Baseline Morpho-molecular Insights Into Indigenous Ornamental Fish Zebra Loach, Botia striata from Koyna River, Western Ghats, India

Botia striata (zebra loach), an endangered ornamental species endemic to the Western Ghats, is threatened by habitat loss and restricted distribution. Limited baseline data exist on its morphology, growth and genetic identity. This study uses an integrative morpho-molecular approach to characterise Koyna River populations and support conservation planning.

A total of 360 specimens were collected from the Koyna River (August 2023-July 2024). Sixteen morphometric traits and five meristic counts were measured. Length-weight relationships and condition factor were estimated using log-transformed regressions. Muscle tissues were preserved for DNA extraction. The COI gene was amplified using universal FishF1-FishR1 primers and the purified PCR products were sequenced to generate consensus sequences. Bioinformatic analyses included BLASTn identification, nucleotide composition, genetic divergence and Maximum Likelihood phylogeny (T92+I model).

Morphometric analysis revealed total length ranging from 3.2 to 5.6 cm, with strong positive correlations among major body dimensions. Meristic counts (D: I-9; A: I-6; C: 18; V: I-8; P: 13) were consistent with earlier descriptions for Botia spp. LWR analyses showed strong length-weight association (R² = 0.880-0.925) and negative allometric growth (b = 2.395-2.597). Condition factor values (1.19-2.799) indicated an overall healthy population status. COI barcoding generated a 662 bp sequence exhibiting low intraspecific divergence (0-0.6%) and formed a well-supported clade (bootstrap 96–97%) with authenticated B. striata sequences, validating taxonomic identity.