Title
Hydrodynamic drag constrains head enlargement for mouthbrooding in cichlids Hydrodynamic drag constrains head enlargement for mouthbrooding in cichlids
Author
Faculty/Department
Faculty of Sciences. Biology
Publication type
article
Publication
London ,
Subject
Biology
Engineering sciences. Technology
Source (journal)
Journal of the Royal Society interface: physical and life sciences. - London
Volume/pages
12(2015) :109 , 4 p.
ISSN
1742-5689
1742-5689
Article Reference
20150461
Carrier
E-only publicatie
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
Presumably as an adaptation for mouthbrooding, many cichlid fish species have evolved a prominent sexual dimorphism in the adult head. Since the head of fishes serves as a bow during locomotion, an evolutionary increase in head volume to brood more eggs can trade-off with the hydrodynamic efficiency of swimming. Here, the differences between males and females in three-dimensional shape and size of the external head surfaces and the effect thereof on drag force during locomotion was analysed for the Nile tilapia (Oreochromis niloticus), a maternal mouthbrooder. To do so, three-dimensional body surface reconstructions from laser scans and computational fluid dynamics simulations were performed. After scaling the scanned specimens to post-cranial body volume, in order to theoretically equalize propulsive power, the external volume of the head of females was 27% larger than that of males (head length + 14%; head width + 9%). These differences resulted in an approximate 15% increase in drag force. Yet, hydrodynamics imposed important constraints on the adaptation for mouthbrooding as a much more drastic drop in swimming efficiency seems avoided by mainly enlarging the head along the swimming direction.
Full text (open access)
https://repository.uantwerpen.be/docman/irua/923f5d/e1078f44.pdf
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