Notes on Renschetrema Rohde, 1964

The transfer of A. bushae from Renschetrema into the newly erected genus Armadoatrium requires amendment of the current diagnosis of Renschetrema. We have also made additional morphological observations of Renschetrema that require changes in the diagnosis of the genus.

Rohde (1964) stated that the male and female genital pores of Re. malayi are situated at a significant distance from each other. Matskási (1973) in his description of Re. rohdei also reported male and female genital pores as separate. Based on our examination of museum specimens and published illustrations, it is obvious that most, if not all, previously studied and described specimens of Renschetrema were of unsatisfactory quality. As part of the present study, we examined type specimens of Renschetrema spp. deposited by Klaus Rohde in the collection of the Natural History Museum, London. They were strongly pressed under the coverslip during their fixation. Our study revealed that Rohde (1964) has probably mistaken an optical section of the distal part of the uterus at one of the turning points for the female genital pore. Another possibility is that Rohde (1964) and Matskási (1973) have mistaken Laurer’s canal opening on the dorsal side of the body for the female genital pore. In the present study, we had the opportunity to examine the morphology of a good-quality specimen of the type species of the genus, Re. malayi, collected in Vietnam. In that specimen, the uterus clearly terminates in the common genital atrium with the male terminal genitalia and the stylet sac. The same was reported by Chermak and Tkach (2022) in high-quality specimens of the closely related genus Armadoatrium. We have also observed the opening of Laurer’s canal in Re. malayi in the area where previous authors showed the female genital pore. Thus, the statement regarding separate male and female genital pores in Renschetrema was erroneous.

By examining unstained and unmounted specimens, we have also confirmed, for the first time, that the stylet in Renschetrema can be at least partly evaginated from the stylet pouch through the genital atrium and plays a role in sperm release (Fig. 3A), although the mechanism remains unclear.

Likewise, careful study of the high-quality specimen of Re. malayi confirmed the presence of a copulatory pouch in this species, contrary to diagnosis of the genus by Deblock (2008), who stated that the male terminal genitalia and the prostatic gland are free in the parenchyma. Our results are in agreement with the observations of Chermak and Tkach (2022), who reported a copulatory pouch in the closely related genus, Armadoatrium.

Kifune (1984) described the species Renschetrema indicum Kifune, 1984 from bats in India. The author did not mention whether the genital pore in Re. indicum is dorsal or ventral. Most importantly, the digenean described by Kifune (1984) did not have the highly characteristic feature of Renschetrema, namely the stylet and stylet sac. Therefore, we reject its placement in Renschetrema. The true systematic position of this species remains unclear.

The amended diagnosis of Renschetrema, incorporating new morphological details, is provided below.