Frog Foam Nest Protein Diversity and Synthesis

Abstract

Some amphibian species have developed a breeding strategy in which they deposit their eggs in stable foam nests to protect their eggs and larvae. The frog foam nests are rich in proteins (ranaspumin), especially surfactant proteins, involved in the production of the foam nest. Despite the ecological importance of the foam nests for evolution and species conservation, the biochemical composition, the long-term stability and even the origin of the components are still not completely understood. Recently we showed that Lv-RSN-1, a 23.5-kDa surfactant protein isolated from the nest of the frog Leptodacylus vastus, presents a structural conformation distinct from any protein structures yet reported. So, in the current study we aimed to reveal the protein composition of the foam nest of L. vastus and further characterize the Lv-RSN-1. Proteomic analysis showed the foam nest contains more than 100 of proteins, and that Lv-RSN-1 comprises 45% of the total proteins, suggesting a key role in the nest construction and stability. We demonstrated by Western blotting that Lv-RSN-1 is mainly produced only by the female in the pars convoluta dilata, which highlights the importance of the female preservation for conservation of species that depend on the production of foam nests in the early stages of development. Overall, our results showed the foam nest of L. vastus is composed of a great diversity of proteins and that besides Lv-RSN-1, the main protein in the foam, other proteins must have a coadjuvant role in building and stability of the nest.

Analysis of abiotic factors associated with foam nests of Cuvier’s foam froglet (Physalaemus cuvieri) in southeastern Brazil

“…While the use of foam nest as reproductive strategy among anurans is well known in the literature (e.g. Tyler and Davies 1979;Hödl 1990Hödl , 1992Kadadevaru and Kanamaedi 2000;Bastos et al 2010;Cruz et al 2016), as well as some of the foams biotechnological applications (Hissa et al 2016;Cooper et al 2017), there are only few studies regarding morphometry and ambient variables associated with P. cuvieri nests (Bokermann 1962; Barreto and Andrade 1995;Andrade 2007). Our current observations of P. cuvieri building nests under herbaceous vegetation close to the studied pond, corroborates findings by Barreto and Andrade (1995) and Uetanabaro et al (2008).…”

Identification of Novel Proteins in Foam Nests of the Japanese Forest Green Tree Frog, Rhacophorus arboreus

“…Moreover, they revealed that the foam nest from L. vastus contained more than 100 proteins. Among them, Lv-RSN-1 was about 45% of the total protein in the foam nest (Hissa et al, 2016). The Japanese green tree frog, Rhacophorus arboreus (Amphibia, Anura, Rhacophoidae), is a frog species that is endemic to Japan (Fig.…”

Transcriptomic analysis of differentially expressed genes in the oviduct of Rhacophorus omeimontis provides insights into foam nest construction

“…In anuran amphibians, foam nest construction is associated with adaptation to terrestrial life, and 10 out of the 41 different reproductive modes found in anurans involve foam nest construction [5–7]. Depending on the anuran species, the foam nests are produced in underground burrows, float on the water surface, or are even suspended from vegetation [4, 8–10]. Several functions have been identified for the production of anuran foam nests, such as protecting eggs and embryos against predators, desiccation, microbial degradation and thermal damage, as well as supplying oxygen and serving as a food source for tadpoles [2, 8, 11–13].…”

“…Recent studies on anuran foam nests have mostly focused on their structure and biochemical composition and the construction behavior leading to them [4, 13, 15–17]. Well-studied foam-nesting species include frogs from the genus Leptodactylus , especially the túngara frog [4, 10, 12, 14, 15]. Hissa et al [16] and Fleming et al [17] reported that the foam nest components of Leptodactylus frogs were a mixture of proteins termed ranaspumins, with surfactant activity, cystatin activity and lectin composition.…”

“…Despite considerable knowledge of the biochemical components of and construction behavior leading to anuran foam nests, little is known about the molecular basis of and metabolic pathways involved in the process of foam nest production. In addition, published studies on anuran foam nests typically concern the water-based foams produced by members of Leptodactylidae, and whether the arboreal foam nests of anuran species have similar components remains unclear [10, 20].…”