Polymastia invaginata Kirkpatrick, 1907

Figure 9, Table 5

Polymastia invaginata Kirkpatrick, 1907: 271; 1908: pp. 15–16, pl. XII(1b), pl. XIV (5–15a); Burton 1929: 446; Koltun 1964: 26, pl. IV (10–14); Boury-Esnault & van Beveren 1982: 36–37, pl. IV (13–14), Figs 9 D–F, Plotkin & Janussen 2008:102- 109, Figs 4–5, Tables 2–3.

Polymastia invaginata var. gaussi Hentschel 1914: 49, Taf. V, Fig. 4.

Material examined: QM G315026, Casey Antarctic Research Base, Windmill Islands, Antarctica, -66.2822, 110.5266, 30 m, SCUBA, Coll. M. Riddle & P. Goldsworthy, 10/XI/1997 ; QM G335958, same collection details as QM G315026; QM G311143, Mc Murdo Base, Cape Armitage, Ross Island, Antarctica, -77.85, 166.67, 20 m, north Jetty, Judy’s 1 st dome site, NCIS Q66C3091 -Z, SCUBA, Coll. Australian Institute of Marine Sciences and National Cancer Institute, 18/X/1989 .

Morphology: Solitary circular sponge with a bulbous cushion base 52–83 mm wide and 25–40 mm in height (Fig. 9 A–G). Partially burrowing with a single large contractile and retractile central papilla, 13–19 mm wide, height 0–3 mm above the dermis in preservative, and judging by Fig. 9 A, B equal in height as width in vivo. There is a large single oscule at the top of the papillae (1–2 mm wide). The sponge is grey/brown in life and in ethanol, reflecting the colouration of the surrounding mud/silt. The papillae are ivory to cream in life and ethanol (Fig. 9 A–G). The sponge is firm but compressible, and is covered in a soft covering of fine hairs (except the papilla).

Skeleton: The ectosomal skeleton is composed of an erect palisade of smaller tylostyles on the base, absent from the papilla, with larger styles protruding out from the choanosomal tracts (Fig. 9 H, I). There is abundant sand/detritus on the surface providing grey colouration to the ectosome. The choanosomal skeleton consists of huge multispicular tracts diverging and providing support to the smaller ectosomal tylostyles (Fig. 9 H, I). Stellate formations of smaller tylostyles occur between the tracts (Fig. 9 J).

Spicules: Choanosomal principal styles tapering sight subtylostyle bases (hastate), tapering to sharp points (Fig. 9 K). Ectosomal tylostyles are straight to slightly curved and have a prominent tylote base (Fig. 9 L). Stellate tylostyles in the choanosome between the tracts, are indistinguishable from the tylostyles in the ectosome. Spicular measurements are given in Table 5.

Distribution: Antarctic and Subantarctic waters

Ecology: Partially burrowing in soft mud

Molecular data: no unambiguous 28S-C region barcode could be generated from this species.

Remarks: These specimens match Kirkpatrick’s (1907) and subsequent authors’ descriptions of this species albeit with some variable spicule measurements between the publications. Plotkin & Janussen (2008) reviewed the various authors’ descriptions and measurements compared to their material, which is not repeated here. The location of this specimen from the Lord Howe Plateau is a range extension from the previous Antarctica and subantarctic records. In Plotkin & Janussen (2008), the P. invaginata samples from Antarctica deposited at the SMF, contain novel sceptre like spicules. Unfortunately, the P. invaginata specimens that were sequenced (Plotkin et al. 2017) were from a different cruise and are deposited at ZMBN. Plotkin et al. (2017) makes no mention of whether these samples have the sceptre like spicules. The morphology, skeleton and spicules match the original and more recent descriptions these new specimens also contain the stellate formations of tylostyles as reported by Kirkpatrick, (1907), Hentschel (1914), Koltun (1964), Boury-Esnault & van Beveren (1982), and Plotkin & Janussen (2008).