Abstract
Two new species of the genus Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from the tropical monsoon forest in southern China are described on the basis of an integrative taxonomic study involving morphology, karyology, histology, and molecular analyses. The new species Dugesiacircumcisa Chen & Dong, sp. nov. is characterised by asymmetrical openings of the oviducts; right vas deferens opening at anterior portion of the seminal vesicle and the left one opening at mid-lateral portion of the seminal vesicle; two diaphragms in ejaculatory duct, the latter being ventrally displaced and opening at the tip of the penis papilla, which is provided with a nozzle; wide duct connecting male atrium and common atrium; chromosome complement triploid with 24 metacentric chromosomes. The other new species, Dugesiaverrucula Chen & Dong, sp. nov., is characterised by the large size of the living worm, usually exceeding 3.5 cm in length; asymmetrical openings of the oviducts; subterminal opening of ventrally displaced ejaculatory duct; vasa deferentia symmetrically opening into the postero-lateral portion of the seminal vesicle; well-developed duct between the seminal vesicle and diaphragm; single dorsal bump near the root of the penis papilla; bursal canal with pleated wall and spacious posterior section; unstalked cocoons; chromosome complement diploid with 16 metacentric chromosomes. Inter-specific molecular distances and their positions in the phylogenetic tree reveal that D.circumcisa and D.verrucula are clearly separated from their congeners.
Highlights
D. circumcisa is part of a clade consisting of two other species, viz., D. sinensis and D. semiglobosa, while D. verrucula belongs to another clade that includes the species D. majuscula and D. japonica
In the three first-mentioned species, the ejaculatory duct runs a central course through the penis papilla, in contrast to the ventral trajectories in D. semiglobosa, D. maghrebiana, D. didiaphragma, and the new species D. circumcisa
The copulatory bursa of the latter lacks the complex stratified epithelium, which projects through an opening of the bursa that is present in D. semiglobosa, while it lacks the large seminal vesicle enclosed by a highly muscularised, elongated penis bulb as present in D. didiaphragma and the knob-like extension on the penis papilla of D. maghrebiana
Summary
96 species of the freshwater planarian genus Dugesia Girard, 1850 are distributed in a major portion of the Old World and Australia (Sluys and Riutort 2018; Song et al 2020), with only five species being known from China, viz., Dugesia japonica Ichikawa & Kawakatsu, 1964, D. sinensis Chen & Wang, 2015, D. umbonata Song & Wang, 2020, D. semiglobosa Chen & Dong, 2021, and D. majuscula Chen & Dong, 2021 (Kawakatsu et al 1976; Chen et al 2015; Song et al 2020; Wang et al 2021). We describe for the first time two new species of Dugesia from the tropical monsoon forest in this part of China on the basis of morphological, histological, karyological, and molecular data
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