Protis melmackenzieae, Kupriyanova & Flaxman, 2024

Protis melmackenzieae View in CoL n. sp.

urn:lsid:zoobank.org:act:A25072A1-D8D4-42D3-A4F5-F390D236725A

Fig. 7A–F View Figure 7 , 8A–F View Figure 8

Material examined. Holotype: W.54485, Cocos (Keeling) Islands Territory , Cocos (Keeling) (12°13'32"S, 96°57'36"E), depth 1113–1343 m, 17/10/ 2022, complete specimen with operculum. GoogleMaps

Paratypes: W.53456 (LK248), Territory of Christmas Island, Karma Seamount (12°49'33"S, 107°02'48"E), depth 2760–2850 m, 11/07/2021 (1 spec. prepared for SEM) GoogleMaps ; W.55294 (LK274), Cocos (Keeling) Islands Territory , Rudist Seamount (11°03'47"S, 99°26'36"E), depth 3780–3839 m, 12/10/2022 (1 spec.) GoogleMaps ; W.55299 (LK309), same locality (1 spec) GoogleMaps ; W.55298 (LK310), same locality (1 spec.) GoogleMaps ; W.54414 (LK305), same locality (1 spec.) GoogleMaps ; W.55291 (LK306), same locality (1 spec.) GoogleMaps ; W.54415 (LK298), same locality (1 spec.) GoogleMaps .

Description. Tube: pink, although tube colour ranging from nearly white, only slightly pinkish to distinctly pink ( Fig. 7A–F View Figure 7 ), entirely opaque, circular in cross section, attached to substrate throughout its length ( Fig. 7A–F View Figure 7 ). Tube surface rough (not smooth), with growth ridges and occasional narrow peristomes; with attachment area narrowly wider than tube width.

Radioles: each lobe bearing 8–10 radioles arranged pectinately, not connected by inter-radiolar membrane ( Fig. 8B View Figure 8 ). Radiolar eyes and distinct long terminal pinnules absent.

Operculum: if present, a membranous transparent globular vesicle with slightly differentiated distal endplate ( Fig. 8A, B View Figure 8 ) on a normally pinnulated left 2 nd radiole. Pseudoperculum absent.

Collar and thoracic membranes: collar with entire edge, short, barely covering radiolar lobes. Trilobed, medio-ventral lobe slightly higher and wider than lateral lobes ( Fig. 8B, C View Figure 8 ); collar continuous with short thoracic membranes ending as rounded flaps at 3 rd thoracic segment, no apron ( Fig. 8D View Figure 8 ). Pairs of small, wart-like protuberances of collar chaetiger absent; tonguelets between ventral and lateral collar parts absent.

Thorax: with collar chaetiger and 6 uncinigerous chaetigers ( Fig. 8B, C View Figure 8 ). Collar chaetae limbate and fin-and-blade, distal blade not separated from proximal dentate zone ( Fig. 8E View Figure 8 ). Subsequent chaetae limbate, of two sizes. Apomatus chaetae present in posterior thoracic segments ( Fig. 8F View Figure 8 ). Uncini along entire thorax saw-shaped, with 5–6 slightly curved teeth and simple pointed fang ( Fig. 8H View Figure 8 ). Prostomial eyes not observed.

Abdomen: up to 40 abdominal chaetigers. Achaetous anterior abdominal zone absent.Anterior uncini saw-shaped, with 7–8 teeth in profile and simple pointed fang ( Fig. 8I View Figure 8 ), posterior rasp-shaped. Abdominal chaetae flat narrow geniculate with rounded teeth and tapered tip ( Fig. 8G View Figure 8 ). Long capillary chaetae of posterior chaetigers not observed. Posterior glandular pad present.

Size: total body length up to 14 mm, including up to 4.0 mm long radioles, 3.2 mm long thorax 6.8 mm long abdomen, width of thorax 0.6 mm. In holotype external diameter of tube mouth 1.2 mm, corresponding lumen diameter 1.0 mm.

Species diagnosis. The new species is clearly different from the rest of the genus Protis due to the distinctly pinkish tube. This is one of the first newly described species (along with H. perneti n. sp.) of the genus in which a detailed illustrated description is accompanied by the molecular sequence data from the type series.

Etymology. The species is named after Melanie Mackenzie, collection manager at Museums Victoria, Melbourne, Australia.

Distribution. Only known from seamounts off Christmas and Cocos (Keeling) Islands, Indian Ocean, 1113–3839 m.