Abstract
Two new species of the genus Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from Hainan Island of China are described on the basis of morphological, karyological and molecular data. Dugesia semiglobosa Chen & Dong, sp. nov. is mainly characterized by a hemispherical, asymmetrical penis papilla with ventrally displaced ejaculatory duct opening terminally at tip of penis papilla; vasa deferentia separately opening into mid-dorsal portion of intrabulbar seminal vesicle; two diaphragms in the ejaculatory duct; copulatory bursa formed by expansion of bursal canal, lined with complex stratified epithelium, which projects through opening in bursa towards intestine, without having open communication with the gut; mixoploid chromosome complement diploid (2n = 16) and triploid (3n = 24), with metacentric chromosomes. Dugesia majuscula Chen & Dong, sp. nov. is mainly characterized by oviducts opening asymmetrically into female reproductive system; hyperplasic ovaries; expanded posterior section of bursal canal; vasa deferentia separately opening into mid-dorsal portion of seminal vesicle; asymmetrical penis papilla due to ventral course of ejaculatory duct, which has subterminal and dorsal opening at tip papilla; mixoploid chromosome complement diploid (2n = 16) and triploid (3n = 24); chromosomes metacentric. Apart from their anatomy, separate species status of the two new species is supported also by their genetic distances and by their positions in the phylogenetic tree. The sexualization process may have been induced by the lower temperatures, in comparison with their natural habitat, under which the worms were cultured in the laboratory.
Highlights
94 species of the freshwater planarian genus Dugesia Girard, 1850 have been reported from a major portion of the Old World and Australia (Sluys and Riutort 2018; Song et al 2020)
The phylogenetic trees and their supporting values resulting from the analysis of the concatenated dataset are very similar for both ML and Bayesian Inference (BI), differing only in nodes weakly supported in at least one of the methodologies (Fig. 2; Suppl. material 1: Figure S1).The new species D. majuscula and D. semiglobosa occupy separate branches that are clearly differentiated from their congeners
Dugesia semiglobosa is characterized by the following features: hemispherical, asymmetrical penis papilla with ventrally displaced ejaculatory duct opening terminally at tip of penis papilla; absence of duct intercalated between seminal vesicle and diaphragm; vasa deferentia separately opening into mid-dorsal portion of intrabulbar seminal vesicle; two diaphragms in the ejaculatory duct; symmetrical openings of oviducts into bursal canal; copulatory bursa formed by expansion of bursal canal, lined with complex stratified epithelium, which projects through opening in bursa towards intestine, without having open communication with the gut; mixoploid chromosome complement diploid (2n = 16) and triploid (3n = 24); chromosomes metacentric
Summary
94 species of the freshwater planarian genus Dugesia Girard, 1850 have been reported from a major portion of the Old World and Australia (Sluys and Riutort 2018; Song et al 2020). 22 species of Dugesia are known from the Oriental region (Sluys et al 1998), while only three species have been recorded from China, viz., D. japonica Ichikawa & Kawakatsu, 1964, D. sinensis Chen & Wang, 2015, and D. umbonata Song & Wang, 2020 (Kawakatsu et al 1976; Chen et al 2015; Song et al 2020). 158) recorded the occurrence of Dugesia on Hainan Island from three localities, no information was provided on the taxonomic identity of the species. In this paper we describe for the first time two new species of Dugesia from Hainan Island, which form new species to the planarian fauna of China, on the basis of an integrative taxonomic approach, using morphological, karyological, and molecular data
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