Experimental Consequences of Low Temperatures on Caiman latirostris Inmune and Endocrine Systems

SIROSKI A; MARÍA V. PARACHÚ MARCÓ; GRACIELA A. JAHN; PIETROBON E; MOLEON S.; REYES S.

santa fe

Congreso; 25th Working Meeting of the Crocodile Specialist Group (CSG/SSC/IUCN),Santa Fe, Argentina; 2018

universidad nacional del litoral

Low temperatures have an inhibitory effect on animal metabolism, causing organisms torespond with physiological mechanisms to reestablish their homeostatic condition.Corticosterone is a glucocorticoid synthesized and secreted under stress conditions inorder to stabilize metabolic functions and maintain the immune response of individuals.This hormone depends on the same metabolism for its synthesis, so if the latterdescends to very low levels the organism is unable to synthesize it and, therefore,generate a regulatory response. For ectothermal animals, such as crocodiles, the releaseof corticosterone is the main compensatory response against the decrease in metabolismin low temperature conditions, but for a certain threshold of temperature the organism isunable to continue its synthesis and the metabolism ceases. In Caiman latirostristolerance range and corticosterone blood levels at low temperatures are unknown. Theobjective of this study was to determine the lowest temperatures in which theconcentration of corticosterone is maintained at adequate levels to maintain a stablemetabolism and immunological parameters. Thus, 6 hatchlings and 6 juvenile wereexposed consecutively to decreasing 3 temperatures during 24hr each: 25°C (baselineand control), then to 17°C and lasts 8°C. Blood samples were taken from all animals tomeasure corticosterone plasma concentrations. In addiction total and differential whiteblood cell count, natural antibody titers and complement system activity were measured.Results showed a total white blood cell count and natural antibodies titers weresignificantly lower in juveniles exposed at 8°C compared to control and 17°C. Activityof complement system was lower at control and 8°C. Similarly, proportion ofheterophils increased significantly between temperatures control and 17°C, anddecreased between 17°C and 8°C. There was no significant change in immunologicalparameters of hatchling between control and 17°C. The results of corticosterone areprocessing to the date. For both groups of treatment, the period of 24 hours at 17°C didnot produce a change in the immunological parameters, this may be due to the action ofcorticosterone. On the other hand, the period at 8°C generated a decrease in theimmunological parameters in juveniles even death in some hatclings, which may berelated to the inability to continue synthesizing corticosterone due subsequently