The stoichiometry of larval anuran development in natural wetlands

Abstract

Understanding the influence of growth and development on the stoichiometry of organisms with complex lifecycles is necessary to understand the spatial and temporal extent of consumer-driven nutrient dynamics. This can be particularly challenging in temporally variable habitats, such as geographically isolated wetlands (GIW), which dry down seasonally. Larval anurans (tadpoles) are excellent model organisms for studies within the framework of ecological stoichiometry because they undergo major anatomical changes during metamorphosis that likely require a shift in body stoichiometric demands. To examine stoichiometry of larval anurans in GIWs, we measured larval Lithobates sphenocephalus tissue carbon (C), nitrogen (N), phosphorus (P) and calcium (Ca) content, excretion NH₄-N, TDN and TDP, and egestion C, N and P across three developmental stage categories (no limbs, hind limbs only, and four limbs). We found that tissue P content increased significantly during later stages when bone development was occurring, which significantly reduced tissue C:P and N:P. Tissue C also increased across stages. Mass-specific excretion of TDN and N:P decreased across stages. Per capita NH₄-N excretion rate had a positive relationship with body size, and per capita excretion N:P had a negative relationship with body size. Mass specific bulk egestion and C egestion varied across stages, as well as C:N and C:P, but we could not distinguish which stages were different from one another. Per capita egestion rates of N and P were positively correlated with body size, and both C:N and C:P were negatively related to body size. We found that development stage of larval anurans was an important indicator of tissue, excretion, and egestion stoichiometry and these differences may influence their functional role in aquatic ecosystems throughout their development.

Keywords:

• Stoichiometry
• anuran
• ontogeny
• excretion
• egestion
• consumer
• nutrient cycling

Acknowledgments

We thank members of herpetology, plant ecology, and aquatics laboratories at the Joseph W. Jones Ecological Research Center for assisting in both field collection and laboratory processing. We thank Stephen W. Golladay at the Joseph W. Jones Ecological Research Center at Ichauway and Jonathan P. Benstead at University of Alabama for review of this article. This study was conducted under University of Alabama Animal Care and Use Committee (protocol # 15-10-0110) and Georgia Scientific Collecting Permit (Permit # 29-WJH-16-58).

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Each of the authors assisted in field collection of data used in this manuscript and each author contributed to writing, editing, and preparation of this manuscript. Laboratory analyses were performed by S. McLeay. Statistical analyses were done by C. Atkinson and S. McLeay.

Additional information

Funding

Funding for the study was provided by the University of Alabama and the Joseph W. Jones Ecological Research Center.