-Alien species have been transported and traded by humans for many centuries. However, with the era of globalization, biological invasions have reached notable magnitudes. Currently, introduction of alien species is one of the major threats to biodiversity and ecosystem functioning. The North American crayfish Procambarus clarkii is one of the most widely introduced freshwater species in the world, especially due to its high economic importance. It is responsible for great modifications in invaded environments causing irreparable ecological and economic damages. Its impressive ability to successfully colonize a wide range of environments is a consequence of its behavioural and biological characteristics that can adapt to features of the invaded location, conferring to this species a notable ecological plasticity. This review summarizes the available information regarding P. clarkii's biology and invasive dynamics around the world in order to contribute to the understanding of the threats posed by its establishment, as well as to support management and impact mitigation efforts.

The implications of climate change for biological invasions are multifaceted and vary along the invasion process. Changes in vectors and pathways are likely to manifest in changes in transport routes and destinations, together with altered transit times and traffic volume. Ultimately, changes in the nature of why, how, and where biota are transported and introduced will pose biosecurity challenges. These challenges will require increased human and institutional capacity, as well as proactive responses such as improved early detection, adaptation of present protocols and innovative legal instruments. Invasion success and spread are expected to be moderated by the physiological response of alien and native biota to environmental changes and the ensuing changes in biotic interactions. These in turn will likely affect management actions aimed at eradicating, containing, and mitigating invasions, necessitating an adaptive approach to management that is sensitive to potentially unanticipated outcomes.

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Procambarus clarkii is an important invasive freshwater species whose ecological plasticity allows for its establishment in different kinds of environments; such plasticity is also reflected in its diet with two main consequences: invasion success and impact on native biota. In order to investigate P. clarkii's feeding habits, examine how its diet varies both seasonally and among different demographic groups (reproductive males, non-reproductive males and females) and explore the two consequences mentioned above, we investigated the trophic role of this species in an Atlantic Forest conservation area in the city of São Paulo (Brazil). A total of 540 specimens collected monthly over a year were measured and weighed. Their stomachs were weighed and classified according to the degree of stomach fullness. Stomach contents were examined, and animal and plant matter weighed. Food items were identified to the lowest possible taxonomic level and the percentage of occurrence of each item was calculated, as well as the diet diversity. Collected data were compared according to seasons and demographic groups through the Analysis of Similarity and Similarity Percentage Analysis. The percentage of animal weight attributed to stomach weight and the degree of fullness of stomachs did not vary significantly among seasons; however, non-reproductive males had significantly less full stomachs. Diet composition was evenly balanced between plant and animal material for both reproductive males and females, while non-reproductive males consumed a lower proportion of animal matter. The diversity in diet composition was high in all seasons and for all demographic groups, although always slightly lower for non-reproductive males. The percentage of occurrence of food items evidenced high consumption of algae and macrophytes throughout the year. It also reflected the seasonal variation of consumed prey, with a shift in consumption of insects and microcrustaceans in spring and summer to decapods and amphibians in fall and winter. The dissimilarity in diet composition was more pronounced among demographic groups than among seasons, being non-reproductive males the most different, with higher ingesting of less evasive prey. Nonetheless, winter differed from other seasons and was the season with least different food composition among demographic groups, indicating a homogenization in diet composition, which might be due to restricted availability of resources. Procambarus clarkii at Jaraguá State Park demonstrated conspicuous dietary variability and flexibility. The occurrence of filled stomachs indicates that food resources are not a constriction for this population. The species presented a diversified and adaptable diet, foraging on algae and macrophytes, and preying on different vertebrate and invertebrate taxa. Its trophic plasticity favors successful establishment in invaded areas and summed to its notable voracity, P. clarkii offers a wide, variable and significant interaction in food webs, being able to generate major impacts on native sp...

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Invasive species are one of the main threats to biodiversity. When an alien species is introduced into a new environment, fast identification and definition of management strategies may avoid or minimize impacts. When an invasive species is already established, the most adopted approaches are population control and monitoring. In order to perform such strategies, assessment of characteristics of the invasive population is imperative. This study tested a new method of population size estimation and monitoring in an invasive population of crayfish Procambarus clarkii in a conservation area in the Atlantic Rain Forest (Southeastern Brazil). The population dynamics was studied for 1 year to examine the efficacy of the selected method and to evaluate if the population is stable. Later, the effect of periodical removal of animals on the population size was tested. The method of population estimation used in this study proved to be very effective. We recommend using it to monitor invasive populations of P. clarkii. The population size varied discretely over the year with variable but low growth rate, indicating that the population is already established which introduce a notable threat to native species. The continuous removal of specimens proved to be inefficient since the growth rate was higher after the removal. One intensive removal event might be more effective than a continuous moderate removal as the one applied in this study.

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Egg incubation on the female abdomen is the parental care behavior observed in aeglids, in which eggs are kept adhered to maternal pleopods and maintained, cleaned and aerated. In A. platensis, egg attachment occurs with the aid of pleopodal setae, which are twisted around their axis in the distal region, forming the funiculus, and pleopodal glands, which are responsible for the production of the adhesive substance that seems to be involved in egg fixation to pleopodal setae. Those glands are acini formed by secretory cells arranged concentrically around a central duct, giving them a rosette appearance. Two types of secretory cells were observed, those that produce electron-lucid vesicles and those having electron-dense ones. Both kinds of vesicles are released in a duct whose opening pore is located on the pleopodal surface and constitute the adhesive substance that coats eggs and pleopodal setae, ensuring egg fixation to the female body and maternal care maintenance. This study investigates the internal and external morphology of Aegla platensis pleopods, to understand the egg attachment process and identify the structures involved in this phenomenon. Three microscopy techniques are used: scanning electron microscopy (SEM), transmission electron microscopy (TEM), and optical microscopy (OM).