title: Corticosterone stimulates hatching of late-term tree lizard embryos.
abstract: The regulation of hatching in oviparous animals is important for successful reproduction and survival, but is poorly understood. We unexpectedly found that RU-486, a progesterone and glucocorticoid antagonist, interferes with hatching of viable tree lizard (Urosaurus ornatus) embryos in a dose-dependent manner and hypothesized that embryonic glucocorticoids regulate hatching. To test this hypothesis, we treated eggs with corticosterone (CORT) or vehicle on Day 30 (85%) of incubation, left other eggs untreated, and observed relative hatch order and hatch time. In one study, the CORT egg hatched first in 9 of 11 clutches. In a second study, the CORT egg hatched first in 9 of 12 clutches, before vehicle-treated eggs in 10 of 12 clutches, and before untreated eggs in 7 of 9 clutches. On average, CORT eggs hatched 18.2 h before vehicle-treated eggs and 11.6 h before untreated eggs. Thus, CORT accelerates hatching of near-term embryos and RU-486 appears to block this effect. CORT may mobilize energy substrates that fuel hatching and/or accelerate lung development, and may provide a mechanism by which stressed embryos escape environmental stressors.
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-1505, USA. sweiss@ups.edu
authors.forename: Stacey L
authors.initials: SL
authors.lastname: Weiss
authors.forename: Gwynne
authors.initials: G
authors.lastname: Johnston
authors.forename: Michael C
authors.initials: MC
authors.lastname: Moore
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000494:pharmacology*; D004625:Embryo, Nonmammalian / Q000187:drug effects* / Q000502:physiology*; D005260:Female; D008116:Lizards / Q000502:physiology*; D008297:Male; D015735:Mifepristone / Q000494:pharmacology; D052287:Oviparity / Q000502:physiology*; D010063:Ovum / Q000187:drug effects; D013997:Time Factors
chemical_list: D015735:Mifepristone; D003345:Corticosterone