Two new species of free-living nematodes genera Microlaimus de Man, 1880 and Aponema Jensen, 1978 (Nematoda: Microlaimidae) from the Black Sea Author Revkova, Tatiana N. text Zootaxa 2017 2017-11-07 4344 2 387 394 journal article 31606 10.11646/zootaxa.4344.2.13 bf8cd782-3d89-4a09-810c-37dc6758b628 1175-5326 1043008 BF66D84F-4686-4305-8DB9-22F6D0632CA9 Aponema pontica sp. n. Figure 1 , Table 1 Material examined : five males, four females. Glycerin-gelatin slides. Holotype: male on slide # FlN/BS–1. Paratypes: males, from FlN/BS–2 to FlN/BS–5; females, from FlN/BS–6 to FlN/BS–9. Type locality : Black Sea, Crimea shelf, oxic/anoxic interface at the region of submarine Dnieper Canyon. Depth 120 m , ( 1–2 cm horizontal layer), sandy silt and 170 m ( 0–1 cm ), silt; Sevastopolskaya Bay, depths 14–17 m , silt. Etymology. The species name is derived from the Greek Pontos = Black Sea. Description. Male Body spindle-shaped, slender. Cuticle transversely striated. Striation beginning immediately posterior to cephalic setae. Somatic setae 3 µm long, scattered along the body. Inner and outer labial sensillae inconspicuous; four cephalic setae, 4 µm long. Head not separated from the remaining body. Cryptocircular amphidial fovea with interruption in the posterior part, located 5–8.5 µm from anterior edge. Buccal cavity small, with one dorsal and two ventrosublateral teeth. Pharynx cylindrical with well-developed terminal rounded bulb, 26 µm in width. Intestine filled with rounded, slightly yellow-brown inclusions. Anterior part of intestine with annular structure. Nerve ring is located at the level of middle of pharynx. Secretory-excretory system present; renette lies ventrally to the posterior part of pharyngeal bulb, cardia and anterior part of the intestine. Secretory-excretory pore located between the nerve ring and the bulb, posterior to nerve ring. Cardia small and triangular. Reproductive system monorchic, single anterior outstretched testis situated to the right of intestine. Spicules arcuate, distally tapering. Gubernaculum with dorso-caudally directed apophyses; dorso-caudal part 5–7 µm long, 5–6 µm wide and dorsally curved part 5–6 µm long. Apophyses are more strongly sclerotized along dorsal margin. Tail conico-cylindrical, elongated, with slightly swollen tip. Somatic setae on tail 3–4 µm long. Three caudal glands presence. Spinneret present. Female Similar to male in most parameters. Reproductive system didelphic, posterior and anterior ovaries of equal length, outstretched. Both ovaries located to the right of intestine. Vulval lips not sclerotized, slightly protruding beyond body contour and situated at 40% from the anterior end. Vagina short, with thin walls. Uteri large, contain large oocytes, 44 µm long. No vulvar glands seen. TABLE 1 . Morphometrics of Aponema pontica sp. n.

L	male 1 holotype 929	males (n=4) 664–747	female 1 paratype 966	females (n=3) 611–858
a b c	21.6 7.8 6.3	16.6–20.6 6.4–7.8 5.2–5.9	16.7 7.7 5.8	13.3–16.5 6.8–7.7 5.1–5.8
c' V, % Amphidial fovea width	6.2 5	4.7–6.3 5–5.5	6.5 40.7 5	6.1–7.1 35.9–37.2 5
Cephalic setae length Buccal cavity width Buccal cavity length	4 2 7	4 2 6–7	4 2 7	4 1–2 5–6
Head diam. at cephalic setae Head diam. at amphids Amphids from anterior end	8 10 7*, 5**	8–9 10–12 6–8.5	8.5 10.5 8	8–8.5 10–12 7–10
Terminal bulb diameter Body diameter at nerve ring Body diameter at cardia	26 29 35	25–26 28–34 32–41	30 30 42	28–30 24–49 35–40
Maximum body diameter Mid-body diameter Anal body diameter	43 41 24	36–45 31–45 23–28	58 51 26	46–52 41–44 20–21
Apophyse dorso-caudally part length Apophyse dorsally curved part length Tail length	6.5 6 147	5–7 5–6 114–143	168	121–150
Spicule length Body length /spicule length	43 21.6	35–42 17.8–21.3
Note: *—left amphid, **—right amphid

Diagnosis. Aponema pontica sp. n. is characterized by slender (611–966 µm) body. Cuticle transversely striated. Head not separated from the remaining body. Amphidial fovea cryptocircular with interruption in the posterior part. Oesophagus narrow, posteriorly forming a rounded and weakly sclerotised lumen of pharyngeal bulb. Female reproductive system didelphic, ovaries outstretched; male reproductive system monorchic. Tail conico-cylindrical, elongated, with slightly swollen tip. Short setae in the pre- and post-cloacal regions present. Discussion. Aponema pontica sp. n. differs from all known Aponema species by the absence of the constriction in head region and in the shape of gubernacular apophyses. New species is morphologically closest to A. torosum (Lorenzen 1973) Jensen 1978 and A. subtile Leduc & Wharton 2008 . A. pontica sp. n. is similar to A. torosum in the shape of the body, size of amphids, the value of ‘b’ and ‘c’, but differs in having small and triangular cardia, rounded and weakly sclerotised lumen of pharyngeal bulb and longer spicules (35–43 µm vs 28–37 µm in A. torosum ). A. pontica sp. n. is similar to A. subtile in the shape and length of the body, structure of pharyngeal region and presence of short setae in the pre- and post-cloacal regions, but can be differentiated from A. subtile in the shape and length of spicules (35–43 µm vs 22–27 µm in A. subtile ), low values: ‘a’ (13.3–21.6 vs 30.8–39.4 in A. subtile ), ‘b’ (6.4–7.8 vs 7.8–8.8 in A. subtile ), ‘c’ (5.1–6.3 vs 6.7–8.4 in A. subtile ), tail setae longer (3–4 vs 1–2 µm in A. subtile ) and size of the amphidial fovea (5.0–5.5 (43.5–53.0%) vs 3–4 (31–40%) in A. subtile ).