Sperm collection in Black-legged Kittiwakes and characterization of sperm velocity and morphology

Background:Collecting and studying live sperm is central to many important fields of biology.Yet,a simple method to collect live sperm is lacking in wild seabird species.Here,we describe a non?invasive method to collect viable sperm samples based on a simple massage technique applied to male Black?legged Kittiwakes(Rissa tridactyla).Methods:We studied a colony breeding at Kongsfjorden,Svalbard and successfully obtained sperm samples from 32 males.With a subset of samples(n = 12 males),we compared the suitability of several extenders(0.9% NaCl,PBS,Earle's balance salt solution,Dulbecco's modified Eagle medium) in maintaining sperm alive long enough for analyses.With another 18 ejaculates,we conducted computer assisted sperm analyses using the CASA plugin for ImageJ.We provide details about the settings to be used for such analyses.Lastly,droplets from 20 ejaculates were smeared on glass slides and preserved with formalin to characterize sperm morphology in terms of total sperm length,sperm head length,midpiece length and flagellum length,and percentage of abnormal sperm.Results:With this method and under field conditions,we were able to obtain sufficient amounts of live sperm to assess traits related to sperm quality(e.g.sperm morphology,percentage of motile sperm,sperm velocity).We found that two extenders,Earle's balanced salt solution and Dulbecco modified Eagle's medium,yielded similarly good results.Additionally,we investigated whether specific behaviours were associated with successful sperm collection and whether sperm collection success depended on how long before laying sperm collection was attempted.Finally,we provide mean values for sperm morphology,sperm swimming ability and percentage of motile sperm,which may prove useful for future comparative analyses,and we report high levels of sperm abnormality and within?ejaculate variation in sperm morphology.Conclusions:We discuss the high percentage of abnormal sperm and high within?ejaculate variation in sperm morphology in light of sperm competition theory and conclude that these figures are likely due to relaxed post?cop?ulatory sexual selection,kittiwakes being strictly monogamous.Finally,we suggest that this method could be applied to other seabird species sharing similar ecology.

Oxidative stress favours herpes virus infection in vertebrates： a meta-analysis

Herpes viruses are responsible for a variety of pathological effects in humans and in both wild and domestic animals. One mechanism that has been proposed to facilitate replication and activity of herpes viruses is oxidative stress （OS）. We used meta-analytical techniques to test the hypotheses that （1） herpes virus infection causes OS and （2） supplementation of antioxidants reduces virus load, indicating that replication is favoured by a state of OS. Results based on studies on mammals, including humans, and birds show that （1） OS is indeed increased by herpes virus infection across multiple tissues and species, （2） biomarkers of OS may change differently between tissues, and （3） the effect size does not differ among different virus strains. In addition, the increase of oxidative damage in blood （tissue commonly available in ecological studies） was similar to that in the tissues most sensitive to the herpes virus. Our results also show that administration of antioxidants re- duces virus yield, indicating that a condition of OS is favorable for the viral replication. In addition, some antioxidants may be more efficient than others in reducing herpes virus yield. Our results point to a potential mechanism linking herpes virus infection to individual health status.