The meeting will be held at the University of Pavia.
Besides the usual talks and posters, there will be a field trip to the North-Western Apennines to see visit lowland sites for Procambarus clarkii and hilly sites for Austropotamobius pallipes.
Early bird registration deadline is 2 May.
Exotic crayfish species are threatening native freshwater ecosystems as well as native crayfish species by affecting all trophic levels of a system, competition and being a vector of the crayfish plague pathogen. The highly invasive marbled crayfish (Procambarus virginalis) is very successful in establishing populations in the wild, due to its parthenogenetic form of reproduction. Three established populations were found at fishing ponds in Salzburg and investigated over a period of ten weeks to shed light on habitat requirements or preferences of this species as well as evaluating and comparing methods for detection and catch. Water temperature and dissolved oxygen concentration, as well as time of the year and macrophyte cover were the main factors affecting the density of active marbled crayfish in this study. Additionally, the obtained data from observations suggests a preference of marbled crayfish for structure-rich habitats providing shelters as well as food sources. Traditional crayfish traps were the most size-selective catching method, followed by fine-meshed fish traps. Hand-catch with landing nets showed no size-selectivity. In almost all samples the eDNA analyses indicated no presence of marbled crayfish, despite numerous observations at night. The false negative results of this method were likely due to insufficient filtering volumes and a low number of sub-samples. qPCR analyses of twenty individuals showed no sign of infection with the crayfish plague pathogen (Aphanomyces astaci), hinting that the population might not have encountered this pathogen yet. The results of this study provide a first insight into the ideal habitats for marbled crayfish. However, this species is known for its high ecological plasticity, which is why further investigations are strongly recommended. Additionally, management measures to supress (sic) population growth in order to avoid a spread to other freshwater systems in close proximity should be continuously undertaken as well as monitoring regarding the infection status with the crayfish plague pathogen.
Keywords: Marbled crayfish • Procambarus virginalis • Austria • habitat preferences • population characteristics • management measures • eDNA • crayfish plague • invasive species
Background
Antennae in crayfish are essential for gaining information about the local topography and localising food, chemicals, conspecifics or predator. There are still gaps in the research on the morphology of antennae in decapods compared to other arthropods.
Methodology
Biometrical and ultrastructural methods were applied using light and cryo-scanning electron microscopies to study the morphology of antennae in six different crayfish species, including marbled crayfish Procambarus virginalis, Mexican dwarf crayfish Cambarellus patzcuarensis, red swamp crayfish Procambarus clarkii, signal crayfish Pacifastacus leniusculus, common yabby Cherax destructor, and spiny-cheek crayfish Faxonius limosus to find their potential morphological differences.
Results
Significant differences in the antenna length, length and width of each segment to carapace length ratios, and the number of segments were found in the six crayfish species. The ultrastructure revealed differences in the distribution of sensory hairs on the antenna and the morphology of the antennal surface.
Conclusions
The different morphology of antennae might reflect adaptation to the conditions of their specific habitats. In addition, results showed that a combination of differences in the morphological features and biometrical measurements of antennae could be used for the distinguishment of different studied crayfish species.
Keywords: antenna • arthropods • biometry • electron microscopy • morphology • crustaceans
Mengal K, Kor G, Kouba A, Kozák P, Niksirat H. 2023. Hemocyte coagulation and phagocytic behavior in early stages of injury in crayfish (Arthropoda: Decapoda) affect their morphology. Developmental & Comparative Immunology 141: 104618. https://doi.org/10.1016/j.dci.2022.104618
Crustacean hemocytes are important mediators of immune functions such as coagulation and phagocytosis. We employed an in situ approach to investigate the ultrastructural behavior of hemocytes during coagulation and phagocytosis in the early stages after injury caused by leg amputation, using transmission electron microscopy technique in marbled crayfish Procambarus virginalis. Hemocytes underwent drastic morphological changes during coagulation. The morphology of the cytoplasmic granules changed from electron-dense to electron-lucent forms in an expanding manner. The transformed granules containing amorphous electron-lucent material were observed to merge and discharge their contents into extracellular space for coagulation. We also observed that the contents of the nucleus participate in the process of coagulation. In addition, leg amputation induced extensive muscle degeneration and necrotic tissues were avidly taken up by the phagocytic hemocytes containing distinct phagosomes. Interestingly, we observed for the first time how the digested contents of phagocytized necrotic tissues are incorporated into granules and other cellular components that change the cell morphology by increasing the granularity of the hemocytes. Nevertheless, the degranulation of hemocytes during coagulation can also reduce their granularity. Given that morphological traits are important criteria for hemocyte classification, these morphological changes that occur during coagulation and phagocytosis must be taken into account.
Keywords: degranulation • hemolymph coagulation • muscle degeneration • phagocytosis
Vogt G. 2023. Environmental adaptation of genetically uniform organisms with the help of epigenetic mechanisms—An insightful perspective on ecoepigenetics. Epigenomes 7(1): 1. https://doi.org/10.3390/epigenomes7010001
Organisms adapt to different environments by selection of the most
suitable phenotypes from the standing genetic variation or by phenotypic
plasticity, the ability of single genotypes to produce different
phenotypes in different environments. Because of near genetic identity,
asexually reproducing populations are particularly suitable for the
investigation of the potential and molecular underpinning of the latter
alternative in depth. Recent analyses on the whole-genome scale of
differently adapted clonal animals and plants demonstrated that
epigenetic mechanisms such as DNA methylation, histone modifications and
non-coding RNAs are among the molecular pathways supporting phenotypic
plasticity and that epigenetic variation is used to stably adapt to
different environments. Case studies revealed habitat-specific
epigenetic fingerprints that were maintained over subsequent years
pointing at the existence of epigenetic ecotypes. Environmentally
induced epimutations and corresponding gene expression changes provide
an ideal means for fast and directional adaptation to changing or new
conditions, because they can synchronously alter phenotypes in many
population members. Because microorganisms inclusive of human pathogens
also exploit epigenetically mediated phenotypic variation for
environmental adaptation, this phenomenon is considered a universal
biological principle. The production of different phenotypes from the
same DNA sequence in response to environmental cues by epigenetic
mechanisms also provides a mechanistic explanation for the
“general-purpose genotype hypothesis” and the “genetic paradox of
invasions”.
Keywords: asexual populations • epigenetic ecotypes • ecoepigenetics •
DNA methylation • environmental adaptation • general-purpose genotype • invasion
paradox • phenotypic plasticity
This is usually a more optimistic exercise for me.
This may be because some of the original research questions about Marmorkrebs – their origin and basic biology – are now resolved. It may also be that because this species is more widespread, new records of introductions are less likely to be reported or published.
The biggest story this year was the expanding use of local legislation to ban or regulate the sale of Marmorkrebs in the pet trade. Someone was actually charged under a law for selling Marmorkrebs for the first time. Ontario and Georgia banned Marmorkrebs, and Minnesota is thinking about it.The Ontario ban is quite significant, given the size and population of the province.
2008 was the best year ever for Marmorkrebs research
2009 was tied for the best year ever in Marmorkrebs research
2010 was the best year ever for Marmorkrebs research
2011 was not the best year ever for Marmorkrebs research
2012 was an average year for Marmorkrebs research
2013 was the second best year ever for Marmorkrebs research
2014 was a good year for Marmorkrebs research
2015 was the best year ever for Marmorkrebs research
2016 was the best year ever for Marmorkrebs research
2017 was the second best year ever for Marmorkrebs research
2018 was the second best year ever for Marmorkrebs research
2019 was the second best year ever for Marmorkrebs research
2020 was not the best year for Marmorkrebs research2021 was the third best year ever for Marmorkrebs research
