Galectin is widely distributed in nematodes, insects, and porifers, as well as vertebrates, and it has also been found to be present in true fungi. Galectin does not just occur in the cytoplasm, it is also present in the nucleus, on the cell surface, in the extracellular matrix, etc., and it is thought to be involved in many biological phenomena, including development, differentiation, morphogenesis, tumor metastasis, cell death, and RNA splicing.