Search

The indigenous crayfish Austropotamobius pallipes complex has been recently defined by IUCN as an endangered species but our knowledge about its status in Italy is still provisional. An assessment of the most suitable environments for its survival is crucial to preserve the species and to develop appropriate conservation protocols for its management. To this end, during 2008 and 2009, we analyzed eight watercourses in a protected area of Central Italy for A. pallipes’ presence and for a number of environmental characteristics. Crayfish were found in four out of the eight analyzed watercourses: only one of three old reports was confirmed, while the species has disappeared from the other two. All the streams are characterized by good quality of both water and soil. The differences found for basin and riparian descriptors, canopy cover, shelters and substrate composition were independent of the crayfish presence. Non-indigenous crayfish populations were not recorded in the study area. Among the several causes of crayfish disappearance, overexploitation through illegal fishing, introduction of fish predators and drought seem to be the more likely. These threats should be urgently faced to guarantee the survival of the indigenous crayfish.

The red swamp crayfish Procambarus clarkii is an invasive alien species spreading worldwide. The sterile male release technique (SMRT) is among the methods used to contrast the growth of P. clarkii populations within invaded areas. In this study males underwent X-ray sterilisation with a dose of 40 Gy and their immunocompetence was analysed in comparison to untreated animals to ascertain whether radiation can affect welfare parameters other than reproductive organs. The present research investigated the immune function in P. clarkii males in term of (1) morphological haemocyte characterisation by transmission electron microscopy to identify the main phagocyting haemocyte after in vivo artificial non-self challenge with latex beads; (2) total and differential haemocyte counts; and (3) basal and total phenoloxidase activities as components of the humoral defence. Three types of circulating haemocytes were characterised via transmission electron microscopy: hyaline, semigranular and granular haemocytes. The ultrastructural features of haemocyte granules allowed the characterisation of a fourth type of haemocyte, the medium granule haemocyte. In vivo artificial non-self-challenge with latex beads identified the semigranular haemocytes as primarily involved in phagocyting activity. Circulating haemocytes of males irradiated with a dose of 40 Gy, after 20 days, showed a significantly lower diameter in the granules of hyaline and semigranular haemocytes, but no other evident ultrastructural alterations in comparison with un-irradiated animals were found. Irradiated males showed a significant decrease of about 80% of circulating haemocytes and an increase in frequency of semigranular and granular haemocytes. No significant differences in basal and total phenoloxidase activity were recorded and this could, in part, explain the good survival level of irradiated males despite the drastic decline of the haemocyte number. This study represents the basis to appraise whether SMRT affects important functions, such as those of the immune system, in addition to altering the gonad tissue. [ABSTRACT FROM AUTHOR]

Since 1973, the red swamp crayfish, Procambarus clarkii, from Louisiana has been successfully introduced into many European aquatic systems, where its ecological plasticity has favored the presence of many reproductive populations (Gherardi and Holdich 1999). Here we present results from studies conducted by our lab through six years of research. Main points of discussion will be: (a) Dynamics of this species invasion throughout Europe (using molecular techniques and radio-telemetry). (b) Biological traits as prerequisites of its invasive potential (e.g. life history patterns, resistance to extreme environments, feeding ecology). (c) Its impact on the invaded habitats. (d) Hypotheses on its control and management. Acknowledgments: Funds were provided by the Italian Ministry of Education, University and Research and by the Tuscan Region.

In 2007, the invasive crayfishProcambarus clarkii(Girard 1852) was identified for the first time in the “Parc Naturel Régional de la Brenne” (Indre department, Centre region, France). Ten infestation sites were found in the park, with 62 fishponds colonised. To better understand how the fishponds could be affected, and changes in invaded ponds, we followed crayfish burrowing activity in recently drained fishponds in two areas. Weekly investigations of burrowing activity by analysing their density, occupation and location with respect to the banks, and micro-habitat features were carried out for 2 months in spring. Burrow densities of 1.16 and 1.05 burrows m–2were found at Le Terrier Blanc and Coudreau 3 respectively.Procambarus clarkiisought humid soil in a dry pond and preferred burrowing on silt substrates. While no statistical differences were found between sites, some differences were observed among weeks independently of the sites. The mean mouth diameter of burrows in the two sites was 5.7 cm (SD = 2.17,n = 214; min. value: 1.2 cm; max. value: 14 cm). Notwithstanding the situation in the last weeks of the study (when most chimneys were built), there was a certain turnover between open and plugged burrows, and in occupancy. Given the scale and duration of the study and the number of fishponds surveyed, this study successfully quantified the dynamics of burrowing in these ponds and conclusions provide a useful basis for future studies and give suggestions of how other colonised fishponds may be affected. [ABSTRACT FROM PUBLISHER]

Since the nineteenth century, the mud snail Potamopyrgus antipodarum (Gray 1843), native to New Zealand, has been introduced into several European countries, Italy included. As a first step to contain its spread and establishment, it seems necessary to understand the characteristics of the environment that are more favourable for this species' invasion. To this aim, we analysed a number of physico-chemical and biotic parameters of four streams, two invaded and two not yet invaded, in the National Park of the Foreste Casentinesi, Monte Falterona, Campigna (Central Italy), where the species was first recorded in 2008. The two categories of streams, invaded and non-invaded, differ in only three of the 20 analysed characteristics of the habitat; that is, availability of crevices, width stream, and maximum water depth. This suggests that, despite P. antipodarum's documented tolerance to pollution, the high-quality waters of the park are highly susceptible to its invasion, if its vectors and pathways are not identified and adequately monitored. Most of the environmental parameters analysed in the studied streams were shown to be similar to those reported in the literature as preferred/tolerated by the species. Our findings pinpoint the vulnerability of nature reserves to species invasions, and call for more effective preventative measures. [ABSTRACT FROM AUTHOR]

Mate choice is often assumed to be a prerogative of females because of their putatively larger reproductive investment than males. However, recent evidence suggests that spermatogenesis is far from being limitless and that males show a high selectivity towards their mates, thus maximizing their reproductive success. We investigated mutual mate choice in the crayfish Procambarus clarkii through two experiments. The first experiment explored the effects of body size, chelar size and chelar symmetry and social status of a potential partner. In the second experiment, we asked whether this species can discriminate between partners of the same body size but with different mating status. We used a binary choice test paradigm, in which two ‘targets’ with opposing characteristics were simultaneously presented to a test animal, the ‘chooser’. The results showed that P. clarkii males are more selective than expected. Similar to the other sex, they were significantly attracted by targets with large body sizes, but not by individuals with larger and symmetric chelae or with a dominant status. An inter-sexual difference was found in the second experiment, in which only males seemed to select virgin potential mates. The several adaptive explanations for these preferences, still under debate, are finally discussed. [ABSTRACT FROM AUTHOR]

Procambarus clarkii is an invasive alien species spreading worldwide. It is therefore mandatory to find new methods to manage this species since traditional techniques are not sufficient for this purpose. The present study investigates gonad damage induced by different doses of ionising irradiation: 20, 40 and 60 Gy. Testis were analysed after 10 and 30 days by means of light, scanning and transmission electron microscopy. Control unirradiated testes present an acinar structure with a well-defined germinative cells maturation from the distal proliferative zone to the proximal stalk of the lobes whilst, in irradiated testes, induced apoptosis of germinative and accessory cells and a high level of vacuolisation inside the acini were identified, progressively increasing in accordance to Gy dosage and time after exposure. We determined the dose of 40 Gy as the best compromise: it causes an extensive damage to germinative tissues without affecting crayfish vitality, differing from 60 Gy. From an applicative point of view, this dose reduces the efforts, in terms of cost and time, for the application of SMRT., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Since the 1970s, the ability of some invertebrate species to recognize individual conspecifics has attracted increased scientific interest. However, there is still confusion in the literature, possibly due to the lack of unambiguous criteria for classifying social recognition in its different forms. Here, we synthesize the results of studies on invertebrates and provide a framework with the purpose of identifying research needs and directions for future investigations. Following in part Sherman et al.'s (Behavioural ecology: an evolutionary approach. Blackwell Science, Oxford, pp 69-96, 1997) definition of 'recognition systems' and Tibbetts and Dale's (Trends Ecol Evol 22:529-537, 2007) classification of 'individual recognition,' we first discuss different case studies that exemplify the categories of 'familiar recognition' and 'class-level recognition.' Then, through the analysis of the invertebrate literature, we illustrate eight key properties that characterize 'true individual recognition' systems. We are confident that the proposed framework will provide opportunities for exciting discoveries of the cognitive abilities in invertebrates.

Background: The crayfish Procambarus clarkii inflicts severe ecological and economic damages in Europe. To develop an efficient method for its control, four experiments were carried out to assess the impact of natural pyrethrum (i.e. Pyblast) on crayfish: (1) the 24 h LC(100) and LC(50) were quantified on crayfish; (2) the breakdown time of the 24 h LC(100) was assessed using Daphnia magna as a bioindicator; the effects of 24 h LC(100) on crayfish were investigated by applying the biocide into burrows (3) and in a drainage channel (4)., Results: Pyblast concentrations of 0.05 and 0.02 mg L(-1) corresponded to 24 h LC(100) and LC(50) respectively. The concentration of 0.05 mg L(-1) broke down after 72 h, whereas 0.02 mg L(-1) did not cause any significant mortality in D. magna after 24 h. However, 0.05 mg L(-1) had no effect on crayfish when introduced into the burrows, but led to a mortality of 95% when applied in the water., Conclusion: Experimental evidence is provided for the efficacy of Pyblast to control invasive crayfish. Obviously, before its use on a large scale, further studies are needed to find a concentration that will achieve the target 100% mortality with the shortest recovery time of the environment., (Copyright © 2012 Society of Chemical Industry.)

Biogenic amines, particularly serotonin, are recognised to play an important role in controlling the aggression of invertebrates, whereas the effect of neurohormones is still underexplored. The crustacean Hyperglycemic Hormone (cHH) is a multifunctional member of the eyestalk neuropeptide family. We expect that this neuropeptide influences aggression either directly, by controlling its expression, or indirectly, by mobilizing the energetic stores needed for the increased activity of an animal. Our study aims at testing such an influence and the possible reversion of hierarchies in the red swamp crayfish, Procambarus clarkii, as a model organism. Three types of pairs of similarly sized males were formed: (1) 'control pairs' (CP, n = 8): both individuals were injected with a phosphate saline solution (PBS); (2) 'reinforced pairs' (RP, n = 9): the alpha alone was injected with native cHH, and the beta with PBS; (3) 'inverted pairs' (IP, n = 9): the opposite of (2). We found that, independently of the crayfish's prior social experience, cHH injections induced (i) the expression of dominance behaviour, (ii) higher glycemic levels, and (iii) lower time spent motionless. In CP and RP, fight intensity decreased with the establishment of dominance. On the contrary, in IP, betas became increasingly likely to initiate and escalate fights and, consequently, increased their dominance till a temporary reversal of the hierarchy. Our results demonstrate, for the first time, that, similarly to serotonin, cHH enhances individual aggression, up to reverse, although transitorily, the hierarchical rank. New research perspectives are thus opened in our intriguing effort of understanding the role of cHH in the modulation of agonistic behaviour in crustaceans.

Sex identification has been studied in several species of crustacean decapods but only seldom was the role of multimodality investigated in a systematic fashion. Here, we analyse the effect of single/combined chemical and visual stimuli on the ability of the crayfish Procambarus clarkii to identify the sex of a conspecific during mating interactions. Our results show that crayfish respond to the offered stimuli depending on their sex. While males rely on olfaction alone for sex identification, females require the combination of olfaction and vision to do so. In the latter, chemical and visual stimuli act as non-redundant signal components that possibly enhance the female ability to discriminate potential mates in the crowded social context experienced during mating period. This is one of the few clear examples in invertebrates of non-redundancy in a bimodal communication system.

To test whether male body size affects female reproductive investment in the polygamous crayfish Procambarus clarkii, we described mating behaviour of virgin females paired with either small or large males, and analysed the number, size and weight of both eggs and juveniles sired by either types of male. Along with confirming the overt selection by females of larger mates, we found that the size and weight of both the eggs and the juveniles were higher when sired by larger fathers. This suggests that P. clarkii females exert a form of cryptic choice for large males, seemingly adjusting the quantity of egg deutoplasm in function of the mate body size. The question of why females spend time and energy to brood low-fitness offspring is finally raised.