Mycale (Aegogropila) phillipensis (Dendy, 1896)

(Fig. 24 A–H)

Examined material. Sample HL 54: Vietnam, Cong Do Island, Hang Toi Dark Cave, depth not stated, 14 September 2003.

Description. Massively encrusting sponge covering the colonies of Carijoa riisei with the exception of the anthocodiae (Fig. 24 A). Light red in situ (Fig. 24 A), yellow-brownish in ethanol (Fig. 24 B). Surface macroscopically smooth, consistency elastic and tough. Sample HL 54 covers a very large colony of C. riisei with varying thickness (up to 5 mm). The colony is strongly branched and about 30 cm long (Fig. 24 B).

Skeleton. In the ectosome mycalostyles are organized in loose tracts (Fig. 24 C) connected by single mycalostyles or paucispicular tracts; microscleres are abundant. The choanosomal skeleton consists of plurispicular, plumose, ascending tracts opening in fans towards the surface, making it microhispid (Fig. 24 D). Numerous microscleres are located in the tracts and scattered in the choanosome.

Spicules. Mycalostyles fusiform and straight with well defined heads (Fig. 24 E), 260 – (309.5 ± 26.4) – 350 x 5 – (8.3 ± 1.7) – 10 μm. Palmate anisochelae often arranged in rosettes (Fig. 24 F), 12.5 – (19.1 ± 3.6) – 22.5 μm. Sigmas I “C” or “S” shaped, 37.5 – (43.3 ± 3.8) – 50 μm (Fig. 24 G). Very rare sigmas II “C” shaped, 10–14 μm (Fig. 24 H), were found in the SEM preparation.

Distribution and remarks. Australia ( Dendy 1896), Ambon Bay (Topsent 1897), Vietnam (Lindgren 1897; Dawydoff 1952) and Hong Kong (Pulitzer-Finali 1982). In the Indo-Pacific, Mycale (Aegogropila) phillipensis is the only species with a single category of anisochelae and sigmas as microscleres. The other known species have additional toxas, raphides or two to three categories of anisochelae. Our specimen fits well with the description of Dendy (1896) in having the same spicule complement that is comparable in size. In particular, Dendy (1896) described the mycalostyles “with a well marked head […] and sharp points” about 300 x 5 µm in length, ordinary anisochelae in rosettes of about 37 µm, and sigmas, simple and contort, of about 45 µm. The small sigmas here recorded are very rare and were only observed with SEM. The sponge is known to be encrusting or irregularly massive.