Willeysthenelais diplocirrus (Grube 1875)

Willeysthenelais diplocirrus (Grube)

Sthenelais diplocirrus Grube, 1875:75, 77.

Sthenelais zeylanica Willey, 1905:258, pl. 2: fig. 48.—Okuda 1937:268, fig. 9a–f.—Gallardo 1968:52, pl. 5: fig. 11.—Not Fauvel 1927:416 [= Willeysthenelais suezensis, new species].—Not Thomassin 1970:60.

Sthenelais orientalis Potts, 1910:348, pl. 21: fig. 62.—Not Horst 1917:113 [= Willeysthenelais suluensis, new species].

Sthenelais variabilis var. colorata Monro 1924:52.

Sthenelais colorata.—Hartman 1949:36.

MATERIAL EXAMINED.—Upolu, Samoa—holotype of Sthenelais diplocirrus (ZMH 612).

Amirante, Seychelles, 46–91 meters—holotype of Sthenelais orientalis (BMNH 1924: 3: 1: 76).

Port Denison, eastern Australia, 7 meters, sand and shells, Alert Expedition—holotype of Sthenelais variabilis var. colorata (BMNH 1925: 1: 28: 51).

Nha Trang, South Vietnam, V. A. Gallardo, collector: station 138, 16 February 1960, 3 meters, coarse sand with shell and coral debris—1 specimen (AHF); station 245, 16 March 1960, 11 meters, muddy sand with shell debris—1 specimen (USNM 43555).

TYPE MATERIAL.—The holotype of Sthenelais diplocirrus consists of an anterior fragment of 40 segments, 42 mm in length, and 10 mm in width, including setae. No simple spinous neurosetae were observed.

The holotype of Sthenelais orientalis is an anterior fragment of 62 segments, about 45 mm long, and 8 mm wide, including setae. A single simple spinous neuroseta was observed on some of the parapodia.

The holotype of Sthenelais variabilis var. colorata consists of an anterior fragment of 36 segments and a middle fragment of 12 segments, with a total length of 40 mm and a width of 7 mm, including setae. A few (1–2) simple spinous neurosetae were observed in some of the parapodia. Some of the elytra show the circular patches of pigmentation surrounding the microtubercles, described by Monro (1924:53). The coloration is due to reddish foreign material and is not present on all the elytra.

DESCRIPTION.—Length more than 45 mm, width up to 10 mm, including setae, segments numerous. Wide middorsal ridge on segments 2–5, with three pairs of small ctenidia alongside (Figures 6a, 8a). Ventral surface papillate, especially more posteriorly (from about segment 20 on; Figures 7i, 8f). Elytra fleshly, opaque, suborbicular to subreniform, with uniformly distributed microtubercles, scattered clavate micropapillae, and lateral borders with long papillae; sometimes with additional submarginal papillae on lateral and posterior borders; microtubercles low, rounded to subconical (Figures 7j–m, 8j).

Prostomium with median antenna with large subtriangular auricles on ceratophore and rather short tapered style; lateral antennae short, subulate; four eyes arranged in square, moderate in size, anterior pair larger than posterior pair (sometimes partially hidden by ceratophore and auricles of median antenna); palps extending about to segment 7 (6–9); nuchal organs prominent (Figures 6a, 8a). Tentacular parapodia with dorsal tentacular cirri subequal in length to median antenna; ventral tentacular cirrus about two thirds as long as dorsal cirrus; inner tentacular lobe extending nearly to tip of ventral tentacular cirrus, fused to shorter, rounded inner palpal sheath; dorsal ctenidium elongate-oval (Figures 6a–c, 8a).

Parapodia of segments II and III directed anteriorly, slightly modified from following segments (Figures 6d,e; 8a–c). All neurosetae compound falcigers; upper ones with long multiarticulated blades (7–12 articles) and stems with faint spinous rows (Figure 6f); blades of slightly stouter middle ones with 1–7 articles and stems smooth or with faint spinous rows (Figure 6g); blades of lower slender ones with 5–10 articles and stems with about six faint spinous rows (Figure 6h). Additional small ctenidia located medial to elytrophores of segments II and IV (Figures 66, 8a).

Parapodia of anterior (Figures 7a–c, 8e) and middle regions (Figures 7h,i; 8f) similar. Cirriform branchiae beginning on segment IV (or small one on II). Clavate notopodia with stylodes (about five) and fimbriated bracts—row of short papillae posteriorly and longer papillae or stylodes on lower anterior part. Neuropodial acicular lobes with 1–3 oval stylodes. Bilobed posterior bracts fimbriated—papillae longer on upper and lower parts. Anteroventral and anterior upper bracts fimbriated, with rows of short papillae. Extra papillae (1–4) on lower side of neuropodia medial to anteroventral bracts, beginning about segment 17, increasing in length and number posteriorly. C-shaped group of stout neurosetae with blades short to longer with 1–2 articles; stems with faint spinous rows (Figures 7f, 8h). Blades of upper anterior group of compound falcigers with 2–6 articles; stems with rather faint spinous rows (Figure 7e); simple spinous neurosetae present (1–2) or absent (Figures 7d, 8g). Blades of anteroventral slender neurosetae with 3–6 articles; stems smooth or with few faint spines (Figures 7g, 8i). Ventral cirri tapered, with outer basal knob elongated to slightly more than half length of style (small on segment III); long papillae on medial bases of ventral cirri beginning about segment 7 (6–9), usually two in number, sometimes increasing to three (rarely four; single papilla only on smaller specimens from South Vietnam).

DISTRIBUTION.—Indopacific—Samoa, Eastern Australia, Palau Islands, South Vietnam, Ceylon, Seychelles. In 3 to 91 meters.

双须维镰虫（学名：Willeysthenelais diplocirrus）为锡鳞虫科维镰虫属的动物。分布于从东澳大利亚到越南的广大海域，包括南海、台湾海峡等海域，属于印度太平洋热带种。