Micronephthys minuta ( Théel, 1879 )

Ravara, Ascensão, Cunha, Marina R. & Pleijel, Fredrik, 2010, Nephtyidae (Annelida, Polychaeta) from southern Europe 2682, Zootaxa 2682 (1), pp. 1-68 : 24-25

Micronephthys minuta ( Théel, 1879)

Figure 7

Nephthys minuta Théel, 1879: 28 , pl. II, fig. 18; Augener 1913: 206; Uschakov 1955: 218, fig. 68G.

Nephtys minuta Annenkova 1937: 164 ; Annenkova 1938: 162; Gorbunov 1946: 38; Zatsepin 1948: 122, table 30 (partim); Uschakov 1955: 217, fig. 68 (partim).

Micronephthys minuta Friedrich 1939: 123 , fig. 3–4; Taylor 1984: 35-5, fig. 35-1 and 2A–E; Jirkov 1989: 74, fig. 15.4 (partim); not Parapar et al. 1993: 375, fig. 7; Jirkov and Paraketsova 1996: 831, fig. 1; not Pettibone 1963: 188, fig. 47B, C; Dnestrovskaya and Jirkov 2001: 192,1 fig.

Micronephtys minuta Hartman 1950: 130 ; Reish 1965: 139; Curtis 1979: 1; Tzetlin 1980: 25 (partim).

Micronephtys sp. aff minuta Fournier and Pocklington 1984: 261 .

Type locality. Besimennїa Bay and occidental region of Matotchkin , Novaya Zemlya, Barents Sea, 7–34 m depth .

Material examined. Barents Sea. Novaya Zemlya, Besimennїa Bay : 72º53’N, 52º53’E, 4–5 fms, N. Semlja Expedition 1875, Jul 1875, 29 complete and 13 incomplete spms, syntypes (SMNH-type-2463). White Sea. Kondalaksha Fiord: 40 m, 1 incomplete spm ( DBUA 01137.01 ) .

Description. Examined specimens up to 14.5 mm long for up to 34 chaetigers. See Fig. 7 for length and width measurements. Body small, slightly wider anteriorly, gradually tapering from middle region to pygidium. Colour in ethanol white; chaetae and aciculae amber. Eyes not visible. Pharynx distal region with 9 pairs of terminal, bifid papillae, separated by dorsal and ventral gap; long middorsal papillae present; subdistal region with 20 rows of 3–7 small subterminal papillae; proximal region smooth. Prostomium subquadrangular, anterior margin slightly convex, posterior margin poorly defined; antennae conical with a broad base and a cirriform tip; palps inserted ventrolaterally on anterior region of prostomium, slightly behind antennae, conical to cirriform, with a small papilla ventrally at the base. Nuchal organs rounded. Parapodia biramous. Parapodia of chaetiger 1 anteriorly directed, parallel to prostomium; noto- and neuropodial acicular lobes conical; pre- and postchaetal lamellae rudimentary; dorsal cirri very small; ventral cirri well developed, cirriform. Acicular lobes of following parapodia conical; pre- and postchaetal lamellae rudimentar; dorsal and ventral cirri conical, very small. Branchiae straight or slightly involute, strongly ciliated; present from chaetiger 6 to 13–14; well developed in all branchiate chaetigers; occupies 1/2 to 2/3 of interramal space when fully developed. Chaetae of three kinds: barred chaetae in preacicular position of the first 20 chaetigers, very finely spinulated chaetae in postacicular position, capillary chaetae in neuropodia of first chaetiger and in preacicular position of the posterior chaetigers. One acicula per ramus, median and posterior ones with curved tips.

Remarks. Micronephthys minuta was recorded a few times in local unpublished studies from Portugal. However, no material from South Europe was examined in this study, and those records should be considered with caution. This species was described from the Barents Sea and seems to be frequent in Arctic and Subarctic regions ( Jirkov 1989; Jirkov & Paraketsova 1996). Parapar et al. (1993) recorded two specimens from Ceuta (N Africa) that differ from M. minuta in having 12 rows of large subterminal papillae in the pharynx, sphaerical to oval dorsal and ventral cirri, and branchiae absent. Thus, the specimens from Ceuta are here considered to belong to a different species.

Théel (1879) and Jirkov and Paraketsova (1996) mention the presence of branchiae on chaetigers 6–9 to 10–14. From the specimens examined in this study, only one (from the White Sea) has branchiae on chaetigers 7–11. All the other 42 specimens (syntypes) have branchiae from chaetiger 6 to 13–16 (to 13 on 16 spms, 14 on 23 spms, 15 on 2 spms and 16 on 1 spm).

Distribution. Arctic Ocean (Barents Sea, White Sea, N Spitsbergen, Chukchi and Beaufort Seas); Atlantic Ocean (from Canada to Gulf of Mexico); Pacific Ocean (Bering Sea) ( Reish 1965; Taylor 1984; Jirkov & Paraketsova 1996; Jirkov 2001).

Habitat. Coarse to fine-very fine sand with moderate mixtures of silt and clay, mud, and foraminiferan ooze, 10–270 m depth ( Taylor 1984; Jirkov & Paraketsova 1996; Dnestrovskaya & Jirkov 2001).

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).