Micronephthys stammeri ( Augener, 1932 )

Ravara, Ascensão, Cunha, Marina R. & Pleijel, Fredrik, 2010, Nephtyidae (Annelida, Polychaeta) from southern Europe 2682, Zootaxa 2682 (1), pp. 1-68 : 27-30

Micronephthys stammeri ( Augener, 1932)

Figures 7 , 9

Nephthys stammeri Augener, 1932: 678 , fig. 2.

Nephthys inermis Augener 1932: 663 .

Micronephthys stammeri Hartman 1950: 131 ; Banse 1959: 302, fig. 6.

Micronephthys maryae San Martín, 1982: figs. 1–3; Rainer and Kaly 1988: 696, figs. 5A–E and 6B; Laborda 2004: 416, fig. 152A–C.

Type locality. Adriatic Sea (Timavo-Geviet region) .

Material examined. Mediterranean Sea. Adriatic Sea, Croatia, Rovinj: 4 complete and 4 incomplete spms ( ZMH-V 12889); Istra, off Rovinj: RV Burin, 45º05.769’N, 13º37.406’E, 18 m, Sep 2008, 1 complete spm ( DBUA 01050). Spain, between Cabo San Antonio and Puerto de Valencia: 1 complete and 1 incomplete spms ( MNCN 16.01/2210 as M. maryae ); Mallorca Island, Santa Ponça: 1 complete spm ( MNCN 16.01/278, paratype of M. maryae ).

Pacific Ocean. Japan, Tanabe Bay : 33º42.772’N, 135º22.248’E, 10 m (?), Nov 2008, 4 complete and 1 incomplete spms ( DBUA 01051-01 ), and 1 incomplete spm ( MB36000144 ); Shirahama, 33º41.481’N, 135º20.181’E, 0.5 m, Nov 2008, 2 complete spms ( DBUA 01051-02 ). Marshall Islands, Parry Island (lagoon side), Enewetak atoll: 11º24’N, 162º23’E, 90 ft, summer 1957, 1 complete spm ( USNM 118681 as M. sphaerocirrata ) .

Description. Examined specimens up to 6 mm long for up to 49 chaetigers. See Fig. 7 for length and width measurements. Body small, slightly wider anteriorly, tapering posteriorly. Poor dorsal delineation between anterior segments. Colour in ethanol white; chaetae and acicula amber. Two pairs of large coalescent eyes visible at level of chaetiger 3. Pharynx subdistal region with 20–22 rows of about 8 long and conical subterminal papillae decreasing in size towards base of pharynx, followed by several minute (wart-like) papillae, extending over 2/3 length of pharynx ( Fig. 9A ); proximal region smooth. Jaws conical ( Fig. 9B ). Prostomium subpentagonal, anterior margin slightly convex; antennae and palps subequal in length, cirriform with swollen tips; palps inserted ventrolaterally on median region of prostomium ( Fig. 9C ). Nuchal organs rounded. Parapodia biramous. Parapodia of chaetiger 1 similar in size to subsequent ones, anteriorly directed, parallel to prostomium; notopodial acicular lobes conical, pre- and postchaetal lamellae rudimentary; neuropodial pre- and postchaetal lamellae forming a cylinder covering acicular lobes; dorsal cirri small and sphaerical; ventral cirri cirriform with swollen tips, similar in size to palps. Following parapodia with conical acicular lobes; pre- and postchaetal lamellae of both rami rudimentary or poorly developed, rounded; dorsal and ventral cirri subsphaerical ( Fig. 9D ). Branchiae absent. Chaetae of five kinds: barred chaetae, with a peak in center of each bar (slightly thicker than barred chaetae from other chaetigers) in preacicular position of notopodia of chaetiger 1 ( Fig. 9E ); simple barred chaetae in preacicular position of following parapodia; finely spinulated chaetae in postacicular position of all parapodia ( Fig. 9F ); lyriform chaetae with unequal rami and thin and long spines on the internal side, in postacicular position of parapodia from chaetiger 3 ( Fig. 9G ), and capillary chaetae in the neuropodia of chaetiger 1. One acicula with curved tips per ramus ( Fig. 9H ).

Remarks. The original description by Augener (1932) is incomplete and the holotype has been lost. Banse (1959) redescribed the species based on specimens also collected from the Adriatic Sea. Those specimens were examined within this study and Banse’s description is here emended and completed with the following features: dorsal cirri are present from chaetiger 1 (instead of chaetiger 2); special chaetae are present in the notopodia of first chaetiger; lyriform chaetae are present from the chaetiger 3 (instead of chaetiger 15). There are no records of this species after Banse (1959). In 1982, San Martín described a new species, M. maryae , for specimens collected in the Mediterranean Sea. However, he did not examined the type material of M. stammeri and based his conclusions on the description given by Banse (1959). Consequently, the differences used by San Martín to distinguish these two species are exactly the characters added here to the emended description of M. stammeri . Therefore we consider M. maryae to be a junior synonym of M. stammeri . Both the description of M. maryae by San Martin (1982) and the description of M. stammeri by Banse (1959) refer the presence of 20–22 rows of subterminal papillae in the pharynx. However, Rainer and Kaly (1988) emended the description of M. maryae to include 14 rows of subterminal papillae, instead of 20– 22, based on a paratype of M. maryae and on specimens from Australia. According to the specimens examined in this study, especially the ones from the Adriatic Sea, the pharynx actually has at least 20 rows of papillae. On the paratype of M. maryae and on the specimens from Japan the 20 rows of papillae were not possible to assess with certainty, although they seem to have more than 14 rows.

Apart from the differences mentioned above, M. stammeri clearly differs from the other two Micronephthys species in body size ( Fig. 7 ). Micronephthys sphaerocirrata is a larger species in length and number of segments. As for M. minuta the scarce data do not allow a reliable conclusion, althought the specimens appear larger than M. stammeri for the same number of segments.

Distribution. Adriatic Sea; Mediterranean Sea (Balearic Islands); Indian Ocean (W Australia); Pacific Ocean ( Japan, Marshall Islands) ( San Martín 1982; Rainer & Kaly 1988; Laborda 2004).

Habitat. Median sand with gravel, 4–7 m depth ( Banse 1959; Laborda 2004).

Figures

FIGURE 7. Relationships between: A. Number of segments and body length. B. Body length and body width. × M. minuta. M. sphaerocirrata. M. stammeri. M. minuta plot is based on the literature (Théel, 1879; Pettibone, 1963; Jirkov & Paraketsova, 1996). M. sphaerocirrata plot includes measurements from Wesenberg-Lund (1949) and Rainer & Hutchings (1977). M. stammeri plot includes measurements from Banse (1959), San Martín (1982) (original description of M. maryae) and Rainer & Kaly (1988) (for M. maryae).

FIGURE 9. Micronephthys stammeri. A. Pharynx, dorsal view. B. Jaw. C. Prostomium and anterior chaetigers, dorsal view. D. Dorsal (left) and ventral (right) cirrus from median parapodia. E. Barred chaeta from notopodia of chaetiger 1. F. Postacicular chaeta of median chaetiger. G. Lyriform chaeta. H. Acicula from median chaetiger.