Paelopatides Théel, 1886

Genus Paelopatides Théel, 1886 View in CoL

Diagnosis. (following Martinez et al., 2019 after SolÍs-MarÍn, 2003) “Body more or less distinctly depressed, with a rather considerable rim surrounding the sides and the extremities. Tentacles 15–20, peltate, or sub digitate on margin of the crown. Mouth ventral. Anus dorsal or subdorsal. The tube feet form a double row along the odd ambulacrum, except on the anterior part where they are absent. The papillae form a simple row around the margin of the rim and are scattered along each of the two dorsal ambulacra as well. Interambulacra naked. Gonads on both sides of the dorsal mesentery. A rete mirabile is sometimes present. One or two Polian vesicles. Stone canals apparently lacking. No calcareous ring. Ossicles: Simple tri-radiate or quadri-radiate rods either smooth or spinous; with slightly branched tips; exceptionally deposits often entirely wanting.”

Remarks. Typically large, purple, gelatinous group, with at least one species, Paelopatides retifer reported to swim ( Miller and Pawson, 1990). Of the 21 currently accepted species of Paelopatides worldwide, four have previously been recorded for Australia: P. appendiculata , P. aspera (one record only), P. ovalis (one record only), and P. quadridens (WoRMS, ALA and NMV catalogue, 2024). Five lots of Paelopatides are recorded here from the IOT voyages at depths of 2000–3839 m and further identified to OTU species level as follows: Paelopatides sp. MoV. 7336 (2 lots), Paelopatides sp. MoV. 7337 (3 lots). The COI sequence data indicates two well-supported Paelopatides lineages that form a clade with IOT Scotothuria herringi (fig. S5). There is 10.9% net genetic divergence between the two Paelopatides lineages. Within each Paelopatides lineage, the IOT samples are more closely related to each other than the GenBank sequences from specimens collected in the eastern Pacific Ocean. Only one IOT specimen was sequenced for 16S. This individual grouped with the same Paelopatides specimen from California, USA as it did in the COI phylogeny. Accurate identification can be difficult in the group due to ossicles often being absent or not diagnostically distinctive, and specimens not maintaining their form when preserved.