Aglaophamus elamellatus ( Eliason, 1951 )

Ravara, Ascensão, Cunha, Marina R. & Pleijel, Fredrik, 2010, Nephtyidae (Annelida, Polychaeta) from southern Europe 2682, Zootaxa 2682 (1), pp. 1-68 : 11-14

Aglaophamus elamellatus ( Eliason, 1951)

Figures 2 , 3

Nephthys elamellata Eliason, 1951: 133 , fig. 2; Kirkegaard 1956: 68, fig.7.

Aglaophamus elamellata Kirkegaard 1980: 85 ; Kirkegaard 1995: 36.

Type locality. Central Atlantic (near Canary and Azores Islands ) .

Material examined. Atlantic Ocean. Central Atlantic: 40º33’N, 35º24’W – 40º34’N, 35º52’W, 4540– 4600 m, Sep 1948, 1 incomplete spm, syntype ( GNHM Polych. 10990). Portugal, Nazaré Canyon: cruise D297, RV Discovery , 39º30.62’N, 9º56.19’W, 3461 m, box-corer, 8 Aug 2005, 4 complete spms ( DBUA 00837-01 ) ; 39º30.02’N, 9º56.17’W, 3465 m, box-corer, 10 Aug 2005, 6 complete and 1 incomplete spm ( DBUA 00837-02 ) ; 39º30.02’N, 9º56.22’W, 3464 m, box-corer, 11 Aug 2005, 3 complete spms ( DBUA 00837-03 ) ; 39º35.00’N, 10º19.04’W, 4336 m, box-corer, 11 Aug 2005, 1 complete spm ( DBUA 00837-04 ) ; cruise CD179, RV Charles Darwin, 39º29.99’N, 9º55.97’W, 3517 m, megacorer, 9 May 2006, 1 complete spm ( DBUA 00838-01 ) ; 39º29.99’N, 9º56.01’W, 3517 m, megacorer, 9 May 2006, 3 complete spm ( DBUA 00838-02 ) ; 39º30.00’N, 9º55.98’W, 3522 m, megacorer, 11 May 2006, 1 complete spm ( DBUA 00838-03 ) ; Cascais Canyon : cruise CD179, RV Charles Darwin , 38º17.97’N, 9º46.89’W, 3214 m, megacorer, 27 Apr 2006, 1 complete spm ( DBUA 00839-01 ) ; 38º18.01’N, 9º47.02’W, 3218 m, megacorer, 27 Apr 2006, 2 complete spms ( DBUA 00839-02 ) ; 38º22.49’N, 9º53.52’W, 4244 m, megacorer, 3 May 2006, 1 complete spm ( DBUA 00839-03 ) ; Setúbal Canyon : cruise CD179, RV Charles Darwin , 38º09.27’N, 9º36.93’W, 3275 m, megacorer, 21 Apr 2006, 3 complete spms ( DBUA 00840-01 ) ; 38º09.26’N, 9º36.94’W, 3275 m, megacorer, 21 Apr 2006, 3 complete spms ( DBUA 00840-02 ) ; 38º09.22’N, 9º37.02’W, 3224 m, megacorer, 23 Apr 2006, 2 complete and 1 incomplete spm ( DBUA 00840-03 ) ; cruise 64PE252, RV Pelagia , 38º17.10’N, 9º06.00’W, 970 m, box-corer, 17 Sep 2006, 1 complete spm ( DBUA 00841-01 ) ; 38º17.10’N, 9º06.00’W, 970 m, boxcorer, 17 Sep 2006, 1 incomplete spm ( MB36000104 ) .

Description. Examined specimens up to 22 mm long for up to 54 chaetigers. See Fig. 2 for length and width measurements. Body small, slightly wider anteriorly, tapering posteriorly. Poor dorsal delineation between segments. Colour in ethanol white, chaetae and aciculae amber. Eyes not visible. Pharynx distal region with 10 pairs of terminal bifid papillae, separated by simple conical dorsal and ventral papilla; middorsal and midventral papillae absent; subdistal region with 20–22 rows of 6–11 lanceolate subterminal papillae with crenulated ventral borders, rows extending to base of pharynx ( Fig. 3A–B ); proximal region without warts. Jaws conical ( Fig. 3C ). Prostomium subpentagonal, anterior margin straight or slightly convex, posterior margin V-shaped, extending over first chaetiger ( Fig. 3D ); antennae and palps conical, subequal in length ( Fig. 2C ), palps inserted ventrolaterally on anterior part of prostomium, directed ventrally (often not visible in dorsal view). Nuchal organs rounded. Parapodia biramous; interramal space “U-shaped” anteriorly and “V-shaped” medially and posteriorly; ciliation not seen. Parapodia of chaetiger 1 slightly longer than subsequent ones, anteriorly directed, parallel to prostomium; noto- and neuropodial acicular lobes acutely pointed; pre- and postchaetal lamellae rudimentary; acicula of neuropodia protruding from acicular lobes (fig. 3E); dorsal cirri rounded, minute ( Fig. 2D ); ventral cirri digitiform, with broad bases and tapered distally. Parapodia of chaetigers 2 and 3 with notopodia smaller than neuropodia. Acicular lobes of following parapodia acutely pointed; pre- and postchaetal lamellae of both rami smaller than acicular lobes (rudimentary on smaller specimens), rounded, becoming rudimentary in posteriormost parapodia; dorsal cirri short, conical to rounded, with broad base; ventral cirri digitiform (fig. 3F–I). Branchiae involute, lightly ciliated, present from chaetigers 11–13, absent on posterior chaetigers (totally absent on specimens with less than 26 chaetigers); occupy 2/3 of interramal space when fully developed. Chaetae thin and very long (preacicular chaetae almost as long as postacicular ones), of three kinds: barred chaetae in preacicular position ( Fig. 3K ), finely spinulated chaetae in postacicular position ( Fig. 3J ), and capillary chaetae in neuropodia of chaetiger 1. One acicula with curved tip per ramus.

Remarks. The species name is here corrected from A. elamellata to A. elamellatus according to the gender of the generic name. This species was originally described by Eliason (1951) from the central Atlantic (Azores and Canary Islands), and has only been recollected a few times since from the Atlantic, Indian and Pacific oceans ( Kirkegaard, 1956, 1980, 1995). This study extends its distribution to the Nazaré submarine canyon off the western coast of Portugal (NE Atlantic). Although the geographical distribution appears to be excessively wide, according to Kirkegaard (1995) there are no apparent morphological differences between the Atlantic specimens and those from the Indian Ocean and around New Zealand. Nevertheless, specimens from those localities were not examined within the present study and the descriptions given by Kirkegaard (1956, 1980, 1995) are not very detailed. Therefore the Indian and Pacific Oceans references should be considered with caution. In the specimens examined, the occurrence of branchiae varies with the number of chaetigers ( Table 1). Thus, although they always start between chaetigers 11 and 14 (most frequently on chaetiger 13), they extend further posteriorly in longer specimens, and are absent in specimens with less than 26 chaetigers. The pharynx is described herein for the first time.

Distribution. Atlantic Ocean (W Portugal, Azores, Canary Islands, off W Africa); Indian Ocean (off E Africa, Sri Lanka); Pacific Ocean (Tasman Sea, Kermadec Trench) ( Kirkegaard 1956, 1980, 1995).

Habitat. Mud, 990–7000 m depth ( Kirkegaard 1956, 1980, 1995).

Figures

FIGURE 2. Relationships between: A. Number of segments and body length. B. Body length and body width. C. Antennae and palps length. D. Length of ventral cirri (VC) and dorsal cirri (DC) of chaetiger 1. Aglaophamus elamellatus. - A. malmgreni. A. pulcher. A. rubellus. Minute dorsal cirri were scored as 0.01. A. elamellatus, A. malmgreni and A. pulcher plots include measurements from the original description (Théel, 1879; Eliason, 1951; Rainer, 1991).

FIGURE 3. Aglaophamus elamellatus. A. Dissected pharynx, dorsal view. B. Detail of pharynx subterminal papillae. C. Jaw. D. Prostomium and anterior chaetigers, dorsal view. E. Left neuropodium of chaetiger 1. F. Right parapodium of chaetiger 10, anterior view. G. Same, posterior view. H. Right parapodium of chaetiger 20, anterior view. I. Same, posterior view. J. Postacicular chaeta from chaetiger 15. K. Preacicular chaeta from chaetiger 15.