Oniscus Asellus Research Articles

Terrestrial isopods (Isopoda: Oniscidea) in the Upper Mežica valley

The distribution of terrestrial isopods in many parts of Slovenia is still poorly documented. This article is a contribution to the knowledge of the terrestrial isopod fauna in the Upper Mežica Valley, which is known for its long mining tradition. Isopods were collected from April to October 2022 by hand from 49 localities in the wider area of two towns – Žerjav and Črna na Koroškem in the area of Podpeca, the area above the Bistra Valley, and in the areas Spodnje Javorje and Javorje. Twelve different taxa of terrestrial isopods were determined, eleven of them to the species level. The most frequently found isopod was Trachelipus ratzeburgii as the researched area is mainly forest covered. However, the highest diversity of species was recorded in urban and semiurban areas. Oniscus asellus was found in the town Črna na Koroškem, which is probably the second documented location of O. asellus in Slovenia.

Food Preferences in Two Detritivore Species: Laboratory Choice Tests Using Leaf Litters of Different Tree Species

Soil fauna, including terrestrial isopods, millipedes and earthworms, play an important role in the decomposition of litter through the process of shredding it during consumption. In the present study, the food preferences in two detritivores, the common woodlouse (Oniscus asellus) and the earthworm (Lumbricus rubellus) over the leaf litter of four common tree species: common black alder (Alnus glutinosa), silver birch (Betula pendula), small-leaved linden (Tilia cordata) and pedunculate oak (Quercus robur) were quantified in the laboratory. For each animal species, two sets of feeding mesocosms were prepared: one set with single litter species and another with mixed litter material (cafeteria-type test), where the animals were allowed to choose among the four litter species at once. The food preferences of the studied animals were determined on the basis of the consumption (mass loss) of litter for each litter species at the end of two-weeks lasting experiments. The results showed that the litter mass losses in both detritivores were significantly influenced by the tree species. The litter mass losses can be ranked in descending order as follows: alder, birch, linden, oak. In the case of O. asellus, litter mixing had no effect on litter mass loss when compared to single alder and birch litter, however mixing clearly accelerated litter mass loss compared to single lime or oak litter. For L. rubellus, litter mixing was found to slow litter mass loss compared to each single alder, birch and lime litter, while accelerating litter mass loss compared to single oak litter. For the interpretation of the results, the literature data on carbon to nitrogen ratio, as well as the proportion of difficult-to-degrade polyphenols and lignins in leaves of the studied tree species were used.

Background-free four-wave mixing microscopy of small gold nanoparticles inside a multi-cellular organ

The ability to detect small metallic nanoparticles by optical microscopy inside environmentally relevant species may have a wide impact for ecotoxicology studies. Here, we demonstrate four-wave mixing microscopy on individual small gold nanoparticles inside the hepatopancreas of Oniscus Asellus, a terrestrial isopod, which ingests metals found in the soil. After the exposure to food containing 10 nm radius gold nanoparticles, hepatopancreas tubules were collected, and nanoparticles were imaged by four-wave mixing microscopy with high contrast, locating them with sub-cellular resolution in the volume, despite the significant light scattering from these multi-cellular organs. Notably, the ultrafast dynamics of the four-wave-mixing non-linearity of gold nanoparticles resonantly excited and probed at their localized surface plasmon allows them to be distinguished from other metal deposits in the hepatopancreas, which manifest as a long-lived photothermal contrast. Our findings bring unexpected insight into the location of gold nanoparticles in relation to the cell types forming the hepatopancreas. Considering its simplicity, volumetric imaging capabilities, specificity, and compatibility with living cell studies, four-wave mixing microscopy holds great potential to investigate the fate of metal nanoparticles inside biological systems.

The nematode Caenorhabditis elegans and diverse potential invertebrate vectors predominantly interact opportunistically

Some small animals migrate with the help of other, more mobile animals (phoresy) to leave short-lived and resource-poor habitats. The nematode Caenorhabditis elegans lives in ephemeral habitats such as compost, but has also been found associated with various potential invertebrate vectors. Little research has been done to determine if C. elegans is directly attracted to these invertebrates. To determine whether C. elegans is attracted to compounds and volatile odorants of invertebrates, we conducted chemotaxis experiments with the isopods Porcellio scaber, Oniscus asellus, and Armadillidium sp. and with Lithobius sp. myriapods, Drosophila melanogaster fruit flies, and Arion sp. slugs as representatives of natural vectors. Because phoresy is an important escape strategy in nature, especially for dauer larvae of C. elegans, we examined the attraction of the natural C. elegans isolate MY2079 in addition to the laboratory-adapted strain N2 at the dauer and L4 stage. We found that DMSO washing solution of Lithobius sp. and the odor of live D. melanogaster attracted C. elegans N2 L4 larvae. Surprisingly, the natural isolate MY2079 was not attracted to any invertebrate during either the dauer or L4 life stages and both C. elegans strains were repelled by various compounds from O. asellus, P. scaber, Armadillidium sp., Lithobius sp., and Arion sp. feces. We hypothesize that this is due to defense chemicals released by the invertebrates. Although compounds from Lithobius sp. and D. melanogaster odorants were mildly attractive, the lack of attraction to most invertebrates suggests a predominantly opportunistic association between C. elegans and invertebrate vectors.

The Effect of Different Foods, Substrates, Moisture, and Temperatures on the Behavior in Oniscus asellus

The Effect of Different Foods, Substrates, Moisture, and Temperatures on the Behavior in Oniscus asellus

Litter chemistry of common European tree species drives the feeding preference and consumption rate of soil invertebrates, and shapes the diversity and structure of gut and faecal microbiomes

Terrestrial isopods and millipedes are key drivers of a litter decomposition in terrestrial ecosystems but the effects of litter chemistry on feeding preference and litter consumption rate as well as on the diversity and composition of gut and faecal microbiome still entails several challenges. We established a mesocosm experiment with terrestrial isopods (Oniscus asellus) and millipedes (Glomeris marginata) fed by leaf litter from six common European tree species (ash, maple, lime, beech, oak and Norway spruce) to reveal the effect of litter chemistry on consumption rate and feeding preference as well as on the compositions of gut and faecal microbiomes. The total percentage of consumed litter showed that O. asellus preferred nutrient-rich and labile-C litter of ash over more recalcitrant litter of oak, beech, and Norway spruce, while G. marginata preferred calcium-rich ash, maple and lime litter over beech and Norway spruce. Consumption of litter by O. asellus and G. marginata increased with concentrations of magnesium, sulphur and potassium but decreased with concentrations of iron, phosphorus, lignin, cellulose and TOC. The millipede G. marginata harboured higher bacterial OTU richness (73.5 ± 12.5) than the isopod O. asellus (49.1 ± 15.9), but fungal OTU richness was similar with 25.8 ± 6.7 in O. asellus and 25.7 ± 2.7 in G. marginata. In total, faeces of both animals hosted higher diversity than gut. In gut and faeces of O. asellus, the fungal OTU richness was highest for individuals fed by litter of Norway spruce, while lowest OTU richness was recorded for individuals fed by litter of more palatable ash. In contrast, the highest diversity of the fungal community in gut and faeces of G. marginata was recorded for individuals fed by palatable lime litter, while the lowest OTUs richness was recorded when millipedes were fed by maple and spruce. The structures of bacterial and fungal communities generally separated between O. asellus and G.marginata. The fungal community structure in gut and faeces differed between animals fed by different foliar litters, while the bacterial community structure mainly differed between gut and faeces regardless of the offered type of litter. The fungal community structure in gut and faeces of O. asellus and G.marginata were shaped by concentrations of magnesium, sulphur, lignin and cellulose. The bacterial communities in gut and faeces of both O. asellus and G. marginata were dominated by copiotrophic bacteria, while fungal communities were dominated by unspecified saprotrophs. Our study suggest that litter quality is a strong driver of feeding preference and consumption rates as well as composition of bacterial and fungal communities in gut and faeces of two species representing the main groups of litter feeding soil fauna in European forests.

Mycorrhizal fungi and invertebrates: Impacts on Tuber melanosporum ascospore dispersal and lifecycle by isopod mycophagy

The icon ectomycorrhizal (EcM) species, Tuber melanosporum, requires mycophagy for ascospore dispersal. Isopods are often found within fruitbodies and to explore why, Oniscus asellus were presented with T. melanosporum as a food source. Fruitbodies were consumed at a rate of 4.0 mg per isopod, over 24 h. Most of the recovered faecal pellets contained ascospores after 12 h. Gut-transit inflicted little mechanical damage to ascospores, and the majority were still contained with an ascus 30 h post feeding. Further, ascospores were observed in faecal pellets 18 days after consumption. Combined, the results suggest a previously overlooked role for isopods in EcM spore dispersal. The impacts for EcM ecology and the role of isopods in Tuber spp. lifecycles, including mating type distribution, is discussed alongside the emerging threat of climate change and how such knowledge can inform management by custodians of relevant habitat types.

Characterizing Fragmentation of Polystyrene Foam Debris by Isopods Oniscus asellus (Isopoda: Oniscidae) and Trachelipus rathkii (Isopoda: Trachelipodidae).

Microplastics present a novel and potentially unique threat to soil ecosystems, one whose effects may be mediated by soil organisms themselves. We investigated fragmentation of polystyrene (PS) foam into microplastic particles by two isopods, Oniscus asellus L. and Trachelipus rathkii Brandt, in laboratory arena experiments. First, we examined the temporal dynamics of fragmentation across a time span of 96 h. O. asellus produced more fragments than T. rathkii, and neither species significantly fragmented the PS foam until 48 h had passed. Second, we asked whether O. asellus would still fragment PS foam in the presence of an alternate, more natural substrate like wood. Wood did not significantly affect fragmentation rates, in line with the few other studies examining the effect of alternate food on soil invertebrates' propensity to consume and/or fragment plastics. Our results provide additional characterization of PS foam fragmentation by isopods and indicate that laboratory experiments involving soil invertebrates and plastic debris can take place over relatively short timespans of four or fewer days, but do not necessarily need to provide alternate food to prove that plastic consumption would still occur in its presence.

Immune priming in Armadillidiumvulgare against Salmonellaenterica: direct or indirect costs on life history traits?

Invertebrate immune priming is defined as an enhanced protection against secondary pathogenic infections when individuals have been previously exposed to the same or a different pathogen. Immune priming can be energetically costly for individuals, thus impacting trade-offs between life-history traits, like reproduction, growth, and lifetime. Here, the reproductive cost(s) and senescence patterns of immune priming against S.enterica in the common woodlouse A.vulgare (Crustacea, Isopoda) were investigated. Four different groups of females were used that either (1) have never been injected (control), (2) were injected twice with S.enterica (7 days between infections), (3) were firstly injected with LB-broth, then with S.enterica, and (4) females injected only once with S.enterica. All females were allowed to breed with one non-infected male and were observed for eight months. Then, the number of clutches produced, the time taken to produce the clutch(es), the number of offspring in each clutch, the senescence biomarkers of females, and parameters of their haemocytes were compared. The result was that immune priming did not significantly impact reproductive abilities, senescence patterns, and haemocyte parameters of female A.vulgare, but had an indirect effect through body weight. The lighter immune primed females took less time to produce the first clutch, which contained less offspring, but they were more likely to produce a second clutch. The opposite effects were observed in the heavier immune primed females. By highlighting that immune priming was not as costly as expected in A.vulgare, these results provide new insights into the adaptive nature of this immune process.

Adaptation to Urban Heat Islands Enhances Thermal Performance Following Development under Chronic Thermal Stress but Not Benign Conditions in the Terrestrial Isopod Oniscus asellus.

AbstractThe effects of chronic thermal stress during development on thermal performance traits are not well characterized under urban heat islands, despite these conditions being biologically relevant for how organisms experience the urban environment and the often strong linkages between thermal performance traits and fitness. Here we use the terrestrial isopod Oniscus asellus to examine the effects of chronic thermal stress during development on voluntary running speed of urban and rural isopods. We used a laboratory common-garden experiment design with two developmental acclimation temperature treatments (21°C, a benign treatment, and 29°C, a stressful treatment) and three test temperatures (19°C, 31°C, 40°C); we tested running speed of individuals from urban and rural populations under each of the temperature combinations. We found that for both urban and rural isopods, running speed across three test temperatures was reduced under developmental acclimation conditions of 29°C compared with 21°C. Importantly, however, urban isopods had a running speed advantage over the rural isopods under the 29°C developmental acclimation conditions at the lower two test temperatures. No population differences were detected under benign developmental acclimation conditions of 21°C. The evolution of higher heat tolerance in urban isopods further supported the interpretation of adaptation to heat stress. Convergence of urban and rural isopod running speed at the highest test temperature, however, suggests potential limits or constraints on adaptation. Our results indicate that thermal adaptation to urban heat islands can mitigate negative effects of chronic developmental thermal stress, even when overall performance is reduced compared with benign conditions.

Soil Invertebrates Generate Microplastics From Polystyrene Foam Debris

To fully understand microplastics' impact on soil ecosystems, one must recognize soil organisms as not just passively enduring their negative effects, but potentially contributing to microplastics' formation, distribution, and dynamics in soil. We investigated the ability of four soil invertebrates, the cricket Gryllodes sigillatus Walker (Orthoptera: Gryllidae), the isopod Oniscus asellus L. (Isopoda: Oniscidae), larvae of the beetle Zophobas morio Fabricius (Coleoptera: Tenebrionidae), and the snail Cornu aspersum Müller (Stylommatophora: Helicidae) to fragment macroscopic pieces of weathered or pristine polystyrene (PS) foam. We placed invertebrates into arenas with single PS foam pieces for 24 h, then collected and assessed the microplastic content of each invertebrate's fecal material, its cadaver, and the sand substrate of its arena via hydrogen peroxide digestion, filtration, and fluorescent staining. All taxa excreted PS particles, though snails only to a tiny extent. Beetle larvae produced significantly more microplastics than snails, and crickets and isopods fragmented the weathered PS foam pieces more than the pristine pieces, which they left untouched. A follow-up experiment with pristine PS foam assessed the effect of different treatments mimicking exposure to the elements on fragmentation by isopods. PS foam pieces soaked in a soil suspension were significantly more fragmented than untreated pieces or pieces exposed to UV light alone. These findings indicate that soil invertebrates may represent a source of microplastics to the environment in places polluted with PS foam trash, and that the condition of macroplastic debris likely affects its palatability to these organisms.

Effects of body size and lung type on desiccation resistance, hypoxia tolerance and thermal preference in two terrestrial isopods species

Terrestrial isopods have evolved adaptations to reduce water loss, which is necessary for life in low humidity environments. However, the evolution of a waterproofed cuticle to prevent loss of water to the environment could also impede oxygen uptake from the environment. We therefore postulate an evolutionary trade-off between water retention and gas exchange in this group of soil animals. The outcome of this trade-off is expected to be affected by both differences across species (different types of lung) and differences within species (body size and resulting surface area to volume ratios).To test these ideas, we compared two sympatric isopods: Porcellio scaber and Oniscus asellus. While P. scaber possesses covered lungs typical for drier habitats, O. asellus has simple open respiratory fields which are in direct contact with external air. For each species, we assessed how individuals across a broad range in body size differed in their hypoxia and desiccation tolerance. In addition, we assessed how hypoxia and low humidity affected their thermal preference.We found clear effects of species identity and body size on tolerance to hypoxia and low humidity. Desiccation resistance was tightly linked to water loss rates (R2 = 0.96) and strongly resembled the interspecific pattern across 20 isopod species. However, our results did not support the postulated trade-off. Tolerance to hypoxia and low humidity covaried, both increasing with body size and being higher in P. scaber. Thermal preference was affected by both hypoxia and low humidity, but not by body size. Our study increases understanding of the ecophysiology of both species, which can be useful in explaining the geographical distribution and use of microhabitats of isopod species in a climate change context.

Chitinase digestion for the analysis of microplastics in chitinaceous organisms using the terrestrial isopod Oniscus asellus L. as a model organism

Chitinaceous organisms have been found to ingest microplastic; however, a standardised, validated, and time- and cost-efficient method for dissolving these organisms without affecting microplastic particles is still required. This study tested four protocols for dissolving organisms with a chitin exoskeleton: 1) potassium hydroxide (KOH) + chitinase, 2) Creon® + chitinase, 3) hydrogen peroxide (H2O2) + chitinase, and, 4) Nitric Acid (HNO3) + hydrogen peroxide (H2O2). The effects on microplastics composed of eight different polymers were also tested. The use of H2O2 followed by chitinase was found to be a highly efficient method. The three other protocols either did not digest the chitin sufficiently or negatively affected the tested polymers. A recovery test using microplastic fibres, beads and tyre particles revealed high recovery rates of 0.85, 0.89 and 1 respectively. This further supported the applicability of the H2O2 and chitinase (protocol 3) for dissolving chitinaceous organisms. Thus, we recommend that future investigations of microplastic (0.05 μm–5000 μm) in chitinaceous organisms (0.3 cm–5 cm) utilise the here presented methodology. This represents an important component of the ongoing validation and harmonization of methodological approaches that are urgently needed for the advancement of microplastic assessments globally.

Evidence for the evolution of thermal tolerance, but not desiccation tolerance, in response to hotter, drier city conditions in a cosmopolitan, terrestrial isopod.

Cities are often hotter and drier compared with nearby undeveloped areas, but how organisms respond to these multifarious stressors associated with urban heat islands is largely unknown. Terrestrial isopods are especially susceptible to temperature and aridity stress as they have retained highly permeable gills from their aquatic ancestors. We performed a two temperature common garden experiment with urban and rural populations of the terrestrial isopod, Oniscus asellus, to uncover evidence for plastic and evolutionary responses to urban heat islands. We focused on physiological tolerance traits including tolerance of heat, cold, and desiccation. We also examined body size responses to urban heat islands, as size can modulate physiological tolerances. We found that different mechanisms underlie responses to urban heat islands. While evidence suggests urban isopods may have evolved higher heat tolerance, urban and rural isopods had statistically indistinguishable cold and desiccation tolerances. In both populations, plasticity to warmer rearing temperature diminished cold tolerance. Although field‐collected urban and rural isopods were the same size, rearing temperature positively affected body size. Finally, larger size improved desiccation tolerance, which itself was influenced by rearing temperature. Our study demonstrates how multifarious changes associated with urban heat islands will not necessarily contribute to contemporary evolution in each of the corresponding physiological traits.

Reproductive senescence and parental effects in an indeterminate grower.

Reproductive senescence is the decrease of reproductive performance with increasing age and can potentially include trans-generational effects as the offspring produced by old parents might have a lower fitness than those produced by young parents. This negative effect may be caused either by the age of the father, mother or the interaction between the ages of both parents. Using the common woodlouse Armadillidium vulgare, an indeterminate grower, as a biological model, we tested for the existence of a deleterious effect of parental age on fitness components. Contrary to previous findings reported from vertebrate studies, old parents produced both a higher number and larger offspring than young parents. However, their offspring had lower fitness components (by surviving less, producing a smaller number of clutches or not reproducing at all) than offspring born to young parents. Our findings strongly support the existence of trans-generational senescence in woodlice and contradict the belief that old individuals in indeterminate growers contribute the most to recruitment and correspond thereby to the key life stage for population dynamics. Our work also provides rare evidence that the trans-generational effect of senescence can be stronger than direct reproductive senescence in indeterminate growers.

Woodlice change the habitat use of spiders in a different food chain.

BackgroundIn old field systems, the common woodlouse may have an indirect effect on a nursery web spider. Woodlice and nursery web spiders feed in different food chains, yet previous work demonstrated that the presence of woodlice is correlated with higher predation success by nursery web spiders upon their grasshopper prey. This finding suggested a new hypothesis which links two seemingly disparate food chains: when woodlice are present, the spider predator or the grasshopper prey changes their location in the vegetative canopy in a way that increases their spatial overlap and therefore predation rate. However, warming temperatures may complicate this phenomenon. The spider cannot tolerate thermal stress, meaning warming temperatures may cause the spider to move downwards in the vegetative canopy or otherwise alter its response to woodlice. Therefore, we would expect warming and woodlice presence to have an interactive effect on predation rate.MethodsWe conducted behavioral experiments in 2015, 2017, and 2018 to track habitat domains—the use of the vegetative canopy space by grasshoppers and spiders—in experimental cages. Then, we used three models of spider movement to try to explain the response of spiders to woodlice: expected net energy gain, signal detection theory, and individual-based modelling.ResultsHabitat domain observations revealed that spiders shift upward in the canopy when woodlice are present, but the corresponding effect on grasshopper prey survival was variable over the different years of study. Under warming conditions, spiders remained lower in the canopy regardless of the presence of woodlice, suggesting that thermal stress is more important than the effect of woodlice. Our modelling results suggest that spiders do not need to move away from woodlice to maximize net energy gain (expected net energy gain and signal detection theory models). Instead spider behavior is consistent with the null hypothesis that they move away from unsuccessful encounters with woodlice (individual-based simulation). We conclude that mapping how predator behavior changes across biotic (e.g. woodlouse presence) and abiotic conditions (e.g. temperature) may be critical to anticipate changes in ecosystem dynamics.

Terrestrial Isopods Porcellio scaber and Oniscus asellus (Crustacea: Isopoda) Increase Bacterial Abundance and Modify Microbial Community Structure in Leaf Litter Microcosms: a Short-Term Decomposition Study.

Invasive terrestrial isopods are likely to have altered leaf litter decomposition processes in North American forests, but the mechanisms underlying these alterations and the degree to which they differ among isopod species are poorly characterized. Using mixed-deciduous leaf litter microcosms, we quantified the effects of two common, invasive isopods (Oniscus asellus and Porcellio scaber) on short-term leaf litter decomposition and microbial community structure and function. Microcosms containing ground litter and a microbial inoculant were exposed to one of the two isopod species or no isopods for 21 days. Mass loss was then quantified as the change in litter dry mass after leaching, and microbial respiration was quantified as the mass of CO2 absorbed by soda lime. Litter leachates were plated on agar to quantify culturable bacterial and fungal abundance, and denaturing gradient gel electrophoresis of amplified leachate microbial DNA was used to characterize shifts in microbial community structure. Isopod presence increased litter mass loss by a modest ~ 6%, but did not affect litter microbial respiration. Bacterial abundance increased significantly in the presence of isopods, while fungal abundance was either unchanged or reduced. Overall litter microbial species richness was reduced by isopods, with O. asellus specifically reducing fungal abundance and diversity. Isopods modified the microbial community structure by suppressing four bacterial and one fungal species, while promoting growth of four other bacterial species (two unique to each isopod species) and two fungal species (one which was unique to O. asellus).

Untangling the Mathematical Relation Between Natural Selection and Adaptive Radiation Using Macromolecules and Microevolutionary Forces

Simulating natural selection over subsequent generations of Oniscus asellus, the fittest selected male and female bugs in different diet was used to analyze the concentration of proteins in their body along their frequency in continuous mapped generations over hundred seed values, further DNA Fingerprinting of these selected bugs revealed a relationship with their parents originated from different geographic areas/borders. It was observed that variation in microevolutionary forces caused variation in macromolecules by setting up a gene-environment interaction which deduced natural selection in order to define adaptive radiation and speciation by micro-evolutionary forces.

The crustacean Armadillidium vulgare (Latreille, 1804) (Isopoda: Oniscoidea), a new promising model for the study of cellular senescence

AbstractSenescence, the decline of physiological parameters with increasing age, is a quasi-ubiquitous phenomenon in the living world. The observed patterns of senescence, however, can markedly differ across species and populations, between sexes, and even among individuals. To identify the drivers of this variation in senescence, experimental approaches are essential and involve the development of tools and new study models. Current knowledge of the senescence process is mostly based on studies on vertebrates and the main information about senescence in invertebrates is mostly limited to model organisms such as Caenorhabditis elegans or Drosophila melanogaster. In this context, we tested whether biomarkers of vertebrate ageing could be used to study senescence in a new invertebrate model: the common woodlouse Armadillidium vulgare (Latreille, 1804). More specifically, we looked for the effect of age in woodlouse on three well-established physiological biomarkers of ageing in vertebrates: immune cells (cell size, density, and viability), β-galactosidase activity, and the gene expression of telomerase reverse transcriptase (TERT), an essential subunit of telomerase protein. We found that the size of immune cells was higher in older individuals, whereas their density and viability decreased, and that the β-galactosidase activity increased with age, whereas the TERT gene expression decreased. These findings demonstrate that woodlouse displays age-related changes in biomarkers of vertebrate senescence, with different patterns depending on gender. The tools used in studies of vertebrate senescence can thus be successfully used in studies of senescence of invertebrates such as the woodlouse. The application of commonly used tools to new biological models offers a promising approach to assess the diversity of senescence patterns across the tree of life.

Survival capacity of the common woodlouse Armadillidium vulgare is improved with a second infection of Salmonella enterica

Immune priming has been widely observed in invertebrates. However, this phenomenon remains incompletely characterized concerning the time course of the protective effect and immune responses. Here, we investigated the existence of a protective effect in the terrestrial isopod Armadillidium vulgare against a second infection with the bacterium Salmonella enterica. We primed animals with a low dose of living bacteria or with the bacterial culture medium. One day, 7 or 15 days later, we measured haemocytes concentration and viability and we injected a LD50 of living S. enterica to monitor the survival rates of infected individuals. We show that A. vulgare is better protected (i.e. survival improvement) upon secondary infection when it has encountered S. enterica 7 days before. This protection, which tends to persist 15 days after the first infection, is however not observed when the priming is performed only 1 day before the LD50 injection. Besides providing a new invertebrate example, we highlight this protection is dynamic and may be partly due to a high haemocyte production.