Nephtys sinopensis Kuş & Kurt & Çinar 2021, n. sp.

Nephtys sinopensis n. sp.

(Figures 9–12)

urn:lsid:zoobank.org:act: B5246F9A-7912-4CE0-A5D8-5B7F9B673F14

Material examined. Holotype: Black Sea: ESFM-POL/2016-243, 26 July 2016, station TRK25, 42°16’60”N, 34°56’14”E, 19.5 m, sand with shell fragments.

Paratypes. Black Sea: ESFM-POL/2016-242, 25 July 2016, station TRK22, 42°2’34”N, 33°49’33”E, 22 m, shell fragments with phytodetritic material, 21 specimens; ESFM-POL/2016-244, 26 July 2016, station TRK25, 42°16’60”N, 34°56’14”E, 19.5 m, sand with shell fragments, 33 specimens; ESFM-POL/2016-245, 27 July 2016, station TRK32, 42°0’57.24”N, 35°9’28.51”E, 60 m, mud with shell fragments, 3 specimens; ESFM-POL/2016-246, 27 July 2016, station TRK35, 41°33’40”N, 36°34’19”E, 50 m, mud and phytodetritic material, 2 specimens.

Additional material. Sea of Marmara: ESFM-POL/2013-1359, 06 June 2013, station Y1, 40°01’08’’N, 26°13’00’’E, 50 m, mud with detritic material, 1 specimen; ESFM-POL/2013-1360, 16 June 2013, station Y27, 40°23’30’’N, 29°03’54’’E, 10 m, mud with shell fragments, 2 specimens; ESFM-POL/2013-1362, 26 June 2013, station Y50, 41°12’16’’N, 29°07’15’’E, 10 m, mud with shell fragments; 8 specimens; Black Sea: ESFM-POL/2014- 645, 12 July 2014, station TRK7, 41°18’40”N, 29°40’10”E, 27 m, mud with shell fragments, 1 specimen; ESFM- POL/2014-646, 13 July 2014, station TRK10, 41°19’40”N, 30°47’55”E, 21 m, coarse sand with shell fragments, 15 specimens; ESFM-POL/2014-644, 13 July 2014, station TRKE1, 41°23’36”N, 31°38’11”E, 21 m, mud with shell fragments, 41 specimens; ESFM-POL/2014-647, 14 July 2014, station TRK13, 41°37’20”N, 31°51’3”E, 21 m, coarse sand with phytodetritic material, 5 specimens; ESFM-POL/2014-648, 15 July 2014, station TRK22, 42°2’34”N, 33°49’33”E, 25 m, mud with shell fragments, 23 specimens; ESFM-POL/2014-649, 15 July 2014, station TRK25, 42°16’60”N, 34°56’14”E, 21 m, mud with shell fragments, 2 specimens; ESFM-POL/2014-650, 17 July 2014, station TRK34Y, 41°33’40”N, 36°34’19”E, 21 m, mud with phytodetritic material, 1 specimen; ESFM-POL/2014-651, 17 July 2014, station TRK37, 41°19’40”N, 36°32’10”E, 10 m, mud with shell fragments, 1 specimen; ESFM-POL/2014-652, 18 July 2014, station TRK44, 41°4’2”N, 38°2’49”E, 52 m, shell fragments with phytodetritic material, 2 specimens; ESFM-POL/2014-653, 19 July 2014, station TRK55, 41°1’45”N, 39°54’15”E, 21 m, mud with shell fragments, 1 specimen; ESFM-POL/2015-294, 02 July 2015, station TRK1, 41°55’34”N, 28°12’27”E, 21 m, shell fragments with fine sand, 3 specimens; ESFM-POL/2015-295, 03 July 2015, station TRK7, 41°18’40”N, 29°40’10”E, 21 m, shell fragments with fine sand, 8 specimens; ESFM-POL/2015-296, 03 July 2015, station TRK10, 41°19’40”N, 30°47’55”E, 20 m, shell fragments with fine sand, 5 specimens; ESFM- POL/2015-293, 04 July 2015, station TRKE1, 41°23’36”N, 31°38’11”E, 13 m, shell fragments with phytodetritic material, 23 specimens; ESFM-POL/2015-297, 04 July 2015, station TRK13, 41°37’20”N, 31°51’3”E, 18 m, fine sand with shell and detritic fragments, 18 species; ESFM-POL/2015-298, 04 July 2015, station TRK13A, 41°35’23.22”N, 32°2’4.73”E, 17 m, shell fragments with fine sand, 7 specimens; ESFM-POL/2015-299, 05 July 2015, station TRK22, 42°02’34”N, 33°49’33”E, 21 m, phytodetritic material with shell fragments, 11 specimens; ESFM-POL/2015-300, 07 July 2015, station TRK35, 41°20’48”N, 36°23’27”E, 48 m, mud with fine sand and shell fragments, 3 specimens; ESFM-POL/2015-301, 08 July 2015, station TRK37, 41°19’40”N, 36°32’10”E, 9 m, mud with shell fragments and fine sand, 1 specimen; ESFM-POL/2016-239, 24 July 2016, station TRK10, 41°19’40”N, 30°47’55”E, 20 m, shell fragments with phytodetritic material, 2 specimens; ESFM-POL/2016-238, 24 July 2016, station TRKE1, 41°23’36”N, 31°38’11”E, 12 m, mud with shell fragments, 21 specimens; ESFM-POL/2016-240, 26 July 2016, station TRK13, 41°37’20”N, 31°51’3”E, 19 m, fine sand with shell fragments, 9 specimens; ESFM- POL/2016-241, 26 July 2016, station TRK16, 41°43’10”N, 32°4’60”E, 20 m, mud with phytodetritic material, 9 specimens; ESFM-POL/2017-198, 26 July 2016, station TRK13, 41°37’20”N, 31°51’3”E, 19 m, fine sand with shell fragments, 23 specimens; ESFM-POL/2017-199, 27 July 2017, station TRK22, 42°2’34”N, 33°49’33”E, 27 m, shell fragments with phytodetritic material, 1 specimen; ESFM-POL/2017-200, 27 July 2017, station TRK25, 42°16’60”N, 34°56’14”E, 19 m, mud with shell fragments, 21 specimens, ESFM-POL/2017-201, 30 July 2017, station TRK34Y, 41°19’40”N, 36°32’10”E, 20 m, mud with phytodetritic material, 1 specimen; ESFM-POL/2017- 202, 31 July 2017, station TRK37, 41°32’60”N, 36°40’40”E, 8 m, shell fragments with phytodetritic material, 1 specimen; ESFM-POL/2018-150, 22 July 2018, station TRK10, 41°19’40”N, 30°47’55”E, 21 m, fine sand, 1 specimen; ESFM-POL/2018-149, 22 July 2018, station TRKE1, 41°23’36”N, 31°38’11”E, 14 m, fine sand with shell fragments, 5 specimens; ESFM-POL/2018-151, 23 July 2018, station TRK13, 41°37’20”N, 31°51’3”E, 20 m, sandy mud with detritic material, 2 specimens; ESFM-POL/2018-152, 25 July 2018, station TRK22, 42°2’34”N, 33°49’33”E, 25 m, mud with shell fragments and detritic material, 5 specimens; ESFM-POL/2018-153, 26 July 2018, station TRK25, 42°16’60”N, 34°56’14”E, 20 m, sand, 1 specimen; ESFM-POL/2018-154, 28 July 2018, station TRK37, 41°32’60”N, 36°40’40”E, 8.5 m, sand, 1 specimen; ESFM-POL/2018-155, 01 August 2018, station TRK61, 41°46’0”N, 41°31’0”E, 45 m, mud with phytodetritic material, 1 specimen; ESFM-POL/2019-52, 05 July 2019, station TRK7, 41°18’40”N, 29°40’10”E, 22 m, mud, 3 specimens; ESFM-POL/2019-53, 07 July 2019, station TRKE1, 41°23’36”N, 31°38’11”E, 14 m, fine sand with shell fragments, 4 specimens; ESFM-POL/2019-54, station TRK22, 09 July 2019, 42°2’34”N, 33°49’33”E, 25 m, mud with shell fragments and detritic material, 1 specimen; ESFM-POL/2019-55, 09 July 2019, station TRK25, 42°16’60’’N, 34°56’14”E, 20 m, mud, 5 specimens.

Other comparative material examined: Nephtys cirrosa Ehlers, 1868, Aegean Sea (Gökçeada), ESFM- POL/2000-625, 13 August 2000, 40˚07’22”N, 25˚39’50”E, 15 m, sand, 26 specimens.

Description. Holotype complete, 11.5 mm long, 0.9 mm wide, with 55 chaetigers. Sizes of paratypes varies between 8–12 mm long and 0.6–0.8 mm wide with 47–58 chaetigers. Body wider anteriorly, gradually tapering from middle region to pygidium. Colour cream in ethanol.

When pharynx everted, prostomium subpentagonal (0.17 mm) as long as wide, anterior margin convex, posterior margin “V” shaped (Figs. 9A, 10B); when pharynx not everted, prostomium subrectangular, anterior margin slightly convex, posterior margin “U” shaped (Fig. 10A), extending over chaetiger 1. Antennae (0.09 mm) and palps (0.07 mm) digitiform with swollen tips, palps slightly shorter than antennae, inserted on ventro-lateral margin of prostomium (Figs. 9A, 10A, B). Pharynx with 10 pairs of terminal bifid papillae (0.09 mm), separated by a dorsal and ventral gap (Figs. 9A, 10C); middorsal papilla slender (0.17 mm), conical, slightly longer than subterminal ones (0.09 mm) (Fig. 10C); midventral papilla absent; with 21–22 rows of 6–7 conical subterminal papillae, (3–4 long, 3–4 small papillae) extending over 2/3 length of pharynx (Figs. 9A, 10B), proximal region of pharynx smooth. One pair of light brown jaws, triangular in shape, on the antero-lateral margin of pharynx. (Fig. 9B). One pair of eyes visible in small specimens on chaetiger 3. Nuchal organ rounded, conspicuous. Parapodia of chaetiger 1 without dorsal cirri or lamellae, smaller than subsequent ones, directed anteriorly, close to prostomium. Ventral cirri of chaetiger 1 digitiform with a broad base and swollen tip (Figs. 9A, 10A, B), almost ½ times shorter than palps (0.03 mm).

Parapodia biramous, interramal space “U” shaped anteriorly, becoming “V” shaped on posterior parapodia, covered with regular ciliated patches (Fig. 11C). Prechaetal lamellae well developed on chaetiger 2–3. Noto- and neuropodial postchaetal lamellae well developed on chaetiger 4 and 2, respectively. On anterior chaetigers (chaetiger 10), prechaetal lamellae well developed, simple and triangular in neuropodia, bilobed in notopodia; similar in size to acicular lobes in notopodia, slightly longer than acicular lobes in neuropodia; noto- and neuropodial postchaetal lamellae rounded, longer than acicular lobes (Figs. 9F, 10D). On middle chaetigers (chaetiger 20–40) prechaetal lamellae reducing gradually and fusing with acicular lobe (Figs. 9G, H, 11A); noto- and neuropodial postchaetal lamellae rounded (Fig. 11B), morphologically similar to those on anterior chaetigers, but neuropodial lamellae much longer, extending beyond acicular lobes. On posterior chaetigers (chaetiger 52) prechaetal lamellae almost reduced and appearing as a small piece of acicular lobe in neuropodia (Figs. 9I, 11C); noto- and neuropodial postchaetal lamellae, rounded, as long as acicular lobes (Figs. 9I, 11C, D). Acicular lobes rounded anteriorly, become conical on middle and posterior chaetigers (Figs. 9F–I, 11A, C, D).

Dorsal cirri long, cirriform, as long as branchiae on first 7–8 anterior chaetigers and last 7–8 posterior chaetigers (Figs. 9F–I, 11D), smaller than branchiae on middle chaetigers, strongly covered with irregular ciliated patches. Ventral cirri long, digitiform with a tapering tip, almost equal in size to parapodial lobes in posterior chaetigers (Figs. 9F–I, 11D, 12C–E).

Branchiae very small on all chaetigers, almost equal in length to dorsal cirri on anterior and posterior chaetigers, recurved in median region, straight in anterior and posterior region; cirriform, starting from chaetiger 4 to posterior end; well developed on chaetigers 9–10; occupying 1/2 of interramal space when fully developed (Figs. 9F–I, 11A, B), with densely ciliated patches, irregularly distributed.

Four types of chaetae present in parapodia; capillary chaetae, barred chaetae, geniculate chaetae and spinose chaetae. Chaetiger 1 with 5–6 capillary chaetae in neuropodia and 6–7 barred chaetae in notopodia. Geniculate chaetae (150 µm) first appearing in noto- and neuropodia of chaetiger 3 or 4, placed on postacicular area, numbering 1–4 in each ramus (Figs. 9C, 12A). Long spinose chaetae (900 µm) contain randomly scattered spines; first appearing in noto- and neuropodia of chaetiger 2, placed on postacicular area, numbering 20–25 in each ramus (Figs. 9D, 12B). Barred chaetae (200 µm) first appearing on chaetiger 1, thick in anterior chaetigers, numbering up to 6 in notopodia and up to 8 in neuropodia, becoming thin in posterior chaetigers; bar covering area of chaetae not significantly changing on chaeta from anterior and posterior regions of body (Figs. 9E, 12B). Number of barred and geniculate chaetae decreasing towards last two chaetigers. Spinose chaetae still outnumbered (15–16) and long even in posterior chaetigers.

One yellowish-brown acicula present in each ramus, with a straight tip in anterior and median parapodia; with a curved tip in posterior parapodia.

Pygidium rounded with one digitiform anal cirrus placed dorsally, as long as the last 2–3 chaetigers.

Reproduction. Almost 1/4 of the population consists of mature individuals. Eggs appears in the coelomic cavity of posterior chaetigers. The diameter of eggs varied between 75 and 90 μm. Eggs are light yellowish in color and the specimens did not have any morphological modification on the body.

Remarks. Nephtys sinopensis n. sp. differs from other Nephtys species by having small body sizes and geniculate chaetae on the postacicular area of the noto- and neuropodia. Nephtys sinopensis n. sp. is morphologically similar to N. cirrosa Ehlers, 1868, but differs from it by a number of characters (see Table 1). The presence of the geniculate chaetae on the postacicular area of the noto- and neuropodia was also mentioned for N. cirrosa, but the number of chaetae in each parapodia are different in these species. Nephtys sinopensis n. sp. bears only up to 4 geniculate chaetae (based on the largest and mature specimen), whereas N. cirrosa has 7–15 geniculate chaetae in each ramus (Fauvel 1923; Rainer 1991; Dnestrovskaja & Jirkov 2001; this study). When compared to N. sinopensis n. sp. (8–12 mm long, 0.6–0.8 mm wide for 47–58 chaetigers), N. cirrosa has larger-body sizes (53 mm long for 95 chaetigers (Ehlers 1868); 70 mm long (Kiseleva 2004); 84 mm long for up to 99 chaetigers (Ravara et. al. 2010); 30 mm long for 70 chaetigers in this study). Nephtys sinopensis n. sp. does not present the spatula-shaped prostomium typical for N. cirrosa. In addition, the ventral cirri of chaetiger 1 are equal or slightly longer than the antennae and palps in N. cirrosa, whereas the ventral cirri of chaetiger 1 are almost half as long as the antennae and palps in N. sinopensis n. sp. The proboscis of N. sinopensis n. sp. possesses 21–22 rows of 6–7 subterminal papillae (some 2–3 irregular papillae also count as a row), whereas the proboscis of N. cirrosa has 22 rows of 9–10 subterminal papillae. Another important difference between these two species is the shape of acicular lobes, which are conical in N. sinopensis n. sp. vs. unequally bilobed in N. cirrosa.

Nephtys cirrosa is commonly known as “catworm” because of having extremely long antennae, palp and ventral cirri on chaetiger 1. Although Nephtys ehlersi Heinen 1911 and N. cirrosa were considered as synonymous by Rainer (1991). Ravara et al. (2010) described two different forms of N. cirrosa (A and B) and proposed that the Form B is quite similar to the original description of N. ehlersi, whereas Form A is similar to the original description of N. cirrosa. The Form A is mainly characterized by having rounded to bilobed acicular lobes, rudimentary notopodial prechaetal lamellae and a middorsal papilla subequal in size to the other subterminal papillae. Nephtys cirrosa Form B is mainly characterized by having rounded to conical acicular lobes, well developed and bilobed notopodial prechaetal lamellae and a middorsal papilla longer than the subterminal papillae. The bilobed notopodial prechaetal lamellae and rounded/conical acicular lobes of N. cirrosa Form B are similar to those of N. sinopensis n. sp. However, N. cirrosa form B has relatively larger postchaetal lamellae and orange pigmentation in the prostomium (see Ravara et al., 2010), whereas N. sinopensis n. sp. has smaller postchaetal lamellae and without pigmentation on the prostomium. In addition, N. cirrosa Form B has bilobed neuropodial prechaetal lamellae in the anterior chaetiger (see Ravara et al., 2010, Fig. 15K), but in N. sinopensis n. sp. they are simple and triangular. More importantly, N. sinopensis n. sp. has longer ventral cirri, as long as the parapodial lobes in the posterior region, which are quite shorter than the parapodial lobes in N. cirrosa Form A and B (see Ravara et al., 2010, Figs. 15M and 15G).

Distribution. Black Sea and Sea of Marmara.

Habitat. This species is typical in fine sand and muddy substratum. It is widely distributed between 10 and 50 m depth. It was found only at three stations in the Sea of Marmara, but very common in the Black Sea.

Etymology. This species name refers from to the type locality, Sinop (Turkey).

Type locality. Sinop, Turkey, Black Sea.