Trissonchulus latispiculum , Chen, Yu Zhen & Guo, Yu Qing, 2015

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: 161-162

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Trissonchulus latispiculum

sp. nov.

Trissonchulus latispiculum  sp. nov.

( Figure 7View FIGURE 7, Figure 8View FIGURE 8, Table 3)

Type material. Five males and two females were collected from Station QZLY H 2 and QZLY H 4 in July 2012.

Holotype, ♂ 1 on slide number QZLY 20120713 H 204. Paratypes: ♂ 2 and ♀ 1 on slide number QZLY 20120713 H 207, ♂ 3 on slide number QZLY 20120713 H 403, ♂ 4 and ♀ 2 on slide number QZLY 20120713 H 204, ♂ 5 on slide number QZLY 20120713 H 206.

Type locality and habitat. All specimens were collected from a mangrove ( Aegiceras corniculatum  ) forest in the Luoyang River estuary in Quanzhou City. Station QZLY: 24.94 °N, 118.67 °E. Characteristics of surface sediments: total nitrogen (mg·g - 1): 1.31; total phosphorus (mg·g - 1): 0.40; organic carbon (%): 1.72; sulfide (10 - 6): 16.89.

Etymology. The name refers to the broad spicules.

Measurements ( Table 3)

Description. Male. Body cylindrical. Cuticle smooth without transverse or longitudinal striations. Head conical, continuous with body contour, with an inner circle of six small labial papillae. Six smaller outer labial papillae and four larger papilliform cephalic sensilla arranged in a crown. Amphids pouch-shaped, about 0.31–0.43 cbd and situated just posterior to the lateral outer labial papillae. Buccal cavity in the shape of a sclerotized tube which Inglis (1961) called a “pharynx rod”, and with a vestibular part, length 54–57 µm and 10–12 µm respectively. Three solid curved claw-like teeth embedded on the anterior edge of the sclerotized tube of buccal cavity, with the two subventral teeth almost equal in size and larger than the dorsal one. The inner wall of the vestibular part of buccal cavity lined with many minute denticles. Pharynx 0.13–0.16 times body length, gradually enlarging posteriorly, corresponding body diameter 75–95 µm at its posterior extremity. Сardia large, nearly heartshaped, surrounded by intestinal tissue. Nerve ring not very distinct, encircling pharynx at about 35–44 % of its length. Excretory pore opening at the labial region, about equal distance to inner labial papillae and to cephalic sensilla. Ventral gland small, situated at 55–60 % of pharynx length. Tail short, stout and blunt, armed with several papillae which are associated with more or less marked elevations of the cuticle. Spinneret opening slightly ventrally.

Reproductive system diorchic with two opposed testes, the anterior one longer than the posterior one; anterior testis situated to left and posterior testis mainly to right of intestine. Spicules paired, broad and alate, with prominent central septum and slight proximal cephalation. The median ridge of spicule slightly swollen to the lateral side. Gubernaculum relatively short and slightly thinner in proximal part, distally thick and well developed.

Female. Similar to male in general characteristics, except tail more round and slightly longer than male (c’ 1.32–1.42 vs. 1.23–1.31), the total length of buccal cavity in female slightly longer than in male (70–81 µm in female vs. 64–68 µm in male).

Reproductive system didelphic, opposed and reflexed, located at right side of intestine. Vulva at about 49.0% of body length. Oviduct twisted, ovaries asymmetrical.

Diagnosis and discussion. The genus Trissonchulus  was erected by Cobb in 1920 with the type species T. oceanus  . The taxonomy of this genus is still uncertain: the generic diagnosis and composition have been changed many times ( Schuurmans Stekhoven 1943, Wieser 1953, Chitwood 1960, Yeates 1967, Gerlach & Riemann 1974). However, the genus Trissonchulus  in general can be distinguished from other genera of Ironidae  by the papilliform or very short setiform head sensilla, the absence of posterior pharyngeal bulb and the relatively short tails, etc.

( Platt & Warwick 1983; Keppner & Tarjan 1989). There are 15 species in this genus at present; most of them were transferred from Dolicholaimus De Man, 1888  or Syringolaimus De Man, 1888  . ( Gerlach & Riemann 1974, Orselli & Vinciguerra 1997, Gagarin et al 2012; Electronic database:; http:// However, T. nudus Schuurmans Stekhoven, 1943  was described from a single female; Gerlach & Riemann (1974) regarded it as a synonym of T. oceanus Cobb, 1920  ; T. reversus Chitwood, 1951  and T. acutus Gerlach, 1953  were described based on juvenile and female specimens respectively. Therefore, there are 14 species including 12 valid species and 2 species inquirenda in this genus ( Schuurmans Stekhoven 1943, Chitwood 1951, Gerlach 1953; Gerlach & Riemann 1974; Platonova & Mokievsky 1994,electronic database:,;). A pictorial key to 12 valid species as well as the newly described species of the genus Trissonchulus  is given in Figure 9View FIGURE 9, differentiating characters of all known male Trissonchulus  species are given in Table 4 ( Bresslau & Schuurmans Stekhoven 1940, Wieser 1953, Gerlach 1967, Wieser 1959, Chitwood 1960, Inglis 1961, Yeates 1967, Orselli & Vinciguerra 1997, Gagarin et al. 2012).

Trissonchulus latispiculum  sp. nov. is characterized by its continuous head (not set off from rest of body), short and blunt tail, buccal cavity with minute denticles, spinneret opening slightly ventrally, spicule broad and alate with proximal end with head, female reproductive system didelphic, etc. It most closely resembles T. latus ( Wieser, 1953) Inglis, 1961  . However, in comparison with the original description of T. latus  by Wieser (1953), the new species can be easily distinguished by its more slender body (a 36.4–54.2 vs. 22.2), shorter tail (c 45.3–61.4 vs. 44.3; c’ 1.2–1.3 vs. 0.9), slightly ventral spinneret opening (opening at the apex in T. latus  ) and differently shaped spicule ( Wieser 1953; Platonova & Mokievsky 1994).

TABLE 3. Individual measurements of Trissonchulus latispiculum sp. nov. (in µm).

    3643 3560 4123 4120    
Nerve ring from the anterior end            
          48.7% 49.1%














Trissonchulus latispiculum

Chen, Yu Zhen & Guo, Yu Qing 2015

T. latus ( Wieser, 1953 ) Inglis, 1961

(Wieser, 1953) Inglis 1961