Morphological Structure And Allometric Growth Pattern Of Saurogobio Dabryi Intestine In Jialing River

Saurogobio dabryi is an endemic fish in East Asia and widely distributed in Chinese major water systems.It is one of the main economic fishes in Jialing River Basin.In our research,we studied on its functional adaptability and environmental adaptability by using the correlation analysis,the t test and segmented analysis to describe the morphological and growth characteristics of S.dabryi's intestine and to compare their growth pattern among different age groups or section groups.The results of the study are as follows:1.Morphological structure characteristics of S.dabryi's intestine in Jialing River.The morphological characteristics of S.dabryi's intestine were relatively simple.And the intestine had different degrees of correlation with various parts of the body.The specific results were as follows:?.Morphological observation results showed that the intestinal structure of S.dabryi was Z-shaped,with only 2 twists and relative short gut length index(RGL=0.6128),belonged to carnivorous fish gut.The foreintestine and midintestine were similar in length,and the hindintestine was obviously longer than those two intestine parts.The foreintestine was the most developed part and the hindintestine is the least.?.Intestinal length correlated most with its body size,followed by the size of its head,and lowest with tail.2.Allometric growth pattern of S.dabryi intestine in Jialing RiverThe growth pattern of S.dabryi intestine was allometry,and its corresponding fish total length(CFTL)was 145.07 mm.Its growth pattern changed from fast stage to slow stage.The growth pattern of intestine was different in each part,too.The growth in the foreintestine and the midintestine was isokinetic.But the hindintestine had significant allometric growth pattern,which had a fast growth stage before growth inflexion point and then changed to isokinetic growth pattern.The difference of growth pattern of S.dabryi among the three parts of intestine might be related to their functional differentiation.3.Allometric growth pattern of S.dabryi intestine in different age groups in Jialing RiverThe sample was divided into 3 age groups in this research.The 2-year age group had the largest sample size,followed by the 1-year age group,and the 3-year age group had the smallest.Only in the 1-year age group,the growth pattern of intestine was allometry,and its CFTL was 145.07 mm.Its growth pattern changed from fast stage to slow stage.In this age group,the growth model of the three parts of intestine had never changed.The hindintestine had the fast growth pattern and the other two had isokinetic pattern.We made a deduction with the general characteristics of fish growth that the 1-year age group was in the early stage of sexual maturity and its fast growth model was the adaptation to energy demand of reproductive behavior.The growth rate of 2 and 3-year age groups did not decrease obviously and these 2 groups might be in the late stage of sexual maturity.4.The comparison of intestine growth model of S.dabryi in different sections of Jialing RiverThe growth model of S.dabryi's intestine differs among different sections of Jialing River.The samples from upstream and downstream had fast growth pattern,but the growth pattern of samples from midstream was isokinetic.This was consistent with the difference of S.dabryi's diet in different sections of this River.As the cluster analysis result showed that the samples from the upstream and downstream had similar food composition,but they both had significant differences in the food composition with midstream.Considering to the environmental conditions of the Jialing River,we speculated that S.dabryi could adapt to distinctive ecological environment of the Jialing River by adjusting their intestines' growth pattern to adapt to different feeding conditions...