My lab has been working on developing the amphipod, Parhyale hawaiensis, as a model system for the study of segmentation and body patterning. This animal is particularly appealing because individual parasegments are formed from single rows of ectodermal precursor cells. Our analysis thus far indicates that orthologs of Drosophila pair-rule genes are responsible for setting up the pattern of segmentation, but without any trace of the pair-rule patterns seen in Drosophila. Many of the expression patterns are particularly dynamic, with some intimately tied to the cell cycle. In addition, we have examined the role of Hox genes in subsequently patterning the Parhyale segments, and results from misexpression and knockdown of Hox gene expression has helped us uncover their function in Parhayle and role in crustacean evolution.

Conventional arthropodology sees the crustacean's double antennae, mouthpart "teeth", swimming appendages, and respiratory gills, the spider's chelicerae, and the insect's wings, epipharynx, hypopharynx, abdominal plate gills, vesicles, ovipositors, gonapophyses, penes and cerci as secondary indigenous lobes. In addition, the conventional approach to the basal arthropod limb considers only six or seven segments. I present evidence pooled from various biology fields to show that these adaptations evolved from the outer and inner rami (exites and endites) of a single, ancestral, polyramous, "Swiss-army knife" type of a limb with 11 limb segments.

Tunas and lamnid sharks have well-recognized morphological and physiological specializations that enable them to perform as fast swimming apex predators in the open oceans. Recent investigations have revealed a much greater degree of evolutionary convergence in structure and function between lamnids and tunas than was previously known. Both groups achieve "thunniform" swimming by the action of highly elongated myomeres and myotendinous linkages that allow the endothermic red muscle to produce thrust at the tail while residing primarily in the mid-body region. Furthermore, the locomotor adaptations of tunas and lamnid sharks for fast and continuous swimming are unlike those of virtually all other fishes.