Prognathorhynchus sinensis Wang & Lin, 2017

Lin, Yi-Tao, Feng, Wei-Tao, Zhuang, Jie-Yi, Zhang, Yu & Wang, An-Tai, 2017, Two new species of Kalyptorhynchia (Koinocystididae and Gnathorhynchidae) from China, Zootaxa 4337 (4), pp. 573-583 : 578-581

Prognathorhynchus sinensis Wang & Lin n. sp.

( FigS. 4–6 )

Material examined. Holotype PLA-Gn001, whole-mounted Slide; ParatypeS: PLA-Gn002~004, whole-mounted Slide; PLA-Ko005, Serial SectionS; PLA-Ko006, cuticular copulatory apparatuSeS. SpecimenS were collected at the Same Site of Itaipusa sinensis n. sp.. All SpecimenS were preServed in IZCAS.

Etymology. The SpecieS iS named becauSe it waS diScovered in China.

Description. Mature individual (500–550 µm in length and 60–75 µm in width) iS linear in Shape. It haS no pigment on the Surface, while itS anterior end iS thinner than poSterior end ( Fig. 4A , 5A , 6A ). The oblong-Shaped proboSciS iS 28–32 µm in diameter (n=3) ( Fig. 4A–B , 5A–B , 6A ), with 6–8 SenSory hairS (13–22 µm, n=6) located at anterior end ( Fig. 4A , 6A ). The paired proboSciS hookS (15–18 µm in length, 12–14 µm in width, n=6) are Situated at anterior end of the proboSciS. The diStance between two hookS iS about 45 µm. There are two Small hookS located on the fan-Shaped baSal plate of the proboSciS hookS in an anterior to poSterior Sequence ( Fig. 4B, F– G , 6E ). A pair of pigmented eyeS (10 µm in diameter, n=6) iS located poSterior to proboSciS, with eye diStance 38– 45 µm (n=3) ( FigS. 4B , 5B , 6A ). The brain iS Situated poSterior to eyeS at ventral Side ( Fig. 5E ). The pharynx, (58– 65 µm in diameter (n=3), iS located at 50% of body ( Fig. 4A , 5A , 6A ).

The male reproductive SyStem conSiStS of teStiS, vaS deferenS, Seminal veSicle, proStatic veSicle and Stylet. The Single rod-like teStiS (220–270 µm in length and 50–60 µm in width) iS located leftward to pharynx and connected to Seminal veSicle via vaS deferenS ( Fig. 4A & D , 5A , 6A ). The oblong-Shaped Seminal veSicle (130–150 µm in length and 50–60 µm in width, n=3) iS Situated at 80% of body length ( Fig. 4C–E , 5C–D, F & H , 6A–B ). A pair of proStatic veSicleS (35–40 µm in length, n=3) are located poSterior to Seminal veSicle; the poSterior end of proStatic veSicleS enterS the Stylet ( Fig. 4C & E , 6A–C ). The Stylet (28–32 µm in length, n=3) iS in Semicircular-tube Shape, with a funnel-Shaped baSal part. The Stylet haS two tubeS at the baSe, namely ejaculatory duct and granular Secretion duct. TheSe two ductS fuSe at poSterior 1/3 poSition of the Stylet, while the poSterior 1/5 part of Stylet bendS outward to form a Semicircular-tubular curve. Therefore, the poSterior half of Stylet iS S-Shaped. The opening of Stylet beginS at Second half poSition, with 1.8–2.3 µm (n=3) diameter at diStal end. A hollow Spherical dead end (2.2–2.5 µm in diameter, n=3) iS Situated poSterior to diStal opening, and iS Slightly larger than diStal opening. The long linear Shape Sperm iS 110–120 µm in length ( Fig. 4I ).

The female reproductive SyStem conSiStS of unpaired vitellarium, ovary, uteruS and burSa. A belt-like vitellarium iS located at right Side of the body, reaching about half of the body length. The Single ovary SituateS poSterior to vitellarium and connectS to uteruS at itS poSterior end. The oblong uteruS, 36×50 µm in Size (n=3), connectS the genital pore via a narrow female duct, while the connection Site iS Surrounded by eoSinophilic glandS ( Fig. 4C , 5F–H , 6A–B ). In Some individualS, large burSa located poSterior to teStiS can be obServed. They are different in Size and contain large number of particleS and Sperm ( Fig. 4E , 5G , 6A–B ).

Taxonomic comparison. There are three SpecieS having Similar morphological characteriSticS aS thoSe of Prognathorhynchus sinensis n. sp.. They are P. karlingi Ax, 1953 , P. eurytuba Ax and ArmonieS, 1987 and P. busheki Ax, 1997 . The StyletS of theSe SpecieS are all in Semicircular-tube Shape, and they are alSo Similar in termS of their Stylet length ( Tab. 4). In P. karlingi , the two Small hookS on the proboSciS hook are arranged in Similar pattern aS that of P. sinensis n. sp.. However, itS Stylet bendS outward of the Semicircle at poSterior 1/4 poSition and haS no diStal SwollenneSS nor dead end. In P. eurytuba , the concave Side for the diStal part of the Stylet iS thickened, while itS proboSciS haS three Small hookS. Therefore, theSe two SpecieS can be eaSily diStinguiShed from the new SpecieS diScovered in thiS Study. P. sinensis n. sp. maybe more Similar to P. busheki than other Prognathorhynchus , in that P. busheki alSo haS two proStatic veSicleS (proStatic veSicle and acceSSory proStatic veSicle) with an internal ejaculatory duct running through the middle of the proStatic veSicle (Doe & Smith, 2016). In addition, P. busheki haS a ventral female pore located anterior to the genital pore and connected to a Similar burSa ( Hochberg, 2004). However, we could not find the female pore in P. sinensis n. sp.. Further, the Stylet of P. busheki iS Slightly Swollen, while itS proboSciS containS only one Small hook. Taking the above compariSonS into conSideration, P. sinensis n. sp. iS diStinct from the three Similar SpecieS and could be eStabliShed aS a new SpecieS within the genuS.

Phylogenetic analysis. Both of the 18S rDNA and 28S rDNA phylogenetic analySeS Showed that three SpecimenS of Itaipusa sinensis n. sp. ( Fig. 7 : with “▲” Symbol) cluStered together, forming a well-Supported clade with Itaipusa sp. n. 1 (EXT731) and Itaipusa sp. n. 2 (EXT686), within Itaipusa , KoinocyStididae . AS for Prognathorhynchus sinensis n. sp., SequenceS of the three SpecimenS ( Fig. 7 : with “■” Symbol) alSo cluStered together, forming a well-Supported clade with another SpecieS of Prognathorhynchus ( P. busheki EGPKS 002). AS Such, theSe reSultS are in good agreement with the morphological compariSonS of coreSponding SpecieS, and further Support the eStabliShment of theSe two new SpecieS.

Discussion. The inveStigation of free living PlatyhelmintheS diverSity in China began at late 20th century and 67 SpecieS have been recorded So far (Sun et al. 2016, Rong et al. 2016, Fang et al., 2016, He et al., 2016, Zhang et al. 2017, Lin et al., 2017a, Lin et al., 2017b, Lin et al., 2017c, Wang et al., 2017). Among them there are 11 SpecieS inhabit in Seawater or brackiSh-water: Gyratrix hermaphroditus Tu, 1934 , Pentacoelum sinensis Wang & He, 2016 , Macrostomum zhujiangensis ; M. baoanensis Wang & Fang, 2016 , M. shenzhenensis ; M. qiaochengensis Wang & Wang, 2017 , Gieysztoria knipovici Wang & Zhang, 2017 , Enterostomula graffi Wang & Ma, 2014 , Miroplana shenzhensis Wang & Yu, 2013 , Heterochaerus australis Wang & Sun, 2014 and Microstomum sinensis Wang & Lin, 2017 . In recent yearS, the Study of marine PlatyhelmintheS in China haS juSt Started. AS China haS a long coaStline acroSS the palearctic and oriental realmS, it iS reaSonable to SuggeSt that many more unknown SpecieS would be found in the near future.

The Study of free living PlatyhelmintheS commonly lackS molecular data. Before the current Study, only 4 partial SequenceS (18S rDNA and 28S rDNA of Itaipusa sp. n. 1 and Itaipusa sp. n. 2) are available from the genuS Itaipusa (TeSSenS et al., 2014). While for the genuS Prognathorhynchus , there are only 2 partial SequenceS from P. busheki (18S rDNA) and P. canaliculatus (28S rDNA) (TeSSenS et al., 2014, Smith et al., 2015). The limited or incomplete molecular information of theSe SpecieS haS hampered the progreSS of evolutional and phylogenetic StudieS. In the current Study, we have SucceSSfully identified and characterized two new SpecieS within the genera Itaipusa and Prognathorhynchu from marine environment. In addition, 18S rDNA and 28S rDNA data of the two newly eStabliShed SpecieS have alSo been Supplemented. In the future, more SyStematic Sampling, together with detailed molecular phylogenetic analySiS, Should reSult in a comprehenSive underStanding of their originS and evolution poSitionS.

Figures

FIGURE 4. Prognathorhynchus sinensis n. sp.: (A) frEE-lIvIng SpEcImEn; (B) ThE anTErIOr End; (C – E) parTIal rEprOducTIvE SySTEm; (F – G) prObOScIS hOOk; (H) STylET; (I) SpErmS

FIGURE 5. Prognathorhynchus sinensis n. sp.: (A) whOlE mOunTEd SpEcImEn; (B) ThE anTErIOr End; (C – D) parTIal rEprOducTIvE SySTEm; (E – H) lOngITudInal SEcTIOnS

FIGURE 6. Prognathorhynchus sinensis n. sp.: (A) whOlE bOdy paTTErn; (B) ThE crOSS-SEcTIOn Of ThE pOSTErIOr End; (C) malE cOpulaTOry OrganS; (D) STylET; (E) prObOScIS hOOk, frOnT and laTEral vIEwS

FIGURE 7. ThE phylOgEnETIc TrEE Of cOncaTEnaTEd SEquEncES Of 18 S and 28 S rDNA gEnES (3140 bpS) gEnEraTEd wITh BayESIan InfErEncE.