Data from: Hydrodynamic drag constrains head enlargement for mouthbrooding in cichlids
Data files
Jul 14, 2016 version files 132.77 MB
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Tilapia_BF10_F_63g_SC_CFD_avg.stl
6.35 MB
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Tilapia_BF11_F_54g_SC_CFD_avg.stl
5.44 MB
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Tilapia_BF13_M_86g_SC_CFD_avg.stl
5.28 MB
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Tilapia_BF17_F_48g_SC_CFD_avg.stl
6.58 MB
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Tilapia_BF18_F_51g_SC_CFD_avg.stl
6.56 MB
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Tilapia_BF19_M_95g_SC_CFD_avg.stl
6.72 MB
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Tilapia_BF2_F_63g_SC_CFD_avg.stl
5.09 MB
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Tilapia_BF20_F_57g_SC_CFD_avg.stl
6.37 MB
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Tilapia_BF22_M_115g_SC_CFD_avg.stl
6.78 MB
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Tilapia_BF5_M_100g_SC_CFD_avg.stl
5.76 MB
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Tilapia_BF6_M_103g_SC_CFD_avg.stl
5.03 MB
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Tilapia_BF8_M_125g_SC_CFD_avg.stl
5.67 MB
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X00_Y00_Z00_full.stl
4.75 MB
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X00_Y00_Z10_full.stl
4.71 MB
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X00_Y00_Z20_full.stl
4.70 MB
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X00_Y00_Z30_full.stl
4.70 MB
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X00_Y00_Z40_full.stl
4.77 MB
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X00_Y10_Z00_full.stl
4.73 MB
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X00_Y20_Z00_full.stl
4.58 MB
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X00_Y30_Z00_full.stl
4.71 MB
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X00_Y40_Z00_full.stl
4.70 MB
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X10_Y00_Z00_full.stl
4.70 MB
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X20_Y00_Z00_full.stl
4.69 MB
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X30_Y00_Z00_full.stl
4.69 MB
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X40_Y00_Z00_full.stl
4.68 MB
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 analyzed 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.