Agonism and interference competition in freshwater decapods

Abstract

SummaryWe tested the hypothesis that agonistic behavior and interference competition induce species replacements in freshwater decapods. Our model organisms were two crayfish (the indigenous Austropotamobius italicus and the non-indigenous and invasive Procambarus clarkii) and the indigenous river crab Potamon fluviatile. A first experiment was aimed at analyzing the agonistic behavior of similarly-sized males in pairs of the three species combinations. Records were taken for an hour per day during five consecutive days of combats. Results showed that P. fluviatile was dominant over the two crayfish species and P. clarkii over A. italicus, as confirmed by their field distribution. In nature, the non-indigenous species might even reach higher levels of dominance over A. italicus. In fact, both the larger body size and the 'stronger' chelae of P. clarkii can induce asymmetries in fighting ability. Pairs composed of the non-indigenous crayfish and either A. italicus or P. fluviatile did not form stable hierarchies, possibly due to the failure of status recognition. In a second set of experiments, the agonistic behavior of the three species combinations was studied in the presence of either food (earthworms) or an artificial shelter (a 10 cm-long piece of a PVC pipe). As expected, resources influenced fighting and dominance translated into a differential capability to compete. In a third experiment, in which we measured shelter use by each species in a non-competitive context, shelters were more extensively occupied by A. italicus (which is dependent on natural crevices as hiding places) than by the other two species (which usually dig burrows). We expected that Potamon and Procambarus would gain less from occupying the offered shelter than Austropotamobius, and therefore their defense should be less vigorous. To the contrary, the presence of a rival strengthened the attraction to the shelter of these two species, in particular when river crabs were opposed to A. italicus.

Shelter Competition Between Two Invasive Crayfish Species: A Laboratory Study

“…Both are known to use shelters (GUAN, 1994;HUNER, 2002) and both dig burrows in the banks. Our results could be explained by a more aggressive behaviour of the red swamp crayfish, but can reflect other factors, such as differences in diel activity pattern during the study period or preferences for shelter (VORBURGER and RIBI, 1999;GHERARDI and CIONI, 2004). The frequency of initial wins by the red swamp crayfish was similar to that observed by ELVEY et al (1997) with Astacopsis franklinii vs. same-sized Cherax destructor.…”

“…Intraspecific competition has been studied both in P. leniusculus LINDSTROM, 1992, 1993;PEEKE et al, 1995) and in P. clarkii juveniles (FIGLER et al, 1999). Other works deal with interspecific competition between dyads composed of indigenous and nonindigenous species (SÖDERBACK, 1994;ELVEY et al, 1997;VORBURGER and RIBI, 1999;NAKATA and GOSHIMA, 2003;GHERARDI and DANIELS, 2004) and crayfish and freshwater crabs (GHERARDI and CIONI, 2004). As far as we know, this is the first study carried out between two nonindigenous crayfish, which behave as invasive species in southern Europe.…”

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

“…the fights ended with the retreat of the opponent to a distance of at least 10 cm; Gherardi & Cioni, 2004). Following the protocol of previous studies (e.g.…”

Structure and dynamics of an invasive population of the red swamp crayfish (Procambarus clarkii) in a Mediterranean wetland

“…Indeed, after the introduction of P. clarkii in southern Europe, populations of A. pallipes were found to decrease in both number and distribution, as the result of a combination of several interacting mechanisms, including competitive exclusion and differential susceptibility to predation in the increasing areas of syntopy (Gherardi & Cioni, 2004). These mechanisms add to the well-known dangers posed by P. clarkii as a vector of the fungus-like Aphanomyces astaci Schikora, 1922 (Dié guez-Uribeondo & Sö derhä ll, 1993), responsible for the several outbreaks of the so-called crayfish plague recorded in Europe since 1860 (Vogt, 1999).…”