Meeting Abstract
P3.3 Tuesday, Jan. 6 The impact of periodic dehydration stress on cardiovascular function in the embryonic American alligator (Alligator mississippiensis) CROSSLEY II, DA*; TATE, KB; EME, J; University of North Dakota; University of North Dakota; University of California, Irvine dane.crossley@und.nodak.edu
Reptilian embryos are unique among amniotic vertebrates due to a virtual absence of parental care following oviposition in most species and high eggshell permeability in comparison to birds. This reproductive strategy leaves the developing embryo subject to abiotic fluctuations in the surrounding nest environment, such as reductions in gas conductance, hypoxia and bouts of dehydration. These fluctuations can be recurrent during long incubations (~70d for alligators), but their impact on the physiology of developing reptiles is poorly understood. We studied the effects of periodic dehydration events on embryonic alligators, including changes in hemodynamic and blood composition parameters. Dehydration (net 15% loss in egg mass across 60-80% of development) significantly (p<0.05) increased hematocrit (34+2 vs 29+1% rbc), plasma osmotic concentration (361+9 vs 290+2 mmol*kg-1), yolk mass (18+1.5 vs 11.1+1.5 g) and ratio of heart to body mass (5.0+0.3 vs 4.0 + 0.3 mg*g-1) compared to control embryos at 90% of development. Conversely, mean arterial pressure (1.2+0.2 vs 1.8+0.2 kPa) and embryonic mass 16.9+2.7 vs 32.9+2.7 g) were significantly reduced by this stress compared to controls, with no significant difference in embryonic stage. Our findings suggest that hydration state of the nest environment can dramatically alter the physiology of developing American alligator and may impact hatchling survival.
