Proschizorhynchella shibazakii Takeda & Kajihara 2018, sp. nov.
Creators: name: Takeda, Naoya
name: Kajihara, Hiroshi
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Platyhelminthes
Rhabditophora
Rhabdocoela
Schizorhynchidae
Proschizorhynchella
Proschizorhynchella shibazakii

description: Proschizorhynchella shibazakii sp. nov.
(Figs 10–14; Table 1)
Material examined. Holotype: ICHUM 4275, adult, whole mount, 43°12′33″N, 140°51′31″E, Oshoro, Hokkaido, Japan, intertidal sand, 13 June 2011. Paratypes: ICHUM 4276–4278, three adults, whole mounts, same data as holotype; ICHUM 4279, 4280, two adults, serial sagittal sections, same data as holotype; ICHUM 4281, 4282, two adults, serial transverse sections, same data as holotype; ICHUM 4283, one adult, whole mount, type locality, 21 May 2012; ICHUM 4861, egg, whole mount, laid by animals collected on 1 July 2013.
Description. Living animal body approximately 2.6 mm long and 0.5 mm wide (Figs 10, 11A). Four pairs of bristles located at slender anterior tip of body (Figs 10, 11C). Proboscis 350 µm long, 120 µm wide; pair of proboscis glands 140 µm long, 80 µm wide (Fig. 10). Pair of black eyes situated anterior to brain (Figs 10, 11C). Gut anteroposteriorly elongated. Two testes 300–330 µm in diameter (Figs 10, 11C). Pair of yolk glands 1 mm long, 180 µm wide (Figs 10, 11A). Pharynx 480 µm long, 330 µm wide (Figs 10, 11A). Two adhesive girdles present; anterior one located at level of posterior end of pharynx, posterior one near caudal end; each girdle comprised of six adhesive papillae arranged in regular intervals (Figs 10, 11B). Pair of seminal vesicles, each 620 µm long, 60 µm wide, located posterior to pharynx (Fig. 10). Male copulatory organ tubular in shape, 240 µm long, 30 µm wide, with ejaculatory duct surrounded by circular muscles and further surrounded by longitudinal muscles (Figs 10, 12A, B, 13); copulatory organ tapering toward its tip, equipped with stylet and situated in male genital canal. Stylet cone shaped, 29–31 µm long (31 µm in holotype), 7 µm wide, comprised of thin sclerotic sheet rolled up three times (Fig. 12C, D). Male genital canal opens to anterodorsal part of common atrium of the latter (Fig. 13). Uterus 90 µm long, 30 µm wide, anterior to common atrium (Figs 10, 13). Each yolk gland connected to each side of common atrium (Figs 10, 13). Common genital pore opening on ventral side of body between two adhesive girdles (Figs 10, 13). Ovary 110 µm long, 70 µm wide, anteriorly connected to posterodorsal portion of common atrium via a common oviduct (Figs 10, 13). Bursa oval in dorsal view, 250 µm long, 150 µm wide; bursal tissue divided into two (smaller anterior and larger posterior) parts by constriction; spermatids observed in posterior bursal tissue in all specimens observed; anterior bursal tissue leading forward to connect to common oviduct near ovary via narrow sperm duct (Figs 10, 13). Egg oval, 260 µm long, 200 µm wide, covered in brown shell with colorless axis (Fig. 14).
Etymology. The specific name is a noun in the genitive case, derived from the name Mr. Kouji Shibazaki, a caretaker of Oshoro Marine Station, Hokkaido University.
Remarks. Proschizorhynchella shibazakii can be distinguished from all congeners based on the characteristics listed in Table 1 except P. papillata. These two species, however, can be distinguished based on the shape of the male copulatory organ. The differences in morphological characteristics between P. shibazakii sp. nov. and P. papillata are (i) the number of the apical sensory bristles, which is eight in P. shibazakii and four in P. papillata; (ii) the male copulatory organ, which is narrow and tubular in P. shibazakii, and bulb shaped in P. papillata; (iii) the internal part of the circular muscles, which is thin in P. shibazakii but thick in P. papillata; (iv) the border cells which are present in P. shibazakii but absent in P. papillata; and (v) the length of the stylet, which is 29–31 µm (31 µm in holotype) in P. shibazakii and 55–57 µm in P. papillata. Proschizorhynchella shibazakii cannot be distinguished from P. caudociliata based on the characteristics listed in Table 1; however, they differ in the structure of the copulatory stylet (see Remarks for P. caudociliata).
description: Published as part of Takeda, Naoya & Kajihara, Hiroshi, 2018, A New Genus and Five New Species of Kalyptorhynchia (Platyhelminthes: Rhabdocoela) Discovered in Northern Japan, pp. 1-11 in Species Diversity 23 (1) on pages 8-9, DOI: 10.12782/specdiv.23.1, http://zenodo.org/record/4583800