A new copepod: Neocyclops hoonsooi

Copepods are small crustaceans found in the sea and every freshwater habitat. About 13 000 species of copepods are known to science. Planktonic copepods are important to global ecology and the carbon cycle. They are usually the dominant group in zooplankton, and are the major food organisms for small fish and other crustaceans such as krill. Some scientists believe they form the largest animal biomass on earth.

One of the plaktonic groups is Cyclopoida. The free-living members of this group are almost identical to each other in physical appearance. The cyclopoid genus Neocyclops inhabits marine environments. It's species are widely distributed in coastal habitats of the Northeast and Tropical Atlantic, the Mediterranean, the Black and Red Seas and the Indo-Pacific. Most of the species are endemic.

The new species was found at a beach in South Korea and the species name is dedicated to the late Professor Hoon Soo Kim in honor of his contribution to the development of invertebrate taxonomy in Korea.

For the experts: A new cyclopoid species of the genus Neocyclops Gurney, 1927 is described. Type specimens were collected from a beach on south-western coast of the Korean Peninsula by rinsing intertidal coarse sandy sediments. Neocyclops hoonsooi sp. n. is most characteristic in showing the conspicuous chitinized transverse ridges originating from the medial margins of the coxae of all swimming legs. The new species is most similar to N. vicinus, described from the Brazilian coast, and N. petkovskii, from Australia. All three species share a large body size (more than 750 µm long), the presence of an exopodal seta on the antenna, two setae on the mandibular palp, the same seta/spine armature on the third endopodal segment of leg 3 (3 setae + 3 spines), and the fairly long inner distal spine on the third endopodal segment of the female leg 4. However, N. hoonsooi sp. n. differs from both species by the much shorter caudal rami (less than 1.7 times as long as wide) and the shorter dorsal caudal seta VII. Furthermore, N. hoonsooi is clearly distinguished from N. vicinus by the 10-segmented antennule (vs 12 segments in N. vicinus), and from N. petkovskii by the elongate inner distal spine on leg 5 exopod and the 3-segmented leg 5 in male (vs 4-segmented in N. petkovskii). A tabular comparison of characters separating N. hoonsooi from its closest allies and a key to Neocyclops species from the Indo-Pacific Ocean are provided. This is the first record of the genus Neocyclops from the northern Pacific.