. 2013 Feb 22;280(1753):20122616. doi: 10.1098/rspb.2012.2616

Table 1.

Interspecific associations between sperm size, velocity and ATP concentration [ATP]. Superscripts following the λ estimates indicate significance levels of the likelihood-ratio tests (first position: against λ = 1; second position: against λ = 0; n.s.: not significant, *p < 0.05).

sperm trait	predictor	slope	t	p-value	λ
[ATP]	midpiece length	1.55	2.36	0.035	0.99^{n.s., n.s.}
[ATP]	total flagellum length	1.71	1.89	0.08	0.99^{n.s., n.s.}
[ATP]	midpiece-free flagellum length^a	−2.26	−2.27	0.04	0.63^{n.s., n.s.}
VCL	[ATP]	−3.71	−1.32	0.21	<0.0001*^{, n.s.}
VCL	mitochondrial efficiency	−4.31	−1.42	0.18	<0.0001*^{, n.s.}

^aLength of the portion of the flagellum not associated with the midpiece.