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Abstract The genus Cyerce Bergh, 1870 has been a model for the study of defensive strategies, including chemical defences, ceratal autotomy, and crypsis or aposematism. Specialization on different algae and diverse genital armatures also make Cyerce a useful system for investigating speciation by host shift versus sexual selection. Here, we review the genus Cyerce in the Pacific and Indian oceans using molecular and morphological data. Two mitochondrial genes (COI and 16S) and one nuclear gene (H3) were sequenced from 154 specimens, including representatives from the Atlantic Ocean. Bayesian and maximum likelihood analyses were used to generate phylogenetic hypotheses. Species delimitation analyses performed on COI sequences recovered 17 genetically distinct Pacific and Indian Ocean species of Cyerce, 10 of which are new to science. Nine new species are named herein (C. takanoi sp. nov., C. katiae sp. nov., C. trowbridgeae sp. nov., C. blackburnae sp. nov., C. tutela sp. nov., C. basi sp. nov., C. whaapi sp. nov., C. goodheartae sp. nov., and C. liliuokalaniae sp. nov.). The 10th species, from the Red Sea, is not named due to the absence of internal anatomical data. These findings increase the species richness in Cyerce by about two-thirds, and demonstrate that even conspicuous taxa harbour considerable cryptic diversity. 

Abstract Sampling impediments and paucity of suitable material for molecular analyses have precluded the study of speciation and radiation of deep-sea species in Antarctica. We analyzed barcodes together with genome-wide single nucleotide polymorphisms obtained from double digestion restriction site-associated DNA sequencing (ddRADseq) for species in the family Antarctophilinidae. We also reevaluated the fossil record associated with this taxon to provide further insights into the origin of the group. Novel approaches to identify distinctive genetic lineages, including unsupervised machine learning variational autoencoder plots, were used to establish species hypothesis frameworks. In this sense, three undescribed species and a complex of cryptic species were identified, suggesting allopatric speciation connected to geographic or bathymetric isolation. We further observed that the shallow waters around the Scotia Arc and on the continental shelf in the Weddell Sea present high endemism and diversity. In contrast, likely due to the glacial pressure during the Cenozoic, a deep-sea group with fewer species emerged expanding over great areas in the South-Atlantic Antarctic Ridge. Our study agrees on how diachronic paleoclimatic and current environmental factors shaped Antarctic communities both at the shallow and deep-sea levels, promoting Antarctica as the center of origin for numerous taxa such as gastropod mollusks.