Clathria (Microciona) stellata, 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 : 49

Clathria (Microciona) stellata sp. nov.

( Fig. 23 )

Material examined. Holotype — MCCDRS9466, Cape Berkeley , Isabela Island, 0.010° S, 91.595° W, 12 m, 29 Nov 2004.

Type locality. Isabela Island .

Habitat and distribution. Only collected from type locality; 12 m, but was commonly observed on the west side of Isabela Island . Found growing on rock .

Description. Thinly encrusting sponge, 1–3 mm thick, with a surface covered in small, rounded nodes, ≤ 2 mm in diameter. A few small, inconspicuous oscules, around 1 mm in diameter, are present, from which drain inflated asterose aquiferous channels. Colour in life is mottled pale peach and white, the lot covered by an inflated translucent white membrane ( Fig. 23A–B ). Colour in ethanol is brown ( Fig. 23E ). Surface is smooth, texture is firm, ectosome is not detachable.

Skeleton. No defined ectosome. A confused layer of paratangential auxiliary styles occurs at the surface of the sponge ( Fig. 23C ). Choanosome consists of erect principal subtylostyles, with their heads embedded in the base of the sponge. The rounded nodes of the sponge arise with ascending plumose tracts of echinating subtylostyles and auxiliary styles, the pointed tips protruding beyond the surface of the sponge ( Fig. 23D ).

Spicules. Megascleres— Auxiliary style, small and slender with a lightly acanthose head; 249 (218–297) × 5 (3–7) µm (n = 20) ( Fig. 23H–I ). Principal subtylostyle, stout and typically curved, with a smooth shaft and a rounded, acanthose head covered in small blunt spines or nodes, a large size range; 360 (163–616) × 16 (9–24) µm (n = 30) ( Fig. 23J ). Echinating acanthostyles, small and curved with a spined shaft and acanthose head covered in small spines and rounded nodes; 101 (64–161) × 7 (5–10) µm (n = 20) ( Fig. 23G ).

Microscleres —Palmate isochelae; 11 (9–13) µm (n = 20) ( Fig. 23F ).

Etymology. Named for co-author Cleveland Hickman’s grand-daughter Stella. The species name also reflects the shimmering, translucent, star-shaped aquiferous canals that emanate from the oscules on the surface of this beautiful sponge (Lat. adjective agreeing with Microciona = ‘starry’).

Remarks. Clathria (Microciona) is a large subgenus containing over 100 species, of which, eight species have been recorded in the eastern Pacific. Clathria (Microciona) stellata sp. nov. can be differentiated from most of these species by the absence of toxa. Only two eastern Pacific species do not possess toxa: C. (M.) brepha ( De Laubenfels, 1930) and C. spongigartina ( De Laubenfels, 1930) , and one species contains rare toxa ( C. mytilifila Hajdu, Desqueyroux-Faúndez, Carvalho, Lôbo-Hajdu & Willenz, 2013 ). Clathria (M.) stellata sp. nov. can be differentiated from these species as follows:

• C. (M.) brepha from California is a salmon red sponge that has principal acanthostyles and arcuate isochelae

(17–25 µm) ( Lee et al. 2007);

• C. (M.) spongigartina from California is a brownish red sponge that has principal acanthostyles and two size categories of chelae that are 23–50 µm in length ( Lee et al. 2007);

• C. (M.) mytilifila from Chile is a yellowish-beige sponge that possesses: ectosomal and choanosomal tylostyles;

acanthtylostyles I (243 (164–286) µm) that are smaller than those of C. (M.) stellata sp. nov.; and rare toxa.

A new, unnamed species of Clathria (Microciona) has been recently described from the Colombian Pacific, but this species is scarlet red in life and possesses toxa ( Lizarazo Rodríguez et al. 2020).

Figures

FIGURE 23. Clathria (Microciona) stellata sp. nov. holotype, MCCDRS9466: A. In situ. B. Close up, in situ. C. Cross section of the ectosome showing auxiliary styles protruding through the surface. D. cross section of the sponge surface lobe showing projecting principal subtylostyles and auxiliary styles. E. Preserved specimen. F. Palmate isochelae. G. Acanthostyles. H. Close up of the lightly acanthose head of an auxiliary style. I. Auxiliary style. J. Principal subtylostyle.