Aquaculture America 2023

February 23 - 26, 2023

New Orleans, Louisiana USA


Lee A. Fuiman* and Cynthia K. Faulk


The University of Texas at Austin
Marine Science Institute
Port Aransas, TX 78373


Hatchery-produced flatfishes often have a high incidence of malpigmentation. This malpigmentation is generally observed to be irreversible and thought to result from the interaction of genetic and environmental factors, such as larval nutrition and rearing conditions, during early development. The physiological pathways that are altered to produce malpigmentation are not well known.

We sampled skin from the ocular and blind sides of 10 normally pigmented juvenile Southern Flounder and 10 juvenile pseudoalbinos (ocular side almost entirely unpigmented). We used the Tag-Seq method to measure mRNA expression, and then identified differentially expressed genes (DEGs) in all combinations of pigmentation and side of the body. There were 216 DEGs between the ocular and blind sides of normally pigmented fish, but only 7 DEGs in the same comparison of pseudoalbinos (Fig 1). There were no DEGs between the blind sides of normal and pseudoalbino fish. These results suggest that the ocular side of pseudoalbinos has essentially the same gene expression as the blind side.

The comparison of ocular sides of normal and pseudoalbino fish revealed 35 DEGs. Gene set enrichment analysis (Metascape) showed that these 35 DEGs were associated with pigment cell differentitation and signaling pathways involved in pigment production. Similar studies of two other flatfish species found many more differences in gene expression between the ocular sides of normal and malpigmented fish (235 DEGs for Olive Flounder Paralichthys olivaceus (Wang et al., 2017) and 271 DEGs for Senegalese Sole Solea senegal-ensis (Pinto et al (2019)). The three studies shared only two DEGs (GCH1 and MREG) but the two Paralichthys shared 18 DEGs.

We plan to use this information to select specific genes that can be monitored at earlier stages of development in experiments designed to identify the causes of malpigmentation or to screen batches of larvae to estimate malpigmentation rates.