Ion channels of the DEG/ENaC family share a similar structure but serve strikingly diverse biological functions, such as Na+ reabsorption, mechanosensing, proton-sensing, chemosensing and cell-cell communication via neuropeptides. This functional diversity raises the question of the ancient function of DEG/ENaCs. Using an extensive phylogenetic analysis across many different animal groups, we found a surprising diversity of DEG/ENaCs already in Cnidaria (corals, sea anemones, hydroids and jellyfish). Using a combination of gene expression analysis, electrophysiological and functional studies combined with pharmacological inhibition as well as genetic knockout in the model cnidarian Nematostella vectensis, we reveal an unanticipated role for a proton-sensitive DEG/ENaC in discharge of N. vectensis cnidocytes, the stinging cells typifying all cnidarians. Our study supports the view that DEG/ENaCs are versatile channels that have been co-opted for diverse functions since their early occurrence in animals and that respond to simple and ancient stimuli, such as omnipresent protons.

Ion channels of the DEG/ENaC family share a similar structure but serve strikingly diverse biological functions, such as Na+ reabsorption, mechanosensing, proton-sensing, chemosensing and cell-cell communication via neuropeptides. This functional diversity raises the question of the ancient function of DEG/ENaCs. Using an extensive phylogenetic analysis across many different animal groups, we found a surprising diversity of DEG/ENaCs already in Cnidaria (corals, sea anemones, hyrdoids and jellyfish). Using a combination of gene expression analysis, electrophysiological and functional studies combined with pharmacological inhibition as well as genetic knockout in the model cnidarian Nematostella vectensis, we reveal an unanticipated role for a proton-sensitive DEG/ENaC in discharge of N. vectensis cnidocytes, the stinging cells typifying all cnidarians. Our study supports the view that DEG/ENaCs are versatile channels that have been co-opted for diverse functions since their early occurrence in animals and that respond to simple and ancient stimuli, such as omnipresent protons.

No abstract

The Thoosidae (Porifera, Demospongiae, Tetractinellida) currently includes the genera Thoosa, Alectona, and Delectona. To this date, molecular data are only available for Alectona. In this study, the phylogenetic affinities of the genera Thoosa and Alectona have been investigated with the species T. mismalolli, T. calpulli, and T. purpurea from the Mexican Pacific using morphology and three molecular loci: the mitochondrial cytochrome oxidase subunit 1 (CO1 mtDNA), 28S rRNA (fragment D2), and 18S rRNA. Morphology and embryology showed that these genera are quite different from the rest of the tetractinellids because larvae of Alectona and Thoosa have unique features in sponges, such as the presence of monaxonic discs in Thoosa and tetraxonic discs in Alectona which disappear in the adult stages. A phylogenetic analysis using selected species from the order Tetractinellida revealed that Thoosa groups with Alectona thus confirming morphological studies. The peculiarities in spiculation and embryology of the Thoosa and Alectona larvae, which are markedly different from species belonging to the suborders Astrophorina and Spirophorina and their distant phylogenetic position (based on three molecular loci), suggest that Thoosidae could be placed in the new suborder Thoosina.