Modification of sperm fatty acid composition during epididymal maturation in bats.

Biochemical properties of polyunsaturated fatty acids (PUFAs) are fundamental to sperm movements. Amongst all adjustments operated during epididymal maturation, sperm membrane lipid composition is remodelled. Specifically, the proportion of PUFAs usually increases from the caput towards the cauda epididymidis. In mammals, PUFAs are predominantly acquired through the diet, which can consequently impact male fertility. We aimed at analysing to what extent n-6 and n-3 PUFAs are incorporated into sperm in the Seba's short-tailed bat (Carollia perspicillata), and at demonstrating the effect of the sperm fatty acid composition on sperm mobility. We therefore provided food varying in fatty acid composition to males of C. perspicillata and measured the fatty acid composition and mobility traits in spermatozoa collected from the caput and cauda epididymides. We found that n-6 and n-3 PUFAs and saturated fatty acids were significantly related to sperm velocity but not to the proportion of progressive sperm (i.e. motility). Concomitant to an increase in sperm velocity, the level of fatty acid saturation increased from the caput to the cauda epididymidis, while the proportion of PUFAs remained similar along the epididymis. A reduction in n-6 PUFAs counterbalanced an increase in n-3 PUFAs. The food treatments did not affect the sperm fatty acid composition. Our results suggest that a precise endogenous control rather than dietary effects determines sperm fatty acid composition in C. perspicillata.

The effect of dietary antioxidant supplementation in a vertebrate host on the infection dynamics and transmission of avian malaria to the vector.

Host susceptibility to parasites is likely to be influenced by intrinsic factors, such as host oxidative status determined by the balance between pro-oxidant production and antioxidant defences. As a result, host oxidative status acts as an environmental factor for parasites and may constrain parasite development. We evaluated the role of host oxidative status on infection dynamics of an avian malarial parasite by providing canaries (Serinus canaria) with an antioxidant supplementation composed of vitamin E (a lipophilic antioxidant) and olive oil, a source of monounsaturated fatty acids. Another group received a standard, non-supplemented food. Half of the birds in each group where then infected with the haemosporidian parasite, Plasmodium relictum. We monitored the parasitaemia, haematocrit level, and red cell membrane resistance, as well as the transmission success of the parasite to its mosquito vector, Culex pipiens. During the acute phase, the negative effect of the infection was more severe in the supplemented group, as shown by a lower haematocrit level. Parasitaemia was lower in the supplemented group during the chronic phase only. Mosquitoes fed on supplemented hosts were more often infected than mosquitoes fed on the control group. These results suggest that dietary antioxidant supplementation conferred protection against Plasmodium in the long term, at the expense of a short-term negative effect. Malaria parasites may take advantage of antioxidants, as shown by the increased transmission rate in the supplemented group. Overall, our results suggest an important role of oxidative status in infection outcome and parasite transmission.