Meeting Abstract
Anguilliformes (true eels) are a large clade of highly elongate fishes that exhibit diverse feeding ecologies. Within Anguilliformes there is surprising diversity in the mechanisms of elongation of the body, including almost every trend for axial elongation known within actinopterygian fishes. In morays (Muraenidae), maximum body length evolves through region-specific increases in vertebral number, elongation of individual vertebral centra, and postembryonic somatic growth. In this study, we investigate postembryonic somatic growth in relation to axial patterning by investigating how organs scale over ontogeny using the California moray (Gymnothorax mordax) as our model. We measured the anteroposterior positions of the organs as well as their relative position to the vertebrae in morays ranging from 320–930 mm in standard length. We also measured lengths and widths of vertebral centra and the vertebral span of each organ system. We find that G. mordax increases its body length faster than tail length over ontogeny by increasing vertebral lengths in the precaudal region over the caudal region. We found that the majority of organ lengths scale negatively with body cavity length but many organ masses have allometric relationships with this region. Body depth scaled positively with body cavity length, which corresponds with the steep increase in mass for most of the organs. The consistent span of organ topology with vertebral number during growth suggests strong morphogen gradients during somatic growth. Our scaling trends within the California moray are interesting in comparison to studies documenting ontogenetic changes in the position of visceral organs in other elongate ectothermic predators such as snakes.
