Oithona Davisae, New Species, and Limnoithona Sinensis (Burckhardt, 1912) (Copepoda: Oithonidae) From the Sacramento-san Joaquin Estuary, California

Abstract

ABSTRACT Zooplankton samples from the Sacramento-San Joaquin Estuary collected by the California Department of Fish and Game and the United States Geological Survey were examined for cyclopoid copepods of the family Oithonidae. Of the three species found, Limnoithona sinensis, Oithona davisae, new species, and O. similis, the first two are described here. Limnoithona sinensis, like its congener L. tetraspina, has been previously reported from delta localities in the Yangtze River, China. In general morphology O. davisae is similar to many estuarine/lagoonal oithonids of temperate and tropical American coastal waters. Two characters, an elongate ventrally pointed rostrum and/or a long distal spine on the inner lobe of the first maxilla, suggest affinities to the Indo-West Pacific estuarine species O. brevicornis, O. aruensis, and O. wellershausi. In the northern hemisphere O. similis is a common subarctic oceanic species. Specimens have also been reported from estuarine areas. Zooplankton samples taken in coastal estuarine localities from Humboldt Bay south to Baja California were examined to determine the distribution of these three species. O. similis was the only species found.