'Sloppy' sperm mixing and intraspecific variation in sperm precedence (P2) patterns

Sperm precedence patterns are typically highly variable within (and between) species. Intraspecific variation in sperm precedence (measured as P2, the proportion of progeny fathered by the last male to mate' is frequently seen as a candidate for adaptive interpretation through either male effects (e.g. body size), female effects (e.g. cryptic female choice) or an interaction between the two. Here we show, using computer simulation, that if ejaculates divide into a number of 'packets' and packets from two males mix randomly, then a variety of patterns of sperm precedence may result. We term this process 'sloppy' mixing. If ejaculates break into a small number of packets, bimodal P2 distributions are predicted. As the number of packets is increased, then a complex series of changes through multimodal and flat to unimodal distributions results. Sloppy mixing can thus result in many of the observed P2 distributions. Sloppy mixing is unlikely to change the predictions of adaptive models of sperm competition.     

Ghrelin gets its GOAT

Ghrelin, a powerful appetite-stimulating hormone secreted by the stomach, is modified by an octanyl side chain on its third amino acid, a serine, which is essential for its activity. A recent study (Yang et al., 2008) reports identification of the enzyme catalyzing the addition of this octanyl, GOAT.     

Iris recognition gets results

Positive results are filtering in from the United Arab Emirates (UAE), demonstrating that iris recognition can be a powerful tool to help verify the identity of passengers. This news comes as the technology is rolled out for use as part of the CANPASS — Air programme at Vancouver International Airport.