Relative medial and dorsal cortex volume in relation to foraging ecology in congeneric lizards

The need to locate distributed resources such as mates, food, and nests is correlated with an enlarged hippocampus in many mammalian and avian species . This correlation is believed to be a consequence of selection for spatial ability. Little is known about how such ecological needs affect non-mammal ian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationshi p between foraging ecology and the size of the DC and MC in congeneric male lizards. We pre dieted based on the mammalian and avian literature that Ac anthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait pred ator, that captures mobile prey. Our previous behavioral studies showed tha t A. boskianus did not differ from A. scutellatus on a spatial task but tha t A. boskianus was significantly better at the reversal of a visual discrim ination, another task that is hippocampally dependent in mammals. In the cu rrent study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, o lfactory, cortex, was similar in size between species. The current anatomic al results suggest that MC and DC size is related to active foraging in liz ards and, along with our previous behavioral studies, show that it is possi ble for this relationship to occur in the absence of evidence for species d ifferences in spatial memory. Copyright (C) 2000 S. Karger AG, Basel.