Laetmonice mensahaedorum, Flaxman & Kupriyanova, 2024

Laetmonice mensahaedorum View in CoL sp. nov.

urn:lsid:zoobank.org:act:6E9AB321-13BC-4DD6-B878-AC34DB4C2F95

Figs. 3c View Figure 3 , 4c View Figure 4

Material examined. Holotype: AM W.53953, Jervis CMR, 2650 m, 29 May 2017 . Paratypes: AM W.53951, Bass Strait, 2760 m, 22 May 2017 ; AM W.53952, Freycinet CMR, 2820 m, 18 May 2017 , NMV F 271067 About NMV , 2806 m, 23 October 2015 .

Description. Holotype ( Fig. 3c View Figure 3 ) with 32 segments, length 33 mm, maximum width 15 mm (most chaetae absent). Body ovate to elongate, dorsoventrally flattened, dorsal felt absent. Ventral surface cream-coloured, covered with fine papillae.

Prostomium rounded and small (one fifth of body width at its widest point), with a small pair of anterolateral cylindrical ocular peduncles, one third length of prostomium, eyes absent. Ceratophore of median antenna large (slightly longer in length than prostomium and greater in width than ocular peduncles) located between ocular peduncles ( Fig. 4c View Figure 4 ); style missing. Palps finely papillated, extending to segment 13. 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, smooth, translucent white, without tubercles or papillae on surface and margins. Dorsal cirri present on segments without elytra; cirrophores large, styles with bulbous tips, four to five times length of parapodia (observed from AM W.53952).

First segment with papillated rectangular elongated uniramous parapodia, compressed laterally, with two tufts of fine, golden acicular chaetae, extending from dorsal and ventral margins of parapodia. Each with a pair of long dorsal and ventral tentacular cirri, with large cirrophores and extending laterally with bulbous tips.

Following segments with biramous parapodia. Segments 2–4 notopodia with pointed aciculum and bunch of fine acicular chaetae on dorsal surface. Segment 2 compressed laterally with approximately 25 fine, translucent medial oriented chaetae. Neuropodium conical, with two tiers of neurochaetae; lower tier with numerous golden bipinnate neurochaetae, upper tier neurochaetae missing on all specimens. 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 short and attached halfway along ventral side of neuropodia.

Elytrigerous notopodia with tuft of approximately 10 translucent acicular notochaetae, tapering with fine, pointed tip, medially oriented from triangular acicular lobe. Posterio-laterally to acicular notochaetae, four harpoon notochaetae (observed from chaetal scars), finely tuberculated with three fangs (observed from AM W.53951).

Cirrigerous notopodia with sharply rounded anterior margin, pointed acicular lobe and three tufts of notochaetae; fine capillary chaetae on anterior and ventral margins of acicular lobe; and approximately 12 long stiff, translucent acicular chaetae projecting from posterior margin. Large cirrophore and aciculum located on posterior margin, oriented posterio-laterally.

Variation. Body length 14–33 mm, number of segments 30–32 and number of elytra pairs 14–15.

Diagnosis. As for the genus; with a combination of 30–32 segments, 14–15 elytra pairs, ocular peduncles small, one third the length of median antennal ceratophore, median antenna ceratophore located between ocular peduncles, palps extending to segment 13, four harpoon chaetae per notopodium with finely tuberculate shafts and three fangs. Most similar to Laetmonice yarramba .

Etymology. The name mensahaedorum came from mensa haedorum meaning “kid’s table” in Latin. This species is named after the self-proclaimed “kids table” at the 2023 Australian Museum Foundation Gala Dinner, by Australian Museum Foundation director Massimo Belgiorno-Nettis and his guests. The group at the table made a generous donation to the foundation and this species is named in their honour.

Distribution. Western Tasman Sea from south of Tasmania (44°S) up to Jervis Bay (35°S), abyssal (2650– 2820 m).