Epacanthion fasciculatum, 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 : 564-566

Epacanthion fasciculatum sp. nov.

( Figs 6 , 7 , Table 3)

Diagnosis. Body length 4.7 mm. Mandible about 15 mm long and 1.5–2 times maximum width. Three onchia of equal size. Twelve pairs of subcephalic setae. Many long cervical setae. A cervical circle of 18 bundles each composed of about 10 distinctly short and densely arranged setae posterior to nerve ring. Spicules about 1.3 anal body diameter, with acicular gubernaculum about one third of spicule length. Precloacal supplement located at 3 anal body diameter anterior to cloaca. Tail elongate conical to cylindrical, about 6.6 anal body diameter.

Type material. Holotype: One male on slide NJ-20140513-110 . Paratypes: 3 juveniles on slides NJ- 20140513-23, -25 and -145. 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 fasciculatum (clustered) refers to a main feature of the species, viz., the clustered setae distributed posterior to the nerve ring.

Measurement. See Table 3.

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 lobes, without 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 posterior part of head capsule. Three mandibles and three onchia. Mandibular columns close to each other, connected with a sheet of cuticle. Mandible about 15 mm long and 1.5–2 times maximum width of mandibles. Three onchia unequal in size, with two subventral onchia larger than the dorsal one. Well-developed pharyngeal glands opening into tips of onchia. Amphideal fovea indistinct. Twelve pairs of subcephalic setae of unequal length in a circle. Many long cervical setae, with no distinct pattern. A cervical circle of 18 bundles each composed of about 10 distinctly short and densely arranged setae located posteriorly to nerve ring at anterior third of pharynx ( Figs 6A , 7C ). Pharynx strongly muscular, without pharyngeal bulb. Cardia triangular. Two testes opposed, located on the left of intestine. Spicules slightly curved, equal in length, about 64 mm long and 1.3 anal body diameter. Gubernaculum acicular, with tip curved downwards, parallel to distal end of spicules, about one third of spicule length. One tubular precloacal supplement about 135 µm distant from cloaca (about three anal body diameters) ( Figs 6B, D , 7D, E ). Three caudal glands, with cells positioned precaudally. Tail elongate conical, posterior half cylindrical, about 6.6 anal body diameter. Several setae on tail. Subterminal and terminal setae absent.

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

Female not observed.

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 7. Epacanthion fasciculatum sp. nov., the male holotype. A, B: different focal layers of mandibles, showing the mandibular columns close to each other, connected with a sheet of cuticle; C: the cervical circle of 18 bundles each composed of about 10 distinctly short setae (arrows) posterior to the nerve ring; D, E: precloacal supplement (arrow), spicules and gubernaculum; F: tail bearing sparse setae. Bar = 30 µm.