The corrected figures are shown below.
None of these errors affected the conclusions of the paper.
The authors apologize for any inconvenience caused by these changes.
© 2018. Published by The Company of Biologists Ltd
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.