Epacanthion sparsisetae, 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 : 566-569

Epacanthion sparsisetae sp. nov.

( Figs 6 , 8 ; Table 4)

Diagnosis. Body length 2.5–2.6 mm. Mandible about 13 µm long with length equal to width. Three onchia of equal size. Twelve pairs of subcephalic setae. A cervical circle of eight bundles each composed of about 10 distinctly short and densely arranged setae anterior to nerve ring, each bundle with a gland-like vesicle beneath. Spicules smooth, about one anal body diameter. Tail elongate conical to cylindrical, 6.5–6.9 anal body diameter. Type material. Holotype: One male on slide NJ-20140513-142. Paratypes: One male on slide NJ-20140513- 31 and two juveniles on slide NJ-20140513-33. 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. Composition of Latin adjective sparsus (sparse) and seta (bristle), referring to the main feature of the species, viz. relatively sparse setae as well as the low number of bundles of short cervical setae in this species. Measurement. See Table 4.

Description. Male holotype. Body cylindrical. Cuticle smooth, apparently with sub-surface annulations. Head slightly tapering, chisel-shaped. Cephalic capsule strongly sclerotized. Lips high, with marked subsidiary lobe, no striation. Cephalic organs circular. 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 the middle of the head capsule. Three mandibles and three onchia. Mandibular columns separated and parallel to each other, with a sheet of cuticle; about 13 µm long and equal to mandible width. Three onchia unequal, with two subventral onchia larger than the dorsal one. Pharyngeal glands opening into tips of onchia. Amphideal fovea indistinct. Twelve pairs of subcephalic setae of unequal length in a circle. Somatic setae relatively sparse. A cervical circle of eight bundles each composed of about ten distinctly short and densely arranged setae located anteriorly to nerve ring at anterior one sixth of pharynx, each bundle with a gland-like vesicle beneath ( Figs 6E , 8C, D ). Pharynx muscular. Two testes opposed, located at the left of the intestine. Spicules slightly curved, equal in length, 32–38 mm long and 1–1.1 anal body diameter ( Figs 6H , 8E ). Gubernaculum and precloacal supplement absent. Three caudal glands, with cells positioned precaudally. Tail elongate conical, with the posterior third cylindrical, 6.5–6.9 anal body diameter ( Figs 6F , 8F ). Several setae at tail. Subterminal and terminal setae absent.

Juveniles similar to males in general body shape, but lack reproductive system.

Female not observed.

Characters Holotype Paratypes

Figures

FIGURE 6. Epacanthion fasciculatum sp. nov. (A – D) and Epacanthion sparsisetae sp. nov. (E – H). A – D: the male holotype, showing the cervical circle of 18 bundles each composed of about 10 distinctly short setae posterior to the nerve ring, the mandibles, spicules and gubernaculum; E – H: the male holotype, showing the mandible, spicules and gubernaculum and the cervical circle of eight bundles each composed of about 10 short and densely arranged setae anterior to the nerve ring. Bars = 10 µm (C, G), 30 µm (A, B, D – F, H).

FIGURE 8. Epacanthion sparsisetae sp. nov., the male holotype. A, B: mandibles and unequal-sized onchia, the long setae at the head region; C, D: the cervical circle of eight bundles each composed of about 10 distinctly short and densely arranged setae (arrows); E, F: spicules and tail. Bar = 30 µm.