Characterization of Lophiotoma leucotropis Mitochondrial Genome of Family Turridae and Phylogenetic Considerations within the Neogastropoda.

Neogastropoda is a group of marine organisms with an extremely wide distribution that is rich in species and economic and ornamental values, the classification of species in this order has been ongoing for a long time, but there is still a great controversy about whether this order is monophyletic. In this study, we obtained the complete mitogenome of Lophiotoma leucotropis by next-generation sequencing and analyzed the basic structural features of the genome, and we found that the number of genes was consistent with that of most of the Neogastropoda snails, containing 37 genes, including 13 protein-coding genes (PCGs), 2 rRNAs, and 22 tRNAs. Analyzing base content, amino acid content, codon usage preference, and tRNA structure, the mitogenomes of eight species of Turridae were selected for analysis of selection pressures, and it was found that the evolution of species in this family was affected by purifying selection. In addition, by analyzing the rearrangement characteristics, it was found that the sequence of L. leucotropis was consistent with the Conoidea consensus order, and four of the eight species involved in the analysis showed rearrangements. Finally, we constructed a phylogenetic tree by combining PCGs of 60 species within Caenogastropoda and found Neogastropoda to be a monophyletic group, validating the results of morphological classification. The results will provide more references for the classification and species evolution of Neogastropoda, as well as phylogenetic analysis.

Coupling DNA barcodes and exon-capture to resolve the phylogeny of Turridae (Gastropoda, Conoidea).

Taxon sampling in most phylogenomic studies is often based on known taxa and/or morphospecies, thus ignoring undescribed diversity and/or cryptic lineages. The family Turridae is a group of venomous snails within the hyperdiverse superfamily Conoidea that includes many undescribed and cryptic species. Therefore 'traditional' taxon sampling could constitute a strong risk of undersampling or oversampling Turridae lineages. To minimize potential biases, we establish a robust sampling strategy, from species delimitation to phylogenomics. More than 3,000 cox-1 "barcode" sequences were used to propose 201 primary species hypotheses, nearly half of them corresponding to species potentially new to science, including several cryptic species. A 110-taxa exon-capture tree, including species representatives of the diversity uncovered with the cox-1 dataset, was build using up to 4,178 loci. Our results show the polyphyly of the genus Gemmula, that is split into up to 10 separate lineages, of which half would not have been detected if the sampling strategy was based only on described species. Our results strongly suggest that the use of blind, exploratory and intensive barcode sampling is necessary to avoid sampling biases in phylogenomic studies.

Data, time and money: evaluating the best compromise for inferring molecular phylogenies of non-model animal taxa.

For over a decade now, High Throughput sequencing (HTS) approaches have revolutionized phylogenetics, both in terms of data production and methodology. While transcriptomes and (reduced) genomes are increasingly used, generating and analyzing HTS datasets remain expensive, time consuming and complex for most non-model taxa. Indeed, a literature survey revealed that 74% of the molecular phylogenetics trees published in 2018 are based on data obtained through Sanger sequencing. In this context, our goal was to identify the strategy that would represent the best compromise among costs, time and robustness of the resulting tree. We sequenced and assembled 32 transcriptomes of the marine mollusk family Turridae, considered as a typical non-model animal taxon. From these data, we extracted the loci most commonly used in gastropod phylogenies (cox1, 12S, 16S, 28S, h3 and 18S), full mitogenomes, and a reduced nuclear transcriptome representation. With each dataset, we reconstructed phylogenies and compared their robustness and accuracy. We discuss the impact of missing data and the use of statistical tests, tree metrics, and supertree and supermatrix methods to further improve phylogenetic data acquisition pipelines. We evaluated the overall costs (time and money) in order to identify the best compromise for phylogenetic data sampling in non-model animal taxa. Although sequencing full mitogenomes seems to constitute the best compromise both in terms of costs and node support, they are known to induce biases in phylogenetic reconstructions. Rather, we recommend to systematically include loci commonly used for phylogenetics and taxonomy (i.e. DNA barcodes, rRNA genes, full mitogenomes, etc.) among the other loci when designing baits for capture.

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.

Estudio histológico del tubo digestivo y aparato venenoso de Gemmula periscelida (Gastropoda: Turridae) / Histologic study of digestive tract and venom apparatus of Gemmula periscelida (Gastropoda: Turridae)

En el presente trabajo se describe anatómica e histológicamente el tubo digestivo y aparato venenoso de Gemmula periscelida (Gastropoda: Turridae) en ejemplares colectados al Noroeste de la Plataforma Continental Yucateca. Se determinó que el tipo de epitelio que reviste a cada una de las zonas del tubo digestivo (probóscide, esófago anterior, medio y posterior, estómago, glándula digestiva e intestino) y al aparato venenoso, es diferente a lo reportado para otros túrridos; por lo que se infiere el posible mecanismo de alimentación para esta especie.

In this paper we realized anatomical and histologically description of the digestive tract and venom apparatus of Gemmula periscelida (Gastropoda: Turridae) specimens collected northwest of the Yucatan Shelf. Results of analysis show that there are differences in the type of epithelium coating each of the areas of the digestive tract (proboscis, anterior, middle and posterior esophagus, stomach, digestive gland and intestine) and of a venom apparatus with respect to that reported for other turrid snails. This suggests the possible feeding mechanism for this species.

Pharmacological characterization of venoms obtained from Mexican toxoglossate gastropods on isolated guinea pig ileum

The protein-containing extracts prepared from the venom ducts of Conus austini, Conus spurius and Polystira albida caused a concentration-dependent inhibition of spontaneous contractions in guinea pig ileum. The most potent extract was obtained from P. albida venom ducts (IC50 equal 0.11 more or less 0.02 microg protein/mL). The three extracts produced a moderate inhibition of contractions elicited by acetylcholine (ACh 1 microM), suggesting the presence of anticholinergic compounds. The contractile response elicited by nicotine (10 microM) was significantly reduced by the extracts prepared from the ducts of C. austini and P. albida, which indicates that the venom produced by these species contains toxins that target neuronal nicotinic receptors. All three extracts significantly inhibited contractions evoked by histamine (0.5 miM), particularly those from C. spurius and P. albida. These findings reveal the presence of antihistaminergic compounds not previously described in any conoidean venom. Finally, we found that only the extract prepared from C. spurius ducts decreased KCl (60 mM)-induced contractions, indicating that the venom of this snail contains compounds that block voltage-dependent Ca2 more or Na more channels.

Estudio Histológico de Boca, Esófago, Estómago e Intestino de Polystira albida (Gastropoda: Turridae) / Histology Study of Mouth, Esophagus, Stomach and Intestine of Polystira albida (Gastropoda: Turridae)

En la presente investigación se realizó la caracterización histológica del tubo digestivo de Polystira albida (Toxoglossa:Turridae) mediante microscopía óptica, utilizando ejemplares colectados en la Sonda de Campeche. Los resultados del análisis muestran que los labios, la boca y la probóscide presentan un epitelio cilindrico simple ciliado. La cavidad bucal tiene un epitelio cilindrico estratificado. El esófago presenta un epitelio cilindrico simple con células glandulares granulares acidófilas (naturaleza proteica), y es el sitio donde comienza la digestión. El estómago se divide en tres regiones histológicas, y tiene dos tipos de epitelio, uno cilindrico simple ciliado y otro cilindrico simple; el primero está formado por abundantes células glandulares acidófilas y basófilas (naturaleza proteica y glicoproteica', respectivamente); y el segundo contiene slo células glandulares acidófilas. La glándula digestiva está constituida por adenómeros túbulo-acinosos con células glandulares acidófilas y basófilas, en diferentes grados de secreción y los conductos presentan un epitelio cilindrico ciliado con células glandulares de ambos tipos. El intestino se divide en cinco regiones histológicas, la primera presenta un tiflosol con dos tipos de epitelio, cilindrico simple y cilindrico simple con chapa estriada; y el resto del tracto tiene un epitelio cilindrico simple ciliado con células glandulares granulares acidófilas y pliegues de diferentes tamaños que aumentan o reducen la cavidad del conducto. Se concluye que existen diferencias, principalmente en la región anterior del tubo digestivo (cavidad bucal, esófago y estómago), con respecto a las descripciones generales realizadas para la subclase Prosobranchia.

In the present investigation it was realized a histological characterization of the digestive tract of Polystira albida (Toxoglossa: Turridae), by using optic microscopy of specimens collected in Sonda de Campeche. Results of analysis show that lips, mouth and proboscis present a simple columnar epithelium with cilia. Buccal cavity has a stratified columnar epithelium. Esophagus presents a simple columnar epithelium with acidophilic granular glandular cells (proteic nature), and it is the place where digestion starts. Stomach is divided in three histological regions that have two epithelial types, simple columnar with cilia and without one; the first is formed by a lot of acidophilic and basophilic glandular cells (proteic and glycoproteic nature respectively), and the second only contains acidophilic glandular cells. Digestive gland is constituted by tubule-acinous adenomers with acidophilic and basophilic glandular cells in different grades of secretion, and ducts have simple columnar epithelium with cilia and scarcely glandular cells. Intestine is divided in five histological regions, the first presents atyphlosole with two types of epithelium, simple columnar with stratified border; the rest of the tract has simple columnar epithelium with cilia, acidophilic granular glandular cells and folds of different sizes that increase or reduce the cavity duct. Based on previous this, we conclude that in this study exist differences principally in front region of digestive tract (buccal cavity, esophagus and stomach) compared to general descriptions realized for Prosobranchia subclass.