Trissonchulus benepapillosus ( Schulz, 1935 )

Chen, Yu Zhen & Guo, Yu Qing, 2015, Three new and two known free-living marine nematode species of the family Ironidae from the East China Sea, Zootaxa 4018 (2), pp. 151-175: 164-167

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Trissonchulus benepapillosus ( Schulz, 1935 )


Trissonchulus benepapillosus ( Schulz, 1935) 

( Figure 10View FIGURE 10, Figure 11View FIGURE 11, Table 5)

Material. Three males and one female were collected from Station ZZDS H 2 and H 3 in May 2013. ♂ 1 on slide number ZZDS 20130518 H 3 U 101, ♂ 2 on slide number ZZDS 20130518 H 3 U 104, ♂ 3 on slide number ZZDS 20130518 H 2 D 116, ♀ 1 on slide number ZZDS 20130518 H 3 D 110.

Material locality and habitat. All specimens were collected from intertidal sandy sediment at Dongshan Island, Zhangzhou City, the East China Sea. Station ZZDS: 117.4836 °E, 23.7081 °N. Silt+clay: 3.27 %.

TABLE 4. Differentiating characters of all known male Trissonchulus  species (in µm): number of male specimens; L: body length; Hd: head diameter; Bl: buccal cavity lenth; abd: clocal body diameter; Tl: tail length; Sc: spicule length as arc; Tn: number of tooth; Hs: head set off

(Y) or not (N); So: spinneret absent (A) or opens terminally (T), ventrally (V), dorsally (D); Cg: candal glands present (Y) or not (N); Tn: number of teeth: three (3), four (4).

Measurements ( Table 5)

Description. Male. Body relatively cylindrical, slightly tapering towards extremities. Cuticle thick and smooth, several papillae present in the anterior cervical region. Head region markedly offset by a deep groove, with three labial flaps, armed with an inner circle of six small labial papillae and an outer circle of ten prominent stout and conical setae length about 2–3 µm, of which six are markedly larger than the others. Amphids pocket-shaped, about 0.62–0.74 cbd and adjacent to cephalic groove. Buccal cavity consists of a cup-shaped anterior section, and a strong cuticularized posterior tube, length 4–6 µm and 36–39 µm respectively. The anterior end of the cuticularized tube bears a small, wholly cuticular tooth dorsally and a single, larger tooth on each ventro-lateral sector. Pharynx 0.16–0.17 times of body length, slightly swelling in stomatal region and gradual enlargement at posterior, corresponding body diameter 35–44 µm at posterior extremity. Сardia semicircular, well developed. Nerve ring encircling pharynx at about 43–48 % of its length. Excretory pore opening in the labial region between the labial papillae and the cephalic sensilla. Ventral gland elongate flask-shaped, contains marked nucleus, lying posterior to the pharynx, situated at the right or left side of body. The excretory system is filled with granules. Tail bluntly conoid, with three pairs of symmetrical small conical papillae arranged in two rows distributed in the postcloacal subventral sector. There are also two rows of asymmetrical small conical papillae present in the precloacal subventral sector, and each row contains three papillae. All of the precloacal and postcloacal small conical papillae are associated with more or less marked elevations of the cuticle, which seem to be tubular under cuticle. Caudal glands slender. Spinneret opens terminally.

Reproductive system diorchic with two opposed testes, situated to left of intestine. Spicules paired and broad, with wide proximal end and blunt distal tips, as well as a central septum. Gubernaculum relatively short and slightly thinner proximally, and distally thick and connected with a short apophysis.

Female. Similar to male in most aspects, except body slightly longer (1841 µm vs. 1490–1699 µm) and caudal region without preanal or postanal conical papillae.

Reproductive system didelphic, opposed and reflexed, located at the right side of intestine. Vulva in the shape of slit, at about 55.7 % of body length.

Diagnosis and discussion. Trissonchulus benepapillosus ( Schulz, 1935) Gerlach & Riemann, 1974  was first described as a species of Syringolaimus  by Schulz on female and juvenile specimens. The description of the male was added by Schulz in 1938. Then this species was transferred to the genus Dolicholaimus  by Gerlach (1952); later it was put in the genus Trissonchulus  by Gerlach & Riemann (1974). T. benepapillosus  is a widespread species, and has been redescribed several times. It is characterized by the set-off head, the papilliform or very short setiform head sensilla, and the bluntly conoid tail. Our specimens are similar to the original description by Schulz, but differ in body size (1.49–1.84 mm vs. 2.2–3.09 mm) and the existence of small conical papillae in male caudal region (small conical papillae absent in original description) ( Schulz 1935, Schulz 1938). According to the description by Wieser (1959), our specimens differ in smaller body size (1.49–1.84 mm vs. 2.49–2.63 mm), relatively longer pharynx (b 6.0–7.0 vs. 8.3–8.7) and tail (c 22.9–26.7 vs. 27.7 –33.0 and c’ 2.1–2.3 vs. 1.75), as well as in the absence of supplements ( Wieser 1959).

TABLE 5. Individual measurements of Trissonchulus benepapillosus (Schulz, 1935) (in µm).

  1600 1490 1669 1841
Nerve ring from the anterior end