Patterns of sperm damage in Chernobyl passerine birds suggest a trade-off between sperm length and integrity

Abstract

Interspecific variation in sperm size is enigmatic, but generally assumed to reflect species-specific trade-offs in selection pressures. Among passerine birds, sperm length varies sevenfold, and sperm competition risk seems to drive the evolution of longer sperm. However, little is known about factors favouring short sperm or constraining the evolution of longer sperm. Here, we report a comparative analysis of sperm head abnormalities among 11 species of passerine bird in Chernobyl, presumably resulting from chronic irradiation following the 1986 accident. Frequencies of sperm abnormalities varied between 15.7 and 77.3% among species, more than fourfold higher than in uncontaminated areas. Nonetheless, species ranked similarly in sperm abnormalities in unpolluted areas as in Chernobyl, pointing to intrinsic factors underlying variation in sperm damage among species. Scanning electron microscopy of abnormal spermatozoa revealed patterns of acrosome damage consistent with premature acrosome reaction. Sperm length, but not sperm competition risk explained variation in sperm damage among species. This suggests that longer spermatozoa are more susceptible to premature acrosome reaction. Therefore, we hypothesize a trade-off between sperm length and sperm integrity affecting sperm evolution in passerine birds.

Genetic and Ecological Studies of Animals in Chernobyl and Fukushima

“…They also found that abnormality rates were correlated with reduced levels of antioxidants in the blood, liver, and eggs of these birds, supporting the hypothesis that antioxidants likely play a significant role in protecting DNA from the direct and indirect consequences of exposure to radionuclides. And a more recent analysis of Chernobyl birds found that in 9 out of 10 species examined, sperm abnormality rates were much larger for birds living in Chernobyl than those living in control areas across Europe, with the highest damage levels observed for species with longer sperm (Hermosell et al 2013), suggesting that sperm abnormalities are likely common for birds living in radioactive areas. Sperm behavior is also negatively affected by radiation exposure history .…”

An unexpected twist: Sperm cells coil to the right in land snails and to the left in song birds

“…For the Passeriformes, sinistrality has previously also been reported in, for example, Hirundo rustica Linnaeus, 1758, Turdus merula Linnaeus, 1758, Fringilla coelebs Linnaeus 1758, Sturnus vulgaris Linnaeus, 1758, and Poephila acuticauda (Gould, 1839 (Retzius, 1909;Vernon and Woolley, 1999;Hermosell et al, 2013;Rowe et al, 2015).…”

Sperm head abnormalities are associated with excessive omega‐6 fatty acids in two finch species feeding on sunflower seeds

“…As such, investigating further adverse effects from supplementary feeding on this species is particularly important, as it could help inform potential conservation actions and ensure that provided foods improve the situation of urban greenfinches rather than contributing to further decline. Finally, we have in the past observed remarkably high rates of abnormal sperm in the greenfinch, especially in when several samples showed around 50% sperm abnormalities (n = 13, mean: 35.23%, range: 0–60%), as well as indications of elevated rates of abnormal sperm in the hawfinch (Hermosell et al ). These observations motivated the collection of more extensive sampling for the current study.…”

“…abnormal sperm in the greenfinch, especially in 2013 when several samples showed around 50% sperm abnormalities (n = 13, mean: 35.23%, range: 0-60%), as well as indications of elevated rates of abnormal sperm in the hawfinch (Hermosell et al 2013). These observations motivated the collection of more extensive sampling for the current study.…”