Abstract
The great northern snakehead (Channa argus) is one of the most important economic and conservational fish in China. In this study, the melanocytes in the skin of two distinct color morphs C. argus were investigated and compared through employment of the microscopic analysis, hematoxylin and eosin (H&E) and Masson Fontana staining. Our results demonstrated the uneven distribution of melanocytes with extremely low density and most of them were in the state of aging or death. Meanwhile, there was no obvious pigment layer and melanocytes distribution pattern found in the albino-type (AT), while the melanocytes were evenly distributed with abundance in the bicolor-type (BT). The transcriptome analysis through Illumina HiSeq sequencing showed that a total of 34.93 Gb Clean Data was obtained, and Q30 base percentage reached 92.66%. The BT and AT northern snakeheads transcriptome data included a total of 56,039,701 and 60,410,063 clean reads (n = 3), respectively. In gene expression analyses, the sample correlation coefficients (r) were ranged between 0.92 and 1.00; the contribution of PC1 and PC2 were 50.25 and 13.73% by using PCA cluster analysis, the total number of DEGs were 1024 (559 up-regulated and 465 down-regulated), and the number of annotated DEGs was 767 (COG 172, KEGG 262, GO 288, SwissProt 548, Pfam 579 and NR 765). Additionally, 46,363 ± 873 and 44,947 ± 392 single nucleotide polymorphisms (SNPs) were compiled via genetic structure analysis, respectively. Ten key pigment-related genes were screened using qRT-PCR. And all of them revealed extremely higher expression levels in the skin of BT than those of AT. This is the first study to analyze the mechanism of albino characteristics of Channa via histology and transcriptomics, and also provide the oretical and practical support for the protection and development of germplasm resources for C. argus.
Highlights
Being the largest number of existing vertebrate subphylums, the fish have over 32,000 species that are distributed across all of the aquatic resources worldwide (Nelson et al, 2016)
The melanocytes in the skin of two distinct color morphs of C. argus were observed under an inverted microscope (20×) and results showed that the main differences were reflected in their distribution, density, and size, as well as in the dendritic branching and the growth state of melanocytes
Our results by these two staining techniques demonstrated that the skins of two distinct color morphs of C. argus were composed of epidermis, tomb membrane, pigment layer, dermis, subcutaneous tissue, and with obvious boundaries, albeit the epidermisin AT was significantly thin, and the pigment layer tended to degenerate without obvious melanocytes
Summary
Being the largest number of existing vertebrate subphylums, the fish have over 32,000 species that are distributed across all of the aquatic resources worldwide (Nelson et al, 2016). The formation of final body color model is based on the movement and interaction among the pigment cells (Irion et al, 2016; Bian et al, 2019). As an important and one of the most common phenomenon of fish genetic variation, albinism is often stably inherited and unique varieties are formed. The formation of zebrafish body color model has a certain genetic mechanism, including cell–cell interaction band and agouti signaling protein (ASIP)-mediated formation mechanism (Ceinos et al, 2015). The albino-type (AT) Channa argus showed a stable inheritance with the white body color over the generations. Our previous study showed that the AT has higher protein content and lower fat content in body composition than that of the bicolor-type (BT; Wang et al, 2018), which implies a higher nutritional value of the AT. The potential ornamental values of BT are increasing day by day
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