Antarctotetilla sagitta

Antarctotetilla sagitta (Lendenfeld, 1907)

Synonymy: Tethya sagitta Lendenfeld, 1907; Craniella sagitta var. microsigma Kirkpatrick, 1908; Craniella sagitta var. pachyrrhabdus Kirkpatrick, 1908.

Material examined: A small piece of the syntype of Tethya sagitta, ZMB Por 3504 Lendenfeld, 1907, Kerguelen, Subantarctic region; Antarctotetilla sagitta, MNHN-IP 2009 31, -65°60'S, 143°03'E, 461–483 m depth, 23 December 2007; MNHN-IP 2 0 0 9 366, -66°20'S, 141°20'E, 207–227 m depth, 13 January 2008 and MNHN-IP 2009 359, -65°60'S, 144°18'E, 229–237 m depth, 12 January 2008, from Terre D’Adélie, Antarctic coasts.

GenBank accession numbers (Carella et al. 2016): MNHN-IP 2009 31 (KT12 4320, KT124332 and KT124370), and MNHN-IP 2009 359 (KT124327 and KT124334).

Description (Fig. 8). Globular sponges of about 8 cm in diameter, enlarged at the equatorial region (Fig. 8a). Surface corrugate with short projections chiefly formed by groups of oxeas, auxiliary oxeas, and protriaenes, supported by a thin collagen layer. Oscules on top, surrounded by a smooth surface area (Fig. 8c). Pores are in subdermal cavities overlaid by sieve-like ectosomal areas (Fig. 8b), which are distributed mainly at the equatorial region. Sponge color brown-greenish in alcohol. Pseudocortex (Fig. 8d–e) composed by auxiliary oxeas loosely arranged perpendicular to the sponge surface. In contrast to A. leptoderma and A. grandis, this species is easily compressible. Anchoring root-tufts composed by anatriaenes.

Spicules (Fig. 9; Table 1). Megascleres: oxeas I (Fig. 9a) large and fusiform: 3700–6418.4–12250 µm x 35 – 62.3–110 µm. Auxiliary small oxeas II (Fig. 9b): 690–1175.5–2007 µm x 6.5–20.6–35 µm. Anatriaenes I (Fig. 9e): 4000–11357.9–19750 µm x17.5–22.5–32.5 µm in size with long thin clades: 100–188.4–250 µm in lenth; rhabdomes fusiform, thicker at the middle and filiform at the terminal part. Anatriaenes II: 3150–3562.5–3900 µm x 12.5–15.8–22.5 µm in size (Fig. 9f) with short clades: 55–74.6–100 µm in length and fusiform rhabdomes. Protriaenes I (Fig. 9c): 3350–10993.3–17450 µm x 12.5 –28.5–50 µm, with clades: 80–152.3–260 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. 9d): 1500–3608.7–5540 µm x 5 –9.9–15 µm, with clades 20–139.3–260 µm in length, usually one clade longer than the other two; rhabdomes tapering to a filiform end. Trichodal protriaenes (Fig. 9g) very small with filamentous rhabdomes: 400–958.8–2840 µm x 2.5–3.5–5 µm long and thin, 5–36–175 µm long clades. Microscleres: sigmaspires (Fig. 9h): 10–11–17.5 µmin length.

Skeletal arrangement. Choanosomal skeleton made of bundles of oxeas, anatriaenes, and protriaenes spiraly arranged. Auxiliary oxeas arranged in palisade at the sponge periphery and scattered throughout the choanosome. Trichodal protriaenes scattered around the oscule rim (Kirkpatrick, 1908) and, sometimes, at the external zone of the ectosome, which they perforate. Sigmaspires distributed through the sponge.

Distribution and habitat. Antarctic coasts, Terre D’Adelie; Subantarctic, Kerguelen (Kirkpatrick 1908; Lendenfeld 1907). Our specimens were collected between 228 and 483 meters of depth.

Remarks. Antarctotetilla sagitta differs from other Antarctotetilla species by a corrugate surface with short projections formed by groups of oxeas, auxiliary oxeas, and protriaenes. Kirkpatrick (1908) stated that the surface pile can vary considerably among specimens. The oscules are placed on top and surrounded by a smooth surface area, while pores are in sub-dermal cavities overlaid by sieve-like areas. Oxeas I, protriaenes, and anatriaenes are longer than in the other Antarctotetilla species examined.