Polycirrus rubrointestinalis, 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 : 456-462

Polycirrus rubrointestinalis n. sp.

( Figs 1 A, 5G–K, 10–13)

Type material. Holotype: AM W.47655, MI QLD 2193, 4 mm long, 1.0 mm wide, posteriorly incomplete, Mermaid Cove (buoy), 14°38'46"S, 145°27'13"E, coarse coral rubble, 7 m, 27 Aug 2010, CReefs. Paratypes: AM W.45457, MI QLD 2449 (on SEM pin), incomplete specimen, 1.5 mm long and 0.4 mm maximum width; AM W.47650, MI QLD 2449 (15), from 1–1.2 mm long and 0.1–0.3 mm maximum width; AM W.47651, MI QLD 2342 (on SEM pin); AM W.47658, MI QLD 2248 (on SEM pin), Bommie Bay, 14°39'41"S, 145°28'19"E, coarse coral rubble, 9 m, 12 Sep 2010, CReefs; AM W.47652 (6), from same locality; AM W.47653, MI QLD 2205 (3), south of Mermaid Cove, 14°38'53"S, 145°27'E, coarse coral rubble, 14.5 m, 1 Sep 2010, CReefs; AM W.47654, MI QLD 2205, south of Mermaid Cove, 14°38'53"S, 145°27'E, coarse coral rubble, 14.5 m, 1 Sep 2010, CReefs.

Other material examined. AM W.44266, MI QLD 2337 (2); AM W.44269, MI QLD 2342 (3); AM W.44598, MI QLD 2396; AM W.44602, MI QLD 2397; AM W.44606, MI QLD 2399; AM W.44618, MI QLD 2410; AM W.44619, MI QLD 2410 (2); AM W.47657, MI QLD 2410; AM W.44590, MI QLD 2396; AM W.47656, MI QLD 2202, MacGillivray Reef, 14°38'53''S, 145°29'11.760"E, coarse coral rubble, 14 m, Aug 2010, CReefs; AM W.47659, LI-10-062, MacGillivray Reef, deep reef slope, 14°39'25"S, 145°28'22"E, coral rubble, 7–12 m, 3 Sep 2010, CReefs.

Comparative material examined. Holotype of Polycirrus rosea , AM W.196900.

Description. Minute worms, in life with whitish transparent body and buccal tentacles, and distinctly red anterior half of the digestive tract ( Fig. 1 A). Transverse prostomium attached to dorsal surface of upper lip; basal part as thick almost semicircular crest, distal part poorly developed, as low lobe of uniform length at base of upper lip ( Figs 1 A; 10A–B, H–J; 11B, E, G–L; 12B–C, G). Buccal tentacles of two types, both of almost uniform width, very slightly spatulated at tips, with deeper groove, long ones with slightly thinner, uniformly cylindrical peduncle before spatulated tip ( Figs 1 A; 10A–L; 11A–L; 12A–G). Peristomium forming lips; almost circular upper lip; swollen lower lip, divided in two parts, rectangular inner region, restricted to oral area, outer region large, cushionlike, rectangular, extending across ventrum ( Figs 10 B–H, K–L; 11A–E, G–I, L; 12A–C, E–G). Segment 1 reduced, only visible mid-dorsally, laterally covered by prostomium and ventrally by expanded lower lip; segment 2 same width as following segments, visible all around or covered by lower lip ( Figs 10 A–L; 11A–L; 12A–C, E–G). Smooth to slightly crenulated ventro-lateral pads of anterior segments, present until segment 12, although less conspicuous posteriorly ( Figs 10 B–H, K–L; 11C–E, G–I, L; 12A–C, E–F). Notopodia extending for 10 segments, until segment 12; short, conical notopodia, not clearly bilobed ( Figs 10 A–L; 11A–K; 12A–C, E–J; 13A–C). Broadly-winged notochaetae on both rows, wings only at tips of chaetae, conspicuous under light microscopy ( Figs 5 G–H; 12H–J; 13B–D). Neuropodia beginning from segments 5 or 6; neurochaetae as type 1 uncini, crest with single elongate and sharp tooth in first row above main fang, with two additional rows of shorter, irregularly sized teeth at base ( Figs 5 I–K; 13E–H). Nephridial and genital papillae present at bases of all notopodia, elongate, anterior to bases of notopodia anteriorly, between parapodial lobes and rounded after beginning of neuropodia ( Figs 11 C–D, G–I, L; 12B–C, E–I; 13A–B). Pygidium smooth ( Figs 11 A–D, M; 12A).

Variation. Among the specimens examined there was considerable variation in the morphology of the anterior end, including upper and lower lips, visibility of segment 2, and position of first pair of notopodia in relation to the lower lip. We attribute such variation to different degrees of muscular contraction at the time of preservation and it is important to document this observation, because these characters are useful to distinguish among species.

The upper lip is usually large, circular, but it may appear longer than wide, circular, or wider than long depending on muscular contraction, and when fully contracted the upper lip may be distinctly shorter (compare Figs 10 D–F, H, L; 11C–D, I, L; 12B–C, E–F).

When the body is fully relaxed, segments 2 and 3 are visible ventrally ( Figs 11 A–L; 12E–G), but in most specimens, including the holotype, the first pair of notopodia originates at the level of the lower lip, the segment 2 is only visible dorsally and in some specimens not even the segment 3 is visible ventrally ( Figs 10 A–L; 12B–C).

Remarks. Members of P. rubrointestinalis n. sp. are minute worms, with the distal part of prostomium restricted to the base of the upper lip; with large, rectangular and cushion-like lower lip extending across the ventrum; clearly defined, smooth to slightly crenulated ventro-lateral pads; 10 pairs of notopodia, extending until segment 12, not clearly bilobed and bearing winged notochaetae in both rows; neuropodia beginning anteriorly, from segments 5–6, with type 1 uncini throughout; and nephridial and genital papillae extending to the last pair of notopodia.

Several species of Polycirrus have neuropodia beginning from anterior segments, up to segment 10, but most of them have a larger number of pairs of notopodia, extending for more than 15 segments. Of the species of Polycirrus known prior to this study, seven have up to 15 pairs of notopodia and uncini beginning from up to segment 10, of those, only P. pumilis Hartmann-Schröder, 1990 , P. ro s e a Hutchings & Murray, 1984, and P. minutus n. sp., all originally known from Australian waters, have type 1 uncini throughout.

Polycirrus rubrointestinalis n. sp. differs from P. minutus n. sp. because this latter species has short, buttonlike and mid-ventral lower lip, uncini beginning from the penultimate thoracic segment, segment 10, and nephridial and genital papillae are only present until segment 6.

Polycirrus pumilis described from northern New South Wales, Australia, shares several similarities with specimens of P. rubrointestinalis n. sp., such as similar body size, morphology of the anterior end, including upper and lower lips, and similar number of pairs of notopodia and segments on which neuropodia begin, 10–11 pairs and segment 7 in P. pumilis , respectively, 10 pairs and segments 5–6 in P. rubrointestinalis n. sp. Members of these species differ, however, because in P. pumilis chaetae of both rows are pinnate, and nephridial and genital papillae are inconspicuous ( Glasby & Hutchings 2014).

FIGURE 13. Polycirrus rubrointestinalis n. sp., paratype AM W.47651. A. Transition between thorax and abdomen; B–C. Progressively closer views of one notopodium of segment 5; E–F. Thoracic neuropodia, segments 6 (1St neuropodium) and 11, respectively; G–H. Abdominal neuropodia, segments 13 (1St abdominal) and posterior one, respectively. Paratype AM W.47658, D. notochaetae, segment 7. Scale bars: A = 70 µm, B–C = 7 µm, D = 10 µm, E = 4 µm, F–H = 2 µm.

Polycirrus rosea , also originally described from New South Wales, Australia, shares with P. rubrointestinalis n. sp. similar dimensions of the body, morphology of the anterior end and ventro-lateral pads, number of pairs of notopodia and type of notochaetae present, and uncinal morphology. These species are distinguished, however, because neuropodia begin on segment 10, and nephridial and genital papillae are inconspicuous among members of P. ros e a ( Glasby & Hutchings 2014); in contrast, in P. rubrointestinalis the neuropodia begin on segments 5 or 6 and nephridial and genital papillae are conspicuous.

Etymology. The specific name “ rubrointestinalis ” refers to the red anterior half of the digestive tract. During the Lizard Island Taxonomic Workshop, members of this species, which were abundant in our collections, were called as “red gut Polycirrus ”, because this character is very distinctive in live specimens.

Habitat. Common species in shallow water around Lizard Island, in amongst coral rubble. Type locality. Mermaid Cove (buoy), 14°38'46"S, 145°27'13"E, Lizard Island, Great Barrier Reef, Australia. Distribution. Known only from the Lizard Region.

Figures

FIGURE 1. Live specimens. A. Polycirrus rubrointestinalis n. sp.; B – C. Polycirrus cruciformis n. sp.; D – E. Polycirrus oculeus n. sp. D, AM W. 44612, other specimens not preserved. Scale bars: A, D, E = 0.3 mm, B = 0.2 mm, C = 0.15 mm. All photos by Alexander Semenov.

FIGURE 5. Lysilla pacifica, AM W. 47520, A. Notochaetae, segment 8. Polycirrus oculeus n. sp., holotype NTM W. 23159, B – C. Progressively closer views of the notochaetae of segment 19; D. Uncini, segment 23; E – F. Uncini of two posterior neuropodia. Polycirrus rubrointestinalis n. sp., paratype AM W. 47658, G – H. Notochaetae, segments 6 and 12, respectively; I – K. Uncini, segments 6, 12 and 24, respectively. Scale bars: A – B, G = 30 µm, C, H = 20 µm, D – F = 5 µm, I – K = 6 µm.

FIGURE 10. Polycirrus rubrointestinalis n. sp., holotype AM W. 47655. A – D. Entire incomplete worm, dorsal, right and left lateral, and ventral views (anteriorly), respectively; E – G. Thorax, ventral, right and left lateral views, respectively; H – I. Closer views of the thorax, right lateral and dorsal views, respectively; J – L. Close ups of the anterior end, dorsal, left lateral and ventral views, respectively. Numbers refer to segments. Abbreviations: ll = lower lip, P = basal part of prostomium, ul = upper lip, * = distal part of prostomium. Scale bars: A – D = 0.4 mm, E – K = 0.2 mm, L = 0.1 mm.

FIGURE 11. Polycirrus rubrointestinalis n. sp., paratype AM W. 47651. A – C. Entire worm, right and left lateral, and ventral (anteriorly) views, respectively; D – G. Thorax, ventral, right lateral, dorsal and left lateral views, respectively; H – K. Anterior end, left lateral, ventral and two dorsal views under slightly different angles, respectively; unspecified arrow in I points to first neuropodium; L. Close up of the oral area; M. Posterior end, left dorso-lateral view. Numbers refer to segments. Abbreviations: i = inner region of lower lip, ll = lower lip, o = outer region of lower lip, P = basal part of prostomium, ul = upper lip, * = distal part of prostomium. Scale bars: A – C = 300 µm, D – G = 150 µm, H = 50 µm, I – K = 70 µm, L – M = 40 µm.