Phascolosoma, Leuckart, 1828

Georgieva, Magdalena N., Wiklund, Helena, Ramos, Dino A., Neal, Lenka, Glasby, Christopher J. & Gunton, Laetitia M., 2023, The Annelid Community of a Natural Deep-sea Whale Fall off Eastern Australia, Records of the Australian Museum (Rec. Aust. Mus.) 75 (3), pp. 167-213 : 205

Phascolosoma undes. sp.

Fig. 31

Sipuncula fam. gen. spp. Gunton et al., 2021: 156

Material examined. NHMUKANEA 2022.405 , AM W.52201 , AMW.52202 , AMW.52203, IN2017_V03_100; 9 June 2017; off Byron Bay , NSW, Australia, beam trawl, start: 28.05°S 154.08°E, 999 m, end: 28.10°S 154.08°E, 1013 m. DNA vouchers: NHMUKANEA 2022.405 ( COI, 16 S, 18 S) , AMW.52201 (18S) , AMW.52202 (18 S) , AM W.52203 (16 S, 18 S) .

Description. Specimens AMW.52201, AMW.52202 and AM W.52203 all in poor condition, only two small anterior fragments (max. 4 mm length) and one posterior fragment remaining ( Fig. 31A–B ), thus morphological description is very difficult. Small papillae onoutside ofbody. No tentacles, introvert hooks, mouth or nephridiopores observed.

Distribution. IN2017_V03, Station 100. Pilot whale carcass, off Byron Bay, New South Wales, Australia in 999–1013 m.

Remarks. Bayesian analysis of combined dataset of COI, 16S and 18S sequence data revealsthat our species isa sister group to Phascolosoma (Phascolosoma) turnerae Rice, 1985 although support is low (pp 0.5) ( Fig. 32 ); average COI pairwise genetic distance between the two species is 26.7% (Table S19). In our analysis Phascolosoma sp. and all other Phascolosoma species, except Phascolosoma capitatum Gerould, 1913 , are recovered as a poorly supported clade (pp. 0.5). This result partly agrees with Bayesian analysis on four genes (18S, 28S, H3 and COI) in Schulze, Cutler, & Giribet (2007), where all species of Phascolosoma except P. capitatum and P. turnerae formed a monophyletic group. Interestingly P. turnerae is also a deep-water species described from 366–1184 m associated withsubmerged wood ( Rice, 1985), whereasallother species of Phascolosoma except for P. capitatum are shallow-water species. Due to the poor morphological condition of the specimens the species is not formally described here.

Figures

Figure 31. Phascolosoma sp. fragments. (A) AM W.52203 anterior fragment, scale bar is 1 mm; (B) AM W.52201 anterior fragment, scale bar is 1 mm; (C) AM W.52202 fragment, scale bar is 1 mm; (D) AM W.52203 anterior fragment, scale bar is 1 mm.

Figure 32. Phylogeny of Sipuncula based on Bayesian analysis of the COI, 16S and 18S gene fragments. Numbers adjacent to nodes indicate posterior probabilities, and taxa for which sequences have been contributed by the present study are indicated in bold.