Stylotheristus flagellicaudatus, Li & Huang & Huang, 2024

Li, Ting, Huang, Yong & Huang, Mian, 2024, Two new species of the order Monhysterida (Nematoda) from the sea of China, ZooKeys 1193, pp. 63-79 : 63

Stylotheristus flagellicaudatus sp. nov.

Figs 4 , 5

Diagnosis.

Stylotheristus flagellicaudatus sp. nov. is characterized by relatively shorter body and longer tail than that of two species already described in this genus; cuticle striated; anterior sensilla arranged in two circles: the first circle consisting of six inner labial setiform papillae (3-4 µm), the second circle consisting of 16 long setae (12-19 µm); amphideal fovea transversely oval; well-developed muscle around funnel-shaped buccal cavity; spicules short, gubernaculum composed of a single piece, precloacal supplements absent; tail elongated, filiform.

Type material.

Four males were collected. Holotype: ♂#1 on slide Sangengzhi 87-4. Paratypes: ♂#2 on slide Sangengzhi 81-10, ♂#3 on slide Sangengzhi 81-11 and ♂#4 on slide Sangengzhi 37-3.

Type locality and habitat.

Holotype and other specimens were collected in the muddy sediment from the intertidal zone of Sangengzhi, Hainan Province (19°26′55″N, 108°37′38″E).

Etymology.

The species epithet “flagellicaudatus” refers to its long and filiform tail.

Measurements.

Measurements are given in Table 2 .

Description.

Males. Body slender, cylindrical, and gradually tapering towards tail end. Cuticle striated. Six longitudinal lines of short somatic setae sparsely distributed throughout the body, 4-6 µm long. Anterior sensilla arranged in two circles: the first circle consisting of six inner labial setiform papillae, conical, 3-4 µm long; the second circle consisting of six outer labial setae (18-19 µm), four cephalic setae (16-17 µm) and six subcephalic setae (12-13 µm), situated at the level of buccal cavity base. Buccal cavity funnel-shaped, with well-developed pharyngeal muscles around it. Pharynx cylindrical, not expanded at posterior end. Amphideal fovea transversely oval, 8 µm high and 11-12 µm wide, occupying 40-50% of corresponding body diameter, located at the position of 24-25 µm from the anterior end. Nerve ring located at the middle of pharynx. Secretory-excretory pore not observed. Tail elongated, conico-cylindrical, posterior three-quarters filiform. Three terminal setae 10 µm long, three caudal glands present.

Reproductive system monorchid, an anterior testis outstretched, to the left side of intestine. Spicules short and thin, almost straight, 46-64% of cloacal body diameter long. Gubernaculum simple, short, and laminar, about 70% of spicules length. Precloacal supplements absent.

Females not found.

Figures

Figure 4. Drawings of Stylotheristus flagellicaudatus sp. nov. A lateral view of pharyngeal region of holotype B lateral view of posterior portion, showing long conico-cylindrical tail C lateral view of anterior portion of holotype, showing the two circles of anterior setaes and oval amphideal fovea D entire view of male E cloacal region of holotype, showing spicule and gubernaculum. Scale bars: 20 µm (A - C, E), 30 µm (D).

Figure 5. Microscopic images of Stylotheristus flagellicaudatus sp. nov. A lateral view of anterior portion of holotype, showing conical inner labial setae (arrow 1), outer labial setae (arrow 2), subcephalic setae (arrow 3) and buccal cavity B lateral view of anterior portion of holotype, showing cephalic setae and amphideal fovea (arrow) C lateral view of cloacal region of holotype, showing spicule and gubernaculum (arrow) D lateral view of posterior portion of paratype 1, showing filiform tail and caudal setae E dorsal view of anterior portion of paratype 3, showing cephalic setae (arrow). Scale bars: 20 µm.