Pseudorogneda shenda Wang & Xie, 2020

Xie, Yao-Hang, Wei, Li-Yang, Huang, Wei-Dong, Zhong, Lin-Hong, Li, Shuang-Fei & Wang, An- Tai, 2020, Two new species of a new genus, Pseudorogneda, of Polycystididae discovered in Southern China, Zootaxa 4808 (3), pp. 589-599 : 592-596

Pseudorogneda shenda Wang & Xie n. sp.

( Figs. 3-4 )

Locality. Specimens collected at Shekou Port (water temperature: 18–20℃; salinity: 17–20‰), Shenzhen City, Guangdong Province, China (22°28′N, 113°54′E), by Yaohang Xie in March, 2018, where the species inhabits the muddy surface of the submersed stones .

Material examined. Holotype: PLA-Po121, one whole-mounted specimen. Paratypes: PLA-Po122-123, two whole-mounted specimens; PLA-Po124-126, three serially sectioned (sagittal) specimens; PLA-Po127-129, three mounted prostate stylets.

Etymology. The new species was named as “shenda”, the Pinyin spelling of abbreviated Chinese name of Shenzhen University.

Description. The animal measures 0.8–1.0 mm long and 130–160 μm wide (n=3) ( Fig. 3A ). Mouth opens at anterior 3/5 ventral side of the body at level of the eyes. Pharynx is spherical and 115–120 μm in diameter (n=3) ( Fig. 3 A–B, 4B). Inverted-Y-shaped brownish-yellow stripes are present dorsally, one anterior around eyes and two extending from pharynx to cauda tip. Proboscis is 125–135 μm (n=3) in length. Paired circular black eyes are situated at anterior 1/4 position of the body, 15–20 μm apart (n=3) ( Fig. 3 A–B, 4A–B). The brain lies ventral to the eyes ( Fig. 4B ).

Paired cylindrical testes, 250–300 μm long (n=3), are located at the posterior end of pharynx. The two seminal vesicles lie at midpoint of the body, measuring 220–235 μm long (n=3) ( Fig. 3 B–D, 4B–C). They fuse at their pos- terior ends to form the ejaculatory duct which enters prostate stylet type IV through prostate vesicle type IV. Prostate stylet type IV is tubular, measuring 50–60 μm in length and 20–35 μm in basal diameter (n=5). It bears a slit and a distal fold ( Fig. 3 C–G, 4B–C, E). Prostate vesicle type II (135–150 μm, n=3) lies between the two seminal vesicles with its distal end entering prostate stylet type II ( Fig. 3 C–D, 4B–C). Prostate stylet type II is double-walled (120– 130 μm in length, n=5) and crescent-shaped (10–15 μm in diameter, n=5), with a sharp-pointed distal end where an elongate funnel-shaped inner wall can be observed ( Fig. 3 C–D, H–J, 4B–D). Male atrium lies at posterior 1/4 of the body and is surrounded by strong muscular layer. It opens to the common genital atrium at the point where the spherical male bursa (75–100 μm in diameter, n=3) ( Fig. 3D , 4 B–C) connects to that common atrium.

Paired vitellaria lie dorsal and extend from pharynx to the cauda tip of the body ( Fig. 4 B–C). The paired ellipsoidal ovaries lie in the posterior 1/3 of the body, measuring 75–90 μm long and 40–60 μm wide (n=3) ( Fig. 3B & D , 4 B–C). Female duct type I is connected to two oviducts and bears a sphincter ( Fig. 4 B–C). The seminal receptacle is spherical and sperm-filled ( Fig. 4 B–C); it measures 60–70 μm in diameter (n=3), and connects to the female duct via a coiled duct ( Fig. 3D , 4 B–C).

The gonopore is located ventrally at 1/4 body length from the posterior tip. The uterus bears a bundle of eosinophilic glands ( Fig. 4 B–C) and connects to the anterior end of the common genital atrium. A mature egg is spherical in shape and encloses two embryos ( Fig. 3K ).

Phylogenetic analysis. We compared sequence similarity of 18S rDNA and 28S rDNA using BLAST (BLAST N) of NCBI. The two new species are most similar to Rogneda Uljanin, 1870 . Specifically the 18S and 28S rDNA sequences of P. sinensis n. sp. are most similar to those of Rogneda reticulata Brunet, 1969 (>95%, n=2) and Rogneda sp. 2 (>91%, n=2), respectively; those of P. shenda n. sp. are most near Rogneda sp. 1 (>95%, n=3) and Rogneda sp. 2 (>89%, n=3).

The phylogenetic trees generated from concatenated 18S rDNA and 28Sr DNA sequence by Bayesian-inference (BI) and Maximum Likelihood (ML) methods with Pogaina sp. and Baicalellia beauchampi (Ax, 1956) Stephenson, Van Steenkiste & Leander, 2018 ( Provorticidae of the Dalytyphloplanida ) as outgroups are shown in Figs. 5 , and the two trees agree with each other. The tree is divided into two main clades. The new species form a well-supported clade and share sister-group relationship with Rogneda Uljanin, 1870 , Alcha Marcus, 1949 and Paraustrorhynchus Karling & Schockaert, 1977 . They themselves form two well-supported clades, with both Bootstrap and Bayesian posterior probability indicating 100%, supporting the establishment of two new species.

Figures

FIGURE 3. Pseudorogneda shenda n. gen. n. sp.: (A)free-living specimen; (B) pressed-living specimen; (C–D) partial reproductive organs; (E–G) prostate stylet type IV; (H–J) prostate stylet type II; (K) egg.

FIGURE 4. Pseudorogneda shenda n. gen. n. sp.: (A) pigmentation on the specimen surface; (B) specimen pattern; (C) caudal sagittal view, partial reproductive system; (D) prostate stylet type II; (E) prostate stylet type IV.

FIGURE 5. The phylogenetic tree inferred from concatenated sequences of 18S and 28S rDNA genes, constructed by Bayesian Inference and Maximum Likelihood, with Bayesian posterior probability and Maximum likelihood bootstrap values indicated.