Paraustrorhynchus shenda Wang & Lin, 2019

Lin, Yitao, Reygel, Patrick, Feng, Weitao, Chen, Jiajia, Tessens, Bart, Van Steenkiste, Niels W. L., Schockaert, Ernest R., Artois, Tom J. & Wang, Antai, 2019, Four new species of the genus Paraustrorhynchus (Rhabdocoela: Kalyptorhynchia: Polycystididae), Zootaxa 4550 (3), pp. 357-373 : 360-362

Paraustrorhynchus shenda Wang & Lin n. sp.

( Figs. 1–2 )

Locality. Eastern Shenzhen City, Guangdong Province, China (22°28′1″N, 114°31′37″E), specimens collected in the intertidal zone (water temperature: 20–21°C, salinity: 19–20‰) by Yitao Lin, 29 th April 2017.

Material examined. One whole mount designated holotype: PLA-Po051. Paratypes: PLA-Po52–058, seven whole mounts; PLA-Po059, whole mount of prostate stylet type II and III; PLA-Po060-1–060-3, three seriallysectioned (horizontal) specimens and PLA-Po060-4–060-5, two serially-sectioned (sagittal) specimens.

Etymology. The species is named after the Pinyin of the abbreviated Chinese name for Shenzhen University— “Shenda”.

Diagnosis. Species of Paraustrorhynchus with a mid-dorsal dark-blue pigment stripe. Prostate stylet type II ± 67 µm long, L-shaped with a fang-like structure at the bend. Prostate style type III ± 31 µm long, ± 40 µm wide proximally, ±8 µm wide in the middle and ±31 µm distally, consisting of a common proximal plate with two arms. One arm broadened distally, the other sickle-shaped. Distal rim of both arms provided with fine teeth in a comblike array.

Description. Specimens are rod-shaped, about 0.8 mm long, and lime-green ( Fig. 1A ). With two eyes situated behind the proboscis. A dark-blue longitudinal pigment stripe is situated mid-dorsally. The length of the pattern varies somewhat between specimens, but commonly starts from the middle of the eyes and extends to the caudal end of the body ( Fig. 1A, B ). The pigmentation consists of small granules under the body wall. Its relation to specific cells is not clear, but the pattern is restricted to the mid-dorsal area.

Internal organisation comparable to that of P. pacificus Karling & Schockaert, 1977 (see Karling & Schockaert 1977 for details). The proboscis is about 0.12 mm long (measured on live specimens; Fig. 1B , 2A ). A pair of testes, almost 1/2 of the body length long, extends alongside the pharynx ( Fig. 1B , 2A ). The seminal vesicles are located ventrally, more or less in the middle of the body, and are connected to the prostate vesicle type III, which is situated at the right hand side of the body ( Fig. 1C , 2A ). The prostate stylet type III has following dimensions: length 27–36 µm (x‾ = 31 µm; n = 4), proximal width: 38–44 µm (x‾= 40 µm; n = 4), width in the middle 7–9 µm (x‾ = 8 µm; n = 4), distal width: 25–32 µm (x‾= 31 µm; n = 4). It is composed of three parts: a proximal triangular lamellar plate with two long arms extending from the plate. The arms are curved towards each other. One arm broadens distally, the other is sickle-shaped. The distal rim of both arms is serrated ( Fig. 1 H–J, 2C). The prostate vesicle type II is located at the left hand side of the prostate vesicle type III and is connected to the prostate stylet type II ( Fig. 1C ). The prostate stylet type II is double-walled and L-shaped, measuring 64–70 µm in length (x‾= 67 µm; n = 4). The proximal part of the outer stylet is funnel-shaped and 15–18 µm wide (x‾= 16 µm; n = 4). This part shows a longitudinal slit. At about its midpoint, the stylet makes a 90° turn and is provided with a fang-like structure; the distal half of the stylet approximates a sinusoidal curve and runs perpendicular to the first part. The stylet tapers gradually to end in a sharp distal point. The inner stylet is present in the distal half of the outer stylet only. The proximal part of the inner stylet is hourglass-shaped ( Fig. 1 E–G, 2B). The common genital pore is located ventrally at approximately 75% and is surrounded by eosinophilic glands ( Fig. 2A ). The male bursa, lined with an irregular thickened basement membrane, is situated opposite to the common genital atrium and is filled with sperm in some specimens ( Fig. 1C , 2A ).

Two vitellaria are located dorsally at both sides of the body, extending from behind the eyes to the caudal end of the body ( Fig. 1B , 2A ). Two globular ovaries are located at 80% and are clearly visible because of their brownish-yellowish pigmentation ( Fig. 1 A–C, 2A). The egg (150 µm in diameter) has a globular shape and has a short stalk ( Fig. 1D ).

Figures

FIGURE 1. Paraustrorhynchus shenda n. sp.: (A) live specimen; (B) squeezed live specimen; (C) reproductive organs (partim); (D) egg; (E–G) prostate stylet type II; (H–J) prostate stylet type III.

FIGURE 2. Paraustrorhynchus shenda n. sp.: (A) habitus from a live animal; (B) prostate stylet type II; (C) prostate stylet type III.