Meeting Abstract
56.5 Sunday, Jan. 5 14:30 Cranial musculoskeletal development in the holosteans Amia calva and Lepisosteus oculatus. DAVIS, M.C.*; CASS, A.N.; SCHEIDT, D.C.; MCCUNE, A.R.; Kennesaw State University; Cornell University; Kennesaw State University; Cornell University mdavi144@kennesaw.edu
The pattern of cranial and pharyngeal musculoskeletal development has been extensively studied in tetrapods and in the derived actinopterygians (teleosts). However, we lack adequate descriptions of muscle and skeletal formation in more basal osteichthyan taxa, such as the non-teleost actinopterygians. Here we assess the patterns of associated cranial muscle and skeletal formation during embryonic and larval development in the holosteans Amia calva (bowfin) and Lepisosteus oculatus (spotted gar). We use nano-CT imaged specimens, supplemented with immunostaining for myogenic and chondrogenic markers to assess the relative timing, order of appearance, and embryonic/larval anatomy of both conserved and derived muscle complexes in each taxon. Our results show conservation in the early recruitment of muscle groups necessary for ventilation, feeding, and vision in both Amia and Lepisosteus, a pattern consistent with that observed for many teleosts (e.g. zebrafish) and basal tetrapods (e.g the axolotl). This observation supports the notion that in addition to phylogenetic history, common environmental and physiological constraints may play a role in determining the order (and timing) of appearance of certain functional musculoskeletal systems. Despite such conservation and constraint, the distinctive morphologies that characterize each taxon emerge relatively early in development. When placed in the phylogenetic context of teleost and tetrapod cranial anatomy, our data provide insights into the conserved musculoskeletal developmental pattern considered primitive for osteichthians and more broadly so for gnathostomes. In addition, our results provide crucial tests of hypotheses of muscle homology and evolution in the more derived vertebrate clades.
