Nephtys caeca ( Fabricius, 1780 )

Ravara, Ascensão, Cunha, Marina R. & Pleijel, Fredrik, 2010, Nephtyidae (Annelida, Polychaeta) from southern Europe 2682, Zootaxa 2682 (1), pp. 1-68 : 34-37

Nephtys caeca ( Fabricius, 1780)

Figures 12 , 13

Nereis caeca Fabricius, 1780: 304 .

Aonis caeca Savigny 1822: 45 .

Nephtys margaritacea Johnston, 1835: 341 , fig. 33; Quatrefages 1865: 423.

Nephtys ingens Stimpson, 1853: 33 .

Portelia caeca Quatrefages 1865: 433 .

Nephtys bononensis Quatrefages, 1865: 425 .

Nephtys oerstedi Quatrefages, 1865: 427 .

Nephthys caeca [misspelling of caeca ] Malmgren 1865: 104, pl. XII, fig. 18; Saint-Joseph 1894: 16, Pl. I, fig. 14–18.

Nephtys nudipes Ehlers, 1868: 635 , pl. XXIII, fig. 61.

Nephthys caeca Ehlers 1868: 588 , fig. 10–34; Möbius 1875: 168 (partim); Verrill 1881: 294, 307, 314; Webster and Benedict 1887: 709; Whiteaves 1901: 82; McIntosh 1908: 8; Heinen 1911: 10, fig. 1; Izuka 1912: 213; Fauvel 1923: 365, fig. 142A–L; Okuda 1938: 123; Okuda and Yamada 1954: 186, fig. 4.

Nephtys coeca [misspelling of caeca ] Michaelsen 1896: 25; Johnson 1901: 401 (partim); Nordgaard 1905: 162, 235; Augener 1912: 191, pl. 6, figs. 24–25; Gorbunov 1946: 38; Thorson 1946: 71, fig. 34; Wesenberg-Lund 1950a: 20; Wesenberg-Lund 1950b: 57; Wesenberg-Lund 1951: 43.

Nephthys johnstoni McIntosh 1908: 34 (partim).

Nephthys hombergi Heinen 1911: 16 (partim).

Nephthys longisetosa Heinen 1911: 26 (partim).

Nephtys caeca Fauvel 1933a: 39 ; Berkeley and Berkeley 1948: 54, figs. 80–81; Hartman 1948: 24–25; Hartman 1950: 95; Uschakov 1955: 217, fig.68; Imajima 1961: 88, fig. 4; Uschakov and Wu 1962: 131; Fauchald 1963: 11, figs. 1D and 3D; Pettibone 1963: 203, fig. 51B; Imajima and Hartman 1964: 156; Wolff 1968: 4, fig. 7; Hartmann-Schröder 1971: 220, fig. 72A–B; Paik 1973: 124, pl. I, figs. B–D; Hartmann-Schröder 1974: 208; Garwood and Olive 1981: 195, figs. 3, 4A, 5B–C and 9; Campoy 1982: 510; Lee and Jae 1983: 24, fig. 2; Imajima and Takeda 1987: 63, figs. 12A–M and 14; Jirkov 1989: 75, figs. 15.5 and 15.6; Rainer 1991: 69, fig. 3C; Kirkegaard 1992: 331, fig. 161; Hartmann-Schröder 1996: 220, fig. 95; Böggemann 1997: 80, fig. 54; Dnestrovskaya and Jirkov 2001: 196,1 fig; Laborda 2004: 398, fig. 146C.

Nephtys caeca var. ciliata McIntosh 1908: 13 , pl. LXVI, fig. 3; Heinen 1911: 13, fig. 2;? Okuda 1939: 231, fig. 6.

Nephtys hombergii var. ehlersi Augener 1939: 137 (partim).

Type locality. Greenland .

Material examined. Arctic Ocean. Greenland: 2 incomplete spms ( NHM 1921.5.1.704).

Atlantic Ocean. North Sea, Sweden, Långholmsrännan : Aug 2001, 1 complete and 1 incomplete spms ( DBUA 01040-01 ) and 1 incomplete spm ( MB36000135 ) . Scotland, off Shetland Islands: 2 incomplete spms ( NHM: 1865.3.9.18 as N. longisetosa ) . England: collected near low water mark, 1 complete spm in poor condition, syntype ( NHM 1847.9.15.10); Blyth , Northumberland: intertidal, Nov 2008, 1 complete spm ( MB36000152 ) . Coast of Spain / Portugal: 1 complete and 2 incomplete spms in poor condition ( NHM 1872.2.3.143) .

Mediterranean Sea. Naples: 1 complete spm ( NHM 1919.11.6.31-33 as N. hombergii ).

Pacific Ocean. Canada, Nanaimo River flats, Vancouver Island , Strait of Georgia, British Columbia: Jun 1912, 7 complete and 5 incomplete spms ( CASIZ 14253 ) .

Description. Examined specimens up to 141 mm long for up to 152 chaetigers. See Fig. 13 for length and width measurements. Body large and stout, slightly wider anteriorly, gradually tapering from median region to pygidium. Poor dorsal delineation between anterior segments. Colour in ethanol brownish cream; prostomium with pigmented area anteriorly; chaetae amber; tip of aciculae red. One pair of eyes visible only in small specimens at posterior limit of chaetiger 3. Pharynx distal region with 10 pairs of terminal bifid papillae, separated by dorsal and ventral small simple papillae; middorsal and midventral papillae when present similar in size to largest subterminal ones ( Fig. 13D ); subdistal region with 22 rows of 4–6 long conical subterminal papillae (papillae of lateral rows slightly larger than dorsal or ventral ones), extending over 1/3 length of pharynx ( Fig. 12A ); proximal region covered with very small warts (better seen in compound microscope). Jaws conical, incised at base. Prostomium subpentagonal, anterior margin slightly convex, posterior margin V-shaped and extending over chaetiger 1; antennae and palps conical; palps slightly longer than antennae, inserted ventrolaterally on median region of prostomium ( Fig. 12A ). Nuchal organs rounded. Parapodia biramous; interramal space “U-shaped”, heavily ciliated. Parapodia of chaetiger 1 slightly smaller than subsequent ones, anteriorly directed, parallel to prostomium; notopodial acicular lobes rounded, prechaetal lamellae rudimentary, postchaetal lamellae well developed but not extending beyond acicular lobes, rounded; neuropodial pre- and postchaetal lamellae forming a cylinder covering acicular lobes; dorsal cirri well developed, cirriform ( Fig. 13C ); ventral cirri digitiform, with broad base and tapering distally. Acicular lobes of following parapodia rounded in smaller specimens to distinctly bilobed in larger specimens; prechaetal lamellae poorly developed, rounded, becoming progressively lower towards median segments; postchaetal lamellae extending well beyond acicular lobes, rounded and directed ventrally in notopodium, triangular in neuropodium; dorsal cirri small, lameliform, with enlarged base and acute tip; ventral cirri conical ( Fig. 12B– D ). Branchiae recurved, cirriform, heavily ciliated, with a small rounded papillae-like basal projection; present from chaetiger 4 (rarely from 5) to near posterior end; occupy all interramal space when fully developed. Chaetae of same size or slightly longer than postchaetal lamellae, of three kinds: barred chaetae in preacicular position ( Fig. 12E ), coarsely spinulated chaetae in postacicular position ( Fig. 12F ), and capillary chaetae in neuropodia of chaetiger 1. One acicula per ramus, posterior ones with curved tips ( Fig. 12G ).

Remarks. Nephtys caeca is a common species in cold-water circumboreal areas, although, occasionally, it can also occur in southern regions. Since it was the first nephtyid species to be described and it is also very common in northern Europe along with other species, much of the older Nephtys material is incorrectly identified as N. caeca . There has been also a considerable confusion between this species and the morphologically close species N. longosetosa , especially when the “ N. caeca var. ciliata ” form is present. This form has unusual long chaetae and is considered to be a pre-reproductive dispersal/migratory phase of the N. caeca life cycle ( Garwood & Olive 1981). Nephtys caeca and N. longosetosa are very similar in size ( Fig. 13 ) but differ by the chaetiger were branchiae starts (4 in the former, 3 in the later), the presence of a long middorsal papilla in the pharynx of N. longosetosa (in N. caeca , when present, the middorsal papilla is of same size as other subterminal papillae), the presence of warts in the proximal region of N. caeca pharynx (proximal region smooth in N. longosetosa ), and the different shape and proportions of the various parapodial lamellae. Postchaetal lamellae in N. caeca are both much larger than acicular lobes and broadly rounded, while in N. longosetosa only the neuropodial postchaetal lamellae extend well beyond the acicular lobes and have a narrower appearance due to a small ventral incision. Garwood and Olive (1981), Fauchald (1963) and Imajima and Takeda (1987) mention that N. caeca does not have middorsal nor midventral papillae. On the contrary, Rainer (1991) mentions that a slender middorsal papilla is often present in N. caeca and large animals may have a similar midventral papilla. In some of the specimens examined, we observed a median papillae of the same length as the other subterminal papillae but slightly more cirriform, although the presence or absence is sometimes difficult to assess.

Distribution. Arctic Ocean ( Greenland); Atlantic Ocean (from the Arctic to the English Channel, including the North Sea, Skagerrak, Kattegat, western and middle Baltic Sea; NW Spain; Portugal); Mediterranean Sea (as far as the Black Sea); Pacific Ocean (Sea of Okhotsk, Japan, Yellow Sea, China Sea; NE Pacific south to central California - rare) ( Hartman 1938; Fauchald 1963; Imajima & Takeda 1987; Rainer 1991; Jung & Hong 1997; Laborda 2004).

Habitat. In a wide variety of sediments (sand, gravel and mud), from the lower intertidal to nearly 1000 m depth ( Fauchald 1963; Rainer 1991; Jung & Hong 1997; Laborda 2004).

Figures

FIGURE 12. Nephtys caeca. A. Pharynx, prostomium and first chaetiger, dorsal view. B. Right parapodium of chaetiger 10, anterior view. C. Right parapodium of chaetiger 20, anterior view. D. Median parapodium of a larger specimen, anterior view. E. Pre-acicular chaeta from chaetiger 20. F. Post-acicular chaeta from chaetiger 20. G. Acicula from chaetiger 20.

FIGURE 13. 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 caeca. N. ciliata. × N. longosetosa.