Description and ultrastructure of Kathablepharis tenuis sp nov and K. obesa sp nov -: Two new freshwater Kathablepharids (Kathablepharididae) from Colorado and Wyoming

The ultrastructure and systematics of two new freshwater kathablepharids, Kathablepharis tenuis sp. nov. and Kathablepharis obesa sp. nov., are described. These descriptions bring the total of described Kathablepharis species to eight. Both new species differ from previously described kathablepharids by having centrally located food vacuoles and posteriorly situated nuclei. Consequently, a modified circumscription of the Kathablepharididae also is proposed. K. tenuis and K. obesa are separated from each other based on differences in cell shape/size, number of cytopharyngeal rings, and feeding behavior. K. tenuis is oblong with rounded ends, possesses twelve cytopharyngeal rings in the feeding apparatus, and forms dense swarms of rapidly swimming, attacking cells when feeding. K. obesa is obovoid in shape, possesses ten cytopharyngeal rings in the feeding apparatus, and does not form dense swarms when feeding. Finally, a new structure in the feeding apparatus of K. obesa, termed the sub-cytostomal ring, is identified, and a similar structure in K. ovalis requires a re-intepretation of its feeding apparatus.