RECORDS OF ROSTRAL ANOMALIES IN Macrobrachium amazonicum (HELLER, 1862) (DECAPODA: PALAEMONIDAE) COLLECTED ALONG THE GREAT AMAZON RIVER BASIN

Morphological anomalies in decapod crustaceans are frequently reported in studies around the world, some of which are due to anthropogenic actions through environmental impacts. These deformities can affect different structures (e.g., carapace, scaphocerite, rostrum, chelipeds, abdomen and telson) and interfere with development, feeding, resource competition, and reproductive behavior of crustaceans. The palaemonid shrimps occur in various ecosystems, covering marine and freshwater areas; however, few studies report morphological anomalies in freshwater shrimps in Brazil. Therefore, this study aimed to report and catalog the morphological anomalies in the rostral forms of the shrimp Macrobrachium amazonicum (Heller, 1862), collected from the Great Amazon River Basin, Pará, Brazil. The specimens were captured during collections carried out along the Xingu River watershed, near the municipalities of Altamira and Vitória do Xingu, using bamboo traps, known as “matapis,” baited with babassu. After the samples, the specimens were sorted out, and transported to the laboratory for subsequent biometric measurements, weighing, taxonomic identification, and registration of the abnormalities. A total of 2.199 specimens of the M. amazonicum were collected, being identified twenty shrimps with anomalies in the rostral region, corresponding to 0.9% of the total number of shrimps analyzed. Herein, the anomalies observed consisted of a reduction in the size of the rostrum, with varying shapes, and a decrease in the number of rostral teeth compared to the expected for the species. Further studies are needed to identify the potential causes of the anomalies in shrimps from the Amazon region.