MULTIPLE OBSERVATIONS OF MORPHOLOGICAL ANOMALIES IN Macrobrachium amazonicum (HELLER, 1862) (DECAPODA: PALAEMONIDAE) FROM AN AMAZONIAN URBANIZED AREA

Herein, we describe multiple occurrences of morphological abnormalities in Macrobrachium amazonicum (Heller, 1862) collected in a hypertrophic urban river that flows through the city of Belém, Pará State, Eastern Amazonia, Brazil. The samples were performed between 2022 and 2025, using traditional local traps called “matapi” placed in shallow areas of the Guamá River (01°27’54.2”S; 048°26’02.6”W). After sampling, all individuals were transported to the Laboratório de Crustáceos (LabCrus/UFRA) where they were identified, sexed, measured, and only the anomalous specimens were photographed. A total of 4,830 individuals of M. amazonicum were collected, of which 54 (8 males and 46 females), corresponding to 1.12% of the total, showed abnormalities. The deformities were observed in the rostrum (68.5%) and in the telson (31.5%). The highest incidence of abnormal females was observed in May and June 2022, with other peaks in March and August 2023; while for males, the highest presence of abnormalities was in August 2025. The Guamá River receives heavy inflows of urban and industrial effluents, which may be one of the causes of the anomalies observed in M. amazonicum. However, other conditions may be associated with these anomalies, such as nutritional or genetic factors. This study increases the knowledge on morphological abnormalities in shrimps, especially in M. amazonicum, and highlights the need for biological and environmental monitoring along the main urban river (Guamá River) in the city of Belém, Pará.