Pseudopolydora nivea Radashevsky, Malyar & Pankova 2024, sp. nov.

Pseudopolydora nivea Radashevsky, Malyar & Pankova sp. nov.

http://zoobank.org:act: 0BC8D111-94E4-449E-8F92-3F33AB26971D

Figure 14

Pseudopolydora cf. rosebelae: Radashevsky 2015: 682−684, figs 31, 32. Not Radashevsky & Migotto 2009.

Material examined. Australia, Queensland, Great Barrier Reef, Lizard Island, lagoon entrance, reef near Bird Island, 14.695222°S, 145.4655°E, 10 m, coral sand, coll. Radashevsky, V.I., 14 August 2013, AM W.45381 (holotype).

Etymology. The species name nivea, feminine for the Latin niveus (snow-white, snowy, of snow), refers to the snow-white pigment on the dorsal side of the head and anterior chaetigers of the holotype.

Diagnosis. Adults with numerous white stellar chromatophores on prostomium, peristomium, and dorsal side of eight anterior chaetigers. Prostomium anteriorly bilobed, extending posteriorly to end of chaetiger 1 as a low caruncle. Occipital antenna present. Thin epithelial hood arising from dorsal anterior edge of chaetiger 3 and forming voluminous pouch over chaetiger 2. Chaetiger 5 with dorsal superior and ventral capillaries; two kinds of heavy spines arranged in notopodia in a J-shaped double row: anterior-row spines pennoned, with curved pointed tip; posterior-row spines simple falcate. Bidentate hooded hooks in neuropodia from chaetiger 8, up to 14 in a series. Branchiae from chaetiger 7, up to 16 pairs. Glandular pouches in neuropodia from chaetiger 1, largest and double in each neuropodium in chaetigers 6 and 7, single in other neuropodia. Digestive tract without gizzard-like structure. Blood transparent, without colored respiratory pigment. Nephridia from chaetiger 4 onwards.

Description (based on Radashevsky 2015). Holotype 25-chaetiger anterior fragment about 6 mm long, 1 mm wide (Fig. 14A–C). Small black spots present on dorso-lateral sides of chaetigers 1 and 3. Numerous white chromatophores scattered on prostomium and eight anterior chaetigers in life, not visible after fixation. Prostomium anteriorly bifurcated, extending posteriorly to end of chaetiger 1 as a low caruncle. Short occipital antenna present on caruncle. Three black eyes present. Palps missing. Chaetiger 1 weakly separated from peristomium, with short capillaries in neuropodia and small postchaetal lamellae in both rami; notochaetae lacking. Chaetigers 2–4 and 6 with slender capillaries in both rami. From chaetiger 7 onwards notochaetae smooth slender capillaries with narrow limbation. Thin epithelial hood arising from dorsal anterior edge of chaetiger 3 and forming a prominent pouch above character 2.

Chaetiger 5 same in size as chaetigers 4 or 6, with six dorsal superior winged capillaries, two kinds of heavy spines in notopodia arranged in a J-shaped double series, and about 20 ventral winged capillaries; notopodial postchaetal lamellae lacking but neuropodial lamellae well developed. Dorsal superior capillaries slightly shorter and fewer than those chaetae on chaetigers 4 or 6. Ventral capillaries same as those chaetae on chaetigers 4 or 6. Anterior-row spines pennoned, with curved pointed tip, 12 in a series; posterior-row spines simple falcate, 10 in a series (Radashevsky 2015: fig. 32A, C, D).

Bidentate hooded hooks in neuropodia from chaetiger 8, up to 14 in a series, not accompanied by capillaries. Lower part of hook shaft bent at right angle (Radashevsky 2015: fig. 32B).

Branchiae on chaetigers 7–22. Nototrochs from chaetiger 7 onwards, each composed of one row of cilia extending onto branchiae.

Digestive tract without gizzard-like structure. Blood transparent, without elements and colored respiratory pigment. Nephridia from chaetiger 4 onwards.

Habitat. A single individual of P. nivea sp. nov. was found in a silty tube in coral sand at a depth of 10 m.

Remarks. The only specimen of P. nivea sp. nov. was found near Lizard Island (Queensland, Australia) by Radashevsky (2015). It was similar to P. rosebelae from Brazil and therefore tentatively identifed as P. cf. rosebelae. However, a genetic comparison of Brazilan and Australian specimens, performed in this study, showed that they are not conspecific, but sister to each other (Fig. 1). Pseudopolydora nivea sp. nov. shares most of the morphological diagnostic characters of P. rosebelae and differs from the latter only in the absence of black pigment on the dorsal side of the anterior chaetigers. Despite this singular color difference, and despite having only one partial specimen in our possession, we are comfortable recognizing the Lizard Island population as a previously undescribed species. More specimens of P. nivea sp. nov. should be examined to understand the morphological variability of this species and its similarity to P. rosebelae.

Distribution. Australia, Queensland, Great Barrier Reef (Fig. 12).