Microcyclops ceibaensis

Microcyclops ceibaensis (Marsh, 1919) Fig. 31 Diagnosis. Adult female, 870 µm in length excluding caudal setae. Caudal ramus 3.3 times longer than wide (but the literature indicates a variation between 2.8–5 times), 5–6 spinules inserted anteriorly to the distal outer seta (Fig. 31A). Genital double-somite 1.1 times longer than wide. P1-endopod last segment with two pores on the surface, close to the outer margin in anterior view; P1 endopod last segment with a row of long spinules gradually increasing in length in the distal margin, close to the terminal spine, and long spinules gradually increasing in length close to the insertion of the distalmost inner distal seta (Fig. 31B). Dorsal margin of prosomites 2 to 4 slightly serrated; urosomites with serrated hyaline fringes. P4 basis has two transverse series of spinules in anterior view. Remarks. The specimen illustrated was collected in the lower stretch of the Paraná River. Reid (1985) reported this species in several countries in South America, in the coastal zone of lakes. Reid (1986) reported this species based on the observation of the type material deposited at the National Museum of Natural History, Smithsonian Institution (USA). Among the Microcyclops species found in the La Plata Basin, it is the only species with two pores in the last endopod segment of the P1. Gutiérrez-Aguirre and Cervantes-MartÍnez (2016) advanced M. diversus as a synonym of M. ceibaensis.