Observations on the taxonomic composition and vertical distribution of cyclopoid copepods in the central Red Sea

Abstract

The taxonomic composition and vertical distribution of cyclopoid copepods, including very small species, in the central Red Sea were analyzed. Samples were taken in a multiple opening and closing net with 0.1 mm mesh size to a depth of 450 m. Most species belong to the genus Oncaea (13 identified and 6 unidentified forms). Nearly one half of these are smaller than 0.4 mm in length. Nine cyclopoid species and three groups of very similar species and forms of Oncaea predominate. In the upper 450 m of the water column, each of these species or groups account for more than 1% of all cyclopoid specimens. In the epipelagic zone (0–100 m) Oithona simplex predominates, accounting for 20% of the total. In the upper mesopelagic zone Paroithona sp. and one of the unidentified Oncaea forms are most numerous from 100 to 250 m. and two groups of Oncaea are most abundant from 250 to 450 m. The dominance of single species among cyclopoids is less pronounced than that reported for calanoids in the mesopelagic zone of the central Red Sea.