## 4 Discussion  
Taxonomic Composition of the Active Microbial Communities in the Hepatapancreas of L. vannamei in Different Stages of Development  
The phylum level composition of the _L. vannamei_ microbiome, throughout all the developmental stages showed high proportions of _Proteobacteria_, _Actinobacteria_, _Firmicutes_ and _Bacteroidetes_. These phyla are considered cosmopolites, and have been reported previously to be present in the surrounding environment and in different types of samples [10; 15; 30; 31; 32; 33; 34; 35; 36; 37]. The phyla composition is similar to those reported in the intestinal microbiome of other marine arthropods and shrimps [10; 16; 38; 39], which suggests that these phyla are involved in several digestive and other vital functions. The presence of the _Gammaproteobacteria_, _Alphaproteobacteria_ and _Betaproteobacteria_ classes was observed in high proportion in the present study and agrees with previous reports of the microbiome of marine organisms [10; 12; 15; 16]. The presence of _Flavobacteriaceae_ and _Rhodobacteraceae_ throughout all the developmental stages of \(L\). _vannamei_ agrees with previous studies, where these families have been reported to be part of the core microbiome of \(L\). _vannamei_[2; 3; 8]. The role of the \(L\). _vannamei_ microbiome in primary metabolic processes could be associated with the nutrient uptake. It can be mentioned that the carbohydrate metabolism was present throughout all the developmental stages of \(L\). _vannamei_. The carbohydrates were supplied in the commercial diet in the form of vegetable starches and fiber, the presence of these types of compounds have been reported to be able to influence the microbiome composition [8; 10; 21] by the promotion of several bacterial classes (_Methanococci_, _Actinobacteria_, _Bacillus_), especially those that are able to generate extracellular enzymes capable of degrading complex carbohydrates [35; 36; 37; 40; 41; 42]. These enzymes are capable of promoting biofilm production, which acts as a support network (physical and physiological) that could supply a series of digestible molecules in the hepatopancreas of \(L\). _vannamei_ throughout the development. These digestible molecules and metabolites produced by the microbiome could have an important role in development and adaptation processes, that could provide an advantage in adverse environmental conditions. Regarding the protein uptake, they provided a high proportion of the nutritional formula, these are supplemented from different sources (plant, animal) and they are delivered in different amounts according to the developmental stage in peneids [43]. The use of proteins derived from plants could contain byproducts that could act as anti-nutritional factors (phenolic compounds, pigments), that could decrease the protein digestibility and weight gain during \(L\). _vannamei_ culture. Other processes related to the microbiome of \(L\). _vannamei_ were related with the vitamin B6 biosynthesis, in larvae (Figure S3)) and adult (Figure S5P), this type of process was reported previously in _Rimicaris exoculata_, where the bacterial classes _Gammaproteobacteria_ and _Epsilonproteobacteria_ participate in the biosynthesis of vitamins [15; 34]. The endogenous biosynthesis of these types of compounds could be considered as a complementary source of vitamins and cofactors, that could enhance the resistance to biotic factors. The high proportion of _Gammaproteobacteria_, _Alphaproteobacteria_ and _Betaproteobacteria_ has been reported previously in marine organisms, these bacterial classes participate in several metabolic processes [10; 12; 15; 16; 34; 35; 44], such as: energy metabolism and carbon fixation (reductive TCA cycle), these functions could provide the host organism an advantage under environmental stress conditions present in culture ponds. In this sense, the presence of subsystems associated with stress response was observed in both the host and the microbiome, with an increasing tendency in \(L\).