Header

UZH-Logo

Maintenance Infos

Greater growth of proximal metatarsals in bird embryos and the evolution of hallux position in the grasping foot


Botelho, João Francisco; Smith-Paredes, Daniel; Soto-Acuña, Sergio; Núñez-León, Daniel; Palma, Verónica; Vargas, Alexander O (2017). Greater growth of proximal metatarsals in bird embryos and the evolution of hallux position in the grasping foot. Journal of Experimental Zoology. Part B: Molecular and Developmental Evolution, 328(1-2):106-118.

Abstract

In early theropod dinosaurs—the ancestors of birds—the hallux (digit 1) had an elevated position within the foot and had lost the proximal portion of its metatarsal. It no longer articulated with the ankle, but was attached at about mid-length of metatarsal 2 (mt2). In adult birds, the hallux is articulated closer to the distal end of mt2 at ground level with the other digits. However, on chick embryonic day 7, its position is as in early theropods at half-length of mt2. The adult distal location is acquired during embryonic days 8–10. To assess how the adult phenotype is acquired, we produced fate maps of the metatarsals of day 6 chicken embryos injecting the lipophilic tracer DiI. The fates of these marks indicate a larger expansion of the metatarsals at their proximal end, which creates the illusory effect that d1 moves distally. This larger proximal expansion occurs concomitantly with growth and early differentiation of cartilage. Histological analysis of metatarsals shows that the domains of flattened and prehypertrophic chondrocytes are larger toward the proximal end. The results suggest that the distal position of the hallux in the avian foot evolved as a consequence of an embryological period of expansion of the metatarsus toward the proximal end. It also brings attention to the developmental mechanisms leading to differential growth between epiphyses and their evolutionary consequences. J. Exp. Zool. (Mol. Dev. Evol.) 328B:106–118, 2017. C � 2016 Wiley Periodicals, Inc.

Abstract

In early theropod dinosaurs—the ancestors of birds—the hallux (digit 1) had an elevated position within the foot and had lost the proximal portion of its metatarsal. It no longer articulated with the ankle, but was attached at about mid-length of metatarsal 2 (mt2). In adult birds, the hallux is articulated closer to the distal end of mt2 at ground level with the other digits. However, on chick embryonic day 7, its position is as in early theropods at half-length of mt2. The adult distal location is acquired during embryonic days 8–10. To assess how the adult phenotype is acquired, we produced fate maps of the metatarsals of day 6 chicken embryos injecting the lipophilic tracer DiI. The fates of these marks indicate a larger expansion of the metatarsals at their proximal end, which creates the illusory effect that d1 moves distally. This larger proximal expansion occurs concomitantly with growth and early differentiation of cartilage. Histological analysis of metatarsals shows that the domains of flattened and prehypertrophic chondrocytes are larger toward the proximal end. The results suggest that the distal position of the hallux in the avian foot evolved as a consequence of an embryological period of expansion of the metatarsus toward the proximal end. It also brings attention to the developmental mechanisms leading to differential growth between epiphyses and their evolutionary consequences. J. Exp. Zool. (Mol. Dev. Evol.) 328B:106–118, 2017. C � 2016 Wiley Periodicals, Inc.

Statistics

Citations

Dimensions.ai Metrics
2 citations in Web of Science®
2 citations in Scopus®
1 citation in Microsoft Academic
Google Scholar™

Altmetrics

Downloads

3 downloads since deposited on 10 Jan 2018
3 downloads since 12 months
Detailed statistics

Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Paleontological Institute and Museum
Dewey Decimal Classification:560 Fossils & prehistoric life
Uncontrolled Keywords:Developmental Biology, Animal Science and Zoology, Molecular Medicine, Genetics, Ecology, Evolution, Behavior and Systematics
Language:English
Date:21 September 2017
Deposited On:10 Jan 2018 19:51
Last Modified:19 Aug 2018 12:39
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:1552-5007
OA Status:Closed
Publisher DOI:https://doi.org/10.1002/jez.b.22697
PubMed ID:27649924

Download