Hicksonella princeps Nutting, 1910

Williams, Gary C., 2018, Illustrated Key and Synopses of Shallow-water Gorgonians and Pennatulaceans of the Central Philippines, Part 2 (Cnidaria: Anthozoa: Octocorallia), Proceedings of the California Academy of Sciences 64 (13), pp. 361-398 : 366-367

Hicksonella princeps Nutting, 1910

Figures 16 , 17 , 18

MATERIAL EXAMINED.— CASIZG 201363; Philippines, Occidental Mindoro Province, Lubang Island (13.79 N 120.09 E); 23 May 2014; coll. G.C. Williams; one partial colony wet-preserved in 95% ethanol.

REMARKS.— Hicksonella princeps is similar in superficial appearance and can be confused with another sympatric zooxanthellate gorgonian, Rumphella aggregata . H. princeps differs by having a more gracile appearance, with thinner branches which are often more pointed at the tips. R. aggregata is more robust with thicker branches with more rounded tips. Both species are similar in colony color — varying from tan or grey to light brown or yellowish brown. In addition, similarly-shaped club-like sclerites are found in the surface of the coenenchyme of both species ( Fig. 17 ; Williams and Chen, 2014:119). However, Hicksonella differs from Rumphella by having some large rods in the inner coenenchyme that are relatively smooth at one end and conspicuously ornamented at the other end ( Fig. 18 : top row, second from the left). These are often undetected or overlooked. All sclerites in both species are colorless.

Many of the sclerites in the present material examined here differs somewhat from other known material of the species from outside the Philippines by having strongly acute or sharply pointed tips on the lateral tubercles ( Figs. 17 , 18 ).

SPECIES.— There are two other described species in the genus, Hicksonella guishanensis Zou and Chen, 1984 , and Hicksonella expansa Alderslade, 1986 .

OCCURRENCE AND DISTRIBUTION.— Hicksonella princeps is a zooxanthellate species that inhabits shallow-water areas of coral reefs flats and slopes, usually less than 15 m in depth. It has been encountered in the northeastern part of central Philippines — the Calatagan Peninsula and the Lubang Islands Group. The genus Hicksonella is known only from the tropical western Pacific.

REFERENCES.— Alderslade (1986a), Fabricius and Alderslade (2001), Ofwegen (2010b).

Figures

FIGURE 16. Hicksonella princeps. A. Underwater photograph, Lubang Island, May 2014. B. Wet-preserved partial colony (CASIZG 201363), Lubang Island, May 2014, scale bar = 25 mm.

FIGURE 17. Hicksonella princeps. Scanning electron micrographs of sclerites from the surface coenenchyme, scale bar = 0.03 mm.

FIGURE 18. Hicksonella princeps. Scanning electron micrographs of sclerites from the subsurface coenenchyme, scale bar = 0.10 mm.