Meeting Abstract
Batrachoidiformes is a monophyletic group of mostly benthic, ambush-predatory fishes. Species of the genus Porichthys, the midshipmen, are unique in this order for having photophores and being relatively pelagic. Despite inhabiting deeper habitats than other Toadfishes, species of Porichthys build nests in intertidal rocky habitats, similar to other Batrachoidiformes. Previous ontogenetic studies have described only the external larval morphology of few species of Batrachoidiformes, and data on the skeleton and soft tissues are lacking. Ontogenetic data are important for understanding homology and the phylogenetic relationships among taxa. An ontogenetic series of the early life stages of Plainfin Midshipmen, P. notatus (5 to 28 mm TL), was collected during the summers of 2017 and 2018, and skeletal ontogeny was investigated using cleared-and-stained specimens. Changes in the neural and muscular system were examined by staining whole specimens with Phophomolybdic Acid and CT-scanning them at resolution of 5.7 microns. The development of the vertebral column occurs in an anterior to posterior direction, as in other percomorph fishes. When larvae hatch from the corion, the basidorsal elements of the first vertebrae are already present. The third dorsal-fin spine, previously proposed to be absent in Porichthys, was observed in early stages (7 mm TL), but is reabsorbed before larvae become free swimming (25 mm TL). The brain displays allometric growth, having an optic lobe that is almost one-half of the length of the brain in early stages (5-8 mm TL); it becomes less than one-quarter of brain length in free-swimming juveniles (>30 mm TL). Individual portions of the adductor mandibulae complex are completely distinct in all observed stages.
