Nephtys triangula

Dixon-Bridges, Kylie, Gladstone, William & Hutchings, Pat, 2014, One new species of Micronephthys Friedrich, 1939 and one new species of Nephtys Cuvier, 1817 (Polychaeta: Phyllodocida: Nephtyidae) from eastern Australia with notes on Aglaophamus australiensis (Fauchald, 1965) and a key to all Australian species, Zootaxa 3872 (5), pp. 513-540 : 522-526

Nephtys triangula n. sp

Figures 6 a–c, 7a–c, 8a–d, 9a–f, 10a–f, Table 2

Material examined. HOLOTYPE: AM W24763 (chaetigers 3, 20, 40, posterior parapodia removed and mounted for SEM), New South Wales: Arrawarra Beach, 30° 4' S, 153° 12' E, June 1994, intertidal, just above low water mark. PARATYPES: Arrawarra Beach, 30° 4' S, 153° 12' E, Jan 1994, 1, AM W24719; Sawtell Headland, 30° 22' 32" S, 153° 6' E, May 2005, 1 AM W41471. Queensland: Gold Coast, beach at Tugun, 28° 08' 36" S, 153° 29' 50" E, May 2008, USNM 1220303, 2, BMNH 2013.438–439, AM W36903, AM W36905 (parapodia 3, 20, 40, 80, removed), AM W43573.

Additional material examined. Queensland: Gold Coast, beach at Tugun, 28° 8' 36" S, 153° 29' 50" E, Dec 2007, 1, AM W36903, Oct 2007, 5, AM W36902, 3, AM W36904, May 2008, 5, AM W36905; beach at Currumbin, 28° 7' 43" S, 153° 29' 15" E, May 2008, 3, AM W36900, Oct 2007, 7, AM W36899; beach at Palm Beach, 28° 7' 9" S, 153° 28' 24" E, Oct 2007, 6, AM W36901. New South Wales: Sawtell Headland, 30° 22' 32" S, 153° 06' E, May 2005, 1, AM W41471; Angourie Beach, 29° 28' 42" S, 153° 21' 44" E, Feb 2003, 1, AM W33123.

Description. Holotype entire, pharynx everted, length 80 mm for 148 chaetigers (not including pharynx), maximum width at 6th chaetiger 5 mm, excluding chaetae. Paratype material ranges from 5–45 mm length, 9–15 mm wide, and 46–126 chaetigers. Body without pigmentation. Prostomium pentagonal with anterior triangular extension ( Fig. 6 a) and distinct brown pigmentation ( Fig. 6 a–c). One pair of antennae and one pair of palps present. Antennae at distal end of anterior extension of prostomium uniform in width, palps slightly longer with bulbous bases inserted at the basal lateral margins of prostomium. Eyespots absent. Body compact with conical parapodia which become more erect posteriorly as body width decreases. Pharynx with 12 pairs of bifid terminal papillae, 22 longitudinal rows of subterminal papillae; each with 7–9. Distinct gap between terminal and longitudinal rows ( Fig. 6 b). Median dorsal papilla absent, slightly raised verrucae present proximally ( Fig. 6 c). Parapodia biramous with long flowing chaetae which become progressively longer posteriorly ( Figs 7 a–c, 8a–d, 9e, f) exceeding body width. Chaetiger 3 (AM W43573, Figs 8 a, 9a, b) notopodia with elongate digitate postacicular lobe, and small rounded acicular and preacicular lobes; dorsal cirrus elongate ( Fig. 7 b). Neuropodia with two rounded conical preacicular and acicular lobes, divergent, postacicular lobe slightly longer, small ventral digitiform cirrus.

Chaetiger 20 (AM W43573, Figs 8 b, 9c): notopodia with elongate postacicular digitiform lobe, acicular lobe rounded, shorter preacicular lobes; neuropodia with two equal-sized pre and postacicular lobes divergent, smaller acicular lobe, with well developed ventral cirrus ( Fig. 9 c). Chaetiger 40 (AM W36905, Figs 8 c, 9d, e): notopodia with elongate digitiform postacicular lobe and rounded acicular and preacicular lobes, small digitiform dorsal cirrus; neuropodia with two conical pre and post acicular lobes and small acicular lobe, well developed ventral cirrus. Chaetiger 70 and posterior chaetigers (AM W24763 Figs 8 d, 9f): notopodia with elongate preacicular digitiform lobe smaller in length than anterior ones, rounded acicular lobe, expanded postacicular lobe; neuropodia with two divergent conical pre and post acicular lobes with rounded margins, smaller in size than anterior ones, small acicular lobe, small digitiform ventral cirrus. Three types of chaetae are present, barred chaetae ( Fig. 10 c), broad bladed capillaries with serrated margins and with longitudinal striations along blades which may be twisted (Fig. 15b) and broad bladed spinose ( Fig. 10 d, e, f). Chaetal counts along the body are provided in Table 2 but are approximate as capillaries very long and twisted especially in posterior chaetigers (see Fig. 9 c–f). Lyrate chaetae absent. Aciculae colourless with rounded tips in anterior chaetigers, becoming darker in posterior ones.

Branchiae present from chaetiger 3 and continue to posterior end, curved outwardly with dorsal lobe ( Figs 7 a, c, 9a–f, 8a–b, f) increase in size and by chaetiger 40 ( Fig. 9 d) occupying two thirds of the interramal space, decreasing in size posteriorly, small dorsal ligule present ( Fig. 9 a). Dorsal ciliated patches visible on some mid body chaetigers ( Fig. 9 d). Single long pygidial cirrus present as long as last 5 chaetigers.

Remarks. Nephtys triangula n. sp., is characterised by the distinctive triangular prostomium and pigmentation, branchiae beginning on chaetiger 3 and continuing posteriorly, and long flowing chaetae. This combination of characters allows it to be easily distinguished from all other species known from the region (See Table 4 ). The only other species with branchiae beginning on chaetiger 3 is N. gravieri Augener, 1913 , but this species lacks the triangular prostomium and both the antennae and palps are inserted on the dorsoectal margins whereas in N. triangula n. sp., the palps are inserted basally on the prostomium. Nephtys longipes Stimpson, 1856 , which has a similar pattern of branchial distribution and long flowing chaetae similar to N. triangula n. sp, also appears to have an expanded prostomium, however in this species it consists of an oval prostomium, with a thin preantennal lobe which is a triangular translucent lobe, marked by an intricate pattern of slightly thicker tissue (see Fig. 6.8 in Paxton 1974); whereas in N. triangula n. sp., it is the entire prostomium which is extended. Also in N. longipes the antennae are situated at the base of the preantennal lobe whereas in N. triangula n. sp., they are on the anterior margins of the prostomium ( Fig. 6 a, c). Ecologically these two species differ in that N. triangula n. sp., is found on more exposed oceanic beaches whereas N. longipes is found in slightly more protected areas, although both are intertidal species occurring in clean sandy sediments.

Chaetiger 3 Noto Pre-acicular 8 barred

Post-acicular 9 broad bladed serrated, Neuro Pre-acicular 10 broad bladed serrated Post -acicular 4 barred, 6 broad bladed serrated

Chaetiger 20 Noto Pre-acicular 12 barred, 5 broad bladed serrated

Post-acicular 15 short barred, 10 broad bladed serrated Neuro Pre-acicular 20 barred, 5 broad bladed spinose Post -acicular 10 broad bladed spinose

Chaetiger 40 Noto Pre- acicular 15 barred

Post- acicular 16 broad bladed spinose Neuro Pre- acicular 20 barred

Post- acicular 20 broad bladed spinose, 5 serrated

Chaetiger 70 Noto Pre- acicular 8 short barred

Post- acicular 18 broad bladed spinose, 8 serrated Neuro Pre- acicular 8 short barred

Post –acicular 12 broad bladed serrated

Etymology. The new species N. triangula was named in reference to its distinctive triangular prostomium ( Fig. 6 a).

Habitat. Intertidally on exposed sandy beaches.

Distribution. Occurs along the east coast of Australia from southern Queensland to northern New South Wales.

Figures

FIGURE 6. Nephtys triangula n. sp. a. anterior view of prostomium (AM W 36899), b. with completely everted pharynx (AM W 24763), c. partially everted pharynx (AM W 41471). an = antenna, p = palp, v = verrucae, b = branchia, bp = brown pigment. All scale bars 0.1 mm.

FIGURE 7. Nephtys triangula n. sp. a: lateral view of anterior end (AM W 41471 b, close up of anterior chaetigers (AM W 36902), c. mid chaetigers (AM W 41471). b = first branchia, dc = dorsal cirrus, numbers refer to chaetiger. Scale bars 0.1 mm.

FIGURE 8. Nephtys triangula n. sp. Line drawings of parapodia (anteroposterior view) (AM W 43573), a. chaetiger 3, b. chaetiger 20, c. chaetiger 40, d. chaetiger 70. Scale bar 0.1 mm.

FIGURE 9. Nephtys triangula n. sp. (AM W 24763) SEM a: chaetiger 3, b. close up of branchia of chaetiger 3 with dorsal ligule, c. chaetiger 20, d. chaetiger 40 showing fully developed branchia, posterior lateral view, e. chaetiger 40, anterior lateral view, f, posterior chaetiger. b = branchia, cp = ciliated patches, dl = dorsal ligule, vc- ventral cirrus. Scale bars 0.1 mm except b = 20 ųm.

FIGURE 10. Nephtys triangula n. sp. (AM W 24763) SEM a. chaetiger 3 showing broad bladed serrated capillaries, b. close up of same, c. barred chaetae of chaetiger 3, d. broad bladed spinose of chaetiger 20, e. broad bladed spinose and serrated from chaetiger 40, f. close up of broad bladed spinose from posterior chaetiger. bb = broad bladed serrated, b = barred, sp = broad bladed serrated. Scale bars 10 ųm except for a = 100 ųm.