Integrative systematics of northern and Arctic nudibranchs of the genusDendronotus(Mollusca, Gastropoda), with descriptions of three new species

Abstract

The taxonomy of common northern nudibranch molluscs of the genus Dendronotus in the vast cold regions of Eurasia remains largely unknown. Abundant material collected in many localities from the Barents Sea, via the Arctic region, to the north-west Pacific was analysed for the first time. An integrated approach combining morphological and ontogenetic data with molecular four-gene (COI, 16S, H3, and 28S) analysis reveals seven species, including three previously undescribed. Dendronotus frondosus (Ascanius, 1774) and Dendronotus dalli Bergh, 1879 were commonly considered as amphiboreal species; however, according to this study they are restricted to the North Atlantic and the North Pacific, respectively. In the north-west Pacific two new species were discovered, Dendronotus kamchaticus sp. nov. and Dendronotus kalikal sp. nov., that are externally similar to D. frondosus, but that show significant distance according to molecular analysis and are considerably different in radular morphology. In the North Atlantic a new species Dendronotus niveus sp. nov., sibling to North Pacific D. dalli, is revealed. The separate status of North Atlantic Dendronotus lacteus (Thompson, 1840) is confirmed, including considerable range extension. The essential similarity of early ontogenetic stages of radular development common for species with disparate adult radular morphology (such as D. frondosus and D. dalli) is shown, and its importance for taxonomy is discussed.

Two new species and a remarkable record of the genus Dendronotus from the North Pacific and Arctic oceans (Nudibranchia)

“…Stout et al (2010: 7) also suggested that “Further examination of additional specimens from various locations may reveal a complex of species currently considered to be Dendronotus frondosus .” This was fulfilled in a recent revision of the genus Dendronotus by Ekimova et al (2015). In this study two new species ( Dendronotus kalikal Ekimova, Korshunova, Schepetov, Neretina, Sanamyan & Martynov, 2015 and Dendronotus kamchaticus Ekimova, Korshunova, Schepetov, Neretina, Sanamyan & Martynov, 2015) were described from the northwestern Pacific Kamchatka waters, both of which are very similar externally to Dendronotus frondosus .…”

“…Using a combination of external and internal morphological characters, Dendronotus arcticus sp. n. can be distinguished from all recently reviewed species of the genus Dendronotus (Stout et al 2010, Ekimova et al 2015, Martynov et al 2015a, b). The molecular data also support the description of Dendronotus arcticus sp.…”

“… A Dendronotus albus MacFarland, 1966, live specimen ZMMU Op-566, dorsal view, Rich Passage, NE Pacific B same, posterior radular teeth, SEM C Dendronotus kamchaticus Ekimova et al, 2015, live specimen ZMMU Op-565, dorsal and lateral view, Rich Passage, NE Pacific D same, posterior radular teeth, SEM. Scale bars B, D = 30 µm.…”

“…Dendronotus kamchaticus was recently described from Kamchatka in the Russian NW Pacific (Ekimova et al 2015). Here an outstanding and unexpected record of Dendronotus kamchaticus is presented from the American NE Pacific (Washington state).…”

“…Dendronotus kamchaticus was described recently (Ekimova et al 2015) and was thought to be endemic of the NW Pacific. However, in this study a surprising record of Dendronotus kamchaticus from NE Pacific is documented.…”