Acanthancora equiformis, Sim-Smith & Hickman & Kelly, 2021

Sim-Smith, Carina, Hickman, Cleveland & Kelly, Michelle, 2021, New shallow-water sponges (Porifera) from the Galápagos Islands, Zootaxa 5012 (1), pp. 1-71 : 44-45

Acanthancora equiformis sp. nov.

( Fig. 20 )

Material examined. Holotype — MCCDRS9456, Nameless Island , 0.67° S, 90.586° W, 8 m, 9 Aug 2003.

Type locality. Nameless Island .

Habitat and distribution. Only known from the type locality. Found growing in a small recess on a vertical rock wall; 8 m.

Description. Very thinly encrusting sponge, less than 1 mm thick, densely covered in small oscules and ostia that are flush with the surface. Faint asterose drainage canals are visible on the surface. Colour in life is pale grey with tinges of white, colour in ethanol is light beige ( Fig. 20A ). Texture is soft.

Skeleton. Unknown, specimen is too thin to section, but assumed to be consistent with the skeletal architecture in species included in this genus, as diagnosed above.

Spicules. Megascleres— smooth strongyles with slightly inequiended tips, one tip being more bulbous than the other, sometimes faintly polytylote; 160 (125–182) × 4 (3–6) µm (n = 20) ( Fig. 20C–D ). Acanthostyles, strongly tapered with a prominent spined head; 84 (71–91) µm long (n = 20) (Fig. B). Microscleres— heavily spined isochelae; 20 (17–22) µm long (n = 20) ( Fig. 20E ).

Etymology. Named for the form of the microscleres which resemble prancing horses (Latin adjective agreeing with Acanthancora = ‘horse-shaped’).

Remarks. Only one species of Acanthancora has been described from the eastern Pacific: A. cyanocrypta ( Laubenfels, 1930) from California. Acanthancora equiformis sp. nov. differs from A. cyanocrypta in that the latter species is blue in life, possesses two size classes of acanthostyles, and has smaller chelae (10–15 µm; measurements from Van Soest 2002a) with blunt spines.

Genus Hemimycale Burton, 1934

Diagnosis. Thickly encrusting to massive, with striking and characteristic areolated porefields; skeleton of plumose columns of slightly inequiended strongyles, which are probably derived from tornotes; styles and oxeas may also be present. The choanosomal columns fan out near the surface and strengthen the raised porefields; no microscleres other than raphides (emended Van Soest, 2002 a and Huguenin et al. 2018).

Figures

FIGURE 20. Acanthacora equiformis sp. nov. holotype, MCCDRS9456: A. In situ. B. Acanthostyles. C. Strongyle tip. D. Strongyle. E. Modified, spined isochelae.