The anatomy of the bill tip of Kiwi and associated somatosensory regions of the brain: comparisons with shorebirds
Date
2013
Authors
Cunningham, Susan J.
Corfield, Jeremy R.
Iwaniuk, Andrew N.
Castro, Isabel
Alley, Maurice R.
Birkhead, Tim R.
Parsons, Stuart
Journal Title
Journal ISSN
Volume Title
Publisher
Public Library of Science
Abstract
Three families of probe-foraging birds, Scolopacidae (sandpipers and snipes), Apterygidae (kiwi), and
Threskiornithidae (ibises, including spoonbills) have independently evolved long, narrow bills containing clusters of
vibration-sensitive mechanoreceptors (Herbst corpuscles) within pits in the bill-tip. These ‘bill-tip organs’ allow birds
to detect buried or submerged prey via substrate-borne vibrations and/or interstitial pressure gradients. Shorebirds,
kiwi and ibises are only distantly related, with the phylogenetic divide between kiwi and the other two taxa being
particularly deep. We compared the bill-tip structure and associated somatosensory regions in the brains of kiwi and
shorebirds to understand the degree of convergence of these systems between the two taxa. For comparison, we
also included data from other taxa including waterfowl (Anatidae) and parrots (Psittaculidae and Cacatuidae), nonapterygid
ratites, and other probe-foraging and non probe-foraging birds including non-scolopacid shorebirds
(Charadriidae, Haematopodidae, Recurvirostridae and Sternidae). We show that the bill-tip organ structure was
broadly similar between the Apterygidae and Scolopacidae, however some inter-specific variation was found in the
number, shape and orientation of sensory pits between the two groups. Kiwi, scolopacid shorebirds, waterfowl and
parrots all shared hypertrophy or near-hypertrophy of the principal sensory trigeminal nucleus. Hypertrophy of the
nucleus basorostralis, however, occurred only in waterfowl, kiwi, three of the scolopacid species examined and a
species of oystercatcher (Charadriiformes: Haematopodidae). Hypertrophy of the principal sensory trigeminal
nucleus in kiwi, Scolopacidae, and other tactile specialists appears to have co-evolved alongside bill-tip
specializations, whereas hypertrophy of nucleus basorostralis may be influenced to a greater extent by other sensory
inputs. We suggest that similarities between kiwi and scolopacid bill-tip organs and associated somatosensory brain
regions are likely a result of similar ecological selective pressures, with inter-specific variations reflecting finer-scale
niche differentiation.
Description
Sherpa Romeo green journal: open access
Keywords
Bill tip structure , Somatosensory regions , Kiwi , Shorebirds , Probe-foraging birds , Apterygidae , Scolopacidae , Threskiomithidae
Citation
Cunningham, S. J., Corfield, J. R., Iwaniuk, A. N., Castro, I., Alley, M. R., Birkhead, T. R., & Parsons, S. (2013). The anatomy of the bill tip of Kiwi and associated somatosensory regions of the brain: comparisons with shorebirds. PLoS ONE, 8(11), e:80036. doi:10.1371/journal.pone.0080036