Effects of heat waves on telomere dynamics and parental brooding effort
in nestlings of the zebra finch (Taeniopygia castanotis)
Abstract
Heat waves are predicted to be detrimental for organismal physiology
with costs for survival that could be reflected in markers of biological
state such as telomeres. Changes in early life telomere dynamics driven
by thermal stress are of particular interest during the early post-natal
stages of altricial birds because nestlings quickly shift from being
ectothermic to poikilothermic to endothermic after hatching. Telomeres
of ectothermic and endothermic organisms respond differently to
environmental temperature, but investigations within species that
transition from ectothermy to endothermy are lacking. Also, ambient
temperature influences parental brooding behavior, which will alter the
temperature experienced by offspring and thereby, potentially, their
telomeres. We exposed zebra finch nestlings to experimental heat waves,
and compared their telomere dynamics to that of a control group at 5, 12
and 80 days of age that correspond to three different thermoregulatory
stages (ectothermic, poikilothermic and endothermic respectively); we
also recorded parental brooding, offspring sex, mass, growth rates,
brood size and hatch order. Nestling mass showed an inverse relationship
with telomere length, and nestlings exposed to heat waves showed lower
telomere attrition during their first 12 days of life (poikilothermic
stage) compared to controls. Additionally, parents of heated broods
reduced the time they spent brooding offspring (at five days old)
compared to controls. Lower brooding effort was associated with shorter
telomeres in 12 day old nestlings. Our results indicate that the effect
of heat waves on telomere dynamics likely varies depending on age and
thermoregulatory stage of the offspring in combination with parental
brooding behavior during growth.