Leptodactylus ocellatus (Amphibia): mechanism of defense in the skin and molecular phylogenetic relationships

Abstract

Amphibian antimicrobial peptides have been known for many decades and several of them have already been isolated. However, the number of species investigated is still small. Herein, we report on the skin secretions of Leptodactylus ocellatus, which were extracted by mild electrical stimulation and its semi-preparative reverse-phase chromatography was resolved in more than 30 fractions. Among these fractions, two novel antimicrobial peptides were isolated and their amino acid sequences determined by de novo sequencing. The ocellatins-5 and -6 (21 and 22 amino acid residues, respectively) are amidated at the C-terminus. Ocellatins inhibited the growth of reference strains of both Gram-negative bacteria (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus) with minimal inhibition concentration values in the range of 32-128 microg/mL. The amino acid sequence of the peptides shows structural similarity with members of the antimicrobial peptides found in the skin secretion of other leptodactylid frogs. This observation is consistent with the hypothesis that many frog skin antimicrobial peptides are related evolutionarily, having arisen from multiple duplications of an ancestral gene that existed before the radiation of the different species.

Characterization and Biological Activities of Ocellatin Peptides from the Skin Secretion of the Frog Leptodactylus pustulatus

“…Another hypothesis for the low antimicrobial activity observed is that, in vivo, ocellatins could act synergistically with the various peptides typically present in the skin or with other secreted molecules, as previously described for other peptides. 23,42 However, in our tests, these molecules being absent from our purified samples would not be able to modulate the peptide's activity. Further work is needed to evaluate this hypothesis.…”

Acoustic monitoring indicates a correlation between calling and spawning in captive spotted seatrout (Cynoscion nebulosus)

“…In this family, fish produce sound by contracting a sonic muscle against an inflated swim bladder (reviewed in Fine & Parmentier, 2015). In most Sciaenids, males are the prominent sound producers; however, in the Atlantic croaker and black drum, both male and female have sonic muscles and call (Hill, Michael & Musick, 1987; Tellechea et al, 2010). In most cases, sound production is associated with defending territory and reproduction.…”

Systematics of the Neotropical GenusLeptodactylusFitzinger, 1826 (Anura: Leptodactylidae): Phylogeny, the Relevance of Non-molecular Evidence, and Species Accounts

“…fallax, Krintler, 1986), and the dermal glands of several species are known to produce defensive skin secretions (Cei et al, 1967), including antimicrobial peptides and other protein toxins found in L. fallax (Rollins-Smith et al, 2005;King et al, 2005a), L. labyrinthicus (Libério et al, 2014), L. laticeps (Conlon et al, 2009), L. latrans (Nascimento et al, 2004(Nascimento et al, , 2007Leite et al, 2010), L. pentadactylus (Habermehl, 1981;Barlow, 1998;King et al, 2005b;Limaverde et al, 2009;Sousa et al, 2009), L. syphax (Dourado et al, 2007). Similarly, the foam nests of L. vastus possess a novel surfactant protein (Hissa et al, 2008(Hissa et al, , 2014.…”