Study On Histology Of Digestive Tract And Mitochondrial Genome Of Rhinogobius Giurinus In Liangzi Lake

The perciform suborder Gobioidei is one of the largest suborders of teleost fishes, with nearly 2000 extant species. They have a worldwide distribution and show a spectacular variety in morphology, ecology, and behavior, as ideal model organisms in many comparative studies aimed at understanding the evolutionary processes underlying diversification. In this paper, we study the histology of digestive tract and complete mitochondrial genome of Rhinogobius giurinus from Liangzi Lake. The main results are are as follows:1. We used histology method to study the digestive tract of R. giurinu.The results showed that the digestive tract was consisted of buccopharyngeal cavity, esophagus, stomach, intestine and anus. The tissue of digestive tract was divided into mucosa, submucosa, muscularis and serosa. The stomach has a large number of gastric glands distributed in the mucosal epithelium of the lamina propria. The the height of mucosal and the thickness of submucosa has no differences in the intestinal tract.This study first described the organization structure of digestive of R. giurinus, which can provide basic data for research.2. The mitochondrial genome of R. giurinu is a circular molecule of 16,520 bp in length and consists of 13 protein-coding genes, 22 tRNA genes, 2 ribosomal RNA genes, and 1 control region. The overall base composition of R. giurinu is 26.08% for T, 29.56% for C, 27.73% for A, and 16.63% for G, with a slight A+T bias of 53.81%. It has the typical vertebrate mitochondrial gene order. All of the 13 protein-coding genes contain the orthodox start codon ATG, except for COX1, which begins with GTG. However, the end codons of the 13 PCGs are varied with TAA, TA, T or TAG.3. The phylogenetic relationships within the suborder Gobioidei were conducted by concatenated 12 PCGs based on ML and BI mothods. The two phylogenetic analysis mothods generated identical topologies and showed that Gobioidei consists of Rhyacichthyidae, Odontobutidae, Butidae, Eleotridae, Gobiidae and Gobionellidae. Our results agree with the traditionally classification of Gobiidae and support the 6 family phylogenetic taxonomy of Thacker(2009). Rhyacichthyidae was rooted in the tree and the “Rhyacichthyidae + Odontobutidae” was paraphyletic with respect to other gobioid lineages. The Eleotridae and Butidae fishes were formed into their own lineage. Gobionellidae includes four subfamilies: Amblyopinae, Gobionellinae, Oxudercinae and Sicydiinae; Gobionellidae had close relationship with Gobiidae.