Sperm Biology and Infertility

In Sperm Biology and Infertility, we address four main fields: Sperm Molecular Biology, Sperm Ecology, Sperm Oxygen Radicals and the Role of the Mitochondria.

Sperm Molecular Biology

Currently, Conni is developing protocols to characterise sperm protamines and its functional significance for fertility. Contact her, if you are interested in that topic. Master theses on the topic are here.

Sperm Ecology

THEORY Our group, together with Jessica Abbott in Lund, has introduced Sperm Ecology as a novel framework to study sperm cells with three aims. We have first described the variety of environmental effects on sperm and concluded that evolutionary and ecological research should not neglect the overwhelming evidence in both external and internal fertilizers, as well as terrestrial and aquatic habitats, that sperm function is altered by many environments, including the male environment. Second, we concluded that the evidence for phenotypic plasticity in sperm function is overwhelming.This, we believe, necessitates a re-appraisal of some evolutionary assumption in sperm competition theory. Third, genotype-by-environment interaction effects on sperm function exist but their general adaptive significance (e.g. local adaptation) awaits further research. Unresolved issues are whether sperm diversification occurs by natural selection acting on sperm function, or on male and female micro-environments that optimise plastic performance of sperm (which we called ‘sperm niches‘). Environmental effects on sperm reduce fitness predictability under sperm competition, but are powerful to predict altered species distributions under global change, explain adaptive behaviour, and highlight the role of natural selection in behavioral ecology and reproductive medicine.

This ‘manifesto’ appeared in Annual Reviews of Ecology, Evolution and Systematics in 2016. Link

Otti O, Johnston PR, Horsburgh G, Galindo J, Reinhardt K. 2015. Female transcriptomic response to male genetic and nongenetic ejaculate variation. Behavioral Ecology, link

Contact Klaus for further information.

EMPIRICAL WORK We have established selection lines of Drosophila melanogaster under two extreme athmospheres, 10% hypoxia and 5% CO2 concentration. Each treatment has been maintained in 4 replicate lines and 4 control lines each. This design allows us to disentangle genetic, environmental and phenotypic plastic effect on sperm function. We find the first evidence that sperm competition success has a tiny genetic but a large environmental component: Sperm offense changed differently over time in an extreme environment, 5% carbon dioxide concentration, compared to a normal atmosphere. Using graphical models we determined that sperm-competition success is strongly influenced by sperm aging. These data suggest a critical re-appraisal of sperm competition may be needed. Contact Ralph for further information.

Sperm Metabolism and Sperm Oxygen Radicals

more to come. For the moment see:

Reinhardt K, Breunig HG, Uchugonova A, König K. 2015. Sperm metabolism is altered during storage by female insects: evidence from two-photon autofluorescence lifetime measurements in bedbugs. Journal of the Royal Society Interface link (open access)

Ribou A-C, Reinhardt K. 2012. Reduced metabolic rate and oxygen radicals production in stored insect sperm. Proceedings of the Royal Society of London B 279: 2196-2203.

Reinhardt K, Ribou A-C. 2013. Females become infertile as the stored sperm’s oxygen radicals increase. Scientific Reports 3:2888

Contact Klaus for further information.

Mitochondria and Sperm Function

Sperm are propelled by energy that is largely provided by the mitochondria. The exclusive maternal inheritance of mitochondria generates the interesting situation that mitochondria-related sperm traits that benefit the father cannot be inherited to the son. This is a theoretical challenge for models that assume that sperm competition drives evolutionary change.

A second area where we look at the role of mitochondria in sperm function is via the interaction of mitochondria with the nucleus. Such mito-nuclear interactions influence fertility and mismatches can cause complete male sterility. In collaboration with Damian Dowling’s lab, Monash University, we address some questions around such mismatches using mitolines – where a certain genotype is combined with either of several mitochondrial haplotypes.

Contact Ralph for further information.