Amphimedon dinae, Helmy, Tamer, Van, Rob W. M. & Soest, 2005

Helmy, Tamer, Van, Rob W. M. & Soest, 2005, Amphimedon species (Porifera: Niphatidae) from the Gulf of Aqaba, Northern Red Sea: Filling the gaps in the distribution of a common pantropical genus, Zootaxa 859, pp. 1-18 : 7

Amphimedon dinae sp.nov. ( Figs. 1 D, 3A–C)

Material examined. Holotype ZMA Por. 17341, Ras Um El Seed, 8m, coll. T. Helmy, 25­07­2000.

Description. Colour: Brown. Shape: Massively encrusting, 2 cm high, 0.5–1 cm thick with clear well distributed oscula 2–4 mm wide. Surface: punctate due to regularly distributed subdermal cavities. ( Figure 3A ). Texture: Compressible, corky, can be torn but not easily.

Skeleton. Ectosomal skeleton ( Figure 3 B) is a paratangential reticulation of spongin fibres forming rounded meshes 40­175­430 µm. Fibres variable in diameter, 9–80 µm. Coring rare or absent. Choanosomal skeleton ( Figure 3 C) is an anisotropic reticulation of primary fibres 42–80 µm and secondary fibres 5­11­16 µm forming polygonal meshes of 60–585 µm wide. Coring rare or absent, overall spicular presence low.

Spicules: Thin oxeas ( Figure 1 D), 52­57­ 61 x 1 –1.5 µm.

Etymology. Named after Dina Helmy , Ismailia, Egypt, for her continuous help during many stages of Tamer Helmy's work.

Ecology: Attached to dead corals or other solid rocky substratum in the coral reef community, in the vicinity of algal mats. When torn off, a mucilaginous substance is found in parts connected to the rocks.

Distribution. It was found in several sites in the Gulf of Aqaba including Ras Um El Seed and Ras Nusrani (pers. obs. T.H.).

Remarks. Amphimedon chloros and Amphimedon specimens described below differ from the new species in having abundant spicules as opposed to the rare almost vestigial spiculation of A. dinae sp.nov.. Our specimen is closest to specimens of the Caribbean Amphimedon complanata (Duchassaing, 1850) as redescribed by Van Soest, 1980. Like A. dinae sp.nov. this has a reticulation of spongin fibres cored sparsely with thin spicules. It differs in being much more elaborate of form with a strong tendency towards a flabelliform habit. It has an irregular surface, and the colour is dark purple to black. We examined the specimens in ZMA (a.o. the type of Duchassaing's Spongia complanata , ZMA Por. 2095) and found that it has rectangular meshes of 50–300 µm formed by paucispicular primary fibres 30–70 µm which contain 0–8 spicules and secondary paucispicular fibres 8–30 µm with 0–4 spicules. Spicules of Amphimedon complanata are exclusively strongylote oxeas 70–120 x 0.5–3 µm. Our new species has clearly shorter spicules and appears to have a coarser spongin fibre skeleton.

Figures

FIGURE 1. Map of the Northern Red Sea showing the localities where the described sponges were observed and collected.

FIGURE 3. A. Amphimedon dinae, habit (scale bar = 1 cm); B. Amphimedon dinae sp. nov., ectosomal skeleton (scale bar = 500 µm); C. Amphimedon dinae sp. nov., choanosomal skeleton showing the thin oxeas embedded in the fibres (scale bar = 100 µm).