The Lakshadweep archipelago constitutes a major coral region of India but still lacks sufficient biodiversity data owing to its remoteness and a low number of faunal studies in the past. The present paper describes two new Pseudoceros species collected from Agatti Island, Lakshadweep, India. Pseudoceros bipurpurea sp. nov. and Pseudoceros galaxea sp. nov. are described based on external and internal characters, supported with histological studies and photographs. Pseudoceros bipurpurea sp. nov. is characterized by a cream background colour and an orange median line surrounded by dense patches of purple spots, which tend to disperse and broaden towards the posterior end. Pseudoceros galaxea sp. nov. displays a brown background colour with numerous white to cream dots covering almost the entire dorsal surface and a thin black margin. This study adds two new species to the polyclad fauna in Indian waters, raising the count to 68 species. An updated checklist of polyclads from Indian coast is also provided.

Although marine phylogeographers have accumulated knowledge of the evolutionary history of various invertebrates, there is a large bias among the taxa regarding genetic data. The order Polycladida is a typical example for which little genetic information at population level is available. Here, we focused on the polyclad flatworm Stylochoplana pusilla, distributed in the Japanese Pacific coastal area. Stylochoplana pusilla is known to have commensal relationships with certain intertidal snails, using snails (mainly Monodonta confusa) as a refugee house. During low tide, S. pusilla hides in the mantle cavity of snails to protect themselves from desiccation and predation. Here, we investigated the genetic structure of S. pusilla using a mitochondrial Cytochrome Oxidase I marker and the species diversity of snails used by it. We found that S. pusilla has high genetic diversity of its populations. While S. pusilla showed a significant genetic differentiation among populations, it was relatively low. In addition, we also showed that S. pusilla used several intertidal snail species which inhabit various coastal environments. The present study suggests S. pusilla has sufficient dispersal ability to connect among its local populations. Also, the range of available snails for S. pusilla may help the connectivity among local populations. We provide important knowledge about this invertebrate taxon with a unique ecology, which has been insufficiently studied.