Abstract:We report the complete mitochondrial genome sequence of Costapex baldwinae, a Caribbean representative of a predominantly Indo-Pacific genus of gastropods that occurs on sunken wood at bathyal depths. The mitogenome is 15,321 bp in length and has a base composition of 29.2% A, 41.8% T, 12.0% C and 17.0% G. It contains 13 protein-coding, two ribosomal RNA, and 22 tRNA genes with the same gene order and strand orientation as other non-toxoglossan neogastropods. Phylogenetic analyses indicate that the superfamily… Show more
“…Many of the previously recovered relationships are recovered here and new ones are revealed (Table 2). At the superfamily level, some superfamilies are recovered monophyletic and supported, often confirming previously published phylogenies, although based on a much more reduced sampling (Choi et al, 2021;Osca et al, 2015;Uribe et al, 2021;Wang et al, 2021). For example, the Conoidea, represented by many mitogenomes covering almost all the family-level diversity of the group, is found monophyletic.…”
Section: Input For Neogastropod Classificationsupporting
confidence: 84%
“…All the previously published phylogenetic studies that, at least partly, dealt with the neogastropod superfamily relationships failed to resolve most of these deep relationships. Two notable exceptions are (a) the recovery of the sister-taxa Tonnoidea (also revised at the family level- Strong et al, 2019) and Ficoidea, two superfamilies currently not recognized as a Neogastropoda, within the neogastropod clade (as sister to all the other neogastropods but the Cancellariidae; Colgan et al, 2007;Fourdrilis et al, 2018;Harasewych et al, 2019;Machkour-M'Rabet et al, 2021;Osca et al, 2015;Wang et al, 2017Wang et al, , 2021; (b) the monophyly of a group that includes all the neogastropods except the Volutoidea (Cancellariidae, marginellids, Volutidae), the Tonnoidea and the Ficoidea (Abdelkrim et al, 2018;Choi et al, 2021;Cunha et al, 2009;Fourdrilis et al, 2018;Harasewych et al, 2019;Machkour-M'Rabet et al, 2021;Osca et al, 2015;Uribe et al, 2021;Wang et al, 2017Wang et al, , 2021.…”
The Neogastropoda (Mollusca, Gastropoda) encompass more than 15,000 described species of marine predators, including several model organisms in toxinology, embryology and physiology. However, their phylogenetic relationships remain mostly unresolved and their classification unstable. We took advantage of the many mitogenomes published in GenBank to produce a new molecular phylogeny of the neogastropods. We completed the taxon sampling by using an in‐house bioinformatic pipeline to retrieve mitochondrial genes from 13 transcriptomes, corresponding to five families not represented in GenBank, for a final dataset of 113 taxa. Because mitogenomic data are prone to reconstruction artefacts, eight different evolutionary models were applied to reconstruct phylogenetic trees with IQTREE, RAxML and MrBayes. If the over‐parametrization of some models produced trees with aberrant internal long branches, the global topology of the trees remained stable over models and softwares, and several relationships were revealed or found supported here for the first time. However, even if our dataset encompasses 60% of the valid families of neogastropods, some key taxa are missing and should be added in the future before proposing a revision of the classification of the neogastropods. Our study also demonstrates that even complex models struggle to satisfactorily handle the evolutionary history of mitogenomes, still leading to long‐branch attractions in phylogenetic trees. Other approaches, such as reduced‐genome strategies, must be envisaged to fully resolve the neogastropod phylogeny.
“…Many of the previously recovered relationships are recovered here and new ones are revealed (Table 2). At the superfamily level, some superfamilies are recovered monophyletic and supported, often confirming previously published phylogenies, although based on a much more reduced sampling (Choi et al, 2021;Osca et al, 2015;Uribe et al, 2021;Wang et al, 2021). For example, the Conoidea, represented by many mitogenomes covering almost all the family-level diversity of the group, is found monophyletic.…”
Section: Input For Neogastropod Classificationsupporting
confidence: 84%
“…All the previously published phylogenetic studies that, at least partly, dealt with the neogastropod superfamily relationships failed to resolve most of these deep relationships. Two notable exceptions are (a) the recovery of the sister-taxa Tonnoidea (also revised at the family level- Strong et al, 2019) and Ficoidea, two superfamilies currently not recognized as a Neogastropoda, within the neogastropod clade (as sister to all the other neogastropods but the Cancellariidae; Colgan et al, 2007;Fourdrilis et al, 2018;Harasewych et al, 2019;Machkour-M'Rabet et al, 2021;Osca et al, 2015;Wang et al, 2017Wang et al, , 2021; (b) the monophyly of a group that includes all the neogastropods except the Volutoidea (Cancellariidae, marginellids, Volutidae), the Tonnoidea and the Ficoidea (Abdelkrim et al, 2018;Choi et al, 2021;Cunha et al, 2009;Fourdrilis et al, 2018;Harasewych et al, 2019;Machkour-M'Rabet et al, 2021;Osca et al, 2015;Uribe et al, 2021;Wang et al, 2017Wang et al, , 2021.…”
The Neogastropoda (Mollusca, Gastropoda) encompass more than 15,000 described species of marine predators, including several model organisms in toxinology, embryology and physiology. However, their phylogenetic relationships remain mostly unresolved and their classification unstable. We took advantage of the many mitogenomes published in GenBank to produce a new molecular phylogeny of the neogastropods. We completed the taxon sampling by using an in‐house bioinformatic pipeline to retrieve mitochondrial genes from 13 transcriptomes, corresponding to five families not represented in GenBank, for a final dataset of 113 taxa. Because mitogenomic data are prone to reconstruction artefacts, eight different evolutionary models were applied to reconstruct phylogenetic trees with IQTREE, RAxML and MrBayes. If the over‐parametrization of some models produced trees with aberrant internal long branches, the global topology of the trees remained stable over models and softwares, and several relationships were revealed or found supported here for the first time. However, even if our dataset encompasses 60% of the valid families of neogastropods, some key taxa are missing and should be added in the future before proposing a revision of the classification of the neogastropods. Our study also demonstrates that even complex models struggle to satisfactorily handle the evolutionary history of mitogenomes, still leading to long‐branch attractions in phylogenetic trees. Other approaches, such as reduced‐genome strategies, must be envisaged to fully resolve the neogastropod phylogeny.
“…Phylogenomic analyses 12 , 13 , 15 , 22 , 55 , 59 , however, demonstrate the separation of B. cancellata from the rest of Volutidae, suggesting that Cancellarioidea and Volutoidea must be considered as separate SPF as also supported by our study. Turbinelloidea is unresolved in our phylogenomic tree though it was considered as sister to a clade formed by Olivoidea + Muricoidea + Babyloniidae (unassigned SPF) + Buccionoidea + Conoidea 67 . Babyloniidae, an unassigned SPF, is sister to SPF Olivoidea with moderate support as previously proposed 13 though its relationship to other SPFs is uncertain on our tree.…”
Aliger gigas is an economically important and vulnerable marine species. We present a new mitogenome of A. gigas from the Mexican Caribbean and use the eight publicly available Strombidae mitogenomes to analyze intra- and interspecific variation. We present the most complete phylogenomic understanding of Hypsogastropoda to date (17 superfamilies, 39 families, 85 genera, 109 species) to revisit the phylogenetic position of the Stromboidea and evaluate divergence times throughout the phylogeny. The A. gigas mitogenome comprises 15,460 bp including 13 PCGs, 22 tRNAs, and two rRNAs. Nucleotide diversity suggested divergence between the Mexican and Colombian lineages of A. gigas. Interspecific divergence showed high differentiation among Strombidae species and demonstrated a close relationship between A. gigas and Strombus pugilis, between Lambis lambis and Harpago chiragra, and among Tridentarius dentatus/Laevistrombus canarium/Ministrombus variabilis. At the intraspecific level, the gene showing the highest differentiation is ATP8 and the lowest is NAD4L, whereas at the interspecific level the NAD genes show the highest variation and the COX genes the lowest. Phylogenomic analyses confirm that Stromboidea belongs in the non-Latrogastropoda clade and includes Xenophoridea. The phylogenomic position of other superfamilies, including those of previously uncertain affiliation, is also discussed. Finally, our data indicated that Stromboidea diverged into two principal clades in the early Cretaceous while Strombidae diversified in the Paleocene, and lineage diversification within A. gigas took place in the Pleistocene.
“…Figure 1Phylogeny and morphology of Vexillum . ( a ) Mitochondrial phylogeny of the Neogastropoda [19]; the family Costellariidae is represented by Costapex baldwinae . ( b ) Life specimen of Vexillum crocatum (photo courtesy of Janette Johnson).…”
Venoms of predatory marine cone snails are intensely studied because of the biomedical applications of the neuropeptides that they contain, termed conotoxins. Meanwhile some gastropod lineages have independently acquired secretory glands strikingly similar to the venom gland of cone snails, suggesting that they possess similar venoms. Here we focus on the most diversified of these clades, the genus
Vexillum
. Based on the analysis of a multi-species proteo-transcriptomic dataset, we show that
Vexillum
species indeed produce complex venoms dominated by highly diversified short cysteine-rich peptides, vexitoxins. Vexitoxins possess the same precursor organization, display overlapping cysteine frameworks and share several common post-translational modifications with conotoxins. Some vexitoxins show sequence similarity to conotoxins and adopt similar domain conformations, including a pharmacologically relevant inhibitory cysteine knot motif. The
Vexillum
envenomation gland (gL) is a notably more recent evolutionary novelty than the conoidean venom gland. Thus, we hypothesize lower divergence between vexitoxin genes, and their ancestral ‘somatic’ counterparts compared to that in conotoxins, and we find support for this hypothesis in the evolution of the vexitoxin cluster V027. We use this example to discuss how future studies on vexitoxins can inform the origin of conotoxins, and how they may help to address outstanding questions in venom evolution.
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