Pseudorogneda sinensis Wang & Xie 2020, n. sp.

Pseudorogneda sinensis Wang & Xie n. sp.

(Figs.1–2)

Locality. Specimens, inhabiting the stem and pneumatophore of mangrove trees, were collected in the intertidal zone of Mangrove Ecological Park (water temperature: 19–20℃; salinity: 7–8 ‰), Shenzhen City, Guangdong Province, China (22°31’ N, 113°59’ E), by Yaohang Xie in March, 2018.

Material examined. Holotype: PLA-Po111, one whole-mounted specimen. Paratypes: PLA-Po112-113, two whole-mounted specimens; PLA-Po114-116, three serially sectioned (sagittal) specimens; PLA-Po117-119, three mounted prostate stylets.

Etymology. The new species was named after the country where it was first discovered.

Description. Individuals are slow-moving. The body is fusiform, measuring 0.8–1.0 mm long and 120–150 μm wide (n=3). Pharynx is spherical, 110–120 μm in diameter (n=3), and is at anterior 1/3 of the body (Fig. 1 A–B, 2B). Brownish-yellow stripes are presented dorsally, namely two anterior stripes converging at pre-pharyngeal end and diverged into four from there to posterior end of the body. Paired black eyes are situated anterior to the pharynx and 15–25 μm apart (n=3). The brain lies ventral to the eyes (Fig. 2B).

Paired testes are cylindrical in shape (280–320 μm long, n=3) and located ventral at the posterior end of pharynx (Fig. 1B, 2B). Seminal vesicle is bar-like and situated at the posterior 1/3 position of the body. Sizes (lengths) of seminal vesicles vary individually and up to 150–200 μm (n=3) long in mature individuals (Fig. 1B, 2 B–C). Two seminal vesicles fuse at their posterior ends to form the ejaculatory duct which enters prostate stylet type IV along with prostate vesicle type IV (Fig. 1D, 2 B–C). Prostate stylet type IV is flattened tubular in shape, measuring 50–70 μm in length and 25–40 μm in basal diameter (n=5). The stylet has a horn-like base and a proximal-to-distal fold on the wall (Fig. 1 C–D, H–J, 2B–C, E). Rod-like prostate vesicle type II (120–150 μm, n=3) is located between two seminal vesicles with its distal end entering prostate stylet type II. Prostate stylet type II is double-walled (120–140 μm in length, n=5) and bent in a semicircle in shape (70–80 μm in diameter, n=5), with a proximal-to-distal fold. The inner wall starts at midpoint of the outer stylet. The prostate stylet tapers the diameter from the proximal end to distal end (Fig. 1 A–D, F–G, 2B–D). Male atrium narrows in the middle to form a dumb-bell shape, surrounded by strong striated muscle (Fig. 1C, E, 2 B–C). The spherical male bursa connects to the posterior end of the male atrium (Fig. 2 B–C).

The paired vitellaria are bar-shaped, dorsal, and extend from posterior end of the pharynx to the cauda tip (Fig. 2 B–C). The paired ellipsoidal ovaries are situated at the posterior 1/5 of the body, measuring 75–85 μm long and 40–55 μm wide (n=3) (Fig. 1 B–C, E, 2B–C). The female duct is a type I and is surrounded with a sphincter (Fig. 2 B–C). The seminal receptacle is spherical and sperm-filled (Fig. 1E, 2 B–C), 30–35 μm in diameter (n=3). Uterus, with massive eosinophilic glands around it, is located at the posterior 1/5 position of the body and connected to the gonopore (Fig. 2 B–C). Mature egg is blunt triangular in shape and provided with a stalk, with two embryos inside (Fig. 1K).