A cytogenetic study was carried out on the early embryonic stages of the cyclopoid species Mesocyclops longisetus longisetus (Crustacea, Copepoda) from freshwater environments of the São Carlos area of south-east Brazil. Chromatin was staining using acetic orcein solution. The species showed 2n = 14 chromosomes and presented chromatin diminution in the 4th embryonic cleavage. The eliminated chromatin was concentrated in the equatorial region of the embryonic cell. The results were compared with data for other cyclopoid species of temperate regions.
Cyclopoida; Mesocyclops longisetus longisetus; cytogenetics; chromatin diminution; chromosomal number