Alternating egg-brooding behaviors create and modulate a hypoxic developmental micro-environment in Children's pythons (Antaresia childreni)

Abstract

SUMMARYParental care is a widespread and ecologically relevant adaptation known to enhance the developmental environment of offspring. Parental behaviors, however, may entail both costs and benefits for developing offspring. In Children's pythons (Antaresia childreni), we monitored both maternal egg-brooding behavior and intra-clutch oxygen partial pressure (P O 2) in realtime to assess the effects of various brooding behaviors on P O 2 in the clutch micro-environment at three stages of development. Furthermore, at the same developmental stages, we measured O 2 consumption rates (V O 2) of eggs at varying P O 2 to determine their critical oxygen tension (i.e. the minimal P O 2 that supports normal respiratory gas exchange) and to predict the impact that naturally brooded intra-clutch P O 2 has on embryonic metabolism. At all three stages of development, a tightly coiled brooding posture created an intra-clutch P O 2 that was significantly lower than the surrounding nest environment. Maternal postural adjustments alleviated this hypoxia, and the magnitude of such corrections increased with developmental stage. Mean intraclutch P O 2 decreased with stage of development, probably because of increasing egg V O 2. Additionally, embryo critical oxygen tension increased with developmental stage. Together, these results suggest that python embryos are unable to maintain normal metabolism under brooded conditions during the final 10% of incubation. These results demonstrate that specific parental behaviors can impose obligatory costs to developing offspring and that balancing these behaviors can mediate deleterious consequences.

Temporal and Spatial Complexity of Maternal Thermoregulation in Tropical Pythons

“…As described previously, we categorized egg brooding into two behavior types that are strongly associated with nest-clutch thermal, hydric, and respiratory dynamics , 2009a, 2010. We defined tight coiling to be when a female was motionless and tightly coiled around her clutch.…”

“…Although most species lack significant thermogenic capability, brooding pythons can behaviorally thermoregulate their eggs in two ways. First, a brooding female can use subtle shifts in her body posture to alter thermal resistance between the nest and clutch environments (e.g., females increase tight coiling when the nest is cooling; A. childreni: Stahlschmidt and DeNardo 2009a). Second, a brooding female may temporarily leave her clutch to gather heat radiated from the sun or conducted from the substrate and then return to her nest to transfer heat to her clutch (black-headed python Aspidites melanocephalus Krefft 1864: Johnson et al 1975; southern African rock python Python natalensis Gmelin 1788: Alexander 2007).…”

“…Studies of captive pythons continue to elucidate the effects of thermoregulatory tactics on offspring at specific stages within reproduction, including during gravidity (egg bearing; Lourdais et al 2008), at oviposition (Stahlschmidt et al 2011a), and during egg brooding (Stahlschmidt and DeNardo 2009a). However, the tactics by which wild female pythons meet the thermal needs of offspring are still unclear because researchers have yet to comprehensively examine the physiological and behavioral aspects of maternal thermoregulation in a natural population of pythons.…”

Proliferation, Migration, and Survival of Cells in the Telencephalon of the Ball Python, Python Regius

“…Some species of female pythons will also undergo shivering thermogenesis. In order to keep their eggs warm during brooding, female pythons will shiver, moving from a series of muscular contractions of the whole body thus generating heat (Harlow and Grigg, 1984;Stahlschmidt and DeNardo, 2008;2009;Vinegar et al, 1970). In order to determine the role the CNS plays in these systems, it is important to do preliminary studies of neuroanatomy and neuroplasticity, and then perform experiments modifying these systems to determine their effect on the brain and vice versa.…”

“…Some species of female pythons also maintain the temperature of their eggs by shivering thermogenesis when brooding. Shivering thermogenesis occurs when a series of muscular contractions of the whole body generates heat for incubating eggs (Harlow and Grigg, 1984;Stahlschmidt and DeNardo, 2008;2009;Vinegar et al, 1970). Pythons experience vomeronasal chemical sensing and possess labial pits for infrared detection (Molenaar, 1978a;Molenaar, 1978b).…”