Evol Ecol Res 17: 291-300 (2016)     Full PDF if your library subscribes.

No evidence of sex reversal
by means of experimentally altered sex ratios in threespine stickleback

Theo C.M. Bakker

Institute for Evolutionary Biology and Ecology, University of Bonn, Bonn, Germany

Correspondence: T.C.M. Bakker, Institute for Evolutionary Biology and Ecology, University of Bonn, An der Immenburg 1, D-53121 Bonn, Germany. email: tbakker@evolution.uni-bonn.de


Background: Among fishes, sex reversal by abiotic or social factors is well documented even in species with genetic sex determination. All species of the family Gasterosteidae studied thus far show genetic sex determination, and natural sex reversal is most likely rare. In threespine stickleback (Gasterosteus aculeatus L.), exposure to sex hormones or endocrine disrupters can induce functional intersexuality or even sex reversal.

Hypothesis: In the presence of a shortage of reproductive males (i.e. a female-biased operational sex ratio), female threespine stickleback may become males.

Methods: A classical male-removal experiment, which induces sex reversal in many protogynous fishes. In six large male-removal tanks, each containing a full-sibling group, every time that a reproductive male appeared, it was removed. In the respective yoked-control tank (one control tank for each male-removal tank), a random fish was removed at the same time. The sex of all removed fish was determined by visual inspection of the gonads.

Results: Approximately 16 months after the appearance of the first reproductive male, the total number of fish (removed and remaining fish) in each male-removal and yoked-control tank showed no significant deviation from an even sex ratio (except for a single female-biased control tank). The male-removal and yoked-control tanks did not differ significantly in sex ratio. Threespine stickleback thus failed to show sex reversal under the applied male-removal regime.

Keywords: Gasterosteus aculeatus, male removal, sex determination, sex ratio, social cues, threespine stickleback.

IF you are connected using the IP of a subscribing institution (library, laboratory, etc.)
or through its VPN.


        © 2016 Theo C.M. Bakker. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

       Subscribing institutions/libraries may grant individuals the privilege of making a single copy of an EER article for non-commercial educational or non-commercial research purposes. Subscribing institutions/libraries may also use articles for non-commercial educational purposes by making any number of copies for course packs or course reserve collections. Subscribing institutions/libraries may also loan single copies of articles to non-commercial libraries for educational purposes.

       All copies of abstracts and articles must preserve their copyright notice without modification.