Meeting Abstract
Most larval fish species must begin feeding upon hatching, but livebearing species such as the mosquitofish, Gambusia affinis, and mollies,Poecilia spp., develop the feeding apparatus before the need to feed.These two closely-related species have different lower jaw morphologies where Poecilia spp. possess an extra joint between the dentary and angular-articular bones,the intramandibular joint (IMJ).The IMJ evolved independently in multiple fish lineages, and in Poecilia spp., has been shown to play a pivotal role in scraping food from substrates, allowing the lower jaw to extend forward when it comes in contact with a food source. In this study, we cleared and stained ontogenetic series of Gambusia affinis and Poecilia spp. (mexicana and sphenops) to determine how the differing lower jaw morphologies develop, in order to make hypotheses about how the IMJ might have evolved in this lineage. Specifically, we establish the onset of lower jaw elements-the dentary, anguloarticular, and Meckel’s cartilage (MC)- and compare the allometric growth of the MC between species. We also compare pre-natal and post-natal growth of the lower jaw elements to gain a better understanding of how viviparity affects trait development.
