Markers for apoptosis vary over time and between species. Graphs show the proportion of ookinete stage parasites displaying DNA fragmentation as measured by TUNEL (solid lines) and Caspase-like activity (dashed lines) as measured by CaspaTag™ Pan-Caspase In Situ Assay Kit, Fluorescein in conjunction with propidium iodide (Chemicon international, USA) in Plasmodium berghei (red lines with crosses) and Plasmodium yoelii (blue lines with circles). Bars show standard errors of the mean and values are based on between 3 and 6 individual infections per time point. For each mouse 8 ookinete cultures were set up which were incubated for 14 hours before the cultures from each mouse were pooled and purified for ookinetes using macs ls cell separation columns (Miltenyi biotec). The resulting purified ookinetes were then alliquated into 8 individual 1 ml cultures (1 per time point for 2 assays) containing complete ookinete media. These cultures were then returned to the incubator until the time relevant time point (15, 18, 21 or 24 hours post culture set up). More detailed methodology is available in Additional file 1.