Comesoma quattuordecimsupplementata, Xiao & Guo, 2023

Xiao, Yueping & Guo, Yuqing, 2023, Three new free-living marine nematode species of the family Comesomatidae from Mangrove wetlands in Jinmen County, Taiwan, Zootaxa 5369 (4), pp. 513-532 : 521-524

Morphological description of Comesoma quattuordecimsupplementata sp. nov. ( Figures 3–4 , Table 3 )

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Type material. Two males and four females were collected from stations JMGNTH 1 in February 2021. Holotype: ♂ 1 on slide number JMGNT20210221 H123 . Paratypes: ♂ 2 on slide number JMGNT20210221 H115, ♀ 1 on slide number JMGNT20210221 H118, ♀ 2 on slide number JMGNT20210221 H19, ♀ 3 on slide number JMGNT20210221 H123 and ♀ 4 on slide number JMGNT20210221 H128 .

Type locality and habitat. All specimens were collected from a mangrove ( A. marina ) forest in Guningtou on Jinmen Island. Station JMGNT: 118°18'15.84″E, 24°29'9.24″N. The sediment is mainly argillaceous with a small amount of sandy.

Etymology. Species epithet refers to its number of fibriform precloacal supplements.

Description

Males. Body slender. Cuticle with transverse rows of fine punctuations (10 μm/ 14–16 punctuations), lateral differentiation with only a bit coarser punctuated pattern. Head slightly set off by a contraction at the level of cephalic setae, and the head diameter (the body width at the level of cephalic setae) is 14 μm. Head sensilla arranged following 6+6+4 pattern. Inner labial sensilla papilliform; six outer labial papilla sensilla. Four cephalic setae 9–10 μm long, located 0.5 head diameter from the anterior end. Somatic setae (about 4 µm long) scattered and numerous. Amphidial fovea in the shape of a spiral with 2.5–2.75 turns, 11 µm wide, and occupying about 70–80% cbd, located immediately posterior to cephalic setae. Buccal cavity small, cup-shaped, without teeth. Pharynx cylindrical, 182– 193 μm long, gradually enlarging posteriorly but not forming true posterior bulb. Nerve ring at about 66–79% of the pharynx length. Secretory-excretory system consisting of unicellular gland located at level of anterior part of intestine; secretory-excretory duct with distinct ampulla and opening just posterior to the nerve ring. Tail composed of a slightly conical anterior half and a cylindrical posterior half slightly swollen posteriorly, about 148–154 μm long and equal to 4.2–4.4 body diameters at the level of cloaca, with two terminal setae about 5 μm long. Three caudal glands and spinneret present.

Two testes, opposed and outstretched. Anterior testis to the left and posterior testis to the right of the intestine. Spermatozoa irregularly oviform. Spicules equal slender, paired, equal and arcuated, 120–128 µm long, about 3.5– 3.6 times as long as cloacal body diameter; spicules with slightly pointed distal end. Gubernaculum small, about 13 µm long, without apophysis. 14 fibriform precloacal supplements present. One short precloacal setae located just in anterior of cloaca, about 2 µm long.

Females. Similar to male in general characteristics. But the diameter of amphid to the body diameter is slightly smaller (Amphid width/cbd 0.6–0.7 times vs. 0.7–0.8 times), the tail shorter (c 8.2–9.0 vs. c 9.0 –9.7).Reproductive system amphidelphic, ovaries outstretched.Anterior ovary to the left and posterior gonad to the right of the intestine. Vulva at 43.1–47.7% of the body length. Short vagina with thick walls perpendicular to the longitudinal body axis.

Diagnosis and relationships

Comesoma quattuordecimsupplementata sp. nov. is characterized by its head set off by a contraction at the level of cephalic setae; the cup-shaped buccal cavity, without teeth; the amphidial fovea in the shape of a spiral with 2.5–2.75 turns; cuticle with transverse rows of fine punctuations, with lateral differentiation; spicules equal arcuate, with slightly pointed distal end; gubernaculum without apophysis; 14 fibriform precloacal supplements present.

Comesoma quattuordecimsupplementata sp. nov. is most similar to C. hermani in having the same number of turns of amphidial fovea, the same ratio of the body (a, c and c’). However, one can distinguish C. hermani by the length of body (L 1293–1498 µm vs. 1694–2108 µm in C. hermani ), the ratio of the pharynx length to body length (b 7.3–7.7 vs. 7.6–9.1 in C. hermani ) and the spicules length (120–128 µm vs. 169–184 µm in C. hermani ). In this paper, differentiating characteristics of all known male Comesoma species are given in Table 4 ( Bastian 1865; Cobb 1898; Filipjev 1918; Ditlevsen 1921; Chitwood 1937; Gerlach 1955; Gerlach 1956; Jensen & Gerlach 1977; Pastor de Ward 1984 and Chen & Vincx 1998).

Figures

FIGURE 3. Comesoma quattuordecimsupplementata sp. nov. A: Lateral view of the male anterior part. B: Lateral view of the female anterior part. C: Lateral view of the male head part (Cuticle). D: Lateral view of the male posterior part (spicule). E: Lateral view of female posterior part. F: Lateral view of female reproductive system. Scale bar: A, B, D, E=25 μm; C =10 μm; F =50 μm.

FIGURE 4. Comesoma quattuordecimsupplementata sp. nov. A: Lateral view of the male anterior part; B: Lateral view of the female anterior part; C: Lateral view of the male head part; D: Amphid of the male; E: Lateral view of the female head part; F: Amphid of the female; G: Lateral view of the male posterior part; H: Lateral view of the female posterior part; I: The spicule and supplement of the male; J: Lateral view of the female reproductive system. Scale bar: A, B, G, H, J=25 μm; C, D, E, F, I =10 μm.