Integrative description of three new species of Dugesia (Platyhelminthes, Tricladida, Dugesiidae) from Henan Province, central China

Three new species of the genus Dugesia from Henan Province in central China, Dugesia tongbaiensis Chen & Zhang, sp. nov., Dugesia fangchengensis Chen & Zhang, sp. nov., and Dugesia lushanensis Chen & Zhang, sp. nov. are described based on an integrative approach involving morphological, histological, karyological, and molecular analyses. Dugesia tongbaiensis is characterized by the following features: a long duct intercalated between the slender saclike seminal vesicle and the diaphragms; two well-developed adjacent diaphragms, with the posterior one larger than the anterior one; an ejaculatory duct running a central course through the penis papilla with a terminal opening; a mixoploid karyotype with diploid chromosome portrait of 2 n = 2 x = 16 and triploid chromosome complement of 2 n = 3 x = 24, and all chromosomes being metacentric.

Dugesia fangchengensis is characterized by the following features: two asymmetric bumps on the middle of the penis papilla, giving it an approximately gyroscopic shape; a pointed diaphragm located at the mid-length of the penis papilla; a short ejaculatory duct displaced ventrally with terminal opening; an asymmetric penis papilla whose dorsal lip is thicker than its ventral one; a mixoploid karyotype comprising diploid (2 n = 2 x = 16) and triploid (2 n = 3 x = 24) metacentric chromosome complements.

Dugesia lushanensis is characterized by the following features: a strongly asymmetric penial valve existing at the base of the penis papilla, with the dorsal portion much larger than the ventral one; a well-developed diaphragm separating the ellipsoidal seminal vesicle from the inverted V-shaped ejaculatory duct; a ventrally displaced ejaculatory duct with a subterminal opening; a highly asymmetric penis papilla, with the dorsal lip thicker and longer than the ventral one; a dorsal bump positioned at halfway the length of the penis papilla.

This species exhibits a purely diploid karyotype (2 n = 2 x = 16) with entirely metacentric chromosomes. The three new species are nested within the Eastern Palearctic / Oriental / Australasian clade but form distinct subgroups in the molecular phylogenetic tree. Their valid species status is supported by molecular genetic distance analyses.