Binds free fatty acids and their coenzyme A derivatives, bilirubin, and some other small molecules in the cytoplasm. May be involved in intracellular lipid transport (By similarity). Expressed in the yolk syncytial layer (YSL) and subsequently in the intestinal bulb in developing embryos and larvae. In adults, expressed in the intestine. By a linolenic acid-rich diet. Forms a beta-barrel structure that accommodates hydrophobic ligands in its interior. The zebrafish genome contains duplicated fabp1b genes (fabp1b.1 and fabp1b.2) which probably arose from a tandem gene duplication event. Belongs to the calycin superfamily. Fatty-acid binding protein (FABP) family. PubMed:16857010 reports that adult expression is restricted to the intestine and absent from the liver, whereas PubMed:19953126 detects expression in the liver, intestine, heart, testis, ovary, and gills.