Abstract:

Aims: Ochetobius elongatus is a critically endangered species, which is primarily distributed in the Yangtze River basin and the region south of this river. To investigate morphological variations of O. elongatus, the multivariable morphometrics was used to analyze different populations from the mid-lower Yangtze River. 

Methods: Based on a total 98 specimens collected from five sampling localities including the Yangtze River main stem at Yichang and Jiayu sections, the Han-Jiang main stem at the Qianjiang section, the Dongting and Poyang lakes from May 2022 to November 2024, thirty-three multivariate morphometric parameters of traditional and truss network measurements were integrated for analysis. 

Results: Significant differences were detected in 28 morphological measurements (84.85% of the total) among populations of O. elongatus, with the largest variation in the trunk, followed by the head part., Cluster analysis, calculated on these morphometric measurements, grouped into three distinct clusters: the first one formed by populations of Jiayu and Qianjiang, the second one by the populations of the Dongting Lake and Poyang Lake, and the third one by the Yichang population. A weak but significant positive correlation was observed between geographic distance and morphological variation (r=0.176, P=0.012), suggesting that geographic distance has limited explanatory for the observed morphological variations. Stepwise discriminant analysis revealed a comprehensive discriminant rate of 74.5%, among which the Jiayu population showed the highest accuracy (95.45%), and the Yichang population was the lowest (25%). 

Conclusion: This study highlights significant morphological variations among the five populations of O. elongatus from the mid-lower Yangtze River basin, suggesting that adaptation to heterogeneous habitats may be the primary driver factor for these variations.

Key words: Ochetobius elongatus, linear measurement, truss network, the endangered species