AN ONTOGENETIC STUDY OF A NEWLY DISCOVERED POPULATION OF CYZICUS GYNECIUS (CRUSTACEA: BRANCHIOPODA: SPINICAUDATA) FROM MUD LAKE (CASSADAGA, NY) USING SEM IMAGERY

The purpose of this project is to document the ontogeny of a newly discovered occurrence of the clam shrimp species, Cyzicus gynecius, in western New York. Though this species is known from Ohio, Pennsylvania, New Jersey, and eastern New York, this is the first record of the species west of the Hudson Valley in New York. Clam shrimp are bivalved branchiopod crustaceans which first appeared nearly 400 million years ago in the Devonian. They are most notable for their bivalved carapace (superficially resembling a mollusc shell), which is a hard, two-sided shell held together by a closing muscle. They, and other branchiopods, are also distinctive due to their unique ability to reproduce via drought-resistant eggs. C. gynecius is particularly notable due to the fact that the species is entirely female; they reproduce via a form of self-cloning called parthenogenesis. This population was discovered in a muddy ATV track near Mud Lake in Cassadaga, New York and samples of mud containing eggs were collected. In the lab, individuals were reared and collected at different points in their lifecycle and observed for morphological analysis with a scanning electron microscope (SEM). Preliminary results from the scanning electron microscope revealed that the young, termed nauplii, have a distinctive labrum with three prominent spines. Other members of the Cyzicidae for which nauplii have been illustrated share this trait, while other clam shrimp outside of the Cyzicidae lack it. This feature may be a developmental synapomorphy of the family Cyzicidae. Further study of spinicaudatan ontogenies may reveal additional transient characteristics that give new phylogenetic insights.