Myxilla (Myxilla) mollis Ridley & Dendy, 1886

Schejter, Laura, Cristobo, Javier & Ríos, Pilar, 2024, New records of demosponges (Porifera) from the South Orkney Islands (Antarctica) with a checklist for the region, Zootaxa 5403 (4), pp. 401-430 : 414-415

Myxilla (Myxilla) mollis Ridley & Dendy, 1886

( Figure 7a )

Restricted synonymy: Lissodendoryx spongiosa ( Ridley & Dendy, 1886) , Myxilla magna Topsent, 1917 , Myxilla mollis Ridley & Dendy, 1886 , Myxilla spongiosa Ridley & Dendy, 1886 .

Material examined: 2 specimens collected in stations 6 ( SOI; 61°25'S, 44°37'W; 290 m; 3/3/2014; MACN-In 44393; IEO-CSIC Col.) and 11 ( SOI; 60°53'S, 42°35'W; 487 m; 10/3/2014; IEO-CSIC Col.) .

Description: Massive sponge, beige in colour, firm in consistency, but crumbly in preserved specimens ( Figure 7a ). Small pebbles are evident at the base of one specimen. The specimen from station 6 has styles of 630–700 µm by 30 µm, tylotes with spined ends of 275–315 µm. Microscleres are anchorate chelae of 70–85 µm and two categories of sigmas: 150–170 µm and 45–90 µm. The specimen from station 11 has styles of 550–640 µm by 30 µm, tylotes with mucronate spined ends of 280–320 µm. Microscleres are anchorate chelae of 25–45 µm and two categories of contorted (S and C shape) sigmas: 60–70 µm and 25–30 µm.

Remarks: This is a common species in the southern hemisphere, has several synonyms and it has been recorded many times from Antarctica. Part of its intrinsic variability regarding spicule sizes was described by Ríos & Cristobo (2007b). This species was recorded from Antarctic waters by Ridley & Dendy (1886), Topsent (1917), Ríos & Cristobo (2007), Desqueyroux, (1975, 1989), Koltun (1964), Boury-Esnault & Van Beveren (1982) and Fernández et al. (2021). It was also recorded from subantarctic waters (e.g. Burton, 1940; Bertolino et al. 2007). Other records in the SW Atlantic Ocean have been published by Burton (1932, 1940) and Bertolino et al. (2007). This is the first record for the SOI region.

Figures

FIGURE 7. a. Myxilla (Myxilla) mollis, general morphology, scale: 3 cm; b–f. Myxilla (B.) lissostyla, b. general morphology, scale: 2 cm; c. chela, scale: 50 µm; d. chela, scale: 30 µm; e. tylote, scale: 55 µm; f. style, scale: 110 µm; g–k. Myxodoryx hanitschi, g. general morphology, scale: 2 cm; h. style, scale: 80 µm; i. tornote, scale: 45 µm; j. acanthostyle, scale: 65 µm; k. acanthostyle, scale: 25 µm.