Meeting Abstract
The lateral line is a crucial sensory system present in many aquatic vertebrates. This sense enables organisms to detect local changes in water flow and pressure which is vital for predator evasion, prey capture and other social or environmental interactions. This system is substantially expanded in Astyanax cavefish compared to closely-related surface-dwelling forms, suggesting this non-visual sensory system is under strong selection in cave forms. Additionally, cave forms also harbor multiple abnormalities in their skulls, specifically in the suborbital (SO) bone complex. Owing to the vicinity of lateral line sensory organs (neuromasts) to the SO bones which underlie them, we explored if there was a developmental interaction between this system and facial bones. We utilized two live fluorescent stains to visualize the lateral line system, and developing bones, to produce a comprehensive longitudinal analysis of bone/neuromast growth within individuals. We discovered that dermal SO bones initiated ossification at the position of specific canal neuromasts. Interestingly, abnormalities in the lateral line led to abnormalities in the SO series. For instance, adjacent bones of the SO series in cavefish frequently fused together. In these cases, the distance between canal neuromasts was significantly shorter than in cases where bony fusion did not occur. We also observed that in certain cavefish individuals, the sixth bone of the SO series was entirely absent. This was only observed when the normally associated canal neuromast was also absent. This work suggests that canal neuromasts provide a fundamental “pre-pattern” for the position of SO bones in vertebrates. Aberrations to this pattern explain multiple abnormalities in the craniofacial complex of an obligate cave-dwelling animal.
