Lysilla longilinea, Nogueira, João Miguel Matos, Hutchings, Pat & Carrerette, Orlemir, 2015

Nogueira, João Miguel Matos, Hutchings, Pat & Carrerette, Orlemir, 2015, Polycirridae (Annelida, Terebelliformia) from Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 437-483 : 444-445

Lysilla longilinea n. sp.

( Fig. 3 )

Type material. Holotype: AM W.47407, CReefs, High Rock, Lizard Island, 20 m, coll. Lynda Avery by SCUBA, Sep 2010, complete, ~ 15 mm long, ~ 0.2 mm wide (uniformly), with 86 segments.

Comparative material examined. Holotype of Lysilla bilobata , AM W.7586. Holotype of Lysilla jenacubinnae , AM W.199643. Holotype of Lysilla laciniata , AM W.199626. Non-types of Lysilla loveni , AM W.9143, USNM 49637. Non-types of Lysilla pacifica , AM W.5219, AM W.12290 (6), AM W.199622 (11), AM W.19334 (3).

Description. Preserved body brown to purple, including tentacles. Elongate and slender body, of almost uniform width throughout, delicate ( Fig. 3 A–G). Prostomium at base of upper lip, basal part as thick horseshoeshaped crest, distal part as flaring lobes; prostomium extending ventrally and posteriorly, both parts meeting midventrally, posteriorly to lower lip ( Fig. 3 B–C, E–F). Three types of buccal tentacles present, short tentacles thin, uniformly cylindrical, intermediate ones spatulated, long tentacles progressively widening towards cylindrical swelling, with blunt tip; tentacles annulated throughout, including tips of long tentacles, with transverse rows of papillae ( Fig. 3 A–F). Peristomium restricted to lips; upper lip short, not clearly visible, covered by mass of buccal tentacles; lower lip short, swollen, hemispherical to cylindrical, surrounded by prostomial ventral extensions ( Fig. 3 B–C, E–F). Body completely covered with rectangular to square papillae, more abundant ventrally, but ventrolateral pads not defined; ventral papillae arranged in 5–6 well defined transverse rows per segment anteriorly, 2–3 rows per segment posteriorly; papillae rectangular and each completely covered with minute rounded to sphaerical papillae ( Fig. 3 A–G). Segment 1 only conspicuous mid-dorsally, laterally and ventrally covered by expanded prostomium; segment 2 conspicuous dorsally and continuing ventrally as short annulation, with relatively large mid-ventral shield at beginning of mid-ventral groove; groove bordered by paired longitudinal crests through posterior body ( Fig. 3 B–C, E–F). Notopodia extending for 5 segments, until segment 7; short, roughly cylindrical notopodia, distally blunt; first pair of notopodia slightly shorter than following pairs and slightly ventral to them. Notopodia with single chaeta in each row, both pinnate, striations only visible under higher magnifications of light microscopy ( Fig. 3 H). Nephridial and genital papillae not visible. Pygidium with pair of large, rounded ventral papillae and 6–7 smaller papillae lateral and dorsally, papillae progressively smaller towards dorsal side ( Fig. 3 G).

Remarks. The holotype and the only known specimen of Lysilla longilinea n. sp. is a very slender and proportionally elongate worm, brown to purple after preservation, with highly specialised long buccal tentacles and only five pairs of notopodia, on segments 3–7, bearing pinnate chaetae.

Of the 13 described species of Lysilla , only two species have notopodia terminating on segment 10 or before, L. loveni Malmgren, 1866 , originally described from Sweden and with notopodia extending until segments 8–10, with winged notochaetae in both rows, and L. macintoshi Gravier, 1907 , described from material from Antarctica and with notopodia extending to segments 7–8, with pinnate chaetae in both rows, as in the holotype of L. longilinea n. sp. Members of L. macintoshi differ from the holotype of Lysilla longilinea n. sp., in being larger animals, anteriorly swollen, with larger lips and large genital papillae surrounding bases of notopodia of segments 6–8.

Etymology. We attribute the name “ longilinea ” for this species as a reference to the remarkably elongate and slender body shape of the holotype.

Habitat. Associated with dead coral substrate.

Type locality. High Rock, 14°44'33"S, 145°33'8"E, Lizard Island, Great Barrier Reef, Australia.

Distribution. Known only from the Lizard region.

Figures

FIGURE 3. Lysilla longilinea n. sp., holotype NTM W. 47407. A, D. Entire worm, dorsal and ventral views (anteriorly), respectively; B – C. Anterior end, left ventro-lateral and right dorso-lateral views, respectively; E – F. Close ups of the anterior end, right dorso-lateral and left ventro-lateral views, respectively; G. Posterior end; H. Notochaetae, segment 5. Numbers refer to segments. Abbreviations: ll = lower lip, P = basal part of prostomium, * = distal part of prostomium. Scale bars: A, D = 1 mm, B – C = 0.15 mm, E – G = 0.1 mm, H = 10 µm.