The initial assessment of bats suggested they lacked the ability to synthesize vitamin C (Birney, Jenness, and Ayaz 1976). However, several recent studies have shown that approximately two thirds of different bat species have functionally expressed GULO genes (Cui et al. 2011a; Cui et al. 2011b). The various bat taxon taxa that lack the ability to make vitamin C have varying levels of deletion degradation in their GULOgenes and the patterns of sequence variation show that they are lineage independent events. Trying to explain the discontinuous GULO deletion patterns within a common descent paradigm has produced a variety of difficult contradictions for a coherent model of bat evolution (Cui et al. 2011b).
Loss of vitamin C pathway function and GULO gene degradation has also been detected in guinea pigs, great apes, and humans (Lachapelle and Drouin 2011; Nishikimi, Kawai, and Yagi 1992; Nishikimi et al. 1994; Ohta and Nishikimi 1999). In addition, naturally occurring scurvy and osteogenic disease pathologies related to GULO inactivating mutations and large-scale deletions have been documented in rats, mice, and pigs (Harris et al. 2005; Hasan et al. 2004; Jiao et al. 2005; Kawai et al. 1992; Mohan et al. 2005). Thus, degradation of the GULO gene in a wide array of mammals and birds is a relatively common occurrence.
