Red tilapia is becoming more popular for aquaculture production in China in recent years. However, the pigmentation differentiation in genetic breeding is the main problem limiting its development of commercial red tilapia culture and the genetic basis of skin color variation is still unknown. In this study, we conducted Illumina sequencing of transcriptome on three color variety red tilapia. A total of 224,895,758 reads were generated, resulting in 160,762 assembled contigs that were used as reference contigs. The contigs of red tilapia transcriptome had hits in the range of 53.4% to 86.7% of the unique proteins of zebrafish, fugu, medaka, three-spined stickleback and tilapia. And 44,723 contigs containing 77,423 simple sequence repeats (SSRs) were identified, with 16,646 contigs containing more than one SSR. Three skin transcriptomes were compared pairwise and the results revealed that there were 148 common significantly differentially expressed unigenes and several key genes related to pigment synthesis, i.e. tyr, tyrp1, silv, sox10, slc24a5, cbs and slc7a11, were included. The results will facilitate understanding the molecular mechanisms of skin pigmentation differentiation in red tilapia and accelerate the molecular selection of the specific strain with consistent skin colors.

Aiming at the problems of low detection accuracy and inaccurate positioning accuracy of light-weight network in traffic sign recognition task, an improved light-weight traffic sign recognition algorithm based on YOLOv4-Tiny was proposed. By improving the K-means clustering algorithm, the anchor with appropriate size is generated for the traffic sign data set to improve the detection recall rate and target positioning accuracy. The strategy of large-scale feature map optimization is proposed, which enriches the feature level of the network by using the low-level information, strengthens the representation of the feature information of the small target, and improves the detection accuracy of the long-range small target. In view of the problem of missed detection of high overlapping targets in the post-processing stage of the model, the paper proposes an improved NMS algorithm to screen the prediction box, avoid deleting the prediction results of different targets, and further improve the detection accuracy and recall rate of the target. Experimental results show that, compared with the original YOLOv4-Tiny algorithm, the improved algorithm in traffic sign recognition task based on TT100K dataset, mAP and recall are improved by 5.73% and 7.29% respectively, and FPS value is maintained at about 87 f/s, which meets the accuracy and realtime requirements of traffic sign recognition task.INDEX TERMS traffic sign recognition, YOLOv4-Tiny, clustering algorithm, large scale, improved NMS algorithm

Background: Long non-coding RNAs (lncRNAs) perform crucial roles in biological process involving complex mechanisms. However, information regarding their abundance, characteristics and potential functions linked to fish skin color is limited. Herein, Illumina sequencing and bioinformatics were conducted on black, white, and red skin of Koi carp (Cyprinus carpio L.). Results: A total of 590,415,050 clean reads, 446,614 putative transcripts, 4252 known and 72,907 novel lncRNAs were simultaneously obtained, including 92 significant differentially expressed lncRNAs and 722 mRNAs. Ccr_ lnc5622441 and Ccr_lnc765201 were up-regulated in black and red skin, Ccr_lnc14074601 and Ccr_lnc2382951 were up-regulated in white skin, and premelanosome protein a (Pmela), Pmelb and tyrosinase (Tyr) were up-regulated in black skin. The expression patterns of 18 randomly selected differentially expressed genes were validated using the quantitative real-time PCR method. Moreover, 70 lncRNAs acting on 107 target mRNAs in cis and 79 lncRNAs acting on 41,625 target mRNAs in trans were investigated. The resulting co-expression networks revealed that a single lncRNA can connect with numerous mRNAs, and vice versa. To further reveal their potential functions, Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were analyzed, and membrane, pigment cell development, cAMP signaling, melanogenesis and tyrosine metabolism appear to affect skin pigmentation. Additionally, three lncRNAs (Ccr_lnc142711, Ccr_lnc17214525 and Ccr_lnc14830101) and three mRNAs (Asip, Mitf and Tyr) involved in the melanogenesis pathway were investigated in terms of potential functions in embryogenesis and different tissues. Conclusions: The findings broaden our understanding of lncRNAs and skin color genetics, and provide new insight into the mechanisms underlying lncRNA-mediated pigmentation and differentiation in Koi carp.

Pigmentation is one of the most diverse characters in vertebrates, with a broad variety of colour phenotypes and colour patterns found in different species, populations and individuals. 1 The diversity and fascinating skin colours and pigment patterns are observed in fish (Figure 1), which coloration widely distributed in the hypodermis of the body as well as the epidermis of scales and fins. 2,3 According to the FAO, global fish production in 2018 was projected to be around 179 million tonnes, with a total first-sale value estimated at USD 401 billion, of which 82 million tonnes from aquaculture and the rest from capture production, and approximately 88 per cent of total fish production was used for direct human consumption, with the remaining 12 per cent going to non-food purposes such as fish oil, fishmeal and ornamental fish. 4 Body colour is an interesting economic feature in aquatic animals, for example fish and shellfish, and the global exports of ornamental fish increased from USD 177.7 million in 2000 to a peak of USD 347.5 million in 2014. 5 The global market for ornamental fish is currently competitive, with a relatively high demand for aquarium fish around the world, and more than