Paracomesoma zhangi, Huang & Huang, 2018

Huang, Mian & Huang, Yong, 2018, Two new species of Comesomatidae (Nematoda) from the East China Sea, Zootaxa 4407 (4), pp. 573-581 : 574-577

Paracomesoma zhangi sp. nov.

( Figs 1–2 )

Type material. Holotype male on slide DH 3-4-8-1.

Type locality and habitat. Seafloor muddy sediment at Station DH 3-4 in the East China Sea (30°0´N, 124°0.1´E, water depth 64.4 m).

Etymology. The species is named in honor of Professor Zhinan Zhang (Ocean University of China), in recognition of his contribution to the field of marine meiofuana.

Measurements. Measurements are given in the following formula.

Holotype ♂: — 216 M 1680 1868 µm; a=42.5, b=8.7, c=9.9, spicule = 152 µm

14 40 44 31

Description. Male. Body slender with a conico–cylindrical tail. Cuticle with fine transverse rows of punctuations, without lateral differentiation. Head slightly set off by a contraction at the level of cephalic setae. Buccal cavity 14 µm long, composed of two parts, the anterior part cup-shaped, with three small teeth, the posterior part in form of a cuticularized tube as long as the labial region width. Head sensilla arranged following the 6+6+4 pattern. Inner labial sensilla papilliform; six outer labial sensilla setiform, 3.5 µm long. Cephalic setae 13.5 µm long, located 0.5 of the head diameter from the anterior end. Somatic setae (about 4 µm long) scattered and numerous. Multispiral amphideal fovea with three turns, located closely behind the cephalic setae, at a distance of 8 µm from the anterior border of amphideal fovea to the head end. Diameter of amphideal fovea 10 µm, i.e. 0.67 of the corresponding body diameter. Pharynx cylindrical, posteriorly gradually enlarging but not forming true posterior bulb. Cardia well developed. Nerve ring at about 54% of the pharynx length. Secretory–excretory system consisting of unicellular gland located at level with anterior part of intestine; secretory–excretory duct with distinct ampulla and opening just posterior to the nerve ring, 132 µm from anterior body end.

Reproductive system diorchic. Two testes opposed and outstretched: anterior one located to left of intestine and stretching forwards; posterior one located to right of intestine and stretching backwards. Spermatozoa irregularly oviform in shape. Spicules slender and elongated with thick cuticularized proximal end, 152 µm long along arc, i.e. equal to 4.3 body diameters at the level of cloaca. Gubernaculum plate-like without apophysis, 26 µm long. Precloacal ventral cuticle thickened. One short precloacal seta located just before the cloaca. Twenty six minute tubular precloacal supplements present. Tail conico–cylindrical, 188 µm long i.e. equal to 5.4 body diameters at the level of cloaca, with an evident spinneret; a single 2 µm subterminal seta present.

Female. Not found.

Diagnosis and discussion. Paracomesoma zhangi sp. nov. is characterized by cuticle with fine transverse rows of dots without lateral differentiation; buccal cavity with three small teeth; cephalic setae 13.5 µm long; multispiral amphideal fovea with three turns; spicules slender and elongated with thick cuticularized proximal end, 4.3 abd long; gubernaculum plate-like without apophysis; 26 minute precloacal supplements. It is particularly similar to P. xiamenense Zou, 2001 in the same body size and the value of de Man’s ratios. However, the new species differs from P. xiamenense in having longer cephalic setae (13 µm, i.e. equal to 1.1 head diameters. vs 9–10 µm, i.e. equal to 0.6 head diameter.); shorter equal spicules (152 µm, i.e. 4.3 anal body diameters vs unequal spicules, longer one 203 µm, i.e. 5.8 anal body diameters, shorter one 188 µm, i.e.5.5 anal body diameters); shorter gubernaculum (16 µm vs 34 µm); a line of 26 tubular precloacal supplements (vs two lines of papilliform precloacal supplements, each with about 28–30 supplements). In addition, P. xiamenense has two rows of small post-cloacal papillae, each row with three papillae. The new species is similar to P. lissum Gagarin & Thanh, 2009 in the body size and absence of lateral differentiation of large dots. But P. zhangi sp. nov. differs from the latter species in having longer cephalic setae (13.5 µm vs 6–7 µm), longer spicules (4.3 vs 3.2 anal body diameters) and fewer precloacal supplements (26 vs 45–47). The new species is also similar to P. minor Gagarin & Tu, 2014 and P. elegans Gagarin & Thanh, 2009 . However, the new species differs from P. minor in having longer body (1868 µm vs 961–977 µm), longer spicules (152 µm vs 93–98 µm), more precloacal supplements (26 vs 8–9), cuticle without lateral differentiation (vs with lateral differentiation). The new species differs from P. elegans in having longer body (1868 µm vs 1042–1218), longer cephalic setae (13.5 µm vs 3.4–4.5 µm), more precloacal supplements (26 vs 8–12), cuticle without lateral differentiation (vs with lateral differentiation).

Figures

FIGURE 1. Paracomesoma zhangi sp. nov. (A) lateral view of male posterior end, showing spicules, gubernaculum and precloacal supplements; (B) lateral view of male anterior end, showing buccal cavity, cephalic setae and amphideal fovea; (C) lateral view of male pharyngeal region, showing secretory-excretory system; (D) lateral view of cloacal region, showing spicules, gubernaculum, precloacal seta and precloacal supplements.

FIGURE 2. Paracomesoma zhangi sp. nov. (A) male anterior end, showing buccal cavity and teeth; (B) lateral view of male anterior end, showing cephalic setae and amphideal fovea; (C) male cloacal region, showing spicules and precloacal supplements; (D) lateral view of male cloacal region, showingspicules and gubernaculum. (Scales:A, B 20 µm; C, D 30 µm).