Lipid Mass and Fatty Acid Composition of Spea spp. in Playa Wetlands as Influenced by Land Use

Abstract

Playas are the primary habitats for amphibians in the Southern High Plains, USA. Spadefoot toads (Spea spp.) are the dominant amphibian species; their demographics, body size, and immunology have been altered in playas in cropland relative to native grassland landscapes. To further understand cultivation effects on spadefoots, we compared percent body lipids and fatty acid profiles of S. bombifrons and S. multiplicata among tadpoles, metamorphs, and post-metamorphic juveniles in cropland versus grassland playas. Generally, tadpoles of both species had lower percent lipids than metamorphs and juveniles. Percent lipids were influenced by cultivation only in S. multiplicata; tadpoles contained more lipids in cropland than grassland playas. Sum of all fatty acids in S. bombifrons increased after metamorphosis regardless of landscape. However, fatty acids in S. multiplicata were similar among stages in cropland whereas in the grassland habitat juveniles had increased levels compared to tadpoles and metamorphs. In both species, saturated fatty acids decreased after metamorphosis. Mono- and polyunsaturated fatty acids generally remained steady or increased after metamorphosis. However, polyunsaturated levels were lower in S. bombifrons tadpoles and S. multiplicata tadpoles and metamorphs in cropland than grassland playas. Thus, cultivation may be affecting nutritional profiles in these species with associated fitness consequences.