A new genus-level classification of the Conoidea is presented, based on the molecular phylogeny of Puillandre et al. in the accompanying paper. Fourteen lineages are recognized and ranked as families to facilitate continuity in the treatment of the names Conidae (for 'cones') and Terebridae in their traditional usage. The hitherto polyphyletic 'Turridae' is now resolved as 13 monophyletic families, in which the 358 currently recognized genera and subgenera are placed, or tentatively allocated: Conorbidae (2 (sub)genera), Borsoniidae (34), Clathurellidae (21), Mitromorphidae (8), Mangeliidae (60), Raphitomidae (71), Cochlespiridae (9), Drilliidae (34), Pseudomelatomidae (= Crassispiridae) (59), Clavatulidae ( 14), Horaiclavidae new family (28), Turridae s. s. (16) and Strictispiridae (2). A diagnosis with description of the shell and radulae is provided for each of these families.
The superfamily Conoidea (Mollusca: Gastropoda) constitutes one of the most diverse and taxonomically challenging groups among marine molluscs. Classifications based on shell or radula characters are highly contradictory and disputed. Whereas the monophyly of the Conidae (cone snails) and Terebridae (auger snails) has not been challenged, the other constituents of the superfamily are placed in a "trash" group, the turrids, the non-monophyly of which has been demonstrated by anatomical and molecular evidence. We present here a new molecular phylogeny based on a total of 102 conoidean genera (87 "turrids", 5 cones and 10 terebrids) and three genes (COI, 12S and 16S). The resulting tree recognizes 14 clades. When the Conidae (Conus s.l.) and Terebridae are ranked as families for consistency of usage, then the "turrids" end up being split into 12 families of comparable rank. A new genus-level classification of the Conoidea is published to accompany the new phylogeny.
The superfamily Conoidea is one of the most speciose groups of marine mollusks, with estimates of about 340 recent valid genera and subgenera, and 4000 named living species. Previous classifications were based on shell and anatomical characters, and clades and phylogenetic relationships are far from well assessed. Based on a dataset of ca. 100 terminal taxa belonging to 57 genera, information provided by fragments of one mitochondrial (COI) and three nuclear (28S, 18S and H3) genes is used to infer the first molecular phylogeny of this group. Analyses are performed on each gene independently as well as for a data matrix where all genes are concatenated, using Maximum Likelihood, Maximum Parsimony and Bayesian approaches. Several well-supported clades are defined and are only partly identifiable to currently recognized families and subfamilies. The nested sampling used in our study allows a discussion of the classification at various taxonomical levels, and several genera, subfamilies and families are found polyphyletic.
Transcriptome-based exon capture methods provide an approach to recover several hundred markers from genomic DNA, allowing for robust phylogenetic estimation at deep timescales. We applied this method to a highly diverse group of venomous marine snails, Conoidea, for which published phylogenetic trees remain mostly unresolved for the deeper nodes. We targeted 850 protein coding genes (678,322 bp) in ca. 120 samples, spanning all (except one) known families of Conoidea and a broad selection of non-Conoidea neogastropods. The capture was successful for most samples, although capture efficiency decreased when DNA libraries were of insufficient quality and/or quantity (dried samples or low starting DNA concentration) and when targeting the most divergent lineages. An average of 75.4% of proteins was recovered, and the resulting tree, reconstructed using both supermatrix (IQ-tree) and supertree (Astral-II, combined with the Weighted Statistical Binning method) approaches, are almost fully supported. A reconstructed fossil-calibrated tree dates the origin of Conoidea to the Lower Cretaceous. We provide descriptions for two new families. The phylogeny revealed in this study provides a robust framework to reinterpret changes in Conoidea anatomy through time. Finally, we used the phylogeny to test the impact of the venom gland and radular type on diversification rates. Our analyses revealed that repeated losses of the venom gland had no effect on diversification rates, while families with a breadth of radula types showed increases in diversification rates, thus suggesting that trophic ecology may have an impact on the evolution of Conoidea.
Venom peptides from predatory organisms are a resource for investigating evolutionary processes such as adaptive radiation or diversification, and exemplify promising targets for biomedical drug development. Terebridae are an understudied lineage of conoidean snails, which also includes cone snails and turrids. Characterization of cone snail venom peptides, conotoxins, has revealed a cocktail of bioactive compounds used to investigate physiological cellular function, predator-prey interactions, and to develop novel therapeutics. However, venom diversity of other conoidean snails remains poorly understood. The present research applies a venomics approach to characterize novel terebrid venom peptides, teretoxins, from the venom gland transcriptomes of Triplostephanus anilis and Terebra subulata. Next-generation sequencing and de novo assembly identified 139 putative teretoxins that were analyzed for the presence of canonical peptide features as identified in conotoxins. To meet the challenges of de novo assembly, multiple approaches for cross validation of findings were performed to achieve reliable assemblies of venom duct transcriptomes and to obtain a robust portrait of Terebridae venom. Phylogenetic methodology was used to identify 14 teretoxin gene superfamilies for the first time, 13 of which are unique to the Terebridae. Additionally, basic local algorithm search tool homology-based searches to venom-related genes and posttranslational modification enzymes identified a convergence of certain venom proteins, such as actinoporin, commonly found in venoms. This research provides novel insights into venom evolution and recruitment in Conoidean predatory marine snails and identifies a plethora of terebrid venom peptides that can be used to investigate fundamental questions pertaining to gene evolution.
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