Regression of olfactory systems in inquiline parasites (IMAGE)
Caption
Micro CT scans show the relative olfactory lobe (OL) size of the hosts and inquilines. The phylogram is an ancestral state reconstruction of OL volumes relative to total brain volumes across the social parasites (A. insinuator, A. charruanus and P. argentina) and their hosts (A. echinatior, and A. heyeri). Barplots show ratios of OL volume to total brain volume in inquiline parasites (in orange) relative to their hosts (in blue). Circles inserted at the tips of bars are proportional to the measured total brain volumes, while the smaller contained circles represent the measured volumes of the right and left OLs. On average, Panamanian species have larger brains than Uruguayan species (2-sample t-test, pt-test = 0.005, df = 2.97, t = ?7.74, n = 5). Relative OL volumes became reduced (pt-test = 0.059, df =2, t = ?2.65, n = 5) as inquiline social parasites evolved their different degrees of specialization along the gradient of inquiline adaptations known as the inquiline syndrome27. Shown below are 3D surface reconstructions of the brains (with the OLs highlighted in yellow) and of the head capsules of A. heyeri, A. charruanus, and P. argentina (from top to bottom).
Credit
Arizona State University
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