Micronephthys cf. sphaerocirrata ( Wesenberg-Lund, 1949 )

Murray, Anna, Wong, Eunice & Hutchings, Pat, 2015, Nephtyidae (Annelida: Phyllodocida) of Lizard Island, Great Barrier Reef, Australia, Zootaxa 4019 (1), pp. 414-436 : 426-428

Micronephthys cf. sphaerocirrata ( Wesenberg-Lund, 1949)

( Figs 8–9 )

Nephthys sphaerocirrata Wesenberg-Lund, 1949: 294 –296, figs 24–26.

Micronephthys sphaerocirrata .— Rainer & Hutchings 1977: 320 –322, figs 12–13.

Material examined. Queensland, Great Barrier Reef: AM W.46983 (9, 1 on SEM), MI QLD 2449.

Other material examined. Queensland: AM W.8463 (2), AM W.8464 (1), Middle Banks, Moreton Bay, 27°13'S, 153°19'E, Sep 1973; AM W.8658 (2), Townsville, 19°21'S, 147°15'E, sand, 4 m, 16 Apr 1975.

Description. Specimens from Lizard Island all incomplete, up to 9 mm long, 1 mm wide, with 51 chaetigers. Body without pigment. Posteriorly, body somewhat moniliform, constrictions at segment boundaries. Prostomium subpentagonal; antennae located on anterior margin; palps anterolateral, slightly ventral to and widely separated from antennae ( Figs 8 A, 9A–B); lateral margin between antennae and palps concave to slightly convex ( Fig. 8 A); posterior margin V-shaped ( Fig. 8 A). Antennae and palps long, tapering with swollen tips, similar in length ( Figs 8 A, 9A–C). Nuchal pits round ( Fig. 9 B). Pair of eyes visible middorsally on chaetiger 2 ( Fig. 8 A). Pharynx with 19 bifid terminal papillae, simple dorsal papilla absent, 22 subdistal rows of elongate papillae (distalmost papillae of mid row as long as or longer than antennae and palps), with 8–15 papillae per row, proximally decreasing in size to small micropapillae, elongate middorsal and midventral subdistal papillae absent. First chaetiger with small papilla-like dorsal cirrus and elongated ventral cirrus, similar in shape and length to palps, following chaetigers with subspherical globular dorsal cirri and ovate ventral cirri ( Figs 8 B, 9B, 9F–G). Parapodial acicular lobes conical ( Fig. 9 G); postacicular lobes reduced, preacicular lobes rudimentary ( Fig. 9 E–G). Interramal branchiae absent. Interramal patches of cilia present ( Figs 8 B, 9F). Aciculae with curved tips ( Fig. 9 G). Four types of chaetae: capillary in the first noto- and neuropodia ( Fig. 9 C); barred chaetae in preacicular position of first notopodia and all following parapodia ( Fig. 9 C–D, H); spinose chaetae in postacicular position of all following parapodia ( Fig. 9 D–F, H); and lyrate chaetae with unequal rami in postacicular position ( Fig. 9 E, G–H), from chaetiger 4.

Remarks. These Australian specimens are remarkably similar to M. sphaerocirrata , which was originally described from the Persian Gulf, but vary from the most recent and detailed description of the species by Ravara et al. (2010b, pp. 26–27) by the insertion of the palps on the prostomium, anterolaterally instead of ventrolaterally, by possessing only 19 bifid and no simple terminal pharyngeal papillae, and having globular dorsal cirri rather than spherical ones with conical tips. They are similar to the specimens from Queensland described by Rainer & Hutchings (1977) as M. sphaerocirrata , and after examination of their material, those specimens were also found to have only 19 bifid and no simple terminal pharyngeal papillae, small micropapillae proximally on the pharynx, and lyrate chaetae starting from chaetiger 4. The specimens differ from M. stammeri ( Augener, 1932) in the lack of thick dentate chaetae in the first notopodia, and from M. platycephala n. sp. in the smaller size and the presence of visible eyes on chaetiger two.

Ravara et al. (2010b) redescribed M. sphaerocirrata from syntype material as well as from South African specimens, but there is no distinction between type and non-type material in their description. They described the species as having a pharynx with “7–10 conical subterminal papillae, followed by several minute papillae, extending to base of pharynx; proximal region smooth” as well as “10 pairs of terminal, bifid papillae, separated by dorsal simple papilla”, none of which agrees with our specimens. However, other specimens that have been attributed to M. sphaerocirrata , also show a large variation in the number of subterminal pharyngeal papillae in each row, and the development of the parapodial lamellae proportions ( Ravara et al. 2010b, p.27). For instance, M. sphaerocirrata orientalis Lee & Jae, 1983 from Korea and Vietnam, reportedly possesses 12–15 subterminal pharyngeal papillae per row, and prominent preacicular lamellae, whereas M. sphaerocirrata from Thailand has well developed neuropodial prechaetal and notopodial postchaetal lamellae ( Nateewathana & Hylleberg 1986). Because of this variation, and because the Australian specimens also show subtle differences to Wesenberg-Lund’s (1949) original description, we refer our specimens tentatively to M. sphaerocirrata . Also, because of the reported morphological variation and the range of depths from which this species has been recorded, we suspect that Micronephthys sphaerocirrata contains a suite of cryptic species, and in order to resolve their identity, further analysis of populations using molecular as well as morphological data is necessary.

Habitat. Sand and muddy sand, in shallow subtidal depths to 500 m.

Distribution. Persian Gulf, southwest Africa, South Africa, Australia (Queensland).

Figures

FIGURE 8. Micronephthys cf. sphaerocirrata, specimen stained with methyl blue, AM W. 46983. A. Anterior end, dorsal view; B. Chaetigers 2 – 8, lateral view. Abbreviations: an = antenna, cp = cilia patch, dc = dorsal cirrus, e = eye, no 1 = notopodium 1, p = palp, vc = ventral cirrus. Scale bars: A – B = 0.1 mm.

FIGURE 9. Micronephthys cf. sphaerocirrata, SEM photos of AM W. 46983. A. Anterior end, dorsal view (prostomium folded over dorsally); B. Prostomium and chaetigers 1 – 4, anterodorsal view; C. Chaetiger 1 and prostomium, anterolateral view; D. Chaetigers 2 – 4, anterolateral view; E. Chaetigers 9 – 11, dorsolateral view; F. Midbody chaetigers, lateral view; G. Midbody neuropodia, ventral view; H. Chaetae, neuropodium 16. Abbreviations: acl = acicular lobe, an = antenna, b = barred chaeta, cp = cilia patch, dc = dorsal cirrus, ly = lyrate chaeta, ne 1 = neuropodium 1, no 1 = notopodium 1, nu = nuchal pit, p = palp, pel = preacicular parapodial lobe, pol = postacicular parapodial lobe, pros = prostomium, sp = spinose chaeta, vc = ventral cirrus. Scale bars: A – B, E – G = 0.1 mm, C – D, H = 0.01 mm.