Morphological Variation Of Organs Related To Ingestion Between Hemiculter Leucisculus And H.tchangi

Related species commonly coexist in nature,they have similar genetic background and are not easily distinguished according to the traditional classification shape.Niche theory points out that no two species have exactly complete niche overlap,even two species with extremely similar shapes in the evolution of species.Because niches are closely related to morphological characteristics,it has been demonstrated that inferring niches from morphological traits is effective.Hemiculter leucisculus and H.tchangi are small fishes,belonging to Cyprinidae,Culterinae,Hemiculter,with similar genetic background,short growth cycle,rapid reproduction and strong adaptability.According to the records of Fish Records,the number of gill rakers is significantly different in H.leucisculus and H.tchangi,which is related to the feeding niche.Few studies have been conducted on the morphological differences of feeding-related organs and the existence of dietary niche between H.leucisculus and H.tchangi.Therefore,H.leucisculus and H.tchangi,who had extremely similar morphology,were taken as the research objects in this study,and the morphological characteristics of their feeding-related organs were analyzed based on the large spatial scale by the method of combining geometric morphology with traditional morphology.We compared and visualized the morphological differences of the feeding-related organs.The main research results are as follows:(1)Significant differences were shown between H.leucisculus and H.tchangi in the organs that selected and filtered the food(gill raker and mouth)(P < 0.05).Based on the head morphology coordinate data,it was concluded that the variation of head characteristics was mainly concentrated on three traits: mouth,eye diameter and head shape.H.leucisculus had a sharp head,short and sparse gill raker,a large and end-position mouth,a narrow eye diameter;H.tchangi had a wide head,long and dense gill raker,a small and upward sloping mouth,a wide eye diameter,relatively.(2)H.leucisculus and H.tchangi showed significant morphology differences in the organs that grind and process food(pharyngeal bones and pharyngeal teeth)(P < 0.0001).H.leucisculus presented wide pharyngeal bones shapes with coarsely compressed teeth;H.tchangi showed the average morphology of narrow pharyngeal bones with extremely compressed teeth.Different morphology of pharyngeal bones and pharyngeal teeth work together to better chew and process different types of food.(3)There was a significant correlation between morphology of food-related organs.There was a strong correlation between the dense gill rakers,the upward sloping mouth,the long and narrow pharyngeal bones and extremely compressed teeth.The few and sparse gill rakers,an end-position mouth,the wide pharyngeal bones and coarsely compressed teeth had a strong correlation.In summary,the results indicated that the food-related organs exhibited significant morphological differences and functional adaptability differences of H.leucisculus and H.tchangi.In addition,there was obvious correlation between the morphology of these organs,and the correlation between the morphology of hypopharyngeal bone and hypopharyngeal teeth was the strongest.This study enriched the biological data related to Hemiculter genus,laid a scientific theoretical foundation for further research on the ecological adaptation mechanism of fish feeding organs,and provided important experimental reference for better accurate identification of closely related species of Cyprinidae.