Abstract
By means of an integrated approach, including molecular, morphological, anatomical and histological data, we describe a new species of freshwater flatworm of the genus Dugesia from southwest China, representing the third species recorded for the country. Morphologically, the new species, Dugesia umbonata Song & Wang, sp. nov., is particularly characterised by the presence of a muscularised hump immediately antero-dorsally to a knee-shaped bend in its bursal canal and by an ejaculatory duct that opens subterminally through the dorsal side of the penis papilla. Four molecular datasets (18S rDNA; ITS-1; 28S rDNA; COI) facilitated determination of the phylogenetic position of the new species, which belongs to a clade comprising other species from the Australasian and Oriental regions. We also analysed the structure of its major nervous system by means of the acetylcholinesterase (AChE) histochemical method and compared these results with data available for three other species of Dugesia.
Highlights
The genus Dugesia Girard, 1850 currently comprises about 93 valid species and exhibits a distribution that comprises a major part of the Old World and Australia
Saturation analysis revealed that the three non-coding gene datasets (18S rDNA, internal transcribed spacer-1 (ITS-1) and 28S rDNA) exhibited only low levels of substitution saturation (Iss < Iss.c with significant difference; nos. 1–6 in Suppl. material 3: Table S3), irrespective of inclusion of all sites or only fully-resolved sites
The substitution saturation tests of the C oxidase subunit I (COI) datasets revealed that gaps and ambiguous codes significantly influenced the accuracy of the tests
Summary
The genus Dugesia Girard, 1850 currently comprises about 93 valid species and exhibits a distribution that comprises a major part of the Old World and Australia (see Sluys and Riutort 2018: fig. 13B). The genus Dugesia Girard, 1850 currently comprises about 93 valid species and exhibits a distribution that comprises a major part of the Old World and Australia China covers a vast territory, covering six temperature zones, resulting in various types of climate. It is to be expected that variations in climate and other physico-geographical conditions have resulted in a rich biodiversity of freshwater planarians, including species of Dugesia. The Dugesia fauna of China is very poorly known, far only being represented by two species. Dugesia japonica Ichikawa & Kawakatsu, 1964 was the only species recorded for this country (Chen et al 2001). It was only recently that a second species for the genus was described from southern China, viz. Dugesia sinensis Chen & Wang, 2015 (Chen et al 2015)
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