Key to the Red Sea Labidocera (Crustacea; Calanoida: Pontellidae) copepods, the distribution of the species in various habitats, with special reference to two new records, and a historical correction

Pontellid copepods of the genus Labidocera from the Red Sea are described in the present work. The species are most easily distinguished according to their fifth leg, "P5", which has a very distinctive shape and is characterized by the presence of an extended claw-like thumb at the proximal end of the exopodite segment. During a survey off the coast of Hurghada, Red Sea, a total of four Labidocera species were identified, two of which were new records for the Red Sea. A historical review showed that a third, presumably new record had already been sampled in the early 1900s but overlooked by previous authors. This increases the total number of species observed in the Red Sea to eight, belonging to three groups. The first is the detruncata group, which includes five species: L. boxshalli, L. detruncata, L. orsinii, L. pavo, and a new record for the Red Sea, L. madurae. The minuta group is the second and includes only one species: L. minuta. The remaining two species, L. acuta and the first record in the Red Sea of L. euchaeta, are included in an unassigned group. All of these species are Indo-West Pacific forms with wide tropical and subtropical distributions. Mistakes can sometimes be made by taxonomists when identifying the presence of a particular species in a specific area, such as the case of denying the existence of L. detruncata in the Red Sea, for which a historical review was carried out in the current work demonstrating its previous existence. Therefore, historical reviews must be continually conducted to evaluate the differences in the spatial and temporal distributions of various species. On the other hand, Habitats with well-balanced ecosystems such as coral reefs are more diverse than those of a competitive nature or that exposed to severe environmental conditions such as seagrass and shallow lagoons. (C) 2019 National Institute of Oceanography and Fisheries. Hosting by Elsevier B.V.