IMPACT OF GAS SUPERSATURATION ON THE DEVELOPMENT OF GAS BUBBLE TRAUMA IN PAEDOMORPHIC EURYCEA SALAMANDERS

There are eleven species of paedomorphic lungless salamanders endemic to Texas. Of these, eight are considered threatened by the International Union for Conservation of Nature (IUCN). One of these, the Barton Springs Salamander (Eurycea sosorum), is found only in springs and aquifers in and around Austin, Texas. A large population of this species is found in Barton Springs, located in Austin, TX–where dissolved gas saturation has been measured as high as 134%. Morbidity and mortality events in Barton Springs Salamanders have been documented coinciding with periods of dissolved gas supersaturation. This study seeks to understand what environmental conditions lead to mortality and morbidity events from gas bubble trauma and to investigate gas bubble trauma lesion distribution. For my study, individuals of a surrogate species–the Fern Bank Salamander (Eurycea pterophila)– were exposed to different levels of gas supersaturation and evaluated for changes in metabolic activity using intermittent-flow respirometry. This species was selected due to genetic, morphological, and habitat similarities. To further investigate gas bubble trauma in this clade, diffusible iodine-based contrast-enhanced computed tomography (diceCT) was performed on animals from four species that succumbed to a supersaturation event at a federal research facility: Eurycea sosorum, Eurycea rathbuni, Eurycea pterophila, and Eurycea nana. A significant increase in standard metabolic rate was detected in animals exposed to gas saturation levels of 120%. Lesions were detected throughout the body using diceCT, including large hemorrhages in the coelom of multiple individuals. Positive buoyancy and rapid change were identified as potential catalysts for gas bubble trauma mortalities. Identifying these factors provides potential opportunities for mitigation efforts.