Meeting Abstract

P3-46   -   A role for canal neuromasts in patterning the facial skeleton of teleost fish Hamm, AR*; Gross, JB; University of Cincinnati; University of Cincinnati hammaa@mail.uc.edu

Since the late 1800s, numerous investigators have suspected that canal neuromasts prefigure facial bones in teleost fish. This was based on the stereotypical positions of lateral line organs on specific facial bones. The developmental basis for this phenomenon, however, has remained unknown. Our recent work showed that sensory neuromasts migrate to the precise position of future primary ossification centers of the orbital skeleton, suggesting they may play a role in inducing bone formation. Here, we explore this notion further in a freshwater teleost model system (Astyanax mexicanus) which includes both surface- and cave-dwelling morphs. In Astyanax, the orbital skeleton is composed of six intramembranous bones encircling the eye, including homologs of the lachrymal, jugal, and dermatosphenoid bones. In surface fish the suborbital bones show an invariant pattern of nine canal neuromasts associated with six bones. Interestingly, cave morphs rarely display this pattern, demonstrating substantial variation in number, shape, and size of bones across the left-right axis. Our first objective was to define the precise critical period of bone induction, to understand how neuromasts may influence this variation. Accordingly, we fluorescently labeled neuromasts (DASPEI) and mineralized bone (Calcein) across several weeks of early cranial development. We focused on the fourth and fifth canal neuromasts since these organs are present in all specimens, and each are associated with a single bone. In a complementary approach, we performed clearing and staining to define the spectrum of orbital bone variation in cavefish as a putative consequence of variable neuromast positioning. This work will inform how sensory systems evolve in complete darkness, and determine how sensory organs may constrain adult cranial form.