Campbell AL et al. (2016), Ocean acidification changes the male fitness la...

ECB-ART-44869

Sci Rep 2016 Aug 17;6:31250. doi: 10.1038/srep31250.

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Ocean acidification changes the male fitness landscape.

Campbell AL , Levitan DR , Hosken DJ , Lewis C .

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Sperm competition is extremely common in many ecologically important marine taxa. Ocean acidification (OA) is driving rapid changes to the marine environments in which freely spawned sperm operate, yet the consequences of OA on sperm performance are poorly understood in the context of sperm competition. Here, we investigated the impacts of OA (+1000 μatm pCO2) on sperm competitiveness for the sea urchin Paracentrotus lividus. Males with faster sperm had greater competitive fertilisation success in both seawater conditions. Similarly, males with more motile sperm had greater sperm competitiveness, but only under current pCO2 levels. Under OA the strength of this association was significantly reduced and there were male sperm performance rank changes under OA, such that the best males in current conditions are not necessarily best under OA. Therefore OA will likely change the male fitness landscape, providing a mechanism by which environmental change alters the genetic landscape of marine species.

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Genes referenced: LOC100887844 LOC100893907 vcl

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	Figure 1. Ejaculate traits in current and OA seawater conditions.(a) Male sea urchin (n = 22) ejaculate performance in seawater treatments (group means ± 95% confidence intervals) and (b) the variance observed in each ejaculate trait. *Indicates the significant reduction in all ejaculate traits under OA conditions and ϕindicates the significant increase in variance in sperm motility under OA conditions (p ≤ 0.05). LIN = average sperm path linearity and STR = average sperm path straightness.
	Figure 2. The GLMM modelled influence of relative male ejaculate traits on competitive fertilisation success.The modelled relationship between (a) average sperm swimming speed (VCL) and secondly the percentage of motile sperm in a male’s ejaculate under current seawater conditions (b), and under future OA conditions (c), and the proportion of larvae sired by the focal male in paired competitive fertilisation trials (n = 11 pairs) in the sea urchin Paracentrotus lividus. Predictions ± 95% confidence intervals were calculated using the ‘best fitting’ GLMM with all other model parameters kept at their observed median values.
	Figure 3. Male sperm performance ranks in current and OA seawater conditions.Male sea urchins (n = 22) ranked by (a) the percentage of motile sperm in an ejaculate and (b) average sperm swimming speed (VCL). Points are coloured by rank in ambient seawater (darker colours represent higher ranks in ambient conditions i.e. faster speed or greater motility) and male ranks in the two seawater treatments are connected by lines.

References [+] :

Alavi, Sperm motility in fishes. I. Effects of temperature and pH: a review. 2005, Pubmed