Hemimycale nathani, 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 : 47-48

Hemimycale nathani sp. nov.

( Fig. 22 , Table 8)

Material examined. Holotype — MCCDRS9453, Beagle Rocks, 0.601° S, 90.633° W, 11 m, 10 Sep 2003. Paratypes — MCCDRS9455, 37836, Guy Fawkes Island , 0.515° S, 90.527° W, 27 m, 3 Aug 2003 ; MCCDRS9454, Beagle Rocks , 0.601° S, 90.633° W, 11 m, 27 Mar 2003 . Other material— MCCDRS9452, 0.601° S, 90.633° W, 7 m, 20 Jan 2003.

Type locality. Beagle Rocks (near Pinzón Island) .

Habitat and distribution. Beagle Rocks and Guy Fawkes Island. Holotype found growing on a branch of black coral ( Antipathes galapagensis ). Other specimens found growing on rock; 7–27 m.

Description. Very thinly encrusting sponge, 1 mm thick, densely covered in tiny delicate, trumpet-shaped papillae that are topped with delicate, lacey, circular areolate porefields. Cylindrical, membraneous oscules are interspersed amongst the porefields. Both papillae and oscules collapse on preservation. Colour in life is orange to yellow, aquiferous structures are translucent white ( Fig. 22A–C ). Texture is very soft, delicate, easily torn.

Skeleton. No ectosome present. Wispy tracts of strongyles ascend towards the surface in the choanosome. Spicule density is very low. Areolate pore sieves are strengthened by brushes of perpendicularly arranged strongyles.

Spicules. Megascleres —very fine strongyles; 197 (164–241) × 2 (1–3) µm (n = 70) ( Fig. 22D–E ).

Etymology. Named for co-author Cleveland Hickman’s grandson Nathan. This species name also reflects the Hebrew origin of this name, meaning “he gave” reflecting the giving of the unusual translucent, trumpet-shaped, areolate porefields, from the surface of the sponge. Remarks. Hemimycale nathani sp. nov. can be differentiated from H. harlequinus sp. nov. by the lack of styles and the smaller strongyles. While Van Soest’s (2002a) diagnosis of the genus implies that both styles and strongyles are present, the majority of species only contain strongyles ( H. ceadensis Huguenin, Salani, Lopes, Albano, Hajdu & Esteves, 2018 , H. mediterranea Uriz, Garate & Agell, 2017 , H. insularis Moraes, 2011 , H. rhodus (Hetschel, 1929)) , and styles are rare or absent from specimens of the type, H. columella ( Bowerbank, 1874) ( Huguenin et al. 2018) . We have emended the diagnosis of the genus to clarify this point.

The gross morphology of H. nathani sp. nov. is very similar to that of H. ceadensis from Brazil. However, the latter species possesses raphides and has longer strongyles (248 (138–289) µm) than H. nathani sp. nov. Given these differences and the geographic separation, separation into two species is justified.

Figures

FIGURE 22. Hemimycale nathani sp. nov. A. Holotype, MCCDRS9453, in situ. B. Close up of paratype, MCCDRS9454, in situ. C. Holotype, preserved. D. Tip of a strongyle. E. Strongyle (all SEM images from holotype).