A Radical Solution: The Phylogeny of the Nudibranch Family Fionidae

Abstract

Tergipedidae represents a diverse and successful group of aeolid nudibranchs, with approximately 200 species distributed throughout most marine ecosystems and spanning all biogeographical regions of the oceans. However, the systematics of this family remains poorly understood since no modern phylogenetic study has been undertaken to support any of the proposed classifications. The present study is the first molecular phylogeny of Tergipedidae based on partial sequences of two mitochondrial (COI and 16S) genes and one nuclear gene (H3). Maximum likelihood, maximum parsimony and Bayesian analysis were conducted in order to elucidate the systematics of this family. Our results do not recover the traditional Tergipedidae as monophyletic, since it belongs to a larger clade that includes the families Eubranchidae, Fionidae and Calmidae. This newly recovered clade is here referred to as Fionidae, the oldest name for this taxon. In addition, the present molecular phylogeny does not recover the traditional systematic relationships at a generic level, and therefore, systematic changes are required. We recognize the following clades within Fionidae: Calma, Cuthona, Cuthonella, Eubranchus, Fiona, Murmania, Tenellia, Tergipes, Tergiposacca gen. nov., Rubramoena gen. nov. and Abronica gen. nov. The type species of Tergiposacca, T. longicerata nov. sp. is described. The other two new genera have a previously described species as their type species. Most of these taxa, with the exceptions of Eubranchus, Tergipes and Fiona are composed of radically different constituent species from their traditional membership, but appear to be supported by morphological synapomorphies as well as molecular data. Aenigmastyletus, Catriona, Phestilla, Tenellia and Trinchesia are nested within other clades and, thus are here considered as synonyms of the larger clades. The phylogenetic position and validity of Myja, Guyvalvoria, Leostyletus and Subcuthona still need to be tested in future studies when material becomes available.

Astonishing diversity revealed: an annotated and illustrated inventory of Nudipleura (Gastropoda: Heterobranchia) from Mozambique

“…The radula is typical of the genus. This species appears to be undescribed and it is illustrated by Gosliner et al (2015) and sequenced by Cella et al (2016). Nevertheless, further studies are needed to confirm its identification and geographic range.…”

“…A phylogenetic review of the aeolid family Tergipedidae by Cella et al (2016) found that this family was not monophyletic. In order to keep the monophyly of the group, the authors established a new classification uniting the Tergipedidae, Eubranchidae and Calmidae under the older family name Fionidae.…”

Phestilla subodiosus sp. nov. (Nudibranchia, Trinchesiidae), a corallivorous pest species in the aquarium trade

“…While many Nudibranchia species and genera have yet to be described (Gosliner et al 2015), the deeper relationships in the systematics of several superfamilies and families within this group have been repeatedly investigated and revised in taxonomic and systematic studies employing both morphological and molecular techniques (Wägele and Willan 2000;Carmona et al 2013;Cella et al 2016;Korshunova et al 2017aKorshunova et al , b, c, 2018aKorshunova et al , b, 2019aMartynov et al 2019). The superfamily Fionoidea is one of these groups that was recently investigated phylogenetically with genetic markers (Wägele and Willan 2000;Cella et al 2016). Based on a phylogenetic hypothesis and morphological reasoning, Cella et al (2016) combined several families (Calmidae, Tergipedidae, Eubranchidae, Cuthonidae, and Trinchesiidae) into the family Fionidae, and several genera (Catriona, Phestilla, and Trinchesia) along with several species from Cuthona into the genus Tenellia.…”

“…The superfamily Fionoidea is one of these groups that was recently investigated phylogenetically with genetic markers (Wägele and Willan 2000;Cella et al 2016). Based on a phylogenetic hypothesis and morphological reasoning, Cella et al (2016) combined several families (Calmidae, Tergipedidae, Eubranchidae, Cuthonidae, and Trinchesiidae) into the family Fionidae, and several genera (Catriona, Phestilla, and Trinchesia) along with several species from Cuthona into the genus Tenellia. However, strong defining morphological characteristics were not suggested and "beyond the scope" of the study.…”

A Victorian emigrant: first observation and range extension of the nudibranch Tenellia catachroma (Burn, 1963) in Western Australia (Mollusca: Gastropoda)

“…At the time, Burn included T. catachroma in the genus Catriona Winckworth, 1941, subgenus Eurycatriona, due to its ceratal and radular morphology, but it was later accepted as Trinchesia Von Ihering, 1879after Miller (2004 (Burn 2006). Most species formerly in Trinchesia are now incorporated in the genus Tenellia A. Costa, 1866 as a result of the phylogenetic work of Cella et al (2016).…”