. 10 m.

DISCUSSION

General Comments

Our work presents multiple new observations of echinoderms in Hong Kong, including five new occurrences for Asteroidea and eleven new occurrences for Echinoidea ( Tables 1 and 2 ). The species outlined herein have been previously recorded from the South China Sea, but not specifically from Hong Kong. Liao & Clark (1995) summarized multiple species from southern China but which were notably absent from Hong Kong. This includes larger, very prominent urchin species such as Prionocidaris baculosa and Coelopleurus maculatus .

Liao & Clark (1995) described the occurrence of Linckia laevigata , Echinaster luzonicus , Diadema savigny i and Tripneustes gratilla as uncommon, with individual species showing uneven distribution patterns. For example, Echinaster luzonicus and Tripneustes gratilla are regularly spotted at specific sites such as the Ninepin Islands. In other instances, some species are not seen frequently. For example, since 2014, only one sighting of Linckia laevigata and four of Diadema savignyi , respectively, have been made. Although commonly encountered elsewhere, these species are not frequently observed in the waters of Hong Kong.

The further discoveries of new occurrence in Hong Kong are attributed largely to improved reporting and surveys of deeper and more remote areas than have previously been accessible without SCUBA. Social media platforms, such as Facebook, have facilitated sharing of images and permitted contact between photographers and professional taxonomists. Citizen scientist platforms, such as iNaturalist (https://www.inaturalist.org/home) have archived records of taxon imagery for specific areas, as shared by regional photographers. This publication would not have taken place without shared images via social media.

Figures

FIGURE 42. Pentaceraster alveolatus/P. sibogae A. In situ, abactinal surface. B. Abactinal surface showing pattern variation. C. & D. Pentaceraster sibogae. Feeding on urchin, Heliocidaris crassispina Photographer: Sam King Fung Yiu.

FIGURE 43. Pentaceraster sibogae A. In situ observation of predation on Scleronephthya. B. In situ observation, possible predation on Scleronephthya. C. In situ, six armed variant. D. In situ, four armed variant. E. In situ abactinal surf showing red variant. F. In situ closeup on actinal surface showing benthic ctenophores with feeding tentacles extended. Photographer: Sam King Fung Yiu.