Nephtys kersivalensis McIntosh, 1908

Ravara, Ascensão, Cunha, Marina R. & Pleijel, Fredrik, 2010, Nephtyidae (Annelida, Polychaeta) from southern Europe 2682, Zootaxa 2682 (1), pp. 1-68 : 55-57

Nephtys kersivalensis McIntosh, 1908

Figure 11 , 21

Nephthys hombergii var. kersivalensis McIntosh, 1908: 20 (partim).

Nephthys incisa Michaelsen 1896: 59 (partim); Augener 1913: 203 (partim); George 1979: 198 (not Malmgren 1865).

Nephthys hombergii forma ehlersii Fage and Legendre 1927: 124, fig. 15.

Nephtys incisa Fauchald 1963: 15 (partim).

Nephtys hombergi kersivalensis Fauchald 1963: 5 .

Nephtys hombergii var. kersivalensis Hartmann-Schröder 1971: 217 , fig. 70C.

Nephtys kersivalensis Rainer 1989: 882 , fig. 2A–F; Rainer 1991: 78, fig. 2D; Hartmann-Schröder 1996: 229, fig. 101; Dnestrovskaya and Jirkov 2001: 203, 1 fig; Laborda 2004: 406, fig. 149A–C.

Type locality. Connemara , Ireland .

Material examined. Atlantic Ocean. SW Ireland, off Valentia Island : 1–160 fms, 19 incomplete spms, syntypes ( NHM 1921.5.1.796-806). England, off Northumberland: 48 m, Apr 2008, 1 complete spm ( MB36000149 ) . Portugal, Sado Estuary : 38º30.994’N, 8º54.077’W, 11 m, Jun 2005, 2 complete and 1 incomplete spms ( DBUA 00864-01 to 03 ); Lagos, 37º04.948’N, 8º38.500’W, 30 m, Apr 2006, 1 incomplete spm ( DBUA 00865-01 ) .

Description. Examined specimens up to 40 mm long for up to 69 chaetigers. See Fig. 11 for length and width measurements. Body slightly wider anteriorly, gradually tapering from middle region to pygidium. Poor dorsal delineation between anterior segments. Colour in ethanol cream; prostomium with dark spot in the medioanterior region; chaetae amber; tip of aciculae dark. One pair of eyes visible only in small specimens at posterior limit of chaetiger 2. Pharynx distal region with 10 pairs of terminal bifid papillae, separated by dorsal and ventral gap; middorsal papilla very long and cirriform ( Fig. 11D ), midventral papilla absent; subdistal region with 22 rows of 3–6 small, conical subterminal papillae, extending over 1/3 length of pharynx ( Fig. 21A ); proximal region smooth. Jaws not examined. Prostomium subpentagonal, anterior margin slightly convex, posterior margin V-shaped extending over first chaetiger ( Fig. 21A ); antennae and palps conical to cirriform, equal in length; palps inserted ventrolaterally on mid-anterior region of prostomium. Nuchal organs rounded. Parapodia biramous; interramal space “V-shaped”, moderately ciliated. Parapodia of chaetiger 1 similar in size to subsequent ones, directed anteriorly, parallel to prostomium; notopodial acicular lobes conical; pre- and postchaetal lamella well developed but not extending beyond acicular lobes; neuropodial pre- and postchaetal lamellae forming a cylinder around acutely pointed acicular lobes; dorsal cirri small ( Fig. 11C ), rounded; ventral cirri conical, with broad base and tapering distally. Acicular lobes of following parapodia conical with rugose area on ventral side, near acicula ( Figs. 21D, F, H ); prechaetal lamellae well developed but not extending beyond acicular lobes, rounded or slightly bilobed anteriorly, clearly bilobed on middle parapodia; postchaetal lamellae extending beyond acicular lobes, rounded; dorsal cirri digitiform; ventral cirri conical ( Figs. 21B, C, E, G ). Branchiae recurved, moderately ciliated, with conspicuous rounded papillae-like basal projection; present from chaetiger 4 to near posterior end (may be reduced in posteriormost chaetigers); occupy 2/3 of interramal space when fully developed. Chaetae short, of three kinds: barred chaetae in preacicular position ( Fig. 21I ), finely spinulated chaetae in postacicular position ( Fig. 21J ), and capillary chaetae in the neuropodia of chaetiger 1. One acicula per ramus, middle and posterior ones with curved tips ( Fig. 21D, F, H ).

Remarks. This species was first described by McIntosh (1908) as Nephthys hombergii var. kersivalensis . Rainer (1989) raised it to specific level and provided a complete re-description and comparison with other north European Nephtys species. This study extends the geographical distribution of N. kersivalensis to the western and southern coasts of Portugal. However, this species seems to be less frequent in Portuguese waters than in northern Europe ( Rainer, 1989). Besides, the Portuguese specimens are usually smaller and with less distinctly bilobed prechaetal lamellae. Differences between N. kersivalensis and other morphologically close species are summarized in Table 5. It differs from N. assimilis and N. hombergii especially in parapodial structures and from N. hystricis in the appearance of the branchiae. Nephtys kersivalensis is unique in having a rugose area on acicular lobes near aciculae. Nephtys kersivalensis and N. hystricis are clearly smaller when compared to N. assimilis and N. hombergii ( Figs. 11 , 19 ).

Distribution. Atlantic Ocean (Outer Hebrides, lreland, North Sea, Kattegat, W France, W and S Portugal) ( Rainer 1991; Laborda 2004; this study); Mediterranean Sea (J. Gil pers. com.).

Habitat. Gravel, silty, muddy and clean sand, from the shallow subtidal to 295 m depth ( Rainer 1991; Laborda 2004).

Figures

FIGURE 11. Relationships between: A. Number of segments and body length. B. Body length and body width. C. Length of ventral cirri (VC) and dorsal cirri (DC) of chaetiger 1. D. Length of pharynx distalmost subterminal papillae and middorsal papilla. Nephtys assimilis. × N. hombergii. N. kersivalensis.

FIGURE 19. Relationships between: A. Number of segments and body length. B. Body length and body width. C. Length of ventral cirri (VC) and dorsal cirri (DC) of chaetiger 1. D. Length of pharynx distalmost subterminal papillae and middorsal papilla. Nephtys hystricis. N. incisa.

FIGURE 21. Nephtys kersivalensis. A. Pharynx, prostomium and first chaetiger, dorsal view. B. Left parapodium of chaetiger 10, anterior view. C. Left parapodium of chaetiger 20, anterior view. D. Detail of notopodial acicular lobe of chaetiger 20. E. Left parapodium of chaetiger 40, anterior view. F. Detail of neuropodial acicular lobe of chaetiger 40. G. Left parapodium of chaetiger 60, anterior view. H. Detail of neuropodial acicular lobe of chaetiger 60. I. Preacicular chaeta from chaetiger 10. J. Postacicular chaeta from chaetiger 10.