Penares astronavis, Sim-Smith & Kelly, 2019

Sim-Smith, Carina & Kelly, Michelle, 2019, Review of the sponge genus Penares (Demospongiae, Tetractinellida, Astrophorina) in the New Zealand EEZ, with descriptions of new species, Zootaxa 4638 (1), pp. 1-56 : 43-44

Penares astronavis sp. nov.

( Fig. 34–36 , Table 11)

Material examined. Holotype— NIWA 82272 , NIWA Stn TAN1206/34, Kermadec Ridge, 36.447° S, 177.839° E, 850–980 m, 18 Apr 2012 .

Type locality. Southern Kermadec Ridge , New Zealand .

Distribution. Only known from type locality, the Southern Kermadec Ridge, New Zealand; 980 m ( Figure 36 ).

Description. Morphology is a thinly encrusting, nodular sponge, growing over dead coral branches ( Figure 34A ); 25 mm × 10 mm × 2 mm thick. Texture is firm but compressible. Surface is slightly scratchy to the touch. No pores or oscules are visible. Colour in ethanol is greyish brown throughout.

Skeleton. Cortical skeleton comprises a densely packed layer of microrhabds, 100–150 µm thick. Microrhabds have no particular orientation in the cortex ( Figure 34C ). Choanosomal skeleton is densely packed with oxyasters ( Figure 34C ). Very short triaenes are common and positioned just below the cortex ( Figure 34B ). Oxeas occur infrequently in the choanosome, having no particular orientation.

Spicules ( Figure 35 ; Table 11). Megascleres —oxeas ( Figure 35A ) are short, very slender and almost straight; 1269 (768–1692) × 21 (13–27) µm (n = 20). Dichotriaenes ( Figure 35B & C ) have a short rhabdome; 180 (117–255) µm long × 593 (407–946) µm wide (n = 20). Deuteroclads are conical, widely separated and longer than proto- clads.

Microscleres —oxyasters ( Figure 35D ), highly modified into asymmetrical shapes. Rays are smooth, strongly conical, of varying length, and have a mixture of sharply pointed and bluntly rounded tips; 54 (39–85) µm in diam- eter (n = 20). Microrhabds ( Figure 35E ) vary from short, very stout, straight rods with pointed or bluntly rounded tips to perfectly spherical balls. Occasionally, fused or cross-shaped microrhabds occur; 40 (16–82) × 13 (6–20) µm (n = 20).

Etymology. Named for the unusual shape of the oxyasters, which resemble a spaceship (astro, of the stars; navis, ship; Latin).

Remarks. The unusual oxyasters of P. astronavis sp. nov. differentiate it from all other Penares species. The species also possesses smooth spherules, but these appear to be a reduced form of microrhabd rather than a separate spicule category in this species. Penares astronavis sp. nov. also has particularly short and wide dichotriaenes (180 (117–255) µm long × 593 (407–946) µm wide). The only other New Zealand Penares that has similar length dicho- triaenes is P. kermadecensis sp. nov. (197 (122–300) µm long × 854 (644–1085) µm wide, but it has a much wider cladome than P. astronavis sp. nov.

Figures

FIGURE 34. Penares astronavis sp. nov., holotype NIWA 82272: A. Holotype preserved in ethanol; B. Section showing the position of the dichotriaenes below the cortex; C. Section showing the dense layer of microrhabds in the cortex and the abundant oxyasters in the choanosome.

FIGURE 35. Penares astronavis sp. nov., holotype NIWA 82272: A. Oxea; B & C. Dichotriaenes; D. Deformed euasters; E. Microrhabds.

FIGURE 36. Distribution of P. astronavis sp. nov. around New Zealand. The white outline shows New Zealand’s Exclusive Economic Zone.