Original paper

Does intersexuality affect precopula and fecundity in Gammarus fossarum (Crustacea, Amphipoda)?

Ladewig, V.; Jungmann, D.; Petzsch, P.; Pitsch, M.; Stäglich, I.; Nagel, R.


Intersexes of Gammarus fossarum and several other gammarid species seem to be functional females, however, knowledge on reproduction variables, which are of crucial importance for the existence of populations, in intersexes is still scarce. We proposed several hypotheses regarding body length (of singles and in precopula pairs), precopula behaviour (e.g. reduced pairing success) and fecundity (e.g. reduced brood size) of intersexes. Data obtained from G. fossarum populations in the streams Friedrichsbach and Lockwitzbach (Germany) were used to examine these hypotheses. At the Friedrichsbach and one of the two sampling sites of the Lockwitzbach, intersex singles were only in tendency larger than female singles. At the other Lockwitzbach site, intersex singles were significantly larger compared to female singles. Pairing success of intersexes was not reduced. Absolute brood size as well as the brood size normalised to body length did not differ significantly between females and intersexes regarding early stages, late stages or pooled data from all stages of egg development before hatching. For females and intersexes, the number of eggs (stage 1-5) in the marsupium did not significantly decrease during egg development. Hence, intersexes might not be a disadvantage for the population at least with regard to the examined reproduction variables in these populations of this gammarid species.


gammarus fossarumintersexualityreproductionpairing successprecopula