To date, the 'marbled crayfish', Procambarus fallax (Hagen, 1870) f. virginalis, in Italy has been reported only from Tuscany (central Italy). Recently, specimens of this alien American crayfish were found in the Po di Maistra Channel, Porto Tolle, south of Venice (northern Italy). The identification of this species was confirmed by its external morphology and colour pattern, as well as by molecular analysis. The present report provides the second record for the marbled crayfish in Italy. RÉSUMÉL' « écrevisse marbrée » Procambarus fallax (Hagen, 1870) f. virginalis a été précédemment signalée en Italie seulement en Toscane (Italie centrale). Récemment, des spécimens de cette écrevisse exotique ont été trouvés dans le canal du Po di Maistra, Porte Toile, sud de Venise (Italie du nord). L'identification de cette espèce a été confirmée par sa morphologie externe et sa couleur, ainsi que par des analyses moléculaires. Le présent rapport fournit la deuxième observation pour l'écrevisse marbrée en Italie.

The composition of the diet of the invasive spiny-cheek crayfish Orconectes limosus was studied using qualitative and quantitative analyses of stomach contents. A total of 368 specimens collected in 2003–2005 and 2008 in Czech localities were examined, predominantly from the Labe (Elbe) and Vltava River basins. Food components were compared for three size classes of crayfish and both sexes. The following conclusions were reached: (1) the spiny-cheek crayfish is an omnivorous species consuming plants, animals and detritus; (2) quantitatively, the main food component of O. limosus is detritus, while the plant component was second; (3) O. limosus may swallow whole food particles up to 4 mm in size, and the bodies of small animals may sometimes be found undamaged in their stomachs.

Mandibles of representatives of the Holarctic crayfish families Astacidae, Cambaridae, and Cambaroididae were examined using SEM, and the results were analyzed in a phylogenetic framework. The intraspecific variability of the incisor process was found to be higher than its interspecific variability, mainly due to extensive abrasion of its ridge during intermolt periods. The plesiomorphic state of the crayfish mandibles highlights the dentate–crenate type of the incisor process and the extensive ribbed molar field with a multicuspidate caudal part, typical of the two parastacid crayfish examined for comparison. For Holarctic crayfish, the initial evolutionary type of the incisor is also the dentate–crenate one, but the molar field has a bowl‐shaped caudal part and reduced cephalic part, both of which have been shown, for example, for Cambaroides. Similar mandibles are also widely present in American cambarids, which further evolved a blade‐like incisor process (some Faxonius spp.) or a tricuspidate or double‐bladed caudal molar field (some Procambarus spp.). The molar field in Astacidae crayfish is subdivided and rugose. The results of the present study indicate that little phylogenetic information is conveyed by the mandible shape at the species or genus level. Evolutionary changes are indicated mainly on the level of the main crayfish families. Research highlights Mandible shape can be an additional characteristic to distinguish crayfish families and selected genera. Obvious differences exist in the molar process rather than in the incisor ridge.