Alexander E. Fedosov

Biodiversity of Cone Snails and Other Venomous Marine Gastropods: Evolutionary Success Through Neuropharmacology

Venomous marine snails (superfamily Conoidea) are a remarkably biodiverse marine invertebrate lineage (featuring more than 10,000 species). Conoideans use complex venoms (up to 100 different components for each species) to capture prey and for other biotic interactions. Molecular phylogeny and venom peptide characterization provide an unusual multidisciplinary view of conoidean biodiversity at several taxonomic levels. Venom peptides diverge between species at an unprecedented rate through hypermutation within gene families. Clade divergence within a genus occurs without recruiting new gene families when a saltatory event, such as colonization of new prey types (e.g., fish), leads to a new radiation. Divergence between genera in the same family involves substantial divergence in gene families. In the superfamily Conoidea, the family groups recruited distinct sets of different venom gene superfamilies. The associated morphological, behavioral, and prey-preference changes that accompany these molecular changes are unknown for most conoidean lineages, except for one genus, Conus, for which many associated phenotypic changes have been documented.

Accessing novel conoidean venoms: Biodiverse lumun-lumun marine communities, an untapped biological and toxinological resource

Cone snail venoms have yielded pharmacologically active natural products of exceptional scientific interest. However, cone snails are a small minority of venomous molluscan biodiversity, the vast majority being tiny venomous morphospecies in the family Turridae. A novel method called lumun-lumun opens access to these micromolluscs and their venoms. Old fishing nets are anchored to the sea bottom for a period of 1-6months and marine biotas rich in small molluscs are established. In a single lumun-lumun community, we found a remarkable gastropod biodiversity (155 morphospecies). Venomous predators belonging to the superfamily Conoidea (36 morphospecies) were the largest group, the majority being micromolluscs in the family Turridae. We carried out an initial analysis of the most abundant of the turrid morphospecies recovered, Clathurella (Lienardia) cincta (Dunker, 1871). In contrast to all cDNA clones characterized from cone snail venom ducts, one of the C. cincta clones identified encoded two different peptide precursors presumably translated from a single mRNA. The prospect of easily accessing so many different morphospecies of venomous marine snails raises intriguing toxinological possibilities: the 36 conoidean morphospecies in this one net alone have the potential to yield thousands of novel pharmacologically active compounds.

Research Article Phylogeny and taxonomy of the Kermia-Pseudodaphnella (Mollusca: Gastropoda: Raphitomidae) genus complex: a remarkable radiation via diversification of larval development

Conoidean gastropods of the genera Kermia, Oliver, 1915 and Pseudodaphnella Boettger, 1895 (Raphitomidae) are common in shallow-water habitats of the tropical Indo-Pacific. They form a distinct morphologically homogeneous complex, easily recognizable by sculpture and colour pattern, encompassing around 80 described species. Examination of a vast material accumulated during recent expeditions in various regions of the Indo-Pacific revealed a number of undescribed species of this complex. Our material included 32 morphospecies available for molecular phylogenetic study; phylogenetic reconstruction based on the COI gene confirmed the species hypotheses based on morphological characters. A total of 18 terminal taxa were attributed to known species and 14 were identified as new species. Of these, 12 species, for which sufficient material was available, are described. Phylogenetic analysis indicated close relationships of the genera Kermia and Pseudodaphnella with members of some other conoidean genera (specifically Exomilus Hedley, 1918, Paramontana Laseron, 1954 and Thetidos Hedley, 1899) and taxonomic implications of the data obtained are discussed. To test the taxonomic value of protoconch and review its wide use in classification of Conoidea, the evolution of the protoconch morphology was reconstructed using a phylogenetic tree. It has revealed that protoconchs of different types may appear in closely related species, sometimes hardly distinguishable by teleoconch morphology. A switch from planctotrophic to non-planctotrophic mode of development occurred at least four times in the evolutionary history of the Kermia–Pseudodaphnella complex, indicating high developmental plasticity of the group. Its role in radiation of the Kermia–Pseudodaphnella complex and applications for use of protoconch morphology in the classification of Conoidea are discussed.

A family of excitatory peptide toxins from venomous crassispirine snails: using Constellation Pharmacology to assess bioactivity.

The toxinology of the crassispirine snails, a major group of venomous marine gastropods within the superfamily Conoidea, is largely unknown. Here we define the first venom peptide superfamily, the P-like crassipeptides, and show that the organization of their gene sequences is similar to conotoxin precursors. We provide evidence that one peptide family within the P-like crassipeptide superfamily includes potassium-channel (K-channel) blockers, the κP-crassipeptides. Three of these peptides were chemically synthesized (cce9a, cce9b and iqi9a). Using conventional electrophysiology, cce9b was shown to be an antagonist of both a human Kv1.1 channel isoform (Shaker subfamily of voltage-gated K channels) and a Drosophila K-channel isoform. We assessed the bioactivity of these peptides in native mammalian dorsal root ganglion neurons in culture. We demonstrate that two of these crassipeptides, cce9a and cce9b, elicited an excitatory phenotype in a subset of small-diameter capsaicin-sensitive mouse DRG neurons that were also affected by κJ-conotoxin PlXIVA (pl14a), a blocker of Kv1.6 channels. Given the vast complexity of heteromeric K-channel isoforms, this study demonstrates that the crassispirine venoms are a potentially rich source for discovering novel peptides that can help to identify and characterize the diversity of K-channel subtypes expressed in native neurons and other cell types.

Morphology of the anterior digestive system of tonnoideans (Gastropoda: Caenogastropoda) with an emphasis on the foregut glands

ABSTRACT Tonnoideans are marine carnivorous caenogastropods that prey on different invertebrates, namely polychaetes, sipunculids, bivalve and gastropod molluscs, and echinoderms. The morphology of the digestive system of 20 species from five families of the Tonnoidea was examined (for most of these species for the first time), and the salivary glands of six of them were studied using serial histological sections. Most of the studied families are rather similar anatomically, except Personidae (Distorsio), which differs both in proboscis morphology and the structure of the salivary glands. In most tonnoideans the salivary glands are split morphologically and functionally into anterior and posterior lobes, the latter synthesising strong sulfuric acid. The ducts of the posterior lobes are lined with non-ciliated epithelium and receive usually paired ciliated ducts from the anterior lobes to form a non-ciliated common duct, opening into the buccal cavity. In Personidae, the salivary glands are not separated into lobes, but are instead composed of ramifying tubules that are histologically different in the proximal and distal parts. Radulae of Tonnoidea are rather variable, with different patterns of interlocking teeth, both in the transverse and longitudinal rows, which may be related to particular feeding mechanisms. Due to the peculiarities of Personidae, the close relationship between that family and the rest of the Tonnoidea is questioned.

Divergence of the Venom Exogene Repertoire in Two Sister Species of Turriconus

Abstract The genus Conus comprises approximately 700 species of venomous marine cone snails that are highly efficient predators of worms, snails, and fish. In evolutionary terms, cone snails are relatively young with the earliest fossil records occurring in the Lower Eocene, 55 Ma. The rapid radiation of cone snail species has been accompanied by remarkably high rates of toxin diversification. To shed light on the molecular mechanisms that accompany speciation, we investigated the toxin repertoire of two sister species, Conus andremenezi and Conus praecellens, that were until recently considered a single variable species. A total of 196 and 250 toxin sequences were identified in the venom gland transcriptomes of C. andremenezi and C. praecellens belonging to 25 and 29 putative toxin gene superfamilies, respectively. Comparative analysis with closely (Conus tribblei and Conus lenavati) and more distantly related species (Conus geographus) suggests that speciation is associated with significant diversification of individual toxin genes (exogenes) whereas the expression pattern of toxin gene superfamilies within lineages remains largely conserved. Thus, changes within individual toxin sequences can serve as a sensitive indicator for recent speciation whereas changes in the expression pattern of gene superfamilies are likely to reflect more dramatic differences in a species’ interaction with its prey, predators, and competitors.

Host specificity of parasitic gastropods of the genus Annulobalcis Habe, 1965 (Mollusca, Gastropoda, Eulimidae) from crinoids in Vietnam, with descriptions of four new species

ABSTRACT Parasitic gastropods of the genus Annulobalcis Habe, 1965 (family Eulimidae), associated with the crinoids (comatulids) are common in Nhatrang Bay (Southern Vietnam). Morphological examination of Annulobalcis specimens, collected in this area revealed four distinct forms, significantly different also in host specificity. Mitochondrial cox1 sequence data have shown these forms to comprise four distinct species, their relationships are discussed. As a result of morphological and molecular studies, four new species of the genus Annulobalcis are described: A. albus n. sp., A. wareni n. sp., A. maculatus n. sp., and A. vinarius n. sp. The three former species appeared to be strictly species specific in their choice of host (parasitizing a single host species each), while the latter was found on a number of hosts, although mostly on a single species. Speciation in relation to host specificity of Annulobalcis is discussed.

Revision of the genus Thetidos Hedley, 1899 (Gastropoda: Conoidea: Raphitomidae) in the Indo-Pacific with descriptions of three new species

The genus Thetidos was established to accommodate a single species Thetidos morsura, a minute turriform conoidean with an unremarkable paucispiral protoconch, but possessing characteristic globose whorls of the teleoconch and three strong denticles on the inside of outer apertural lip. Subsequently, Thetidos was considered synonymous with Lienardia, and has rarely been mentioned in literature until the recent discovery of a remarkably similar species Thetidos tridentata, though it is different in protoconch morphology. Both molecular data and protoconch morphology unequivocally suggested placement of the new species in Raphitomidae. Examination of shells from the Indo-Pacific identified a number of similar forms, all referable to the genus Thetidos. Six species are now recognized within the genus; of them three, Thetidos puillandrei n. sp., Thetidos minutissima n. sp., Thetidos pallida n. sp., are here described as new. Thetidos species are now known from subtidal depths from the Philippines and Sulawesi to French Polynesia. Thetidos morsura is the only species of the genus that possesses a paucispiral protoconch suggestive of a non-planktotrophic development, although it displays a wide geographic range and a high morphological variability. http://zoobank.org/urn:lsid:zoobank.org:pub:1F2001CC-6BEA-4B26-AFB8-6B337E101FDB

COI and RAD-seq trees

MrBayes, BEAST and RAxML trees for COI; RaxML trees for the RAD seq dataset, with the loci shared by at least 30, 40, 50, 60, 70, 80% of the samples.

Delimiting species of marine gastropods (Turridae, Conoidea) using RAD-sequencing in an integrative taxonomy framework

Species delimitation in poorly known and diverse taxa is usually performed based on monolocus, DNA‐barcoding‐like approaches, while multilocus data are often used to test alternative species hypotheses in well‐studied groups. We combined both approaches to delimit species in the Xenuroturris/Iotyrris complex, a group of venomous marine gastropods from the Indo‐Pacific. First, COI sequences were analysed using three methods of species delimitation to propose primary species hypotheses. Second, RAD sequencing data were also obtained and a maximum‐likelihood phylogenetic tree produced. We tested the impact of the level of missing data on the robustness of the phylogenetic tree obtained with the RAD‐seq data. Alternative species partitions revealed with the COI data set were also tested using the RAD‐seq data and the Bayes factor species delimitation method. The congruence between the species hypotheses proposed with the mitochondrial nuclear data sets, together with the morphological variability of the shell and the radula and the distribution pattern, was used to turn the primary species hypotheses into secondary species hypotheses. Allopatric primary species hypotheses defined with the COI gene were interpreted to correspond to intraspecific structure. Most of the species are found sympatrically in the Philippines, and only one is confidently identified as a new species and described as Iotyrris conotaxis n. sp. The results obtained demonstrate the efficiency of the combined monolocus/multilocus approach to delimit species.