Foraging in moles, bees, and birds

Star nosed mole, eastern mole, African hedgehog, and masked shrew (bottom right).

Star-nosed mole Lives in wet, marshy soil Burrowing habitat in dark tunnels Eats earthworms and other prey Eyes are greatly reduced and even in light, visual information is not prioritized Uses sense of touch to find food and navigate

Goal: use the star-nosed mole as a model to understand cognitive representations of sensory space

Eimer’s organs are mechanoreceptors Eimer’s organs are mechanoreceptors. Respond to deformation of the membrane, probably by opening of stretch sensitive ion channels that depolarize the neuron. Most highly innervated organ in nature. Smallest receptive fields known.

Detection of an object by any appendage stimulates the appropriate head adjustment so the object can be sampled by appendage 11. A disproportionate number of nerve fibers send information from appendage 11 to the brain than any other. Sensory bias is matched by cortical bias in somatosensory cortex, where 25% of the ss cortex devoted to the nose is responsible for analyzing information from appendage 11.

Cortical magnification reflects adaptive sensory biases

Figure 3. Transcriptome profiling of mole trigeminal and dorsal root ganglia. Green=TG higher, Grey=DRG higher What are the cellular and molecular building blocks that enable this great touch sensitivity in the star? Gerhold KA, Pellegrino M, Tsunozaki M, Morita T, et al. (2013) The Star-Nosed Mole Reveals Clues to the Molecular Basis of Mammalian Touch. PLoS ONE 8(1): e55001. doi:10.1371/journal.pone.0055001 http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055001

Figure 5. Expression of candidate transducers in mouse ganglia. Conservation of mole identified target genes in mouse TG (easier to study function in mice) Gerhold KA, Pellegrino M, Tsunozaki M, Morita T, et al. (2013) The Star-Nosed Mole Reveals Clues to the Molecular Basis of Mammalian Touch. PLoS ONE 8(1): e55001. doi:10.1371/journal.pone.0055001 http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055001

Figure 2. Functional enrichment of light touch-sensitive neurons in the star-nosed mole trigeminal ganglia. A fura-2 calcium dye shows that TG innervating the star nose has greater responses to touch (stretch) than the DRG, which innervates the rest of the body sensation Both respond the painful capsaicin with increases in calcium B. A greater proportion of TG neurons respond to touch stimuli than painful stimuli, and than DRG neurons. Conclude, the TG relays the touch information of the star nose, while the DRG may process touch info from other places on the body Gerhold KA, Pellegrino M, Tsunozaki M, Morita T, et al. (2013) The Star-Nosed Mole Reveals Clues to the Molecular Basis of Mammalian Touch. PLoS ONE 8(1): e55001. doi:10.1371/journal.pone.0055001 http://www.plosone.org/article/info:doi/10.1371/journal.pone.0055001

Food storage in birds While some species find food and consume it immediately, others store their cache for days, weeks, or months at a time Jays Some use a sticky saliva to cement their cached items to a tree crevice Nuthatches Hoarders able to find more seeds than naïve birds Clark’s nutcrackers Size of the seed May cache 100,000 seeds in the fall Tufted titmouse does not hoard but can watch a nuthatch hide a seed, then steal it

Individual birds seeds recovered,, storers vs non--storers

Individual differences Climate is more harsh and demanding in Alaska; black capped chickadees there are better at finding hidden food Hippocampal size?

NON-STORER STORER Log HIPPOCAMPAL VOLUME (mm3) BODY WEIGHT Krebs et al 1996

Learned differences Experiment in lab raised birds examined environmental contributions to hippocampal development Birds were given full seeds to eat or hide or powdered seeds to eat Birds given full seeds had more cells in their hippocampus than the birds denied a food storing experience.

Seed storing modifies hippocampal volume Sperry 2007

Depends on experience Clayton, 1998