Diplocirrus branchiatus (Rullier, 1965) Rullier, 1965

Salazar-Vallejo, Sergio I. & Buzhinskaja, Galina, 2011, Revision of Diplocirrus Haase, 1915, including Bradiella Rullier, 1965, and Diversibranchius Buzhinskaja, 1993 (Polychaeta, Flabelligeridae), ZooKeys 106, pp. 1-45 : 12-15

Diplocirrus branchiatus (Rullier, 1965) comb. n. Fig. 2

Bradiella branchiata Rullier 1965:188-190, Fig. 7; Darbyshire and Mackie 2009:97, Table 1.

Diplocirrus cf. capensis Spies 1975:187, 189, 190, Pl. 3, Fig. 7, Pl. 6, Fig. 18.

Type material.

Australia. Holotype of Bradiella branchiata Rullier, 1965 (AM-W3793), Moreton Bay (27°15'00"S, 153°15'00"E), Brisbane, Queensland, 1.2 km SW of M3 red beacon, coll. Party, 10 Nov. 1961. Two permanent slides (IRFA-W40, -W40'); W40 has three chaetal lobes and a small piece of skin; W40' has a branchial blade.

Additional material.

Australia. One anterior fragment (NTM-18913), anterior end exposed, appendages lost, Stat. A16a (12°11.7'S, 136°41.3'E), Melville Bay, 2.7 m, 7 Jul. 1991, Marine Ecology Unit, coll. (14 mm long, 2 mm wide, chaetiger 1 chaetae 0.5 mm long, 17 chaetigers, gonopores in chaetigers 3-12). One complete specimen (QM-G10334), Southwest Rocks, 0.8 km south of Peel Island (27.3° S, 153.21° E), Moreton Bay, Queensland, 6.4 m, shell, grit and sand, Sep. 1970, W. Stephenson, coll. (id. R. B. Spies; dorsally dissected, some parapodia removed, damaged, 13.5 mm long, 3 mm wide, chaetiger 1 chaetae 1 mm long, 21 chaetigers, gonopores pale, in chaetigers 3-8). Anterior fragment (QM-G10379), 1.6 km SE off Southwest Rocks, Peel Island (27.3° S, 153.21° E), Moreton Bay, Queensland, 4-7 m, mud, Mar. 1970, S. Cook, coll. (id. R. B. Spies; dorsally dissected, some parapodia removed, damaged, 38 mm long, 4 mm wide, chaetiger 1 chaetae 1.2 mm long, 18 chaetigers, gonopores reddish, in chaetigers 3-16). Anterior fragment (SAM-GR-201), under Edithburgh Jetty (35°05.172' S, 137°44.825' E), Victoria, South Australia, 5 m, in sediment, 1 Mar. 2004, G. Rouse, coll. (it is 12 mm long, 2.5 mm wide, chaetiger 1 chaetae 0.5 mm long, 15 chaetigers, gonopores pale, in chaetigers 3-6).

Description.

Holotype brown yellowish (other specimens pale, dirty orange or rusty). Body cylindrical, tapering posteriorly (Fig. 2A), contorted, with a previous dorsal longitudinal dissection, and other smaller ones to remove chaetigers 5 and 18; 53 mm long, 6 mm wide, cephalic cage 1.3 mm long, 37 chaetigers. Tunic with abundant papillae, long, cirriform, slightly capitate, with a thin layer of fine sediment particles, forming a thick base, arranged in over 20 irregular bands per segment.

Cephalic hood exposed, with smaller sparse papillae, as long as the following 3-4 chaetigers (swollen in holotype, annulated in QM-10334); cephalic hood mar gin smooth. Anterior end not everted, observed through the already done dissection. Prostomium elevated, eyes and caruncle not seen because it is bent and covered by the lateral lips (Fig. 2B, C, in SAM-GR201 prostomium flat lobe, no eyes). Palps lost (in SAM-GR201 palps thick, as long as branchiae); palp lobes reduced (thick, rounded in SAM-GR201, and two lateral well-developed lobes. Caruncle projected dorsally to the base of branchiae, lateral ridges elevated, posteriorly separated, laterally expanded. Dorsal lip projected anteriorly; lateral lips thicker; ventral lip reduced. Nephridial lobes in branchial plate not seen).

Holotype with branchial plate damaged. Posterior branchiae compressed, lateral filaments lost, median filament bent towards the mouth, lamellate; cirriform branchiae lost, two lateral scars per side, placed below a dorsal crest. Slide IRFA-W40' shows a branchial blade made of fused branchial filaments. Another specimen (SAM-GR201), with head slightly exposed (Fig. 2H), branchiae complete of two different types. Posterior row with four prismatic, thicker, lamellate branchiae, tips bare (Fig. 2J); lateral branchiae smaller (one in regeneration), each with dorsal keel reduced, with longitudinal bands, dorsal surface laterally expanded with a thin axis, provided with two rounded lateral lobes; median branchiae larger, dorsal keel large, foliose, markedly corrugated. Distal branchiae with ventral side with a blade made of fused branchial filaments, convoluted, looking like a series of successive blades, but actually made by a single convoluted blade. Anterior branchial row with four thin, cirriform filaments, shorter than palps, arranged in two lateral pairs, each filament with a convoluted lamella along its basal third (Fig. 2I), and successive ciliary bands medial- and distally. Branchial basal lobes between median and lateral branchiae (dorsal), and outside the lateral ones (lateral); dorsal lobes small, rounded, lateral lobes rounded, larger).

Cephalic cage chaetae slightly longer than following ones. First chaetiger displaced dorsally, with multiarticulated capillaries. Notochaetae in a short transverse tuft, with 6-7 multiarticulated capillaries. Anterior dorsal margin of first chaetiger papillated, as following segments. Anterior chaetigers without longer papillae, chaetiger 1 shorter than following ones, chaetal lobes lateral, very close to each other. First 10 chaetigers without marked segmentation between them; following chaetigers shorter, better defined. Ventral gonopores in chaetigers 3-12, orange-red, low papillae (Fig. 2D, E).

Parapodia poorly developed; chaetae emerge from the body wall. Notopodia and neuropodia with papillae as long as other papillae. Noto- and neuropodia close to each other. Median neuropodia lateral, very close to notopodia.

Chaetal transition from first chaetiger to body chaetae abrupt; notochaetae of chaetigers 2-3 large multiarticulated hooks, distal article hooked, entire. All other notopodia with multiarticulated capillaries. Median notochaetae arranged in a longitudinal line. Notochaetae of chaetigers 1 and beyond the third, multiarticulated capillaries; by chaetiger 11, as long as half body width, 10-11 per bundle (6-7 in smaller specimen), each with long articles throughout the chaeta (Fig. 2F). Neurochaetae multiarticulated hooks from chaetiger 1, arranged in a short J-shaped pattern, 4-5 per bundle, each with long articles of about the same length, tips falcate (Fig. 2G), with a hood-like membrane.

Posterior end invaginated in holotype; other specimens with truncated rounded lobe; notochaetae directed posteriorly; without anal cirri.

Variation.

Pigmentation varies from pale orange to dark yellowish, or to dirty pink with gonopodial pores reddish or pale. Further, there are two main variations related to body size: papillae are longer in larger specimens, and gonopores become more pigmented, and are probably present along more segments as body enlarges.

Remarks.

Diplocirrus branchiatus (Rullier, 1965), comb. n. is very similar to Diplocirrus nicolaji (Buzhinskaja, 1994), comb. n. because both species have bodies without sediment particles, ventrolateral gonopores along several anterior chaetigers, short chaetae in the first chaetiger, and their caruncle tapers posteriorly. They differ in the relative development of neurochaetae and of the extent of the lamellate area in their cirriform branchiae; thus, in Diplocirrus branchiatus median chaetigers have neurochaetae with about 23 articles, tapering to a delicately falcate tip, and the lamellate region might be up to one-fifth of the branchial length, whereas in Diplocirrus nicolaji , neurochaetae are barely tapering, having about 10 articles, their tips are markedly falcate, and the lamellate region might extend up to one-third of branchial length.

Diplocirrus branchiatus (Rullier, 1965) has been known only through the original description. Spies (1975) studied some specimens from the type locality (herein re-examined); they fit the original description but the anterior end was previously removed. Rullier’s description is fairly complete, though the presence of multiarticulated hooks in notopodia 2-3 was overlooked, as well as the presence of the gonopores. The anterior end has a symmetrical pattern and the original description does not provide complete details about branchiae; however, the drawings show that there were two larger lamellate branchiae (his figure 7C), and that there were smaller lateral branchiae (his figure 7D), but there are no details on cirriform branchiae; they might have been lost during dissection. As originally shown by Rullier (1965), and confirmed by the observation of one permanent slide, branchial blades include a series of parallel filaments; however, they are not arranged as successive, independent blades but rather as a continuous, convoluted, branchial blade. So far, this special type of branchial pattern is only known for a few species in Diplocirrus . Further, Rullier illustrated that neurohooks are distally tapering (his figure 7G), but he described them as (p. 190) "plus courtes et recourbées à leur extrémité” (shorter and distally curved), which is the correct description. Spies (1975) made some observations and his drawings are slightly inaccurate in several features: the caruncle does not taper posteriorly, and does not reach the posterior margin of the branchial plate, interbranchial lobes were not illustrated, and the lateral palp lobes were not seen.

Distribution.

Originally described from Eastern Australia, Diplocirrus branchiatus is present from Northeastern Australia to Southern Australia, in shallow water sediments. The data in the same publication by Rullier (1965), indicate that the type specimen was found in muddy bottoms in shallow depths.