High-resolution genetic linkage map is critical for QTL mapping, genome sequence assembly and marker-assisted selection in aquaculture species. The ridgetail white prawn Exopalaemon carinicauda is one of the most economic shrimp species naturally distributed in the coasts of eastern China and western Korea. However, quite limited genomics and genetics information have been exploited for genetic improvement of economic traits in this species. In the present study, we conducted genome survey and constructed high-resolution genetic linkage maps of the ridgetail white prawn with reciprocal-cross mapping family genotyped using next-generation sequencing approaches. The estimated genome size was 9.33 Gb with a heterozygosity of 0.26% and a repeat sequence ratio of 76.62%. 65,772 protein-coding genes were identified by genome annotation. A total of 10,384 SNPs were used to high-throughput genotyping and assigned to 45 linkage groups (LGs) from reciprocal backcross families of E. carinicauda, and the average marker distances were 0.73 cM and 0.55 cM, respectively. Based on the high-resolution linkage map, twenty-three QTLs related to five growth traits were detected. All QTLs could explain 8.8–15.7% of the total growth-traits variation. The genome size of E. carinicauda was estimated more accurately by genome survey analysis, which revealed basic genomic architecture. The first high-resolution backcross genetic linkage map and QTLs related to growth traits will provide important information for QTL fine mapping, genome assembly and genetic improvement of E. carinicauda and other palaemon shrimps.

Tannic acid (TA) has great potential as a new feed additive. In this study, we investigated the effects of dietary TA on growth, digestion, nonspecific immunity, and resistance to ammonia stress and intestinal microbiota in Litopenaeus vannamei. The shrimp were fed diets containing different levels of TA: 0 mg/kg (TA-0), 200 mg/kg (TA-200), 400 mg/kg (TA-400), and 800 mg/kg (TA-800) for 56 days, followed by acute ammonia stress for 48 h. The results showed that dietary TA increased the survival rate of the TA-800 group. Dietary TA could improve the morphology of the hepatopancreas and intestinal tissues. After feeding different levels of TA for 56 days, the activities of amylase (AMS) and trypsin (Tryp) were increased, but the activity of lipase (LPS) was decreased. The activities of T-AOC, SOD, and PPO were higher in the hepatopancreas of the three TA treatment groups (p < 0.05). When shrimp were exposed to ammonia stress for 48 h, the activity of immune enzymes (LZM, T-AOC and SOD) and the expression levels of immune genes (LZM, proPO and Cu/Zn-SOD) were higher in the three TA treatment groups (p < 0.05). Furthermore, dietary TA also changed the composition of intestinal microflora by increasing the abundance of Planctomycetes, but decreasing the abundance of Bacteroides and Proteobacteria. The abundance of Rhodopirellula, Ruegeria, and Rhodobacter were higher, but that of Paracoccus, Algoriphagus, Cellvibrio, Flavobacteriaceae, and Bacteroides were lower in response to dietary TA. These results revealed that dietary TA had a positive effect on growth and intestinal microbial composition and enhanced the immune response to ammonia stress in shrimp. Therefore, TA can be a potential natural alternative antibiotic substitute for feed additives in shrimp, and the appropriate supplemental dosage is 400–800 mg/kg in the diet.