A new species of Cyanea jellyfish sympatric to C. capillata in the White Sea

Cyanea is a genus of large bloom-forming scyphozoans, including some of the most conspicuous representatives of megaplankton. Its taxonomy has been revised repeatedly throughout the last century due to the fact that most of the morphological characteristics of Cyanea species, such as color, structure of gastrovascular system and number of tentacles, may overlap greatly in different populations. Here, we report a new species of Cyanea , Cyanea tzetlinii sp. nov., from the White Sea, which is distinguishable from all previously described Cyanea species by an eye-spot-bearing bulb formed at the base of each rhopalium. This well-recognizable morphological characteristic is supported at the molecular level by a substantial genetic distance in mitochondrial (CO1: 9.6–10.6 %, 16S RNA: 3.1–3.5 %) as well as nuclear (ITS: 5.0 %, 18S RNA: 0.1 %) loci, making it the sister species to Cyanea capillata . Taking into account the young geological age of the White Sea and a substantial genetic divergence between C. tzetlinii sp. nov. and the nearest sister species, we suppose that C. tzetlinii sp. nov. has been advected to the White Sea from elsewhere and may also inhabit other Arctic seas. Past ecological studies in the White Sea and possibly in other Arctic Seas could have conflated C. tzetlinii sp. nov. with other species, which likely affected the analyses.