Laetmonice murrayae, Flaxman & Kupriyanova, 2024

Laetmonice murrayae View in CoL sp. nov.

urn:lsid:zoobank.org:act:B16F0BB5-1F1A-4CFB-AF0E-D5B6CE6746B1

Figs. 3b View Figure 3 , 4b View Figure 4

Material examined. Holotype: AM W.54337, Scrooge Seamount, 2900 m, 10 October 2022 . Paratype: AM W.54335, Scrooge Seamount, 2900 m, 10 October 2022 . Additional material is listed in Appendix 1.

Description. Holotype ( Fig. 3b View Figure 3 ), with 34 segments, length 43 mm, maximum width 23 mm (including chaetae) and 17 mm (excluding chaetae). Body ovate to elongate, dorsoventrally flattened, dorsal felt absent. Ventral surface cream-coloured, covered with minute papillae.

Prostomium rounded, with a small pair of anterolateral cylindrical ocular peduncles, one third length of prostomium, eyes absent. Ceratophore of median antenna large (length of prostomium) located between ocular peduncles ( Fig. 4b View Figure 4 ); style slender with a bulbous tip, five to six times length of prostomium (observed from AM W.54524). Palps finely papillated, extending to segment 13 (observed from AM W.53964). Nuchal flaps absent. Facial tubercle located below ocular peduncles with long papillae.

Elytra 15 pairs, attached to elytrophores on segments 2, 4, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 28 and 31, completely covering dorsum; elytra rounded, white in colour with patches of brown speckled pigmentation, without tubercles or papillae on surface and margins. Dorsal cirri present on segments without elytra; cirrophores short and cylindrical, styles with blunt tips, four to five times length of parapodia (observed from AM W.55156; a specimen in good condition, though PCR was unsuccessful and therefore is not listed in Appendix 1).

First segment with elongated uniramous parapodia, inserted anterolaterally to prostomium; two tufts of fine, golden acicular chaetae, extending from dorsal and ventral margins of parapodia. Each with a pair of dorsal and ventral tentacular cirri, with large cirrophores, extending laterally with bulbous tips.

Following segments with biramous parapodia. Segments 2–4 notopodia with pointed aciculum and fans of fine acicular chaetae. Segment 2 with approximately 11 stiff yellow medial oriented acicular chaetae. Neuropodium conical, with two tiers of neurochaetae; lower tier with numerous golden bipinnate neurochaetae, upper tier with approximately five neurochaetae, with basal spur and distal fringe of hairs. Neuropodia from segment 5 to posterior end elongated, cylindrical with inflated base; three golden yellow neurochaetae with basal spur and distal fringe of hairs. Ventral cirri on segment 2 reaching base of bipinnate neurochaetae, attached on ventral base of neuropodium. From segment 3 onwards, ventral cirri are short and attached halfway along ventral side of neuropodia.

Elytrigerous notopodia enlarged with tuft of up to 22 golden acicular notochaetae, tapering with fine, pointed tip, medially oriented from triangular acicular lobe. Posterio-laterally to acicular notochaetae, up to 10 (observed from chaetal scars) notochaetae, tuberculated with four recurved fangs (observed from AM W.55155 and AM W.53440).

Cirrigerous notopodia dorsoventrally flattened with pointed acicular lobe and three tufts of notochaetae; fine capillary chaetae on ventral margin of acicular lobe; approximately 30 fine, pale golden acicular chaetae along rounded anterior margin; approximately 14 long stiff, golden acicular chaetae projecting posterio-laterally from dorsal margin. Large cirrophore and aciculum located on posterior margin, oriented posterio-laterally.

Variation. Body length of examined specimens ranged from 24 to 44 mm, number of segments from 32 to 34, and number of elytra pairs from 14 to 15. Brown speckled pigmentation faint or absent in some specimens. Ventral papillae extremely fine on some specimens, some appear smooth. Up to 25 stiff yellow medial oriented acicular chaetae found on segment 2.

Diagnosis. As for the genus; with a combination of 32–34 segments, 14–15 elytra pairs, ocular peduncles distinctly small, one third the length of the prostomium; median antenna located between ocular peduncles; palps extending to segment 13, up to 10 harpoon chaetae per notopodium with tuberculate shafts and four recurved fangs. Most similar to Laetmonice yarramba .

Etymology. This species is named in honour of Anna Murray (Australian Museum) to recognise her important contributions to the taxonomy of polychaetes, especially of scale worms.

Distribution. The Great Australian Bight and the Eastern Australian abyss from off Tasmania (40° S) up to Bermagui, Southern NSW (36° S). Off Australian West coast and seamounts of the Indian Ocean Territories. Abyssal (2760– 5000 m).