Revisiting reproduction and population structure and dynamics of Procambarus clarkii eight years after its introduction into Lake Trasimeno (Central Italy)

Understanding population dynamics and regulation is fundamental for predicting establishment and spread of invasive alien species. In addition, the population biology of invasive alien species offers an opportunity to study basic ecological processes. In this context, we investigated reproductive and growth plasticity in the invasive crayfish Procambarus clarkii in Lake Trasimeno (central Italy). In total, 3153 crayfish were collected monthly from June 2007 to July 2009. The molt status was assessed by evaluating the exoskeleton hardness. To assess the reproductive cycle, the gonado-somatic and wet hepato-somatic indices were calculated for females. The reproductive status of males was appraised as well. We estimated growth and longevity using the von Bertalanffy growth function, and calculated the total, natural and fishing mortality indices. We then compared our present data with those obtained from the same population eight years before. Our results indicate some changes in population dynamics and in both molting and reproductive periods since the initial invasion of the shallow lake investigated. Long-term differences in the life history of the Trasimeno population may be the result of selective pressures different from those of the native range, but may also result from colonization events and human interference caused by professional fishing activities

The freshwater grass shrimp Palaemonetes antennarius in the diet of fish in Lake Bracciano (Central Italy)

We evaluated the importance of the freshwater grass shrimp Palaemonetes antennarius as trophic source for the lacustrine fish of the Lake Bracciano (Central Italy) analyzing 6120 stomach contents of 10 species. Shrimp was recorded for all size classes of the investigated species with a variation in frequency and abundance depending on seasons. P. antennarius was occasionally preyed by cyprinids, and systematically by small individuals of carnivorous fish. Our findings acquire more importance if we take the shrimps ecological niche into account, as it is potentially acting as detritivorous/generalist and predator of benthic invertebrates as well. This feeding behavior makes P. antennarius an important network ring, being a taxon that ought to receive the same attention recommended for other freshwater decapods as proposed for Austropotamobius pallipes and Potamon fluviatile

Mycoflora on the cuticle of the invasive crayfish Procambarus clarkii

A total of 18 genera and 22 fungal species was detected on adults of the red swamp crayfish Procambarus clarkii of both sexes collected in Lake Trasimeno from June 2007 to June 2008. The most frequent fungal species was Phoma glomerata, isolated from 67.82 % (N = 59) of the analyzed individuals. Cladosporium cladosporioides and Penicillium spp. occurred at prevalence greater than 20 % on P. clarkii. Other taxa frequently recorded were Fusarium spp. (17.24 %, N = 15), Aspergillus spp. (14.94 %, N = 13), F. oxysporum (13.79 %, N = 12), Alternaria alternata (12.64 %, N = 11), A. chlamydospora (11.49 %, N = 10), F. proliferatum (10.34 %, N = 9), Rhizopus stolonifer (9.20 %, N = 8), F. verticillioides (6.9 %, N = 6) and Paecilomyces lilacinus (3.45 %, N = 3). The presence of Chaetomella raphigera (9.20 %, N = 8) and of Graphium sp. (only found once) deserve to be mentioned as they are rarely isolated. The highest fungal diversity occurred in September 2007 and April 2008 with 15 species isolated, the lowest in July and August 2007 (4 species). During the mycological investigation, unidentified yeast and bacteria were also recorded. Fungal species did not differ between female and male crayfish. The ecological significance of the recorded fungi and their potential sanitary implications are discussed. The red-swamp crayfish may act as a vector for potentially dangerous fungi; a cause for concern as this is an invasive species

Phoma glomerata, a potential new threat to Italian inland waters

Non-indigenous crayfish species, carrier of the oomycete Aphanomyces astaci, are the most important threats to European crayfish species. However, other ectoparasite species have been reported to be the pathogen of aquatic organisms. As little is known about other potential pathogens carried by the red swamp crayfish Procambarus clarkii, a total of 86 individuals of this species was collected in Lake Trasimeno from June 2007 to 2008. Phoma glomerata, never recorded in Italy, colonised more than 65% of the captured crayfish. No significant differences in prevalence were recorded between sexes, among life stages and between soft- and hard-shelled crayfish. This Coelomycetes is the causal agent of many diseases in plants, animals and humans. These results may contribute to a better understanding of the implications of epibiontic microfungi on the invasive crayfish P. clarkii, for both ecological and sanitary purposes