P1.107 Jan. 4 Myofiber hyperplasia underlies polyphenic development in spadefoot toad larvae STORZ, Brian/L*; MOERLAND, Timothy/S; Florida State University, Tallahassee, FL; Florida State University, Tallahassee, FL email@example.com
Tadpoles of at least two species of spadefoot toads show developmental polyphenism, in which one genotype can produce multiple phenotypes. Larvae hatch with the “typical” omnivorous phenotype, but soon after (3-5 days post hatching) some may transform in both morphology and behavior into a carnivore that actively preys on microcrustaceans and cannibalizes conspecifics. A number of traits in carnivores display up or down modifications of growth rate; further, these modifications occur in two, temporally dissociated suites: an increase in growth rate of the jaw musculature just after hatching and an increase in the growth rate of tail musculature at mid-development. In a continuing series of investigations to understand myodevelopmental program modification in the carnivore phenotype relative to the omnivore phenotype, we have determined that hyperplasia––an increase in myofiber number––underlies myoenlargement of both the orbitohyoideus jaw muscle and the tail muscle in carnivore tadpoles relative to omnivores. This finding helps to limit the potential pool of growth factors regulating modification of the myodevelopmental program in carnivores because different myoenlargement forms (e.g. hypertrophy or hyperplasia) are regulated by different factors.