Ptychopera japonica Ax 2008
Creators: name: Van Steenkiste, Niels W. L.
name: Leander, Brian S.
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabdocoela
Trigonostomidae
Ptychopera
Ptychopera japonica

description: Ptychopera japonica Ax, 2008: 356–358, figs 160–161.
New locality: Mud Bay Park, Surrey, British Columbia, Canada (49°05 ′ 09 ″ N, 122°51 ′ 39 ″ W), mud and algae in intertidal mudflat (29/07/2015; 26/10/2015).
Known distribution: Northwest Pacific Ocean: Japan (Ax, 2008).
Material: Observations on eight live animals. Five whole mounts (BBM MI4050 – MI4054). 18S rRNA (G e n B a n k a c c e s s i o n # M F3 2 1 7 5 1), 2 8S r R N A (GenBank accession # MF321760).
Remarks: Animals about 0.5 mm long. Live specimens with a parenchymatous brownish to reddish coloration (Fig. 6A). General appearance typical of species of Ptychopera with the pharynx in the first third of the body right behind the lenticular eyes. Epidermis with oblong rhabdites.
Internal organization similar to other species of Ptychopera with paired testes and paired seminal vesicles entering the large, globuliform copulatory bulb. The large bursa appears striated and its basement membrane is slightly sclerotized (Fig. 6F). It connects to the seminal receptacle through a slender, slightly sclerotized spermatic duct provided with a sphincter. The seminal receptacle in turn connects to the female system through another longer, slightly sclerotized duct (‘bursal appendage’ in Den Hartog, 1964). Paired ovaries and vitellaria.
The stylet measures 67–78 μ m (x = 70 μ m; n = 5) and consists of two curved, funnel-shaped and digitiform tubes surrounded by a folded sclerotized mantle that distally ends in a large triangular plate with a serrated edge (Fig. 6F). The digitiform tubes are of equal length, but differ in width with the wider tube being the stylet proper for the evacuation of sperm and prostate secretion. The more narrow tube connects to the sclerotized mantle at its base. The triangular plate folds over in its proximal half and continues as a weakly sclerotized girdle surrounding and connecting to the stylet in its middle portion. The proximal part of the stylet consists of the bases of the two digitiform plates and has several folds. A slightly curved, slender spur protrudes from the outer edge of one of these folds on the outer side of the larger digitiform tube (arrow in Fig. 6F).
Ptychopera japonica was first described by Ax (2008) from brackish salt marshes on the Pacific coast of Japan. Our specimens clearly belong to this species based on the morphology of the stylet. While the different parts of the stylet are discernable in the pictures of the Japanese specimens (see Ax, 2008: 357, fig. 161), Ax did not recognize the triangular plate as a separate structure and wrongly attributes the serrated edge to the larger digitiform tube. Furthermore, specimens from Japan lack pigment and have a slightly shorter stylet (up to 62 μ m).
As already mentioned by Ax (2008), P. japonica is probably closely related to P. westbladi and P. plebeia (Beklemischev, 1927) Den Hartog, 1964. The stylets of P. westbladi and P. plebeia also consist of two more or less funnel-shaped tubes and a sclerotized mantle with several folds, plates or protrusions. Particularly, the stylet of P. westbladi is similar to the stylet of P. japonica, but it lacks a serrated triangular plate and it also has a large projection that extends to the tip of the stylet. This structure is possibly homologous with the smaller spur-like projection of the stylet in P. japonica. The stylet of P. plebeia lacks a projection and serrated mantle edges.
description: Published as part of Van Steenkiste, Niels W. L. & Leander, Brian S., 2018, Molecular phylogeny of trigonostomine turbellarians (Platyhelminthes: Rhabdocoela: Trigonostomidae), including four new species from the Northeast Pacific Ocean, pp. 237-257 in Zoological Journal of the Linnean Society 182 on pages 250-251