Symbiotic bacteria are crucial for the survival of hematophagous arthropods, forming diverse relationships throughout evolutionary history. These bacteria typically exist in commensal or mutualistic associations. Various hematophagous arthropods house specific symbiotic bacteria in their gut. In a scanning electron microscopic study clusters of bacilli were observed in the gut of a haematophagus crustacean ectoparasite of fish Argulus bengalensis. The cultured colonies of the bacteria were isolated and subjected to biochemical characterization and identification through 16S rRNA sequencing. The study unveiled a Gram-negative bacillus different from Acinetobacter baumannii and Aeromonas hydrophila. Obtained in the earlier study. The strain was identified as Aeromonas veronii .This bacteria prefers acidic environments and is capable of metabolizing a broad spectrum of substrates to produce acid. Notably, Aeromonas veronii shows high sensitivity to norfloxacin, suggesting potential control methods for the parasite. Aeromonas veronii, commonly found in various environments, has increasingly been isolated from diseased fish exhibiting ulcers and fin rot, with Argulus parasites potentially facilitating its transmission through skin punctures. Symbiotic Aeromonas veronii in blood-feeding leeches synthesize B vitamins, aid in blood digestion, and inhibit other bacteria, suggesting a similar role in Argulus. These findings indicate possible symbiont replacements, evolutionary renewal, and high bacterial diversity in blood-feeding parasites.