Tetramine in the Salivary Glands of Marine Carnivorous Snails: Analysis, Distribution and Toxicological Aspects

Focusing on tetramine, tetramethylammonium ion, contained in the salivary glands of marine carnivorous snails, this paper gives an overview of analytical methods, distribution in marine snails, and toxicological aspects. Some Neptunea snails have often caused food poisoning in North Atlantic and Northeast Asia regions, especially in Japan. The toxin of both N. arthritica and N. antiqua was first proven to be tetramine in 1960. Subsequent research on marine snail tetramine has progressed with the development of analytical methods. Of the various methods developed, the LC/ESI-MS method is most recommended for tetramine analysis in terms of sensitivity, specificity, and versatility. Accumulated data show that tetramine is ubiquitously contained at high concentrations (usually several mg/g) in the salivary glands of Neptunea snails. Tetramine is also found in the muscle and viscera of Neptunea snails and even in the salivary gland of marine snails other than Neptunea species, although mostly at low levels (below 0.1 mg/g). Interestingly, the major toxin in the salivary glands of Fusitriton oregonensis and Hemifusus tuba is distinguishable from tetramine. In tetramine poisoning, diverse symptoms attributable to the ganglion-blocking action of tetramine, such as visual disturbance, headache, dizziness, abdominal pain, and nausea, develop within 30 min after ingestion of snails because of rapid absorption of tetramine from the gastrointestinal tract. The symptoms are generally mild and subside in a short time (within 24 at most) because of rapid excretion through the kidney. However, it should be kept in mind that tetramine poisoning can be severe in patients with kidney dysfunction, as shown by two recent case reports. Finally, given the diffusion of tetramine from the salivary gland to the muscle during boiling and thawing of snails, removal of salivary glands from live snails is essential to avoid tetramine poisoning.

Alterations in lipids and minerals in relation to larval trematode infections of Nerita polita marine snails

Summary Marine snails provide an important source of vitamins, proteins, minerals, and essential fatty acids, and their mucus has a therapeutic significance. Parasitic infection of larval trematodes in these snails affects their nutritional value. The present study aimed to screen Nerita polita marine snails for the prevalence of cercarial infections and to evaluate the changes in lipids and some minerals in the infected as well as non-infected ones. Snails were collected randomly from February 2018 to January 2019 from the Red Sea Obhor bay, Jeddah city, Saudi Arabia. The amount of triglycerides, cholesterol, and phospholipids in the Digestive Gland Gonad Complex (DGG), hemolymph, and Snail Conditioned Water (SCW) of non-infected and infected Nerita polita snail was estimated using a spectrophotometer. Minerals content such as Ca, Zn, Pb, Na, Mn, Mg, K, Fe, Cu, and Cd, in the DGG and shell in the infected and non-infected snails were analyzed using an Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Two types of cercariae were detected, ocellate furcocercus cercaria (Trichobilharzia regent) and xiphidiocercaria (Litorina saxatilis VII). The study showed that there is a fl uctuation in the concentration of lipids and minerals between increase and decrease in DGG, hemolymph, shell, and SCW in infected snails. The nutritive value of the snails is affected with infection through the decrease of some lipids and minerals in infected snails. Further qualitative studies are needed.

Complete Mitochondrial Genomes of Babylonia Formosae and Babylonia Zeylanica (Neogastropoda: Babyloniidae) and Increased Sampling Give New Insights Into Neogastropoda Phylogeny

The phylogenetic relationships of Neogastropoda, a group of highly complex predatory marine snails, have been controversial. The two newly sequenced mitogenomes of Babylonia formosae and Babylonia zeylanica (Neogastropoda: Babyloniidae) are described. The mitogenomes of B. zeylanica and B. formosae were 16, 214 bp and 16, 181 bp in length, respectively. The mitogenomes of both species contain 13 PCGs, 22 tRNA genes, and 2 ribosomal RNA genes. The sequence of genes differed from the ancestral mitochondrial gene arrangement of Caenogastropoda mitogenomes. Also, 63 Neogastropoda species were analyzed for the genome organization of seventeen major lineage of Neogastropoda, five types of mitochondrial genome arrangement were identified. Bayesian Inference phylogenetic trees and Maximum likehood of Neogastropoda were established according to complete mitogenome. The monophyly of Neogastropoda families is strongly supported by this study, in contrast to previous molecular studies. Our results shed light on gene sequence distribution/arrangement characteristics of Neogastropoda mitogenomes, provide fundamental information for further phylogenetic studies on Neogastropoda.

Investigating Sources of Conflict in Deep Phylogenomics of Vetigastropod Snails

Phylogenetic analyses may suffer from multiple sources of error leading to conflict between genes and methods of inference. The evolutionary history of the mollusc clade Vetigastropoda makes them susceptible to these conflicts, their higher level phylogeny remaining largely unresolved. Originating over 350 million years ago, vetigastropods were the dominant marine snails in the Paleozoic. Multiple extinction events and new radiations have resulted in both very long and very short branches and a large extant diversity of over 4000 species. This is the perfect setting of a hard phylogenetic question in which sources of conflict can be explored. We present 41 new transcriptomes across the diversity of vetigastropods (62 terminals total), and provide the first genomic-scale phylogeny for the group. We find that deep divergences differ from previous studies in which long branch attraction was likely pervasive. Robust results leading to changes in taxonomy include the paraphyly of the order Lepetellida and the family Tegulidae. Tectinae subfam. nov. is designated for the clade comprising Tectus, Cittarium and Rochia. For two early divergences, topologies disagreed between concatenated analyses using site heterogeneous models vs. concatenated partitioned analyses and summary coalescent methods. We investigated rate and composition heterogeneity among genes, as well as missing data by locus and by taxon, none of which had an impact on the inferred topologies. We also found no evidence for ancient introgression throughout the phylogeny. We further tested whether uninformative genes and over-partitioning were responsible for this discordance by evaluating the phylogenetic signal of individual genes using likelihood mapping, and by analyzing the most informative genes with a full multispecies coalescent model. We find that most genes are not informative at the two conflicting nodes, but neither this nor gene-wise partitioning are the cause of discordant results. New method implementations that simultaneously integrate amino acid profile mixture models and the multispecies coalescent might be necessary to resolve these and other recalcitrant nodes in the Tree of Life.

Venom-Derived Neurotoxins Targeting Nicotinic Acetylcholine Receptors

Acetylcholine was the first neurotransmitter described. The receptors targeted by acetylcholine are found within organisms spanning different phyla and position themselves as very attractive targets for predation, as well as for defense. Venoms of snakes within the Elapidae family, as well as those of marine snails within the Conus genus, are particularly rich in proteins and peptides that target nicotinic acetylcholine receptors (nAChRs). Such compounds are invaluable tools for research seeking to understand the structure and function of the cholinergic system. Proteins and peptides of venomous origin targeting nAChR demonstrate high affinity and good selectivity. This review aims at providing an overview of the toxins targeting nAChRs found within venoms of different animals, as well as their activities and the structural determinants important for receptor binding.

High Levels of Tetrodotoxin (TTX) in Trumpet Shell Charonia lampas from the Portuguese Coast

Tetrodotoxin (TTX) is a potent neurotoxin, considered an emerging toxin in Europe where recently a safety limit of 44 µg TTX kg−1 was recommended by authorities. In this study, three specimens of the large gastropod trumpet shell Charonia lampas bought in a market in south Portugal were analyzed using a neuroblastoma cell (N2a) based assay and by LC-MS/MS. N2a toxicity was observed in the viscera of two individuals analyzed and LC-MS/MS showed very high concentrations of TTX (42.1 mg kg−1) and 4,9-anhydroTTX (56.3 mg kg−1). A third compound with m/z 318 and structurally related with TTX was observed. In the edible portion, i.e., the muscle, toxin levels were below the EFSA recommended limit. This study shows that trumpet shell marine snails are seafood species that may reach the markets containing low TTX levels in the edible portion but containing very high levels of TTX in non-edible portion raising concerns regarding food safety if a proper evisceration is not carried out by consumers. These results highlight the need for better understanding TTX variability in this gastropod species, which is critical to developing a proper legal framework for resources management ensuring seafood safety, and the introduction of these gastropods in the markets.

Oyster-Predator Dynamics and Climate Change

Oysters are one of the most important natural resources found in coastal and estuarine areas of Florida, but some Florida oyster populations appear to be declining. One possible driver of oyster population decline is increased mortality from oyster predators, including marine snails. But other environmental factors, such as changes in temperature or salinity, may also affect oysters. This 5-page fact sheet written by Gabrielle Love, Shirley Baker, and Edward V. Camp and published by the UF/IFAS School of Forest Resources and Conservation, Program in Fisheries and Aquatic Sciences describes how a changing climate may affect oysters directly but also indirectly by affecting their predators.https://edis.ifas.ufl.edu/fa228

Diet Diversity in Carnivorous Terebrid Snails Is Tied to the Presence and Absence of a Venom Gland

Predator-prey interactions are thought to play a driving role in animal evolution, especially for groups that have developed venom as their predatory strategy. However, how the diet of venomous animals influences the composition of venom arsenals remains uncertain. Two prevailing hypotheses to explain the relationship between diet and venom composition focus on prey preference and the types of compounds in venom, and a positive correlation between dietary breadth and the number of compounds in venom. Here, we examined venom complexity, phylogenetic relationship, collection depth, and biogeography of the Terebridae (auger snails) to determine if repeated innovations in terebrid foregut anatomy and venom composition correspond to diet variation. We performed the first molecular study of the diet of terebrid marine snails by metabarcoding the gut content of 71 terebrid specimens from 17 species. Our results suggest that the presence or absence of a venom gland is strongly correlated with dietary breadth. Specifically, terebrid species without a venom gland displayed greater diversity in their diet. Additionally, we propose a revision of the definition of venom complexity in conoidean snails to more accurately capture the breadth of ecological influences. These findings suggest that prey diet is an important factor in terebrid venom evolution and diversification and further investigations of other understudied organisms, like terebrids, are needed to develop robust hypotheses in this area.