Micronephthys derupeli, Dixon-Bridges, Kylie, Gladstone, William & Hutchings, Pat, 2014

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 : 516-521

Micronephthys derupeli n. sp.

Figures 1 a–c, 2a–c, 3a–d, 4a–f, 5a–e, Table 1

Material examined. HOLOTYPE: AM W41508, Australia, New South Wales, Port Stephens, Big Swan Bay South, 32° 43' 22" S, 151° 58' 1" E, Apr 2009. PARATYPES: AM W41509 (1 gravid, 22 mm in length, 2 mm in width), AM W41510 (1), AM W41732, (1 on SEM), AM W43573 (2), all from same location as holotype; USNM 1220304 (1), Port Stephens, Big Swan Bay South, 32º 43' 37.3" S, 151º 58' 0 2.3 "E, Apr–May 2009; USNM 1220305 (1), Port Stephens, just west of Soldiers Point, muddy/sand site, 32º 41' 58" S, 152° 03’16” E, June 2009; BMNH 2013.442–443 (2), Port Stephens, 32º 42' 49.0" S, 152º 01' 22.1" E, Apr 2009.

Additional material examined. New South Wales. Port Stephens, 32° 41' 35" S, 152° 3' 9" E, Apr 2009, 1, AM W41581; Big Swan Bay South, 32° 43' 22" S, 151° 58' 1" E, Apr 2009, 1, AM W41548, 1, AM W41550, 1, AM W41552, 7, AM W41553; N of Soldiers Point, 32° 41' 22" S, 152° 3' 32" E, Apr 2009, Oct 2011, 1, AM W41547; Lemon Tree Passage, 32° 44' 30" S, 152° 2' E, Apr 2009, 1, AM W41551, 1, AM W41549 (parapodia 4, 8, 20, 35 mounted for SEM). Hawkesbury River, 1 km S of eastern end of Spectacle Island, 33° 32' S, 151° 7' 30" E, May 1984, 2, AM W41566, Aug 1984, 2, AM W41567; 300 m NE of Green Point, 33° 34' S, 151° 13' 30" E, Aug 1979, 1, AM W41562, May 1982, Aug 1972, 2, AM W41568, May 1983, 1, AM W41569, Nov 1983, 1, AM W41570; 50 m NE of Green Point, 33° 34'S, 151° 13' 30" E, Aug 1983, 1, AM W41563, 1, AM W24728, Nov 1983, 1, AM W41564, May 1984, 1, AM W41572, 1, AM W41573; near Juno Head, 33° 34' S, 151° 16' E, Feb 1984, 1, AM W41571; near Hungry Beach, 33° 35' S, 151° 17' E, May 1983, 1, AM W41565; 200 m S of eastern end of Spectacle Island, 33° 32' S, 151° 12' 30" E, May 1984, 2, AM W41561. Pittwater, W of Sand Point, 33° 35' 51" S, 151° 18' 25" E, Sep 2004, 1, AM W41555, 3, AM W41558, 1, AM W41559, Dec 2004, 1, AM W41560; Pittwater, 33° 35' 56" S, 151° 18' 38" E, Apr 1994, 1, AM W23958; Pittwater, 33° 35' 50" S, 151° 18' 39" E, Apr 1994, 1, AM W23959; Pittwater, 33° 35' 57" S, 151° 18' 43" E, May 1994, 1, AM W23960; 33° 35' 50" S, 151° 18' 39" E, Apr 1994, 1, AM W23959; Pittwater, 33° 35' 51" S, 151° 18' 21" E, Jun 1994, 2, AM W23961; 33° 35' 55" S, 151° 18' 40" E, Oct 1994, 1, AM W23963; 33° 35' 50" S, 151° 18' 43" E, Oct 1994, 1, AM W23962; Pittwater, west of Sand Point, 33° 35' 48" S, 151° 18' 39" E, Dec 2004, 1, AM W32539; 33° 35' 51" S, 151° 18' 38" E, May 1995, 2, AM W23965; 33° 35' 52" S, 151° 18' 37" E, Jan 1995, 1, AM W23964; Pittwater, W of Sand Point, 33° 35' 49" S, 151° 18' 50" E, Sep 2004, 1, AM W41557. Botany Bay, E of end of airport runway, 33° 58' 21" S, 151° 12' 1" E, Dec 2004, 2, AM W41556.

Description. Holotype entire, 48 chaetigers, pharynx not everted (examined by dissection of paratype material); length 18 mm, maximum width 2 mm. Paratype material ranges from 13–22 mm in length, 1.5–2.5 mm width with 30–50 chaetigers. Body robust, rectangular in cross-section, preserved animal without pigmentation, chaetae golden-coloured with orange-coloured bases, eyespots absent.

Prostomium approximately square and slightly convex anteriorly ( Fig. 1 a, b) with one pair of simple short antennae and one pair of palps, all similar in length and conical in shape basally ( Fig. 1 c). Nuchal organs round, situated dorsolaterally at margin of prostomium adjacent to chaetiger 1 ( Fig. 1 a). Pharynx (based on paratypes) divided into muscular terminal region with 18 bifid terminal papillae, and subterminal region with 22 longitudinal rows each with 7–9 papillae which commence just below terminal papillae. Single elongate median dorsal papilla present, up to 4 times longer than other subterminal papillae. Base of pharynx smooth without verrucae ( Fig. 1 b). Jaws paired and brown in colour. Parapodia biramous with noto- and neuropodia widely divergent ( Fig. 2 b, c). Preacicular and postacicular lobes low and not foliaceous, absent posteriorly. Parapodia of 1st chaetiger projecting anteriorly, adjacent to prostomium ( Fig. 1 a). Chaetiger 1 notopodia with conical acicular lobe and short rectangular postacicular lobe, dorsal cirrus visible on posterior face as small sphaerical papilla; neuropodia with conical acicular lobe, low rectangular postacicular lobe and small digitiform ventral cirrus. Aciculae on all chaetigers thick, colourless except for tips which are strongly chitinised, dark reddish brown, and knob shaped with straight tips, conspicuous on anterior chaetigers (see Fig. 1 c, on paratype AM W41509). Chaetiger 4 notopodia with pointed conical acicular lobe longer than rounded postacicular lobe, notopodial cirrus small, pyriform, neuropodia with pointed conical acicular lobe, rectangular postacicular lobe and small digitiform ventral cirrus (see Figs 1 c, 3a of paratypes AM W41509, AM W43573). Chaetiger 8 notopodia with pointed conical acicular lobe, and shorter rectangular pre- and postacicular lobes of similar size, small dorsal pyriform cirrus; neuropodia with pointed conical acicular lobe and shorter rectangular pre- and postacicular lobes and small digitiform ventral cirrus (see Figs 1 c, 2a, 3b, from paratype AM W43573). Chaetiger 21 notopodia with elongate pointed conical acicular lobe, and low rounded pre- and postacicular lobes, small conical dorsal cirrus, neuropodia with pointed conical acicular and postacicular lobes, former slightly longer, small digitiform ventral cirrus ( Fig. 2 b, AM W41581 shown). Chaetiger 40 notopodia with elongate pointed acicular lobe and rounded short postacicular lobe, small globular dorsal cirrus, neuropodia with elongate pointed acicular lobe and short postacicular, with small conical ventral cirrus ( Figs 2 c, 3d from paratypes AM W41509, AM W43573). Dorsal cirri small and sphaerical on postbranchial chaetigers, ventral cirri also reduced and digitiform. Two types of chaetae present: barred chaetae present in preacicular notopodial fascicle and neuropodial fascicle of anterior chaetigers only ( Table 1), ( Fig. 5 a) absent from mid and posterior chaetigers ( Table 1); broad-bladed asymmetrical capillaries with finely serrated margins tapering to fine tips ( Fig. 5 c) present throughout body ( Fig. 5 b–e, Table 1). Bases of all chaetae heavily chitinised. Lyrate and spinose chaetae absent. Fifteen pairs of branchiae present on chaetigers 8–22, increasing in size up to chaetiger 20, foliaceous with ciliated margins and occupying from 1/3 –1/2 of the interramal space, mostly straight, then last 2 pairs of branchiae smaller ( Figs 2 a–b, 4a–c, paratype AM W41732). Up to 10 raised ciliated patches also present on branchial and postbranchial chaetigers ( Fig. 4 a, d).

Chaetiger 4 Noto Pre-acicular 15 barred

Post-acicular 9 broad bladed serrated Neuro Pre-acicular 12 barred, 12 broad bladed serrated

Chaetiger 8 Noto Pre-acicular 4 barred

Post-acicular 7 broad bladed serrated Neuro Pre-acicular 9 barred, 20 broad bladed serrated

Chaetiger 21 Noto Pre- acicular 20 broad bladed serrated Post- acicular 9 broad bladed serrated Neuro Pre- acicular 14 broad bladed serrated

Chaetiger 40 Noto Pre- acicular 14 broad bladed serrated Post- acicular 8 broad bladed serrated Neuro Pre- acicular 12 broad bladed serrated Variation. Paratypes possess branchiae from chaetiger 7–8 through to chaetiger 22 (15–16 pairs). One of the more posterior branchiae (C20) on several paratypes is somewhat involute, and a few non-type specimens also exhibit a few curved branchiae (e.g. AM W41549). Large non-type specimens may also possess more branchial pairs, from chaetiger 8 through to chaetiger 24–27, i.e. 17–20 pairs (e.g. AM W23962, with 19 pairs, body 26 mm in length, 3 mm max. width, 51 chaetigers). Some of these larger specimens also have different numbers of branchiae on each side of the body e.g. AM W23959 has 14 pairs on one side and 20 pairs on the other. Other nonparatype material of much smaller body size (AM W41553, 7 specimens of 5–12 mm length, for complete specimens of 25–37 segments) display branchiae that range from chaetigers 7–8 through to chaetigers 16–17 (10–11 pairs), and which extend into ½ – 2/3 of the interramal space. In summary, specimens of this species thus exhibit 10–20 pairs of (mostly) straight foliaceous branchiae, starting from chaetigers 7–8, and the number of pairs increases with the size (age) of the specimen. The subdermal eyes within the body at the level of chaetiger 2 of small specimens (less than 13 mm in length) are also much more prominent and may be seen without manipulation of the specimen.

Remarks. We were initially unsure with which genus this species is aligned— Micronephthys or Nephtys , or Aglaophamus . These three genera are difficult to distinguish if specimens possess the shared generic characters such as simple palps and antennae, round nuchal organs, 22 rows of subterminal pharyngeal papillae, conical or pointed acicular lobes, the absence of lyrate chaetae, the presence of barred preacicular chaetae, finely spinulated postacicular chaetae, and presence of branchiae. According to Dnestrovskaya and Jirkov (2010), the genus Micronephthys can only be characterised by a reduction in branchial size and a reduced number of segments, features which are often possessed by juveniles of the other two genera. As most of our specimens are mature adults, we are confident that the poor development of parapodial lobes or lamellae and the low number of segments are characteristic enough features to place the specimens within Micronephthys ; however the branchiae are not quite “poorly developed”, or always straight, as, on some of our specimens, they may occupy almost 2/3 of the interramal gap, a few may be somewhat involute, and are of a similar size to those possessed by some small specimens of Nephtys spp, that we have observed. But based on current diagnoses of the three genera we are conservatively placing this new species in Micronephthys .

Micronephthys derupeli n. sp., is characterised by having 10–20 pairs of branchiae starting on chaetiger 7–8, pharynx with an elongated middorsal subterminal papilla, verrucae absent, barred chaetae present on chaetigers 1–9, serrated capillary chaetae present in all other chaetigers, and lyrate chaetae absent. This combination of characters distinguishes this species from all other twelve species of Micronephthys . Of the other species, the majority lack branchiae completely ( Table 3 ). Rainer and Hutchings (1977) recorded M. sphaerocirrata ( Wesenberg-Lund, 1949) from Queensland, however Ravara et al. (2010b) cast some doubt on this identification but did not examine this material. Given that this species was originally described from the Gulf of Iran we have listed it as M. cf. sphaerocirrata in the key, but it lacks branchiae and therefore cannot be confused with M. derupeli n. sp.

Of the four other species which possess branchiae, M. hartmannschroederae Jirkov and Dnestrovskaya in Jirkov, 2001 has branchiae from chaetigers 5–6 continuing to chaetiger 19 and possesses four types of chaetae; M. maryae ( San Martin, 1982) has poorly developed branchiae although this has been synonymised with M. stammeri ( Augener, 1932) fide Ravara et al. (2010b), which has no branchiae, and possesses lyrate chaetae; M. minuta ( Théel, 1879) has 10 pairs branchiae from chaetiger 6 continuing to 13–16 (as reported for syntypes by Ravara et al., 2010b, p. 25) as well as three types of chaetae; and M. neotena ( Noyes, 1980) has fewer pairs of branchiae from chaetiger 5–7 continuing to chaetiger 12–18, as well as possessing three types of chaetae. These characters distinguish them all from M. derupeli n.sp, which has branchiae from chaetigers 7–8, continuing to chaetigers 17–27, as well as only two types of chaetae. For this reason this species is described as new.

Etymology. The new species is named from a combination of initials of close family members of the first author; Dean Bridges, Ruth Dixon, Peter Dixon and Lisa Dixon.

Habitat. Specimens were found in sites containing mud, muddy/sand and Zostera , in depths from 1.6–3.6 m.

Distribution. Occurs from Port Stephens to Botany Bay, NSW, in shallow protected areas.

Figures

FIGURE 1. Micronephthys derupeli n. sp. a. anterior dorsal view (paratype AM W 43573), b. anterior dorsal view with pharynx partially everted (AM W 41581), c. lateral anterior view (paratype AM W 41509). All scale bars 0.1 mm. a = aciculum, an = antenna, b = branchia, e = nuchal organs, dc = dorsal cirrus, n = neurochaetae, p = palp, pon = postacicular notochaetae, prn = preacicular notochaetae, vc = ventral cirrus.

FIGURE 2. Micronephthys derupeli n. sp. a. lateral view of anterior chaetigers (paratype AM W 43573), b. mid chaetigers (AM W 41581), c. posterior chaetigers (paratype AM W 41509). b = branchia, cp = ciliated patches. All scale bars 0.1 mm.

FIGURE 4. Micronephthys derupeli n. sp. SEM a. chaetiger 8, b. chaetiger 13, c. chaetiger 20, d. chaetiger 23, e. chaetiger 43, f. chaetiger 47. b = branchia, cp = ciliated patches. (paratype AM W 41732). All scale bars 0.1 mm.

FIGURE 5. Micronephthys derupeli n. sp. a. barred chaeta from chaetiger 6, b. broad bladed serrated capillary from chaetiger 8, c. chaetiger 20, d. broad bladed serrated from chaetiger 35, e. close up of broad bladed serrated from chaetiger 20. b = barred chaeta, ew = broad bladed serrated. Scale bars a, b, d, e = 10 ųm, c = 100 ųm. All from AM W 41549.