Intestinal Microbial Evolutionary Adaptation Increased The Ecological Invasion Potential Of Asian Carp And Bighead

Asian Silver carp(Hypophthalmichthys molitrix)and Asian Bighead(Hypophthalmichthys nobilis)are typical filter-feeding fish.They cause ecological invasion in the Mississippi River(USA).In addition,interspecific hybridizationd between Asian silver carp and Bighead in the Mississippi River.Not only their genome may evolved,but also their intestinal microflora evolved together,because there is a strong interaction between intestinal microflora and its host.On the one hand,the intestinal microflora were selected by its host,which dependde on the host genetic background and dietary factors;On the other hand,intestinal microflora of fish plays an irreplaceable role in digestion,nutrient absorption,metabolism,immune and growth of its host.In this paper,275 gut microbiomes samples of pure parents(silver carp and bighead)and two hybrids F1-SB and F1-BS(F1-SB:first generation hybrid from female parent silver carp and male parent bighead;F1-BS:the first generation hybrid from female parental bighead and male parental silver carp)from the crossing and growth experiments,together with 1 pond water and 5 pond soil samples were conducted by High throughput sequencing.More than 3.9 million 16S rDNA bacterial sequences were detected.The main results and conclusions are as follows:1)Phyla Firmicutes,Proteobacteria,Cyanobacteria,CKC4,Planctomycetacia,Fusobacteria and Bacterioidetes dominated among the gut microbes in intestinal tract of these fish.Firmicutes has the highest relative abundance,its Proportion in the intestinal tract of the hybrid F1-SB and F1-BS were 36.61%and 29.15%repectively,which were higher than that in the two kinds of pure parents(silver carp:27.47%;Bighead:27.17%).Lactococcus(Firmicutes),Aeromonas(Proteobacteria),Pirellula and Rhodopirellula(planctomycetes)wereare the dominant microorganisms in the intestine of four kinds of fish.These abundant bacteria have specific function.The high abundance of these cellulose degrading bacteria(eg:Aeromonas)in the intestinal tract suggests that gut microbes may play an important role in the digestion of phytoplankton.2)There was overlap in intestinal flora of pure parent silver carpand and bighead(depending on their genomesimilarity)as well as a certain degree of differentiation of theri intestinal flora.There are two different strains for specific function in two parents gut(depending on their trophic niche differences).The highest proportion of Fusobacteria in pure bighead carp and Cyanobacteria in silver carp,corresponding well with their feeding habits.3)Taxonomically and functionally differentiated gut microbial communities in bighead and silver carps were admixed in hybrids.There were more abundant protease-producing bacteria in gut of Hybrids F1 versus pure parental silver carp,In addition,a greater proportion of cellulose-decomposing bacteria in Hybrids than the parental Bighead.There was a greater proportion of unclassified bacteria in the two Hybrids compared with their parents.It can be concluded that the hybrids may have a wider range of diet resources than pure parents.Interspecific hybridization between bighead and silver carps may therefore increase the invasiveness of Asian carps by expanding the spectrum of food resources and possibly outcompeting indigenous species that consume similar food resources.In conclusion,the genetic characteristics of Asian silver carp and Bighead facilitate their early establishent in the Mississippi River.The followeing extensive interspecific hybridizationd promote their intestinal microbial evolutionary adaptation,which may increase their genetic resiliency and ecological adaptability to further promoting their invasion.In this paper,We give an insight into substantial hybridization of silver carp and Bighead enhance the ecological invasion potential by researching the gut microbes combined with the researchs of genomic characteristics of introduced species.