Vertical and horizontal distribution patterns of Littoraria angulifera (Lamarck, 1822) on the Ceará and Pacoti Rivers’ estuaries, Ceará State

Abstract

The present study evaluated the hypothesis that shell size and abundance of Littoraria angulifera (Gastropoda, Littorinidae) are related with their position on mangrove trees (vertical gradient) and stream distance (horizontal gradient) in response to desiccation. The specimens were collected on two estuaries in Fortaleza metropolitan region, the Pacoti river and Ceará river. The organisms’ abundance and size didn’t differ between the studied estuaries but the length: width ratio of the shell was highest at Ceará River’s estuary. The periwinkle abundance was high below breast height in studies areas. The shell size showed an inverse pattern, the highest value was found above breast height. The shell shape did no) differ to the position. Also, on horizontal gradient was found differences in abundance and size of L. angulifera but the shell proportionality did not vary between the plots in both estuaries. The study results indicate shell morphological variation of L. angulifera in response to the environment conditions with study area. This knowledge is essential, because mangroves are being intensively disturbed and subjected to global changes.