Meeting Abstract
Skeletal reduction is a common feature among deep-sea fishes, including snailfishes. However, these fishes must still perform the same functions as their shallow water relatives, thus skeletal reductions may not be uniform. Snailfishes (Liparidae) are found across a large bathymetric range (0-8,200 m), with intertidal ancestors giving rise to speciose deep-sea lineages. We used microcomputed tomography (micro-CT) to estimate average bone mineral density (BMD) and take morphometrics of the jaw, pectoral girdle, and neurocranium. Using correlations of phylogenetic independent contrasts, we found that length of the dentary, pectoral radials, and neurocranium did not vary with collection depth. However, lengths of the premaxilla, angulo-articular, and pectoral girdle decreased with greater depth. Maxillary width decreased with depth, implying more gracile bones. Average BMD of the jaw decreased with increasing depth. The ventral suction disc was also lost multiple times within the deep sea lineage. Our results suggest at least three mechanisms of skeletal reduction: (1) reduction of bone size, (2) reduction of bone density, and (3) loss of skeletal elements. These skeletal reductions may be an adaptation to environmental conditions of high pressures, low temperatures, declining luminosity and sporadic food availability. We conclude that some skeletal elements are maintained at the expense of others as species balance the functional demands in the deep sea.
