Placospongia melobesioides Gray, 1867

Becking, Leontine E., 2013, Revision of the genus Placospongia (Porifera, Demospongiae, Hadromerida, Placospongiidae) in the Indo-West Pacific, ZooKeys 298, pp. 39-76 : 49

Placospongia melobesioides Gray, 1867 Figure 6

Placospongia melobesioides Gray (1867): figs 1-4.

Material examined.

Holotype. BMNH 52.4.1.14, Indonesia, Borneo island.

Vosmaer & Vernhout (1902), Siboga expedition: RMNH POR. 756, RMNH POR. 761, RMNH POR. 758, RMNH POR. 757, RMNH POR. 760, RMNH POR. 759. Other material:: RMNH POR. 4497, RMNH POR. 4496, RMNH POR. 4495, RMNH POR. 4114, RMNH POR. 3978, RMNH POR. 3977, RMNH POR. 3976, RMNH POR. 3942, RMNH POR. 3941, RMNH POR. 3940, RMNH POR. 3939, RMNH POR. 3938, RMNH POR. 3937, RMNH POR. 3935, RMNH POR. 3934, RMNH POR. 3933, RMNH POR. 3932, RMNH POR. 3177, RMNH POR. 3166, RMNH POR. 3154, RMNH POR. 2464, RMNH POR. 2463, ZMA Por. 13097, ZMA Por. 10459 (See Table 3 for full details per specimen)

Description.

Holotype BMNH 52.4.1.14 dry, chalky white angular branches, hard. Other examined material encrusting to branching, hard, thicker specimens slightly compressible. External morphology follows the description of the genus. Size ranging between 5-50 cm, though encrusting specimens may be larger growing within crevices. Ectosome color in life ranging from purple, dark black brown, chocolate brown, orange brown to light beige (Fig. 1, 2). Choanosome pale beige. After preservation color of ectosome is similar to live color.

Spicules. Holotype BMNH 52.4.1.14 (Fig. 6): Megascleres large straight tylostyles with blunt ends 670-880-1010 × 10-13-18 × 10-16-20 μm, small concave to straight tylostyles with sharp ends 205-293-420 × 5-10-13 × 5-10-13 μm. Microscleres selenasters 58-63-68 × 45-52-68 μm, spherasters 15-17-18 μm (five measurements, not abundant), spherules 1-2-3 μ m. The range within the examined material (Table 1): large tylostyles 460-1040 × 5-16 × 8-18 μ m, small tylostyles 190-470 × 3-13 × 3-15 μ m, selenasters 45-83 × 30-65 μ m, spherules 1-3 μ m, spherasters only found in singles in some individuals 15-20 μ m. Streptasters and microrhabds absent.

Skeleton. As description of genus with addition of sporadic spherasters lodged amidst selenasters in cortex and high abundance of spherules in choanosome and cortex.

Ecology.

Depth: 0-45m. Reefs, rocky shores, reefflats, mangroves, and marine lakes.

Distribution.

Type locality: Borneo. Distribution from Seychelles to Micronesia (Fig. 9, Table 3). Possibly further east to Central Pacific.

Remarks.

In the original description by Gray (1867) there is no mention of two size classes of tylostyles. I reexamined the original slide and conclude that the holotype does contain two size classes of tylostyles. The Systema Porifera indicates that the holotype has two size classes, the large 720-963-1200 × 13-14.1-19 μm and the small 350-438.8-560 × 8-9.1-10.5 μm, based on 10 measurements per spicule type ( Rützler 2002). These measurements deviate from the holotype measurements in the present study that were based on 25 measurements per spicule type (670-880-1010 × 10-13-18 μm and 205-293-420 × 5-10-13 μm respectively), and also deviate from the range of sizes within the examined material of this study (Table 1). There is great variation in tylostyle length and spherasters are only sporadically present, often absent.