Contributions to Zoology, 86 (4) – 2017Menno Schilthuizen; Rob Langelaan; Nicola Hemmings; Wesley van Oostenbrugge; Stefan Visser: An unexpected twist: Sperm cells coil to the right in land snails and to the left in song birds

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We thank Tim Birkhead for providing samples, and Bertie-Joan van Heuven and Ewan Richardson for technical assistance. Three reviewers, Rich Palmer, Marco Oliverio, and Yumi Nakadera provided comments that helped us improve the paper. The specimens of Helix pomatia were collected under permission FF/75A/2010/021a from the Netherlands Ministry of Agriculture, Nature, and Food Quality.

Received: 2 September 2017

Revised and accepted: 14 November 2017

Published online: 22 December 2017

Editor: A. Minelli