Taxonomy, venoms and evolution of the Conoidea – CONOTAX

The methodology applied in the CONOTAX project is mainly based on Next-Generation Sequencing methods, whether to clarify species complexes (RAD-sequencing), establish the phylogenetic relationships within Conoidea (exon-capture, mitogenomics), describe the toxin diversity (sequencing of the venom gland transcriptome) and the preys (metabarcoding of the gut content and isotopic signatures). These innovative techniques will allow identifying the evolutionary processus explaining the diversification of venomous organisms.

The first 30 months were devoted to obtaining the data, their analysis (ongoing) and the poublication of the first taxonomical articles:
- several new species of Conoidea have been revealed by the sequencing of their DNA. Some have been described already in scientific articles, the others will be soon.
- the phylogenetic relationships between the different Conoidea families have been clarified.
- the results confirm that the shell of the Conoidea is not a good predictor of their taxonomy, different species sharing similar shells, and vice-versa.
- the toxins have not been analysed yet, but preliminary results also show differences between species.
These preliminary results would thus confirm the hypothesis: closely related Conoidea species have different toxin arsenals and tend to feed on different preys.

The first part of the CONOTAX project is a success because the sequencing methods, mostly new for our laboratory, have been correctly applied. The next months will be devoted to the final phylogenetic reconstruction of the Conoidea, to the analysis of the sequences transcriptomes and of the results of the metabarcoding of the stocks. At the species level, the approch applied tp the Xenuroturris complex will be also applied to other species complexes, in particular within the Turridae.
Furthermore, the identification of new lineages, either at the species level or at hight taxonomic ranks (genera, families), each producing unknown toxins, will potentially provide new material to identify novel therapeutic applications.

Several scientific articles linked to the CONOTAX project have been published. They concern:
- results linked to the taxonomy of the group, with around 20 species descriptions (published in 9 different articles) and a phylogeny and a classification of a particular group within the Conoidea, the cone snails (3 articles).
- articles dealing with concepts and methods in taxonomy, linked to discussions that took place in the framework of the CONOTAX project (3 articles).
These articles will be followed in the next years by others, with a description of the toxins and preys of the Conoidea.
The results obtained so far have been also presented in ficecongresses, one of them being an invited conference in Madrid (Cone Meeting 2014).

For a long time venomous organisms have fascinated the scientific community, not only because of the danger they represent for humans, but also for their importance in the ecosystems. Indeed, the relatively recent discovery that the multitude of toxins each of these animals produce in their venom glands can be used as drugs to treat pain, diabetes or hypertension even further reinforced their enthusiasm. Among venomous animals, the Conoidea, a hyperdiverse group of venomous gastropods, remain largely unknown. Most taxonomical or biochemical studies on these organisms have focused on one small group within the Conoidea, the cone snails. Consequently, understanding how these organisms have been able to diversify at such a high rate, indicating an exceptional evolutionary success in marine molluscs, requires that we improve our knowledge of the group. Moreover, most Conoidea are waiting to be discovered, and finding a new species is the guarantee to discover new bioactive peptides and proteins, opening the doors to innovative pharmacological and therapeutic applications.
The main goal of the CONOTAX project is to understand the role of different factors in the diversification of the Conoidea, here used as a model to test hypotheses related to the underlying evolutionary processes. Because the acquisition of a highly sophisticated venom apparatus is frequently given as the main hypothesis to explain the evolutionary success of the Conoidea, the project will consist in the acquisition of data on species, toxin and prey diversities from which hypotheses regarding the evolution of the Conoidea will be proposed. In a first stage, we will focus on the acquisition of new taxonomic hypotheses. Most species of Conoidea being currently unknown (4,500 described species for an estimated total of 10-20,000 species), the analysis of recently or newly collected samples will surely lead to the discovery of new species. Additionally, the molecular phylogeny currently available for the group will be updated. In a second stage, the toxins of several species complexes will be sequenced and, together with the anatomy of the venom gland, analyzed in an evolutionary context using a phylogenetic approach to describe the variability of the venomous function in the Conoidea. Additionally, this approach is part of a “Concerted discovery" strategy, where phylogenetic tools are used to facilitate the identification of new toxins, the starting point of the process leading to the development of new pharmaceutical compounds from bioactive molecules. In a third stage, prey diversity of several conoideans will be identified using both a metabarcoding of the gut content and stable isotope analyses, to detect differences in diets between closely related species.
The triplet species, toxin and prey diversities will then provide the ground for understanding the evolution of the group at two scales. First, at the micro-evolutionary scale, several species complexes will be analyzed to identify factors that may act on the speciation events. The main hypothesis is that a speciation event can be linked to a prey shift and to modifications of the venomous function. Then, at the macro-evolutionary scale, a dated molecular phylogeny will be used to estimate the temporal and between-lineage variations of diversification rates during the evolutionary history of the Conoidea. Potential correlations between the changes in diversification rates and the different parameters and characters available (i.e. anatomy, morphology, ecology or venom) will be tested.
CONOTAX is a multidisciplinary project, in which taxonomic and transcriptomic approaches are combined and complement each other, the first providing the conceptual framework and tools for analyzing the evolution of toxins and identifying new lineages, the second facilitating the acquisition of data that will provide the keys to understand how a group of marine molluscs has undergone such an evolutionary success.