Two new species of palaemonid shrimp associated with ascidian hosts, Odontonia bagginsisp. n. from Tidore and Odontonia plurellicolasp. n., from Ternate, Indonesia are described and figured. Through phylogenetic analyses based on both morphological and molecular datasets (mitochondrial Cytochrome c oxidase subunit I gene and the 16S mitochondrial ribosomal gene) of the genus Odontonia, the phylogenetic positions of the new species have been reconstructed. Scanning Electron Microscopy has been used to observe additional characters on dactyli of the ambulatory pereiopods. Odontonia plurellicolasp. n. appears to be more closely related to O. simplicipes and O. seychellensis, but it differs most notably in the morphology of the rostrum and mouthparts. Odontonia plurellicolasp. n. appears to be the only Odontonia species living inside a phlebobranch ascidian Plurella sp. Odontonia bagginsisp. n. is closely related to O. sibogae, but differs markedly in the abundance of setae on the propodi of the ambulatory pereiopods. In the present paper, O. maldivensis Fransen, 2006 is regarded as a junior synonym of O. rufopunctata Fransen, 2002 based on both morphological and molecular aspects.
Keywords: Ascidians; Caridea; Odontonia; Palaemonidae; Ternate; Tidore; new species; symbiosis.