Paracomesoma paralissum, 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 : 526-527

Morphological description of Paracomesoma paralissum sp. nov.

( Figures 5–6 , Table 3 )

urn:lsid:zoobank.org:act:A406CD23-363C-47A2-9FCB-B59E3BABA942

Type material. Two males were collected from stations JMJGYL 1 in February 2021. Holotype: ♂ 1 on slide number JMJGY20210221 L123 . Paratype: ♂ 2 on slide number JMJGY20210221 L13 .

Type locality and habitat. All specimens were collected from a mangrove ( A. marina ) forest in Jiangongyu on Jinmen Island. Station JMJGY: 118°18'3.24″E, 24°25'12″N. The sediment is mainly argillaceous with a small amount of sandy.

Etymology. Species epithet refers to its body similar to P. lissum Gagarin & Thanh, 2009 .

Description

Males. Body slender. Cuticle with transverse rows of fine punctuations, without lateral differentiation. 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 sensilla about 1 μm long. Four cephalic setae 4–6 μm long, located 0.5 head diameter from the anterior end. Somatic setae scattered and numerous. Amphidial fovea in the shape of a spiral with 3.0 turns, 7–8 µm wide, and occupying about 40–50% cbd, located immediately posterior to cephalic setae. Buccal cavity small, conical, with three small teeth. Pharynx cylindrical, 207–226 μm long, gradually enlarging posteriorly but not forming true posterior bulb. Nerve ring at about 63–65% 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. Tail conico-cylindrical, about 235–236 μm long and equal to 5.1–5.3 body diameters at the level of cloaca, with two terminal setae about 5 μm long. Three caudal glands and spinneret.

Two testes, opposed and outstretched. Anterior testis to the left and posterior testis to the right of the intestine. Spermatozoa irregularly oviform. Spicules equal thick, paired, equal and arcuated, 126 µm long, about 2.7–2.8 times as long as cloacal body diameter; spicules with slightly pointed distal end. Gubernaculum small, about 13 µm long, without apophysis, and wraped around the anterior of the spicule. 40 fibriform precloacal supplements present. One short precloacal setae located just in anterior of cloaca, about 3 µm.

Females. Not found.

Diagnosis and relationships

Paracomesoma paralissum sp. nov. is characterized by its head slightly set off by a contraction at the level of cephalic setae; the buccal cavity conical, with three teeth; the amphidial fovea in the shape of a spiral with 3.0 turns; cuticle with transverse rows of fine punctuations, without lateral differentiation; spicules equal arcuated, with slightly pointed distal end; gubernaculum without apophysis; 40 fibriform precloacal supplements present.

Paracomesoma paralissum sp. nov. is most similar to P. lissum . However, it differs from the latter species in the length of cephalic setae (Cs 4.3–5.8 μm vs. 6.0–7.0 μm in P. lissum ), the value of the tail (c’ 4.3–5.8 μm vs. 6.0–7.0 μm in P. lissum ), the length of the spicules (126 μm vs. 88–98 μm in P. lissum ) and gubernaculum. It also differs in the number of fibriform precloacal supplements (Sup 40 vs. 45–47). In this paper, differentiating characteristics of all known male Paracomesoma species are given in Table 5 ( Schuurmans Stekhoven 1950; Gerlach 1956; Allgén 1959; Timm 1961; Jensen & Gerlach 1977; Zhang 1991; Zou 2001; Gagarin & Thanh 2006; Riera et al. 2006; Gagarin & Thanh 2009; Tu et al. 2013; Gagarin & Tu 2014; Semprucci 2014; Gagarin & Tu 2018; Huang & Huang 2018; Huang et al. 2021).

Figures

FIGURE 5. Paracomesoma paralissum sp. nov.A: Lateral view of the male anterior part. B: Lateral view of the male head part. C: Lateral view of the male posterior part (Spicule). Scale bar: A, C =25 μm; B =10 μm.

FIGURE 6. Paracomesoma paralissum sp. nov.A: Lateral view of male anterior part; B: Male head; C: Amphid of the male; D: Lateral view of male posterior part (Spicule); E: Supplements of the male. Scale bar: A, D=25 μm; B, C, E=5 μm.