Nonrandom mating, mate choice, and male-male competition in the crayfish Austropotamobius italicus, a threatened species

Abstract

Abstract:The omnivorous habit and food selection in freshwater macroinvertebrates was investigated in the white-clawed crayfish, Austropotamobius pallipes, a threatened species. First, during an annual cycle we analysed gut contents for vascular plant detritus, moss, amorphous plant material, and animal remains, and evaluated their organic content. Second, we ran preference experiments in the laboratory, in which crayfish had to choose, in the first trial among three vegetal items, in the second trial among three animal prey, and in the third trial between the two preferred items of the previous two trials (i. e. moss and insect larvae). Third, we analysed whether the assimilation efficiencies of different food items affected crayfish food choice. Our results revealed that this species mostly acted as a detritus consumer, obtaining nutrition from the associated microbes, fungi, proto-and metazoans, but also showed herbivorous and carnivorous habits. However, at least when food resources were not limited, crayfish displayed distinct feeding preferences, often ruled by factors other than the nutritional quality and the assimilation efficiency of the selected food.

Reproductive Plasticity in Freshwater Invader: From Long-Term Sperm Storage to Parthenogenesis

“…Females with the opportunity to mate in both mating seasons had the highest possibility of selecting the best mates or collecting spermatophores from the maximum number of males. Mechanisms of sexual selection in crayfish have been described [47], [48], [49], but it is unclear whether females can strictly limit mating only to the best males. In addition, the number of males from which a female can store the spermatophores is not known.…”

Mutual mate choice in crayfish: large body size is selected by both sexes, virginity by males only

“…Gwynne, 1981), in spiders (Uhl, 1998) and in a few non-decapod crustaceans (gammarid amphipods, Elwood, Gibson & Neil, 1987;isopods, Ridley & Thompson, 1979), but, except in the spiny lobsters (MacDiarmid & Butler, 1999), it has never been demonstrated in decapods (see, e.g. Villanelli & Gherardi, 1998;Gherardi et al, 2006). The only indirect evidence comes from Rubolini et al (2006), who showed the ability by male Au.…”

“…In the majority of the species studied so far, large males are successful when competing with other males for access to females (Jennisons & Blackwell, 1996). Large crayfish males are dominant over smaller ones (Berrill & Arsenault, 1984;Villanelli & Gherardi, 1998) and more easily force females to copulate (Snedden, 1990;Gherardi et al, 2006). However, the advantage of large males outcompeting other males or coercing females does not necessarily imply a female preference for large males, as found in the present study and suggested for other crayfish species (Austropotamobius italicus Gherardi et al, 2006; Cherax quadricarinatus Barki & Karplus, 1999).…”

“…Female preference for larger males has been demonstrated in crustaceans (e.g. isopods Shuster, 1981;decapods, Greenspan, 1980), including crayfish (Astacus astacus, Furrer, 2004; Austropotamobius pallipes Villanelli & Gherardi, 1998;Gherardi et al, 2006;and Orconectes rusticus Berrill & Arsenault, 1984). In the majority of the species studied so far, large males are successful when competing with other males for access to females (Jennisons & Blackwell, 1996).…”

“…We followed a binary choice test paradigm, in which pairs of live crayfish, the 'targets', with opposing characteristics, were simultaneously offered to an experimental individual, the 'chooser'. On the basis of previous studies in other crayfish species (Stein, 1976;Berrill & Arsenault, 1984;Snedden, 1990;Villanelli & Gherardi, 1998;Galeotti et al, 2006;Gherardi et al, 2006), we hypothesized that P. clarkii females would select dominant males, according to the perceived hierarchical status and/or to their large body and chelar size, whereas males would be attracted only by potentially more fecund females, i.e. females with a large BS.…”