Epacanthion hirsutum, Shi & Xu, 2016

Shi, Benze & Xu, Kuidong, 2016, Four new species of Epacanthion Wieser, 1953 (Nematoda: Thoracostomopsidae) in intertidal sediments of the Nanji Islands from the East China Sea, Zootaxa 4085 (4), pp. 557-574 : 559-561

Epacanthion hirsutum sp. nov.

( Figs 2 , 3 ; Table 1)

Diagnosis. Body 1.9–2.4 mm long. Mandible length to width ratio about 1.9. Three onchia of equal size. Eight pairs of subcephalic setae in males. Numerous long setae at pharyngeal region. A cervical circle composed of a single row of distinctly short and densely arranged setae posterior to nerve ring. Spicules about 0.7 anal body diameter, with small conical gubernaculum. Tail conical-cylindrical, about 4.5 anal body diameter. Four long setae at the joint of the conical and cylindrical portion of tail, two long subterminal setae and two short terminal setae.

Type material. Holotype: One male on slide NJ-20140513-1 . Paratypes: nine males on slides NJ-20140513-1, -3, -9, -10, -14, -21 and -108 and five females on slides NJ-20140513-1, -21 and -108. All type slides have been deposited in the Marine Biological Museum of Chinese Academy of Sciences .

Type locality. Intertidal sandy sediment from Dasha’ao Beach of the Nanji Islands in the East China Sea.

Etymology. The Latin adjective hirsutus (hirsute) refers to a main feature of the species, viz., the many setae covering the anterior region of the body.

Measurements. See Table 1.

Characters Holotype Paratypes Description. Body cylindrical. Cuticle smooth, apparently with sub-surface annulations. Head slightly tapering, chisel-shaped. Cephalic capsule strongly sclerotized. Lips high, with marked subsidiary lobes, internally with semi-lunar striation. Cephalic organs circular ( Fig. 2E ). Anterior sensilla (6+10) in two circles: six inner labial setae, six outer labial setae and four short cephalic setae in the second row. Cephalic setae inserted at posterior part of head capsule. Three mandibles and three onchia (= teeth). Mandibular columns thin, separated by a sheet of cuticle, 13–17 mm long and about 1.5–2 times maximum width of mandibles between tips of apical teeth. Onchia of equal size, reaching the base of mandibles ( Fig. 3A, B ). Pharyngeal glands opening into tips of onchia. Amphideal fovea indistinct. Pharynx strongly muscular, with anterior end at base of buccal cavity swollen. Cardia triangular. Three caudal glands, with cells positioned precaudally. Tail conical-cylindrical, length 160–198 mm and 3.7–5 abd. Four long setae in a circle located at the joint of the conical and cylindrical part of tail. Several median setae without distinct pattern. Two long subterminal setae and two short terminal setae present ( Figs 2B, D , 3E, F ).

Males. Anterior region hirsute. Eight pairs of subcephalic setae of unequal length in a circle. Numerous long setae exist at pharyngeal region: two rough circles each composed of about 20 setae at anterior portion, posteriorly followed by many scattered setae. A characteristic cervical circle composed of a single row of distinctly short and densely arranged setae located posteriorly to nerve ring at the anterior third of pharynx ( Figs 2A, E , 3C ). Setae become scarcer posterior to nerve ring. Two testes opposed, both located on the left of intestine. Spicules slightly curved, equal in length, 21–33 mm (about 0.7 anal body diameter) long. Gubernaculum small, conical, parallel to distal end of spicules, only about one fifth of spicule length. Precloacal supplement absent.

Females. Females similar to males in body shape, slightly larger in size. Subcephalic setae absent. The number of setae at pharyngeal region lower than that of males, with a rough circle of about 12 setae posterior to cephalic setae. Vulva located at 59%–64% of the body length. Ovaries paired, opposed reflexed, both at left side of intestine. Vagina short.

Figures

FIGURE 2. Epacanthion hirsutum sp. nov. A, B: anterior and posterior portion of the male holotype; C, D: anterior and posterior portion of a female; E: anterior posterior portion of a male showing the numerous scattered cervical setae and the cervical circle composed of a single row of distinctly short and densely arranged setae posterior to the nerve ring. Bar = 30 µm.

FIGURE 3. Epacanthion hirsutum sp. nov. A: head of the male holotype; B: female head; C: a cervical circle composed of a single row of distinctly short and densely arranged setae in the male holotype; D: lateral view of spicules and gubernaculum; E, F: tail with two short terminal setae and two long subterminal setae. Bars = 30 µm.