Polycirrus karadenizicus, Çinar & Erdoğan-Dereli, 2023

Çinar, Melih Ertan & Erdoğan-Dereli, Deniz, 2023, Polychaetes (Annelida: Polychaeta) off Kıyıköy (Black Sea, Türkiye) with descriptions of three new species, Zootaxa 5383 (4), pp. 537-560 : 547-552

Polycirrus karadenizicus n. sp.

urn:lsid:zoobank.org:act:7074D1EA-F81D-4F7C-8CB2-B0AF41EF138C

Figures (7–9), Table 3

Material examined: Holotype, ESFM-POL/2022-007 , 25.09.2022, station S2 . Paratypes: ESFM-POL/2022-008 , 25.09.2022, station S2, 2 specimens (two specimens for SEM).

Description. Holotype complete, 17.02 mm long (1.6–14.5 in paratypes) and 1.21 mm wide (0.2–1.3 in paratypes) with 56 chaetigers (21–68 in paratypes). Colour in alcohol transparent white.

Transverse prostomium attached to dorsal surface of base of upper lip; slightly curved; with distinctive, thick, projecting lateral processes, extending to segment 4 ( Figs. 7A, B ; 8D ; 9A, D, E ). Buccal tentacles emerging on prostomium (also on lateral processes) one type, long, slightly grooved, strongly annulated, uniformly cylindrical ( Figs. 8A ; 9A, E, G ).

Peristomium forming lips; upper lip trefoiled, elongate, tessellated on dorsal side, medial lobe prominent, distinctly longer than wide, margins convoluted and thickened, lateral ones well-developed and thick; lower lip semicircular with smooth surface, extending to anterior margin of segment 1 ( Figs. 7A, B ; 8D ; 9A, D ).

Segment 1 (SG1) and 2 (SG2) visible entirely as distinct rings, body gradually becoming broader after segment 3 until neuropodia becoming visible (SG 15), tapering to pygidium.

Body surface on anterior part strongly tessellated on dorsal and ventral side, extending to segment where neuropodia present; body surface getting smooth afterwards; strongly annulated at posterior part of body ( Figs. 7A, B ; 8A, B, D ; 9A, D–F ). Antero-ventrum with a mid-ventral groove and poorly defined ventro-lateral pads; pads deeply tessellated, extending from segment 1 to 12 ( Figs 7B ; 8A, D ; 9D ). Mid-ventral groove from segment 1, present until end of body as a stripe ( Fig. 9D, F ).

Notopodia from SG3, extending for 4–6 segments; short, rectangular, notopodial lobes reduced ( Figs 7F ; 9B, C, E ). Notochaetae one row, two types; first type limbate, smooth, uniformly tapered, found only on chaetiger 1; second type pinnate present on all chaetigers ( Figs 7D, E ; 8C ; 9B, C ). Neuropodia beginning on SG15, 5–13 uncini per row. Neuropodial tori ridge-like, becoming more erect posteriorly ( Figs. 8A ; 9F ). Uncini have a long neck and concave base (Type 2), main fang thick with round tip, crest with two elongate, central, and sharp teeth almost reaching tip of main fang; subrostral process present as high protuberance, heel globular in shape ( Figs 7C ; 8E, F ; 9H, I ).

Nephridial papillae present from segment 5 to 7, globular in shape situated at the ventral base of notopodia ( Fig. 8B ).

Pygidium rounded with a ventral papilla ( Figs 8A ; 9F ).

Methyl green pattern. The tessellate structures on the anterior part of the body stained intensely.

Etymology. This species is named after its type locality “Black Sea”, which is called as Karadeniz in the Turkish language.

Habitat. It occurs at 25 m depth on muddy sand with shell fragments.

Remarks. Polycirrus karadenizicus n. sp. is mainly characterized by having prostomial lateral processes; strongly tessellated tegument in the antero-dorsal and -ventral sides of the body; 6 pairs of notopodia with reduced lobes; type 2 uncinus; and neuropodia starting after achaetous gap after the termination of the notopodia.

Polycirrus karadenizicus n. sp. belongs to a species group of Polycirrus that has prominent prostomial lateral processes. This character was not mentioned in the world-wide revision of Polycirrus by Glasby & Hutchings (2014) and was first described for P. nonatoi Carrerette & Nogueira, 2013 and P. paivai Garraffoni & Costa, 2003 ( Carrerette & Nogueira, 2013). Although this structure has not been exactly defined as prostomial lateral processes in species descriptions, this structure was described as a “ dorsal lobe ” in the original description of P. decipiens ( Gravier, 1905) and as “ two smaller laterally projecting lobes with buccal tentacles ” in the original description of P. quadratus Hutchings, 1990 . In the drawings of these two species, the prostomial lateral process with buccal tentacles were clearly evident. Potts (1928) did not draw this structure in the description of the P. twisti Potts, 1928 , but he described it as “ greatly developed lateral lobes ”. Çinar (2009) re-described and photographed the prostomial lateral process for the specimens of P. twisti collected from the southern coast of Türkiye. Nougeira et al. (2015) stated that the species having prostomial lateral process were P. brutus Nogueira, Hutchings & Carrerette, 2015 , P. nonatoi Carrerette & Nogueira, 2013 and P. coccineus Grube, 1869 . Table 3 provides the main diagnostic characteristics of all Polycirrus species with prostomial lateral processes.

Among the species of Polycirrus with prostomial lateral processes, P. karadenizicus n. sp. is similar to P. coccineus , P. quadratus and P. twisti , all having an uncinus of type 2. However, P. karadenizicus n. sp. differs from these species by the following characters: 1) the number of notopodial pair and notopodial lobes: 6 pairs notopodia, notopodial lobes reduces in P. karadenizicus n. sp.; 20 pairs notopodia, notopodial lobes inequal in size and digitiform in P. coccineus ; 12 pairs notopodia, notopodial lobes equal in size and digitiform in P. quadratus ; 30 pairs notopodia, notopodial lobes inequal in size and digitiform in P. twisti , 2) notochaetae: two types, pinnate and limbate in P. karadenizicus n. sp.; one type, pinnate in P. coccineus ; two types, narrowly winged with hirsute and hirsute capillaries in P. quadratus ; two types, pinnate and smooth narrowly winged in P. twisti , and 3) subrostral process: present in P. karadenizicus n. sp.; absent in P. coccineus , P. quadratus and P. twisti .

An achaetous gap between chaetigers was also a distinctive character of P. karadenizicus n. sp. Such a gap was also previously reported on P. octosetus ( Hutchings, 1977) , but, in contrast to P. karadenizicus n. sp., this species lacks the prostomial lateral process.

Figures

FIGURE 7. Polycirrus karadenizicus n. sp. (Holotype, ESFM-POL/2022-007).A, Antero-dorsal view; B,Antero-ventral view; C, Uncinus from posterior chaetiger; D, Limbate chaeta on chaetiger 1; E, Pinnate chaeta on chaetiger 4; F, notopodium of chaetiger 4. Scale Bar: A, 593 µm; B, 620 µm; C–D, 10 µm; E, 12 µm; F, 77 µm.

FIGURE 8. Polycirrus karadenizicus n. sp. A, (Holotype, ESFM-POL/2022-007) General view of body, stained with methyl green; B,Antero-lateral view of body with nephridial papillae (Paratype, ESFM-POL/2022-008); C, Pinnate chaetae on chaetiger 3; D, Ventral view of body with lateral process, stained with Shirlastain-A (Paratype, ESFM-POL/2022-008); E–F, Uncini on abdominal chaetigers (Paratype, ESFM-POL/2022-008). Scale Bar: A,1008 µm; B, 1000 µm; C, 29 µm; D, 695 µm; E, 12 µm; F, 18 µm.

FIGURE 9. Polycirrus karadenizicus n. sp. (Paratype, ESFM-POL/2022-008).A, Antero-dorsal view of body with prostomial lateral process; B, First notopodium with limbate chaeta; C, Pinnate chaetae on chaetiger 5; D, Antero-ventral view of body; E, Antero-lateral view of body; F, Postero-ventral view of body with a mid-ventral groove and pygidium; G, Buccal tentacles; H, Lateral view of uncini on abdominal chaetiger; I, Uncini on abdominal chaetiger. Abbreviations: P*, basal part of prostomium; plp, prostomial lateral process; ul, upper lip; ll, lower lip; Numbers refer to segments. Scale Bar: A, 472 µm; B, 36 µm; C, 22 µm; D, 737 µm; E, 548 µm; F, 936 µm; G, 272 µm; H, 8 µm; I, 9 µm.