First report of aberrant Mystus vittatus (Bloch, 1794) from wild population in the Gomti River, Uttar Pradesh, India, based on integrative approach: a new conservation concern

This present study documents first recorded abnormality in Mystus vittatus (Bloch 1794) from the Gomti River near Thauri, Sultanpur District, Uttar Pradesh, India. Collected fish specimens were identified using integrative taxonomy, combining morphological and molecular data (Sanger or dideoxy sequencing). Interestingly, both the morphologically abnormal M. vittatus (MYAB1) and normal (NKG44N) exhibited 0% genetic divergence based on analysis of COI datasets. Molecular result indicates that the reported deformity is not associated with mitochondrial genetic variation and may instead be attributed to environmental factors. Comparative assessment of normal and abnormal individuals revealed no significant differences in morphological characters, except for the complete absence of caudal fin in abnormal fish. The total weight and length of the abnormal specimen were recorded as 9.59 g and 7.17 cm, respectively. Radiographic (X-ray) imaging further exposed underlying vertebral fusion at the hypural region from the 23rd to 27th vertebrae. Recorded water parameters included temperature (28.2 ± 7.2 °C), dissolved oxygen (5.1 ± 0.4 mg/L), pH (7.7 ± 0.7), ammonia (0.39 ± 0.05 mg/L), salinity (0.41 ± 0.20 ppt), TDS (264 ± 31 mg/L), conductivity (930 ± 40 µS/cm), and transparency (22 ± 3 cm). These values indicate potential environmental stress that may have contributed to the reported abnormality. Potential etiological and environmental factors include chemical contaminants, microplastics (MPs), heavy metals, essential nutrient deficiencies, and genetic mutations during larval development. In riverine habitats and other water bodies, documented exposure to agricultural and urban pollutants could also be responsible, emerging as plausible drivers of observed abnormalities. Malformation of the caudal fin may be referred to as "saddleback syndrome," which is often attributed to physical injury or developmental disruption during early life stages. Additionally, any predatory attack on its caudal region during its early development stages could have resulted in physical and traumatic injury. Despite such predatory attack, suspected individual might have escaped, survived, and healed, albeit with severe and permanent deformity. This study underscores the utility of radiology as critical diagnostic tool for detecting sub-surface anatomical abnormalities in wild fish populations. Our findings highlight the urgent action for targeted water quality monitoring in the Gomti River to mitigate anthropogenic impacts on native aquatic genetic resources (AGR). Future research should include both temporal and spatial assessments of water quality with fish health, particularly focusing on skeletal and soft tissue abnormalities.