Choriaster granulatus Lütken, 1869

Mah, Christopher L., 2023, A new species of Astrosarkus from Western Australia including new Mesophotic occurrences of Indian Ocean Oreasteridae (Valvatida, Asteroidea), Memoirs of Museum Victoria 82, pp. 143-165 : 150

Choriaster granulatus Lütken, 1869

Figure 5a–b

Lütken, 1869: 35; Goto 1914: 604; Fisher 1919: 367; Domantay and Roxas 1938: 217; Hayashi 1939: 424; Chang et al., 1964: 61; A.M. Clark 1967: 37; Liao 1980: 154; Marsh and Marshall 1983: 675; Jangoux 1986: 124; Marsh and Fromont 2020: 295

Diagnosis. Body stellate (R/r=2.6), strongly thickened, arms round in cross-section. Interradial arcs acute. Surface smooth covered by finely granulate dermal covering. Reticulate skeleton present but covered by a thick, dense fibrous tissue bearing minute plates. Although obscured by granulate dermal covering, abactinal, marginal and actinal plates well developed. Papular pores present only on abactinal surface, terminating at superomarginal plates. Furrow spines slender, 8–9; subambulacral spines large, flat and truncate, three to four (exceptionally five). Modified from Marsh and Fromont (2020), Mah (2003).

Comments. A readily recognizable species, primarily encountered in shallow-water coral-reef related habitats, depth range, 0–40 m (Marsh and Fromont, 2020). Recent ROV video accounts from the Indian Ocean discovered this species in the Maldives at 60–70 m and in the Comoros at a depth of 80 m, indicating that the lower limit of this species likely occurs at mesophotic depths. Mesophotic individuals were observed on rocky substrates covered by epizoic, encrustations adjacent to light, sandy sediment.

Biology of this species is poorly understood. Spawning has been reported in April with planktotrophic larvae. They scavenge on dead fish and other animals, and likely feed on microbial biofilm (Marsh and Fromont, 2020).

Color variation ranges from pink with light to dark papular regions. Specimens from the Indian Ocean, especially Tanzania, Madagascar and adjacent areas, as well as those in the Red Sea, seem to show especially dark papular regions with strong contrast to the lighter surrounding pink to peach coloration.

Occurrence. Widely occurring throughout the Indo-Pacific. Southern China and Japan ( Ryukyu Islands ), Vietnam, Singapore, eastern Caroline Islands, New Caledonia, Fiji, Tonga, Australia on the Great Barrier reef and Ashmore reefs off Western Australia , Indonesia, Papua New Guinea, Philippines to the Red Sea, and east Africa. 0–40 m.

Depth/new occurrences. Maldives to 60–70 m

Moheli Island, Comoros at 80 m.

Material/video referenced. Comoros Video, Moheli Island (Comos) 12° 27.531" S, 43 38.286" E, 80 m. Observed 10 Oct 2018. Image by CEPF / ACEP Comoros Biodiversity Project .

Figures

Figure 5. Choriaster granulatus a, In situ image from Comoros, 80 m. Image courtesy Comoros Biodiversity Project; b, In situ image from Maldives, 60–70 m. Image courtesy Maldives Ocean Research Expedition.