Haliclona (Halichoclona) pellucida Bispo & Willenz & Hajdu 2022, sp. nov.

Haliclona (Halichoclona) pellucida sp. nov.

(Figure 10, Table 3)

Holotype. MNRJ 12149 (Vouchers: RBINS-IG 32240 -POR 12149, MHNG 85591)— Punta Hornillos, Matarani, Arequipa Region (16°52’49.80” S, 72°17’18.24” W), depth 11 m, coll. Y. Hooker, U. Zanabria & Ph. Willenz (28/ XI/2008).

Diagnosis. The only Haliclona in the Eastern Pacific with a combination of thickly encrusting to cushion-shaped habit, white colour alive with translucent smooth surface, isotropic, slightly confused to isodictyal choanosomal reticulation of oxeas 129–184 µm in length.

Description (Fig. 10A, B). Thickly encrusting to cushion-shaped, ca. 7 mm thick, spreading laterally to cover an area larger than 20 x 7 cm. Surface smooth, but uneven, just slightly punctate, translucent. Oscula common, circular, 1–3 mm wide, just slightly elevated or at the top of small volcaniform projections, up to 5 mm high. Consistency firm, nearly incompressible Colour alive is white, with a translucent surface that gives to the sponge an icy aspect.

Skeleton (Fig. 10C–E). Ectosomal skeleton a dense isotropic reticulation, with some ill-defined paucispicular tracts without a clear orientation. Choanosomal skeleton a dense and confused isotropic reticulation with occasional ill-defined paucispicular (1–4 spicules) tracts perpendicular to the surface. In some parts, the skeleton becomes a regular isodictyal reticulation, of uni- to bispicular triangular to squared meshes, Choanosomal spaces are common, especially closer to the surface, 284–756 µm wide. Spongin at the nodes of the reticulation.

Spicules (Fig. 10F–H). Oxeas, hastate, mostly curved, 129– 161– 184 µm x 3.0– 7.5– 12 µm (n = 40 x 20).

Ecology. Found on rocky substrate, underneath an overhang at about 11 m depth, co-occurring with shrimps and other sponges. Water temperature during collection was 15°C.

Etymology. The epithet “ pellucida ” refers to the vitreous aspect of this sponge (L. pellucidus = clear, transparent).

Distribution (Fig. 3D). Only known from its type locality, Matarani (Arequipa Region), in Peru.

Remarks. The new species has a mainly dense, isotropic skeleton, with choanosomal spaces and firm consistency, matching the H. (Halichoclona) definition. Even though, its skeleton turns into a more regular isodictyal reticulation in parts, resembling that of H. (Reniera). However, the also dense and confused ectosomal skeleton markedly deviates from the very regular and unispicular ectosome of typical H. (Reniera) as H. (Re.) aquaeductus (Schmidt, 1862), H. (Re.) cinerea (Grant, 1826) and H. (Re.) implexiformis (Hechtel, 1965). Thus, the new species is best classified in H. (Halichoclona).

Two species that are similar to H. (Halich.) pellucida sp. nov. in shape and colour are the Easter Island endemics H. rapanui and H. translucida (Table 3). The former is close to the new species in face of its thickly encrusting habit (up to 19 mm thick), oscula 2–3 mm wide and similar sized oxeas. However, the two species are easily distinguished based on their hispid surface, presence of ascending multispicular tracts in the choanosome, and oxeas usually modified to styles or strongyles in H. rapanui (Desqueyroux-Faúndez 1990). Haliclona translucida is also similar to the new species, given its white to yellow colour alive, thickly encrusting habit, oscula 1.5–2.0 mm wide, and an isodictyal to isotropic reticulation with triangular or squared meshes and no spicule tracts (Desqueyroux-Faúndez 1990). However, the latter can be differentiated from H. (Halich.) pellucida sp. nov. based on their non-overlapping oxeas’ dimensions, 94–116 µm long in the Easter Island species (Desqueyroux-Faúndez 1990), and 129–184 µm in the new one.

Haliclona (Halich.) pellucida sp. nov. is similarly close to H. (Halich.) arequipaensis sp. nov., H. (Halich.) paracas sp. nov., H. (Re.) algicola, and H. (S.) spuma given their habit (overall similar shape, and somewhat similar colouration). However, H. (Halich.) pellucida sp. nov. has a distinct translucent aspect on the surface, without the same punctate aspect present in these species (Thiele 1905; Sim-Smith et al. 2021; present study). In addition, H. (S.) spuma has a subanisotropic reticulation with primary multispicular lines, whereas the new species has an isotropic to isodictyal reticulation (Sim-Smith et al. 2021). Finally, H. (Re.) algicola also has longer oxeas (193–208 µm, (Hajdu et al. 2013), than those of H. (Halich.) pellucida sp. nov. (129–186 µm long).

The firm consistency of H. (Halich.) pellucida sp. nov. warrants comparison with two other white-coloured Eastern Pacific haplosclerids, namely Xestospongia dubia (Ristau, 1978) and Neopetrosia vanilla (de Laubenfels, 1930). Both are white, encrusting, hard, and with a very dense isotropic reticulation, that in X. dubia is reinforced with multispicular tracts. These features make them distinct from the new species (de Laubenfels 1930; Ristau 1978; Lee et al. 2007). In fact, the generic assignment of X. dubia is not clear, with oxeas smaller than expected for Xestospongia, but approaching Neopetrosia. The similarities between X. dubia and N. vanilla suggests their synonymy should be evaluated.