Variable Boring Sponge

Siphonodictyon coralliphagum

HOLOTYPE.—USNM 24095 (Figure 5; Plates 3 e,f, 4 a–d; Table 2). Discovery Bay, Jamaica; 25 m; 24 March 1966.

DIAGNOSIS.—Epilithic ectosomal portions, if present, are brittle crusts, hollow cones or tubes. They extend over 2 to 600 cm2. Color deep yellow, lemon yellow to whitish yellow. Circular oscula on top of elevations, if such are existing. Surface microhispid. Choanosome usually endolithic, ovoid to irregular massive. Color: beige yellow to yellow tan. Oxea, large: 135.9–169.3 × 4.7–6.9 μm oxea, small: 118.9–159.6 × 2.1–3.2 μm (range of means of all 22 specimens attributed to the species).

Based on morphological and spicule-dimension differences, four forms can be distinguished which might be different ecophenotypes and or growth stages:

Forma typica: Ectosomal structures consisting of single conical chimneys or tubes protruding from the substratum. Oxea, large: 142.1–156.3 × 5.0–6.4 μm; oxea, small: 129.0–142.9 × 2.2–2.7 μm (range of means).

Forma obruta: No ectosomal structures present. Oxea, large: 135.9–144.0 × 4.9–6.2 μm; oxea, small: 118.9–129.4 × 2.1–2.7 μm (range of means).

Forma tubulosa: Clusters of ectosomal tubes, trumpets or finger-shaped hollow processes. Oxea, large: 165.9–169.3 × 6.1–6.9 μm; oxea, small: 144.5–152.2 × 2.2–3.2 μm (range of means).

Forma incrustans: Extensive flat ectosomal crusts or pillows. Oxea, large: 150.0–164.9 × 4.7–5.7 μm, oxea, small: 140.5–154.7 × 2.3–2.8 μm (range of means).

Siphonodictyon coralliphagum forma incrustans

MATERIAL.—YPM 4757; Runaway Bay, Jamaica; 30–33 m; 16 July 1961; D. Fraser, E. Graham, col. (specimen representative for the form). YPM 4816; Runaway Bay, Jamaica; 24 m; 21 July 1961; E. Graham, col. YPM 4831; Runaway Bay, Jamaica; 15–27 m; 21 July 1961; I. Goodbody, R. L. Walker, col. YPM 4930; Runaway Bay, Jamaica; 15 m; 23 July 1961; T. F. Goreau, E. Graham, R. Dalzeel, col. YPM 5346, YPM 5359, YPM 5388, YPM 5395; Runaway Bay, Jamaica; 33–39 m; 21 May 1961; T. F. Goreau, D. Fraser, L. M. Passano, col. YPM 6496, YPM 6896; Discovery Bay, Jamaica; 57 m; 21 July 1966; J. Lang, col.

DESCRIPTION.—Shape and size: Flat crusts, irregular pillows, or flat cones show above substrate level. Oscula, if present are not, or only slightly, elevated. The maximum diameter of these structures varies between 2 and 26 cm, surface area is approximately 3.5 to 350 cm2. The choanosome is buried in the substrate; its thickness is about one-third the diameter of the whole sponge.

Color: The ectosome varies from deep to lemon yellow, the choanosome is mustard yellow to yellowtan. Preserved specimens are ochre to dark brown; the preservation alcohol of larger specimens is also stained brown.

Consistency: the ectosome is firm but brittle; the choanosome soft, compressible, and very mucous.

Surface: Microhispid and porous. Oscula are distinct only in larger specimens.

Apertures: The oscula are usually level with the sponge surface, are sometimes slightly elevated, and are surrounded by a slight rim; their shape is typically circular. Occasionally, however, two or more adjoining ones become fused together presenting an oval to irregular outline (very distinct in specimen YPM 6496). The interior of the oscula appears as dark in color as the choanosome (in preserved state). The ostia measure 80–300 μm.

Skeleton: Structure of the skeleton and size of the spicule bundles is not different from the typical form.

Spicules: The oxea are usually slightly, sometimes sharply bent. A central canal is distinct only in the ectosomal spicules. Separation into two size categories in the choanosome is only slight since there are many transitional forms. Some styles are present. Tips are blunt, mammiform or mucronate, degenerated where there is a wide central canal developed.

Measurements: Given in table 2.