Astiotrema emydis Ejsmont, 1930

Karar, Yasser F. M., Blend, Charles K., Dronen, Norman O. & Adel, Asmaa, 2021, Towards resolving the problematic status of the digenean genus Astiotrema Looss 1900: An updated concept and revision of species composition for Astiotrema (sensu stricto), Zootaxa 4991 (1), pp. 36-72 : 50-52

Astiotrema emydis Ejsmont, 1930

( Figs. 15 & 16 )

(Syn.: Leptophallus emydis [ Ejsmont, 1930] Yeh & Fotedar, 1958)

Records (see Table 1 ): 1. Ejsmont (1930); 2. Modrzejewska (1938).

Remarks: Ejsmont (1930) proposed A. emydis for specimens from the stomach and duodenum of the European pond turtle, Emys orbicularis (Linnaeus) ( Testudines : Emydidae ), from Poland. Yeh & Fotedar (1958) proposed removal of A. emydis to Leptophallus Lühe, 1909 ; however, no reasons were given for this reassignment. Following comparison of A. emydis with two closely related species, Leptophallus nigrovenosus ( Bellingham, 1844) Lühe, 1909 and Metaleptophallus gracillimus ( Lühe, 1909) Yamaguti, 1958 , Grabda-Kazubska (1961) concluded that the transfer of A. emydis to Leptophallus was mistaken based on the fact that A. emydis can be distinguished from species of Leptophallus by the former having a seminal receptacle and a large cirrus-pouch of a different structure without an external seminal vesicle. Grabda-Kazubska (1961) recommended that A. emydis should be retained within Astiotrema . Agrawal (1966a) concurred with Grabda-Kazubska (1961) and also noted that A. emydis could be easily distinguished from Leptophallus based on the nature of the vitellarium and the position of the cirrus-pouch.

The most obvious intra-specific variation observed in this species concerns the position of the cirrus-pouch relative to the ventral sucker and ovary; it varies from either situated between ovary and ventral sucker (i.e., ventral sucker sinstral to both cirrus-pouch and ovary) (see dorsal mount of Ejsmont 1930, fig. 1) or sinistral to both ventral sucker and ovary (i.e., ventral sucker between ovary and cirrus-pouch) (see ventral mount of Modrzejewska 1938, fig. 1). Astiotrema emydis is characterized by the following diagnostic combination of morphological features: (i) oral sucker conspicuously larger than ventral sucker, (ii) vitelline fields short, extend from level midway between ventral sucker and intestinal bifurcation to level immediately posterior to posterior testis, and the anteriormost extent of vitelline fields confluent medially in pre-acetabular region, (iii) ceca long and terminate near posterior extremity or slightly anterior, (iv) ovary is either the size of testes or slightly larger and it is closer to the ventral sucker than anterior testis and (v) the esophagus of A. emydis is indistinct.

Astiotrema reniferum is similar to A. emydis in its ceca extent but these species can be easily differentiated by (i) an oral sucker larger than ventral one in A. emydis vs suckers roughly equal in size in A. reniferum ; (ii) A. emydis has an ovary slightly larger or equally-sized with the testes vs A. reniferum with an ovary distinctly smaller than both testis; (iii) the post-testicular area in A. emydis is larger and exceeds 2/5 of body length vs A. reniferum with a smaller area that does not exceed 1/4 of body length; (iv) A. reniferum has a distinctly long esophagus vs A. emydis with an indistinct esophagus; and (v) the vitelline field anterior to the ventral sucker is confluent in A. emydis vs not confluent in A. reniferum .

Figures

FIGURES 15 & 16. Intra-specific variations observed in Astiotrema emydis Ejsmont, 1930. 15. A. emydis, dorsal view, redrawn from Ejsmont (1930, fig. 1). 16. A. emydis, ventral view, redrawn from Modrzejewska (1938, fig. 1). Abbreviations:AT, anterior testis; Ce, cecum; CP, cirrus-pouch; EP, excretory pore; Es, esophagus; EV, excretory vesicle; GP, genital pore; OD, ovarian duct; OS, oral sucker; Ov, ovary; P.Ph, prepharynx; Ph, pharynx; PP, pars prostatica; PT, posterior testis; SR, seminal receptacle; SV, seminal vesicle; Ut, uterus; VD, vitelline duct; V-D, vas-deferens; VF, vitelline follicle; VR, vitelline reservoir; VS, ventral sucker. Scale bars: Fig. 15 = 500 µm; Fig. 16 = 500 µm.