Rhinothelepus oculeus, Hutchings, Pat, Nogueira, João Miguel Matos & Carrerette, Orlemir, 2015

Hutchings, Pat, Nogueira, João Miguel Matos & Carrerette, Orlemir, 2015, Telothelepodidae, Thelepodidae and Trichobranchidae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 240-274 : 243-244

Rhinothelepus oculeus n. sp.

( Figs 2 , 3 )

Type material. Holotype: AM W.47507, MI QLD 2337, complete specimen, in excellent state of preservation, 6 mm long, 0.8 mm maximum width (segments 11–12). Paratype: AM W.44945, MI QLD 2337, 4 mm long, ~ 0.6 mm wide, 34 segments, incomplete, in relatively good state (broken in two pieces between segments 13–14 due to manipulation / dissection).

Comparative material examined. Holotype of Rhinothelepus buku , NTM W.009549. Holotype of Rhinothelepus lobatus , AM W.5234. Holotype of Rhinothelepus macer , AM W.6783. Holotype of Rhinothelepus occabus AM W.201903.

Description. Short bodied species. Transverse prostomium attached to dorsal surface of upper lip; basal part with small eyespots, densely packed in two horizontal rows at each side, terminating dorso-laterally by oblique row of three eyespots; distal part of prostomium low, restricted to base of upper lip, mid-dorsal process elongate, attached to the upper lip basally, distally free ( Fig. 2 A–B, F, J–K). Buccal tentacles all uniformly cylindrical, of two widths ( Fig. 2 A–H, J–M), thicker tentacles originating exclusively from both laterals of mid-dorsal process, basally. Peristomium forming lips, continuing dorsally as narrow annulation, with nuchal organs on anterior margin; upper lip large, distinctly longer than wide, slightly convoluted; lower lip expanded, cushion-like, extending across entire ventrum ( Fig. 2 B–E, G–H, K–M). Anterior body highly glandular ventrally, swollen and slightly corrugated; segment 1 conspicuous dorsally and laterally, ventrally covered by expanded lower lip; segment 2 forming complete ring, segments 4 and 5 longer than remaining anterior segments, especially segment 4 ( Fig. 2 A–H, J–M). Two pairs of branchiae on segments 2–3, filamentous, each pair with less than 10 filaments on either side, originating from swollen cushion-like areas of body wall and with narrow mid-dorsal gap inbetween; branchial filaments of segment 2 extending to same level or slightly laterally in relation to notopodia of segment 3, filaments of second pair anterior and dorsal to notopodia ( Fig. 2 A–H, J–M). Notopodia extending for 15 segments, until segment 17; notopodia of segments 3–5 inserted progressively more laterally, then longitudinally aligned; anterior notopodia with slender bayonet-like chaetae in anterior row and narrowly-winged chaetae in posterior row ( Fig. 3 A); posterior notopodia bearing narrowly-winged chaetae in both rows, wings present from middle third of chaetae in posterior row; chaetae from anterior row about half length of chaetae from posterior row throughout ( Fig. 3 B–C). Neuropodia beginning from segment 8, uncini throughout with dorsal button at middle third of base and crest with 2 rows of secondary teeth ( Fig. 3 D–G). Elongate nephridial and genital papillae, posterior and longitudinally aligned to bases of notopodia of segments 5–7. Pygidium smooth ( Fig. 2 A–E, I).

Remarks. Five species of Rhinothelepus are known: R. buku Hutchings, 1997a , R. lobatus Hutchings, 1974 , R. macer Hutchings, 1977 , R. occabus Hutchings, 1990 , and R. oculeus n. sp. described above.

Both R. lobatus and R. occabus differ from R. oculeus n. sp. in having a longer prostomial process; a longer and highly convoluted upper lip and shorter deeply corrugated lower lip; in both species segment 1 is forming complete annulation around the body and segment 2 is not continuing ventrally, and both species have many more branchial filaments, ~20–30 filaments on each side of pairs ( Nogueira et al. 2010). In contrast, in Rhinothelepus oculeus n. sp. the lower lip is cushion-like and almost smooth, segment 1 is incomplete and segment 2 forms a complete annulation, and there are less than 10 branchial filaments per pair.

Rhinothelepus macer is more similar to R. oculeus n. sp. than to other described species. Both species share a similar morphology of the anterior end, including lips and segments 1 and 2, and number of branchial filaments, however a prostomial process is absent among members of R. macer and present in R. oculeus n. sp., and in that species the segments are progressively longer until segments 7–8, while in R. oculeus n. sp., segments 4–5 are longer than following ones. In addition, the bayonet-like chaetae of R. macer are much longer, about the same size as chaetae from posterior row, while in R. oculeus n. sp., the bayonet-like chaetae are about half the length of chaetae from posterior row.

Rhinothelepus buku has a longer prostomial process and a longer convoluted upper lip than R. oculeus n. sp. In addition, the lower lip of R. buku forms a convoluted tongue-like projection almost as long as upper lip margins, folded and corrugated, and nephridial and genital papillae are inconspicuous or absent ( Hutchings 1997a), with segment 1 conspicuous only ventrally and segment 2 forming a complete ring, with the first pair of branchiae.

Etymology. The specific name “ oculeus ” is Latin and refers to the presence of the prostomial eyespots ( oculeus = full of eyes).

Habitat. In amongst coral rubble of patch reefs in shallow waters, 9 m.

Type locality. Big Vicki's reef, 14°41'9"S, 145°26'31"E, Lizard Island, Great Barrier Reef, Queensland, Australia.

Distribution. Known only from type locality.

Figures

FIGURE 2. Rhinothelepus oculeus n. sp., holotype AM W. 47507. A – E. Entire worm, left dorso-lateral, left lateral and three progressively more ventral views, from right ventro-lateral to ventral, respectively; F – H. Close ups of the anterior end, left dorso-lateral and two progressively closer right ventro-lateral views, respectively; I. Posterior body, right lateral view; J – M. Close ups of anterior end, left dorso-lateral, left lateral, right ventro-lateral and ventral views, respectively. Abbreviations: numbers refer to segments, unspecified arrows point to genital papillae, ll = lower lip, P = basal part of prostomium, PP = prostomial process, ul = upper lip. Scale bars: A – E = 0.4 mm, F – G, I = 0.2 mm, H, J – M = 0.15 mm.

FIGURE 3. Rhinothelepus oculeus n. sp., holotype AM W. 47507. A – B. Notochaetae, segments 7 and 14, respectively; C. Tips of notochaetae from posterior row, segment 14; D – G. Uncini, segment 8 and three last neuropodia, respectively. Scale bars: A – C = 15 µm, D – G = 5 µm.