ARMGARDT, Emily, T. ; Seattle University: Insects of the Sea: A Morphological Analysis of Copepod Evolution and Development

Copepods are found in nearly all aquatic and marine habitats, yet little is known about their embryonic development. Using the phosphorescent stains phalloidin, DAPI, and propidium iodide, the early development of musculature in two harpactoicid copepods, Tigriopus sp. and Harpacticus sp. was observed and compared. The musculature of both nauplii and adults is strikingly dissimilar; Harpacticus sp. more closely resembles a calanoid copepod, Calanus helgolandicus than Tigriopus sp. despite their close phylogenetic relationship. Tigriopus sp. had limb buds that resembled a chelicerate mite, Archegozetes longisetosus and a barnicle, Ibla quandrivalvis. Limb buds were conspicuously absent in Harpacticus sp. These results demonstrate that musculature may be more plastic evolutionary than previously thought.