An integrative description of a new interstitial species of Boninia (Platyhelminthes, Polycladida) from the South China Sea

Some members of the genus Boninia are interstitial flatworms that have attracted research attention owing to their miniaturized body size and ecological significance. Here, we establish a new interstitial species of this genus, Boninia corolla sp. nov. , collected from a coarse-grained sandy beach in Huidong, China. The new species is characterized by (i) a narrow and slender body; (ii) 9–15 prostatoid organs with stylets arranged into a single girdle; and (iii) uterine canals connecting to the vagina immediately anterior to the entrance of Lang’s vesicle. Results from both Bayesian Poisson Tree Process (bPTP) and Automatic Barcode Gap Discovery (ABGD) analyses support B. corolla sp. nov. as a distinct species. Molecular phylogenetic analyses based on four gene markers (18S, 28S, 16S, and COI) showed that the new species is nested within a clade composed of other Boninia species. We also calculated genetic distances between species based on the 28S, 16S, and COI markers and found that COI represents the most suitable DNA barcode for distinguishing species within the genus.