Nephtys hystricis McIntosh, 1900

Ravara, Ascensão, Cunha, Marina R. & Pleijel, Fredrik, 2010, Nephtyidae (Annelida, Polychaeta) from southern Europe 2682, Zootaxa 2682 (1), pp. 1-68 : 48-52

Nephtys hystricis McIntosh, 1900

Figures 18 , 19

Nephthys hystricis McIntosh, 1900b: 259 ; Marenzeller 1904: 304–308; McIntosh 1908: 27, pl. LVII, figs. 8–9; pl. LXVI,

figs. 10; not Fauvel 1914: 200, pl. XVIII, figs. 1 and 2; not Fauvel 1923: 373, fig. 146A–E (= N. incisa ); Fauvel

1936: 41. Nephtys hombergii var. kersivalensis McIntosh 1908: 20 , pl. LXXVII, fig. 4 (partim). Nephthys malmgreni Heinen 1911: 29 , fig. 8 (partim). Nephthys incisa Heinen 1911: 23 (partim); Fauvel 1914: 198, pl. XVIII, fig. 3; Fauvel 1923: 369, fig. 144A–B;?Foret-

Montardo 1969: 814, Pl. 3, figs. 8–10 (partim); (not Malmgren 1865). Nephthys incisa var. bilobata Heinen 1911: 25 , pl. I, figs. 1 and 2 (partim); Fauvel 1923: 370, fig. 144B. Nephtys incisa Fauchald 1963: 15 , figs. 1H, 2C, 3B, 7B, 9 (partim); Wolff 1968: 4, fig. 10; Kirkegaard 1969: 51, fig. 23

(partim); Hartmann-Schröder 1971: 217, fig. 70d–e; Hartmann-Schröder 1974: 207 (partim);? Campoy 1982: 516;

Kirkegaard 1992: 338, fig. 165. Nephtys (Nephtys) hystricis not Day 1967: 345. Nephtys incisa bilobata Campoy 1982: 518 .? Nephtys hystricis not Guille and Laubier 1966: 267; not Wolff 1968: 6, fig. 11 (= N. incisa ); Laborda 2004: 402, fig. 147D–E.

Nephtys hystricis not Campoy 1982: 514; Rainer 1990: 362, fig. 1A–E; Rainer 1991: 75, fig. 2C; Hartmann-Schröder 1996: 225, fig. 99; Dnestrovskaya and Jirkov 2001: 201,1 fig.

Type locality. Off Bergen , Norway .

Material examined. Atlantic Ocean. Norway, off Bergen: 1 incomplete spm, lectotype ( NHM 1921.5.1.291). North Sea , Sweden, Skagerrak, Bohuslän: 58º17.103’– 58º17.455’N, 10º28.948’– 10º28,681’E, 335–395 m, Aug 2006, 4 complete and 3 incomplete spms ( DBUA 01132-01 ) ; 58º07.422’– 58º08.068’N, 10º48.549’– 10º48,074’E, 206–248 m, Aug 2006, 1 incomplete spm ( MB36000155 ) ; 58º24.178’– 58º23.770’N, 10º31.053’– 10º30,702’E, 329–367 m, Aug 2006, 1 incomplete spm ( MB36000156 ) . SW Ireland, off Valentia Island : 1–160 fms, 3 spms ( NHM 1921.5.1.796-806, syntypes N. kersivalensis ). Portugal, off Cape Sagres : Porcupine Expedition , 2 incomplete spms ( NHM 1921.5.1.769-770); Gulf of Cadiz, near Kidd mud volcano: TTR14 cruise, RV Prof. Logachev, 35º24.777’N, 6º43.782’W, 552 m, box-corer, Aug 2004, 1 incomplete spm ( DBUA 00861-01 ) ; Kidd mud volcano: cruise TTR14, RV Prof. Logachev, 35º25.602’N, 6º44.099’W, 526 m, box-corer, Aug 2004, 2 incomplete spms ( DBUA 00861-02 ) , and 1 incomplete spm ( MB36000127 ) ; Pen Duick Escarpment: cruise M2005, RV Pelagia , 35º18.029’N, 6º47.437’W, 570 m, box-corer, May 2005, 1 incomplete spm ( MB36000162 ) ; Mercator mud volcano: cruise MSM01-03, RV M. S. Merian, 35º17.918’N, 6º38.717’W, 353 m, box-corer, May 2006, 1 incomplete spm ( DBUA 00863-01 ) .

Description. Examined specimens up to 31 mm long for up to 74 chaetigers. See Fig. 19 for length and width measurements. Body small, slightly wider anteriorly, gradually tapering posteriorly. Poor dorsal delineation between anterior segments. Colour in ethanol cream; prostomium without pigmentation; chaetae amber; tip of aciculae of median chaetigers black. One pair of eyes visible only in small specimens at level of chaetiger 2. Pharynx distal region with 10 pairs of bifid terminal papillae, separated by dorsal and ventral gaps; middorsal papilla cirriform, very long ( Fig. 19D ); midventral papillae absent; subdistal region with 22 rows of 3–6 very small, conical subterminal papillae, extending over 1/3 length of pharynx ( Fig. 18A ); proximal region smooth. Jaws conical. Prostomium subpentagonal ( Fig. 18A ), anterior margin slightly convex, posterior margin rounded; antennae and palps conical; palps slightly longer than antennae, inserted ventrolaterally on anterior region of prostomium, near antennae. Nuchal organs rounded. Parapodia biramous; interramal space “V-shaped”; ciliation not seen. Parapodia of chaetiger 1 similar in size to subsequent ones, directed anteriorly, parallel to prostomium; notopodial acicular lobes conical; pre- and postchaetal lamellae well developed but not extending beyond acicular lobes, rounded; neuropodial pre- and postchaetal lamellae forming a cylinder covering acicular lobes; dorsal and ventral cirri conical, equal in size ( Fig. 19C ). Acicular lobes of following parapodia conical; prechaetal lamellae well developed but not extending beyond acicular lobes, bilobed in middle parapodia, postchaetal lamellae extending beyond acicular lobes in anterior and middle parapodia, smaller than acicular lobes in posterior parapodia, rounded; dorsal cirri flattened, triangular and ventral cirri conical ( Fig. 18B–F ). Branchiae recurved, cirriform, present from chaetigers 5–7 (usually chaetiger 6), absent in posterior parapodia; occupy all interramal space when fully developed. Chaetae of three kinds: barred chaetae in preacicular position ( Fig. 18G ), finely spinulated chaetae in postacicular position ( Fig. 18H ), and capillary chaetae in neuropodia of chaetiger 1. One acicula per ramus, posterior ones with curved tips.

Remarks. Nephtys hystricis was originaly described by McIntosh (1900b) for specimens collected in Berehaven, Ireland (during Royal Irish Academy’s Expedition), in the Mediterranean Sea (during “Porcupine” Expedition of 1870), and off Bergen, Norway. Rainer (1990) examined all these syntypes and designated the specimens from Bergen as lectotype and paralectotypes.

Nephtys hystricis has often been confused with the morphologically close species N. incisa and many of the earlier descriptions include characteristics of both, suggesting that the authors had a mixture of the two species. Examples of this are in Foret-Montardo (1969), Campoy (1982) and Laborda (2004), who provide descriptions for both species although with some mixed characters and figures often corresponding to only one of the species ( N. incisa in Foret-Montardo (1969) and N. hystricis in Laborda (2004)). Rainer (1990) re-examined much of the old material and provided a re-description of the two species. Specimens from both species are small (up to 75 chaetigers) and fragile and can be found simpatrically. The main differences between the two species are the chaetiger where branchiae start (5–7, usually 6, in N. hystricis , 9–10 in N. incisa ) and the shape and size of parapodial lamellae. In N. hystricis the prechaetal lamellae of the median parapodia are bilobed and shorter than the acicular lobes, and the postchaetal lamellae are larger than the acicular lobes and broadly rounded, while in N. incisa pre- and postchaetal lamellae are both broadly rounded and of the same length or slightly smaller than the acicular lobes. Also the number and pattern of pharynx papillae is somewhat different in the two species (22 rows of 3–6 subterminal papillae for N. hystricis and 20 rows of 1–5 papillae for N. incisa ). Nephtys hystricis generally has fewer posterior chaetigers without branchiae, when comparing with N. incisa . Rainer (1990) mentioned 15–18 posterior chaetigers without branchiae for N. hystricis and a relatively constant number of 25 posterior chaetigers in N. incisa . In the specimens examined in the present study those values showed a larger variation; 11–21 posterior chaetigers without branchiae in N. hystricis (4 entire specimens examined) and 19–30 in N. incisa (9 entire specimens examined). We also found differences in the preacicular chaetae of the two species; in N. hystricis they are barred in all its extension ( Fig. 18G ), while in N. incisa they are only distally barred ( Fig. 20H ).

Nephtys kersivalensis is another species that is morphologically similar to N. hystricis . However, the two species can be differentiated by the chaetiger number where branchiae start and end (from chaetiger 4 to the end of body in the former, from chaetigers 5–7 to before the end of body in the later) and by the presence of a rugose area near the aciculae on the acicular lobes of N. kersivalensis . Besides, N. hystricis usually occurs in deeper water than N. kersivalensis .

Laborda (2004) reported this species from the Red Sea and the Indian Ocean. However, these records were not confirmed and should be considered with caution. One specimen from off Mozambique ( NHM 1934.1.19) was examined and had been incorrectly identified as N. hystricis .

Distribution. Atlantic Ocean (from Norway to Gulf of Cadiz); Mediterranean Sea ( Rainer 1990, 1991). There are further reports of this species from the Red Sea and Indian Ocean (E Africa) ( Laborda 2004), but these records require confirmation.

Habitat. Mud and sandy mud, 100–800 m depth ( Rainer 1991; Laborda 2004).

Figures

FIGURE 18. Nephtys hystricis. A. Pharynx, prostomium and anteriormost chaetigers, dorsal view. B. Right parapodium of chaetiger 10, anterior view. C. Right parapodium of chaetiger 20, anterior view. D. Same, posterior view. E. Right parapodium of a posterior chaetiger, anterior view. F. Same, posterior view. G. Preacicular chaeta from chaetiger 20. H. Postacicular chaeta from chaetiger 20.

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 20. Nephtys incisa. A. Pharynx, prostomium and anteriormost chaetigers, dorsal view. B. Jaw. C. Right parapodium of chaetiger 11, anterior view. D. Same, posterior view. E. Right parapodium of chaetiger 20, anterior view. F. Same, posterior view. G. Right parapodium of chaetiger 40, anterior view. H. Preacicular chaeta from chaetiger 20. I. Postacicular chaeta from chaetiger 20. J. Acicula of chaetiger 40.