Phylogeny, biogeography, and systematics of Branchipolynoe (Polynoidae, Annelida), with descriptions of four new species from Costa Rican methane seeps

There are currently four named species of Branchipolynoe, all found living symbiotically in mytilid mussels in the genus Bathymodiolus, which all occur at hydrothermal vents or methane seeps. Here, phylogenetic analyses using mitochondrial (CO1 and 16S) and nuclear (ITS) genes, as well as morphological analysis were conducted on a collection of Branchipolynoe from Pacific Costa Rican methane seeps. This revealed four new species of Branchipolynoe and these are formally described here. These newly discovered species live in three different species of Bathymodiolus mussels (also new) at depths ranging from 1000 m to 1800 m. Branchipolynoe kajsae sp. nov. and Branchipolynoe halliseyae sp. nov. are found in hosts Bathymodiolus billschneideri, B. earlougheri, and B. nancyschneiderae. Branchipolynoe meridae sp. nov. is found in hosts Bathymodiolus earlougheri and B. billschneideri. Branchipolynoe eliseae sp. nov. is found in hosts Bathymodiolus billschneideri and B. nancyschneiderae. The phylogenetic and biogeographical implications of this high sympatric diversity of Branchipolynoe are discussed