Is There Hybrid Vigor in Dogs? Oxidative Stress and Cytokine Concentrations in Low- To Mid-Content Wolf-Dog Hybrids

AbstractChanges of deleterious traits in mitochondria within hybrids of two different species are likely to be reflected across whole-animal phenotypes. Two processes linked to mitochondrial fitness are oxidative stress and inflammation. Here, plasma oxidative stress (lipid oxidative damage, total antioxidant capacity, and activities of catalase, glutathione peroxidase, and superoxide dismutase concentration) and cytokine concentrations (IL-1β, IL-6, and TNF-α) from wolf-dog hybrids of low to mid wolf content are presented and then compared with previously published values for similar-sized dogs and gray wolves. Results indicate that lipid oxidative damage and catalase activity were not significantly different across species and hybrids. Total antioxidant capacity and glutathione peroxidase were significantly lower in wolf-dog hybrids than in domestic dogs and wolves (although total antioxidant capacity significantly increased with wolf content), but superoxide dismutase concentration was higher in hybrids. Thus, it seems that a low percentage of wolf content decreases several aspects of antioxidants but without any accumulating lipid oxidative damage. Additionally, wolf-dog hybrids had higher IL-1β and IL-6 concentrations but lower TNF-α concentrations than domestic dogs. And there was a significantly positive correlation between percentage of wolf content and IL-1β. These data imply either a mitonuclear incompatibility or a nuclear-nuclear incompatibility within wolf-dog hybrids, a case that does not support heterosis.