Abstract:
In Westernport and Port Phillip Bays, Victoria, Australia, copepods previously identified as Acartia clausi Giesbrecht or Acartia tranteri Bradford form polymodal length-frequency distributions at some times of the year. The three size morphs of Acartia ("large," "medium," and "small") closely resemble each other in characters other than size. Allozyme electrophoresis of medium and large morphs demonstrated that fixed gene differences occur between these morphs, confirming their diagnosis as separate species. Using comparative morphometrics, we provide taxonomic notes on A. tranteri sensu stricto, describe each of the large and small morphs of Acartia from Victoria, and describe the medium morph as a new species, Acartia fancetti. This new species exhibits morphological variability in size and pigmentation, depending on habitat.
