Fatty acid transfer proteins (FATPs) are a family of integral membrane proteins that facilitate transport of fatty acids into cells, including transport of dietary fatty acids into enterocytes. FATPs act in concert with acyl-coA synthetases (ACSs), which activate the newly imported fatty acids so that they are ready to form ester bonds and be incorporated into complex lipids (48, 49). There is evidence from mammalian and cell culture models that both the FATP and ACS families play roles in regulating preferential uptake of some dietary fatty acids over others, and in the partitioning of dietary fatty acids among complex lipids (48, 50). The zebrafish genome encodes 9 ACSL (ACSs specific to long-chain fatty acids, the type of fatty acid most abundant in animals including zebrafish) gene paralogs in six families. Expression of this class of genes is ubiquitous in adults, with proteins corresponding to seven of nine paralogs detectable by Western blot in most tissues including the gut (51). Expression of ACSL genes in the larva is more regionalized: in the acsl1 family, acsl1b mRNA is detectable in the YSL and gut in early larval stages. The acsl1a paralog is not expressed in the YSL, and no expression data are available for early-gut development (17). Only acsl1a is expressed in the gut in adults (51). Acsl4a mRNA is present in both the YSL and the larval gut (52). Expression of acsl4b and acsl5 is detectable in the YSL, but expression data are not available from larval stages after the gut has begun to develop (17) (Figure 2). Expression data are unavailable for the other acsl paralogs at any embryonic or larval stage, but what is known about expression of acsl genes in this model suggests potential division of function among paralogs similar to that suggested by regionalized apolipoprotein gene expression.