22.7 Wednesday, Jan. 4 Critical periods during teleost development: a case study of two cypriniform fishes KA'APU-LYONS, C.; GIBB, A.C.*; Northern Arizona University; Northern Arizona University firstname.lastname@example.org
During early development, teleosts undergo intervals of extremely high mortality. These intervals, often termed “critical periods,” have been attributed to various causes, including starvation and predation. However, the proximal mechanisms that underlie such periods of increased vulnerability have yet to be identified. We suggest that, at least for some teleosts, the ontogenetic transition from the embryonic, cartilage-based feeding mechanism to the juvenile/adult, bone-based feeding mechanism may compromise feeding performance and thereby increase the likelihood of death due to starvation. In fact, when feeding kinematics for two species of cypriniform fish (Xyrauchen texanus and Gila robusta) are examined across early development, the movements used to procure prey become absolutely slower during the time period when the bony elements of the cranium are forming; feeding movements become rapid again when juvenile cranial morphology has been attained. Slower feeding mechanics will likely decrease feeding rates of animals in the wild and make it difficult for them to acquire the resources necessary to support growth and morphogenesis; thus, functional demand may outpace structural capacity (sensu Galis) to generate a “critical period.” However, this period of vulnerability may be avoided in teleosts that provision their young with sufficient endogenous (yolk) resources such that young fish can avoid exogenous feeding until the bony elements of the skull are fully formed.