Biomarker and hematological fieldwork with amphibians: Is it necessary to sample all night?

Abstract

In the context of the global amphibian crisis, biomonitoring constitutes a valuable assessment tool to provide critical up to dateinformation on the status and health of amphibians worldwide. The aim of the current study was to evaluate the possible confoundingeffects of sex, size, and time since capture on enzymatic biomarkers and hematologic parameters of the South American frogLeptodactylus latrans. Frogs were collected by hand between 9 pmand 12 amon two consecutive nights. On the first night, capturedfrogs were transported for 2 h by car to laboratory installations, maintained overnight in plastic containers, and blood and tissuesampled on the next morning. In contrast, frogs collected on the second night were blood and tissue sampled in the field,immediately after the capture period. Hematological parameters were analyzed, and enzymatic activities of catalase, cholinesterase(ChE), and glutathione S-transferase (GST) were determined in the plasma, liver, kidney, andmuscle. Asex difference was observedonly for total white blood cell counts (WBC), females exhibiting significantly greater values than males. The packed cell volume(PCV), mean corpuscular hemoglobin concentration (MCHC), WBC, and muscle ChE activity were significantly correlated withsnout-vent length (SVL). The correlation was inversed in the case of MCHC, WBC, and muscle ChE, while the correlation waspositive between PCVand SVL. Most examined parameters presented similar values when frogs were sampled at night followingcapture or the next morning. Total red blood cells (RBCs) count, and plasma enzymatic activities of ChE and GST were the onlyparameters that presented significantly increased values in morning samplings compared with night samplings. Overall, the currentstudy indicates that it is best to sample the frogs as soon as possible after capture if hematologic or plasmatic biomarkers areexamined. Nevertheless, it is possible to sample on the next morning if tissular biomarkers are employed.