Enables beta-galactoside (CMP) alpha-2,3-sialyltransferase activity. Involved in several processes, including ganglioside biosynthetic process via lactosylceramide; memory B cell differentiation; and negative regulation of activated CD8-positive, alpha-beta T cell apoptotic process. Acts upstream of or within protein glycosylation and protein phosphorylation. Predicted to be located in Golgi medial cisterna membrane; Golgi trans cisterna membrane; and trans-Golgi network membrane. Is expressed in several structures, including alimentary system; ear; hemolymphoid system; integumental system; and nervous system. Orthologous to human ST3GAL1 (ST3 beta-galactoside alpha-2,3-sialyltransferase 1). [provided by Alliance of Genome Resources, Apr 2022]