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04 November 2022
02 November 2022
Gallardo and colleagues, 2022
Abstract
- The management of invasive species requires analytical tools that can synthesise the increasing and complex information generated through risk assessment protocols. To that end, fault tree analysis (FTA) provides a means to conceptually map all of the events leading to a particular undesired scenario with associated probabilities and uncertainty.
- We used a peer-reviewed dataset (the GB Non-Native Species Risk Assessments) to build and quantify a FT of all the events leading to the transport, introduction, establishment and spread of harmful aquatic invasive species in Great Britain. We also simulated management scenarios.
- Individual barriers to invasion, either natural or human, were largely unsuccessful in hindering invasion (42%–91% probability of failure in a 5-year period); yet the high interdependence of events in the tree resulted in an overall probability of harmful invasion of about 3%. This figure is much greater than that estimated by the tens rule, which posits that 10% of non-native species manage to colonise a new area, and only 10% of those become invasive, resulting in a 1% overall probability of harmful invasion.
- We used the FTA to explore different management intervention scenarios and found that pre-border management reduced the overall risk of invasion by 86%, followed in importance by early action after introduction (85%), and detection at the border (81%). In contrast, post-establishment management techniques, such as eradication and containment, had a limited impact reducing the probability of widespread invasion (18%–24%).
- Synthesis and applications. While prevention has been long recognised as the most cost-effective action against biological invasions, here we were able to quantify the reduction in invasion risk under a range of management scenarios. Optimising all management elements included in the FT reduced the overall probability of invasion by three orders of magnitude.
- We conclude that FTA provides a baseline to capitalise on a growing source of peer-reviewed risk assessments, which allows systematic assessment of the effectiveness of future actions to prevent and manage invasive species at the national and international levels. The analytical framework can be extended to other biological threats (e.g. pests, pathogens, diseases) and scenarios (e.g. climate change, war), so that breach and leverage points in biosecurity can be identified.
Keywords: None provided.
Dobrović and colleagues, 2022
Abstract
Invasive alien crayfish threaten the diversity of freshwater ecosystems and native crayfish fauna. In Europe, this is largely due to transmission of the crayfish plague to susceptible native crayfish. Many invasive species tolerate crayfish plague, but the infection still has the potential to reduce the fitness of a tolerant host due to energy trade-offs between immune response maintenance and life-history traits, such as growth and reproduction. In combination with other unfavourable conditions, such a response could alter further invasion success of an otherwise successful crayfish invader. We examined whether repeated infection with one of the most virulent haplogroups of crayfish plague agent (Aphanomyces astaci) affects growth or survival of the juvenile marbled crayfish (Procambarus virginalis). Juveniles were exposed to i) two levels of pathogen concentrations, and ii) two different feeding regimes under the higher pathogen concentration. In all performed trials, repeated infection reduced growth rates, while the combination of recurring infection and food limitation significantly increased mortality. The average energy cost of the immune response was estimated at 12.07 J/day for individuals weighing 0.3 grams. Since infections were frequent and pathogen concentrations high, results suggest that marbled crayfish is resistant to A. astaci pathogen and its survival is only affected by adding the stress of food limitation. The survival of almost half of the individuals exposed to high pathogen loads and extreme food limitation indicates that chronic infection by crayfish plague is unlikely to be an important factor impeding invasion success of the marbled crayfish, even under harsh conditions. Our results add to the growing body of evidence that marbled crayfish has potential to become one of the most successful freshwater invaders.
Keywords: food limitation • freshwater • immunity cost • infection • invasive species • trade-off
26 September 2022
Faiad, 2022
Abstract
The human burden of environmentally transmitted infectious diseases can depend strongly on ecosystem factors, including the presence or absence of natural enemies. Like natural enemies, non-native species influence the abundance and distribution of their prey and competitors, yet the impact of these invaders on the transmission of diseases remains largely unexplored. One environmentally transmitted infectious disease with potential to be influenced by natural enemies is schistosomiasis, a parasitic disease infecting over 200 million people across South America, Asia, and Africa. The marbled crayfish (Procambarus fallax f. virginalis) first appeared in Madagascar in 2005 and quickly spread across the country, overlapping with the distribution of freshwater snails that serve as the intermediate host of Schistosoma spp. worms. Marbled crayfish can tolerate a wide range of ecological conditions, colonize diverse habitats, and may serve as an enemy of schistosome-competent snails in areas where natural predators cannot–something that is urgently needed in a country where schistosomiasis prevalence in some villages can range up to 94%. Here, I experimentally assessed marbled crayfish consumption of uninfected and infected schistosome-competent snails (Biomphalaria glabrata and Bulinus truncatus) across a range of temperatures, reflective of the habitat range of the marbled crayfish in Madagascar. Crayfish consumption was significantly influenced by crayfish weight, as well as the interaction between weight and temperature. Compared to small crayfish, large crayfish experienced a greater increase in consumption at moderate temperatures (25 and 30°C) relative to extreme temperatures (15, 20, and 35 °C). The temperature at which the rate of consumption was highest (i.e., the thermal optimum) was estimated to be 31.1 °C for small crayfish (<3.90 g), 27.7 °C for medium crayfish (3.91 – 6.62 g), and 28.7 °C for large crayfish (> 6.3 g). Neither snail species nor snail infection status were significantly associated with consumption. My results suggest that ecological parameters, such as temperature and crayfish weight, influence rates of consumption and, in turn, the potential regulatory impact of the marbled crayfish on snail host populations.
20 September 2022
Brown and Therriault 2022
Brown NEM, Therriault TW. 2022. The hidden risk of keystone invaders in Canada: a case study using non-indigenous crayfish. Canadian Journal of Fisheries and Aquatic Sciences 79(9): 1479-1496. https://doi.org/10.1139/cjfas-2021-0245
Abstract
Invasive species have long been recognized as a serious threat to freshwater ecosystems. This is especially true for invasive species in keystone positions in food webs that can cause major disruption and can lead to unexpected outcomes. Crayfish occupy a central trophic position and non-indigenous crayfish have been shown to substantially disrupt ecosystems they invade. Here, we assess eight non-indigenous crayfish to 21 freshwater ecoregions in Canada using a screening-level risk assessment. We found that ecoregions in Canada that were warmer and contained high native freshwater diversity were most at risk from crayfish invasions, particularly: the Laurentian Great Lakes, St. Lawrence, English-Winnipeg Lakes and Coastal British Columbia ecoregions. Four crayfish species consistently had higher scores: rusty (Faxonius rusticus), virile (Faxonius virilis), signal (Pacifastacus leniusculus), and red swamp (Procambarus clarkii). Of these high-risk crayfish, only the red swamp crayfish is not yet established in Canada but is present in US waters of the transboundary Great Lakes ecoregion. Our study is the first to evaluate the relative risks that non-indigenous crayfish pose to freshwater ecosystems in Canada.
Keywords: None provided.
Bláha and colleagues 2022
Bláha M, Weiperth A, Patoka J, Szajbert B, Balogh ER, Staszny Á, Ferincz Á, Lente V, Maciaszek R, Kouba A. 2022. The pet trade as a source of non-native decapods: the case of crayfish and shrimps in a thermal waterbody in Hungary. Environmental Monitoring and Assessment 194(10): 795. https://doi-org.libaccess.lib.mcmaster.ca/10.1007/s10661-022-10361-9
Abstract
Ornamental aquaculture and the related pet industry are known to be important sources of non-native species worldwide. In the temperate zone, thermal waterbodies are attractive places for irresponsible owners to release unwanted freshwater pets including decapod crustaceans. Several non-native ornamental species have been reported in the thermal locality of Miskolctapolca (a suburb of Miskolc, Hungary). So we surveyed this site in March 2019–November 2021 to update local occurrence records and detect potentially newly released species. A well-established population of Neocaridina denticulata and the occurrence of Caridina cf. babaulti had previously been noted. However, for the first time at this site, we found the shrimps Atyopsis moluccensis, Caridina gracilirostris and C. multidentata, as well as the crayfish Procambarus virginalis, P. clarkii, Cherax quadricarinatus, C. boesemani and C. snowden, and several formally undescribed Cherax species originating from New Guinea. Furthermore, in most species, gravid females carrying eggs were also noticed. Three shrimps, A. moluccensis, C. gracilirostris and C. multidentata, were recorded for the first time in European wild. Further monitoring of this locality and better education of the general public regarding the risks associated with the release of non-native species are strongly recommended.
Keywords: Ornamental species • invasive species • Decapoda • Europe • thermal water
24 August 2022
Boštjančić and colleagues 2022
Abstract
Background
For over a century, scientists have studied host-pathogen interactions between the crayfish plague disease agent Aphanomyces astaci and freshwater crayfish. It has been hypothesised that North American crayfish hosts are disease-resistant due to the long-lasting coevolution with the pathogen. Similarly, the increasing number of latent infections reported in the historically sensitive European crayfish hosts seems to indicate that similar coevolutionary processes are occurring between European crayfish and A. astaci. Our current understanding of these host-pathogen interactions is largely focused on the innate immunity processes in the crayfish haemolymph and cuticle, but the molecular basis of the observed disease-resistance and susceptibility remain unclear. To understand how coevolution is shaping the host’s molecular response to the pathogen, susceptible native European noble crayfish and invasive disease-resistant marbled crayfish were challenged with two A. astaci strains of different origin: a haplogroup A strain (introduced to Europe at least 50 years ago, low virulence) and a haplogroup B strain (signal crayfish in lake Tahoe, USA, high virulence). Here, we compare the gene expression profiles of the hepatopancreas, an integrated organ of crayfish immunity and metabolism.
Results
We characterised several novel innate immune-related gene groups in both crayfish species. Across all challenge groups, we detected 412 differentially expressed genes (DEGs) in the noble crayfish, and 257 DEGs in the marbled crayfish. In the noble crayfish, a clear immune response was detected to the haplogroup B strain, but not to the haplogroup A strain. In contrast, in the marbled crayfish we detected an immune response to the haplogroup A strain, but not to the haplogroup B strain.
Conclusions
We highlight the hepatopancreas as an important hub for the synthesis of immune molecules in the response to A. astaci. A clear distinction between the innate immune response in the marbled crayfish and the noble crayfish is the capability of the marbled crayfish to mobilise a higher variety of innate immune response effectors. With this study we outline that the type and strength of the host immune response to the pathogen is strongly influenced by the coevolutionary history of the crayfish with specific A. astaci strains.
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