Nitella opacaNitella opaca is a species of algae in the family Characeae.DescriptionNitella opaca is a dioecious species very similar to Nitella flexilis and difficult to distinguish from it.DistributionNitella opaca has been observed in fresh waters, mostly lakes. Can be found up to 12 m deep.EtymologyFrom the Latin adjective opaca, meaning "opaque", "not shining".