Examination of Eucyclops populations coming from Algerian water bodies and identified as Eucyclops cf. serrulatus showed three morphotypes, based on morphometric characters and microcharacters. Morphotype 1 was the most abundant, collected in the east and the west of Algeria. Morphotype 2 was sampled in the south of the country, characterised by posterolaterally elongated thoracic segments and the fourth thoracic segment bearing cilia on its lateral angles. Morphotype 3 was found in a small temporary pond in the north of the country and was the smallest one. Other differences were observed on surface microcharacters of antenna basipodite, coxopodite and intercoxal plate of the fourth leg. The characters of the most widespread morphotype (morphotype1) were stable in all localities despite the fact that these were located in two geographically separated regions (eastern and western Algeria).
Three morphotypes of Eucyclops serrulatus group (Fisher, 1851) (Crustacea, Copepoda, Cyclopoida) from Algerian water bodies were identified. The characters of the most widespread morphotype (morphotype 1) were stable in all localities despite the fact that these were located in two geographically separated regions (eastern and western Algeria).