Phakellia rubra, Samaai & Pillay & Janson, 2019

Samaai, Toufiek, Pillay, Ruwen & Janson, Liesl, 2019, Shallow-water Demospongiae (Porifera) from Sodwana Bay, iSimangaliso Wetland Park, South Africa, Zootaxa 4587 (1), pp. 1-85 : 48-50

Phakellia rubra sp. nov.

( Fig. 20 A–F)

Material examined. Holotype. SAMC–A24773 (cross-reference TS 907 & Saf 03-Sod 33), Five Mile reef, Sodwana Bay (27,495°S; 32,6902°E), South Africa, 0 3 November 2003, collected by T. Samaai; depth 20 m. Type locality. Five Mile reef, Sodwana Bay, east coast of South Africa.

Description. Erect, massive, stipitate sponge, 70 × 70 × 30 mm diameter ( Fig. 20A ). Surface smooth, fleshy and conulose, with a skin-like dermal membrane stretched between the ends of the fibres (lost in preservative). Oscules, 4–5 mm diameter, sunken on the surface. Ostia, <1 mm diameter spread all over surface. Texture firm, flexible, compressible. Colour in life dark-red; in preservative, beige.

Skeleton ( Fig. 20B ). Choanosomal skeleton consists of a dense interwoven mass of sinuous strongyles and styles. Axial spicules disposed longitudinally in a dendritic fashion. Spicule tracts definable for very short distance in choanosome before becoming obscured. Choanosomal peripheral region not well formed; spicules predominantly styles and oxeas, arranged individually, branching tangentially from the axis becoming plumoreticulate and protrude through the ectosome. Styles in the axial and peripheral skeleton do not appear to be differentiated, overlying the axial strongyles. Specialized ectosomal skeleton absent.

Spicules. Megascleres ( Fig. 20 C–F). Strongyles, sinuous, occasional stylote modifications occur, 901 (895– 911) × 3 (3) µm, n = 10. Styles, usually slightly curved one-third the distance from the head; some distinctly curved midway, 527 (521–532) × 7 (7) µm, n = 10. Oxeas, slightly curved midway, with one end hastate, 389 (384–392) × 6 (6) µm, n = 10. Microscleres. Absent.

Substratum, depth range and ecology. Found usually on coral rubble, in sheltered locations and rock ledges at a depth of 20 m.

Geographical distribution. Sodwana Bay, east coast of South Africa.

Etymology. Named for the dark red colour of the sponge (ruber meaning dark red, L.).

Remarks. Phakellia is similar to, and often confused with, Acanthella due to the presence of sinuous spicules in the choanosome. They differ primarily in the arrangement of the choanosomal skeleton ( Alvarez et al. 1998). Members of Phakellia have a well-defined axial region and an extra-axial skeleton and a reticulate peripheral skeleton ( Bergquist 1970; Carvalho et al. 2007; Alvarez & Hooper 2009). Members of Acanthella lack the axial and extra-axial skeleton, and have a central axial column producing a dendritic skeleton of branching spicule tracts ( Hooper & Levi 1994). This species clearly fits within the definition of Phakellia ( Carvalho et al. 2007; Alvarez & Hooper 2009). The majority of Phakellia species are described from all over the world and the genus contains 32 valid of which two are described from the WIO (Van Soest et al. 2017). This is the first record of this genus in the South African region. Phakellia radiata ( Dendy, 1916) , described by Dendy (1916, 1922), is a thin crust (with a large large number of independent but closely located conules on the surface) and differs from the new species in having a dull orange colouration and the presence of trichodragmata. Comparison of spicules dimensions indicates that P. radiata has smaller styles (600 × 23 µm) and strongyles (430 × 17 µm) and a skeleton of spicule tracts with a reticulation of rounded meshes. Lamarck (1814) described P. labellum ( Lamarck, 1814) from Madagascar. Phakellia rubra sp. nov. has a similar spicule complement to P. labellum but differs in spicule geometry with having two size categories of styles and in that the strongyles are reduced to very thin and sinuous stylesstrongyles. Phakellia labellum has not since been recorded from Madagascar even though Thomas (1979) produced an extensive sponge monograph from this region. Based on the morphological differences between all three species, and the limited distribution potential of sponges, P. rubra sp. nov. is considered as a new member of Phakellia .

Key diagnostic characters.

• Sponge massive and stipitate.

• Dark red colour.

• Axial spicules disposed longitudinally in a dendritic fashion in choanosome.

• Strongyles, styles and oxeas present as spicules.

Figures

FIGURE 20. Phakellia rubra sp. nov. A. In situ; B. Skeletal architecture (B, x5); C. Strongyles (sinuous); D. Style; E. Oxeas; F. Oxeas with hastate modifications