Relative Medial and Dorsal Cortex Volume in Relation to Foraging Ecology in Congeneric Lizards

Abstract

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-mammalian, non-avian species. In lizards, the putative hippocampal homologues are the dorsal cortex (DC) and medial cortex (MC). We examined the relationship between foraging ecology and the size of the DC and MC in congeneric male lizards. We predicted based on the mammalian and avian literature that Acanthodactylus boskianus, an active forager that captures clumped, immobile prey would have a larger MC and DC than A. scutellatus, a sit-and-wait predator, that captures mobile prey. Our previous behavioral studies showed that A. boskianus did not differ from A. scutellatus on a spatial task but that A. boskianus was significantly better at the reversal of a visual discrimination, another task that is hippocampally dependent in mammals. In the current study, we found that, relative to telencephalon volume, the MC and DC were larger in the active forager whereas a control region, the lateral, olfactory, cortex, was similar in size between species. The current anatomical results suggest that MC and DC size is related to active foraging in lizards and, along with our previous behavioral studies, show that it is possible for this relationship to occur in the absence of evidence for species differences in spatial memory.

Towards a multi‐trophic extension of metacommunity ecology

“…; Baird Day et al . ). Similarly, animals with larger brains, for example mammals, have a greater degree of behavioural flexibility and are better able to successfully colonise new environments (Sol et al .…”

Concerted and mosaic evolution of functional modules in songbird brains

“…Brain composition is associated with ecological niche occupation and behavioural capacities in mammals [16], birds [17,18] and fishes [19][20][21]. Residual variation in discrete brain regions is correlated with specific sensory [22][23][24][25][26][27], motor [28][29][30] and cognitive abilities [31][32][33], including from artificial selection [34,35]. Therefore, according to the mosaic model, selection for specific behaviours targets genes that specify characteristics of their underlying brain modules, such as numbers of neurons or intra-and inter-region connectivity [36], and variation in brain composition results from accretion of many isolated changes.…”

Reptilian Cognition: A More Complex Picture via Integration of Neurological Mechanisms, Behavioral Constraints, and Evolutionary Context

“…Day et al found that active forgers that presumably have increased demands on spatial processing abilities also have larger relative dorsal and medial cortices compared to sit and wait predators. Interestingly, their previous study found no difference between the two species on a spatial memory task, suggesting that differential spatial memory abilities may not underlie the relationship between foraging strategy and the cortices . Spatial area use may be another factor that can influence spatial processing and the brain; male cottonmouth snakes traverse a greater area than do females, and have larger medial cortices .…”

“…Interestingly, their previous study found no difference between the two species on a spatial memory task, suggesting that differential spatial memory abilities may not underlie the relationship between foraging strategy and the cortices. [77] Spatial area use may be another factor that can influence spatial processing and the brain; male cottonmouth snakes traverse a greater area than do females, and have larger medial cortices. [78] Similarly, in male sideblotched lizards, increased spatial area use within the context of territoriality correlates with increased DC volume.…”