Antarctotetilla pilosa Carella & Uriz 2018, nov. sp.

Antarctotetilla pilosa nov. sp.

Material examined: 1 individual (holotype, CEAB. POR. BIO.502a ANT 27211), South Orkneys, Subantarctic region, - 61° 8.74‘S, -43° 58.15‘W, 407 m depth, 19 February 2011 (Carella et al. 2016).

GenBank accession numbers (Carella et al. 2016): CEAB.POR.BIO.502a ANT 27211(KT124313 see S1, KT124355 and KT124361).

Description (Fig. 12). Globular, 8 cm in diameter sponge (Fig. 12a, b and c).Long hairy hispidation protruding up to 2 cm, throughout the surface, caused by long fusiform oxeas, protriaenes, and sometimes anatriaenes. This hispidation becomes much longer (up to 4 cm) after sponge desiccation due to flesh retraction. Oscules of several sizes spread on the sponge body (Fig. 12d). Pores grouped in more or less deep surface depressions (Fig. 12e). Pseudocortex (Fig. 12f) composed of loose auxiliary oxeas perpendicular to the sponge surface. Megascleres: oxeas, protriaenes, anatriaenes, and trichodal protriaenes; microscleres: sigmaspires. A basal root-tuft system of anatriaenes.

Spicules (Fig. 13; Table 1). Megascleres: oxeas I (Fig. 13a) large and fusiform: 4050–7682.5–10950 µm x 35 – 83.5–120 µm. Auxiliary small oxeas II (Fig. 13b): 630– 1137–1780 µm x 12.5–22.4–35 µm. Anatriaenes I (Fig. 13f): 7180–12460–16880 µm x 22.5–24.5–27.5 µm in size with long and thin clades: 160–190.5–210 µm long; rhabdomes fusiform, thicker at the middle and filiform at the terminal part. Anatriaenes II: 3220–3806.7–4960 µm x 15 –17.5–22.5 µm in size (Fig. 13e) with short clades: 62.5–85.8–130 µm and fusiform rhabdomes. Anatriaenes III (Fig. 13g): 4400–10265–14350 x 17.5–24.4–27.5 µm in size with thick, 70–117.6 –140 µm long clades; rhabdomes fusiform, thicker at middle and filiform at the terminal part. Protriaenes I (Fig. 13d): 4300–6986.2– 10880 µm x 20–30–40 µm with clades: 100–181.7–260 µm long, usually one clade longer than the other two; rhabdomes tapering from the base of the clades to end in a filamentous termination. Protriaenes II (Fig. 13c): 2400– 2767.5–3250 µm x 10 –11.9–17.5 µm, with clades: 80–142–240 µm in length, usually one clade longer than the other two; rhabdomes tapering to a filiform end. Trichodal protriaenes (Fig. 13h) very small with filamentous rhabdomes: 405–1063.6–2480 µm x 2 –2.6–5 µm long and thin, 10–51.4–175 µm long clades. Microscleres: sigmaspires (Fig. 13i): 10–11.6–12.5 µm in length.

Skeletal arrangement. Choanosomal skeleton composed by bundles of oxeas protriaenes and anatriaenes spirally arranged from the central part toward the periphery. Auxiliary oxeas either disposed in palisade at the sponge periphery or scattered in the choanosomal zone. Trichodal protriaenes distributed at the peripheral zone; sigmaspires spread through the sponge. Anatrianes III form part of the dense hair-like surface tufts.

Distribution and habitat. The only individual available was collected from the Subantarctic (South Orkneys) at a depth of 407 meters.

Remarks. Morphologically, this species fits within Antarctotetilla as it has their pores grouped in surface depressions and a pseudocortex. Antarctotetilla pilosa differs from other species of the genus by the presence of a hair-like hispidation through the whole sponge, and a third type of anatriaene with short and thick clades (anatriaene III).