Periphytic Actinella Lewis (Ochrophyta, Bacillariophyceae) species from an Environmental Protection Area in Brazilian Amazon

Luís Gustavo de Castro Canani


Abstract: Aim: The aim of this study is to present the Actinella species found in periphytic samples, collected in the Environmental Protection Area of Alter do Chão (Santarém, Pará, Brazil), and to comment on their morphology, comparing with the existing records and to increase the knowledge of the genus distribution in the Pará state. Methods: The ten periphytic samples used in the study were collected at seven sampling stations in the Alter do Chão Environmental Protection Area (Santarém, Pará, Brazil), in October 2015 and February and July 2016. The pH, dissolved oxygen, conductivity and water temperature were measured in the collections of 2016. The samples were oxidized and analyzed under light microscope. Results: The studied water bodies presented low conductivity and acidic pH. The genus Actinella was represented by 11 taxa. Several of them were originally described from samples collected in the Amazon, mainly on the lower Tapajós River region. Actinella rionegrensis is recorded for the first time in the state of Pará and outside the type locality, as well as for the first time its habit (wisp-shaped colonies). Conclusion: It seems that the Environmental Protection Area is being effective in terms of preservation of the aquatic ecosystem’s integrity, since the Actinella species identified in the mid-20th century are still present. Some species of this genus present taxonomic issues to be cleared and need revision, since they present overlapping of diagnostic features between them and between species belonging to the genus Eunotia.

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