Avoidance of conspecific injury-released chemical cues by free-ranging Gammarus lacustris (Crustacea:Amphipoda)

Integrative biology of injury in animals

Mechanical injury is a prevalent challenge in the lives of animals with myriad potential consequences for organisms, including reduced fitness and death. Research on animal injury has focused on many aspects, including the frequency and severity of wounding in wild populations, the short- and long-term consequences of injury at different biological scales, and the variation in the response to injury within or among individuals, species, ontogenies, and environmental contexts. However, relevant research is scattered across diverse biological subdisciplines, and the study of the effects of injury has lacked synthesis and coherence. Furthermore, the depth of knowledge across injury biology is highly uneven in terms of scope and taxonomic coverage: much injury research is biomedical in focus, using mammalian model systems and investigating cellular and molecular processes, while research at organismal and higher scales, research that is explicitly comparative, and research on invertebrate and non-mammalian vertebrate species is less common and often less well integrated into the core body of knowledge about injury. The current state of injury research presents an opportunity to unify conceptually work focusing on a range of relevant questions, to synthesize progress to date, and to identify fruitful avenues for future research. The central aim of this review is to synthesize research concerning the broad range of effects of mechanical injury in animals. We organize reviewed work by four broad and loosely defined levels of biological organization: molecular and cellular effects, physiological and organismal effects, behavioural effects, and ecological and evolutionary effects of injury. Throughout, we highlight the diversity of injury consequences within and among taxonomic groups while emphasizing the gaps in taxonomic coverage, causal understanding, and biological endpoints considered. We additionally discuss the importance of integrating knowledge within and across biological levels, including how initial, localized responses to injury can lead to long-term consequences at the scale of the individual animal and beyond. We also suggest important avenues for future injury biology research, including distinguishing better between related yet distinct injury phenomena, expanding the subjects of injury research to include a greater variety of species, and testing how intrinsic and extrinsic conditions affect the scope and sensitivity of injury responses. It is our hope that this review will not only strengthen understanding of animal injury but will contribute to building a foundation for a more cohesive field of 'injury biology'.

Acetic acid-induced nociception modulates sociability in adult zebrafish: influence on shoaling behavior in heterogeneous groups and social preference

Due to the recognition of fishes as sentient beings, the zebrafish (Danio rerio) has become an emergent animal model system to investigate the biological processes of nocifensive responses. Here, we aimed to characterize the zebrafish social behavior in a nociception-based context. For this purpose, using a three-dimensional analysis of heterogeneous shoals, we investigated the main behavioral responses in two 6-min trials: before (baseline) and after a single intraperitoneal (i.p) injection of 10μL phosphate-buffered saline (PBS) (control), acetic acid 5% (AA), morphine 2.5mg/kg (MOR) or acetic acid 5% plus morphine 2.5mg/kg (AA+MOR) in one subject from a four-fish shoal. The social preference of individuals for tanks with shoals of fish treated with PBS, 5% AA, or to an empty aquarium were also tested. We verified that AA administration disrupted the shoal homogeneity by eliciting dispersion of the treated fish with simultaneous clustering of non-manipulated fish. Morphine coadministration protected against AA-induced behavioral changes. The social preference test revealed a clear preference to conspecifics (PBS and AA) over an empty tank. However, a prominent preference for PBS- over AA-treated shoal was verified. Overall, our novel findings show that nociception can modulate zebrafish sociability, possibly due to the visual recognition of nocifensive responses. Although future studies are needed to elucidate how nociception modulates zebrafish social behavior, our results contribute to improve the welfare assessment of zebrafish shoals under distinct experimental manipulations.

Infochemicals Influence Neonicotinoid Toxicity-Impact in Leaf Consumption, Growth, and Predation of the Amphipod Gammarus fossarum

Infochemicals act as inter- or intraspecific messengers. The literature suggests complex interactions between infochemicals (mainly predator cues) and chemical (e.g., pesticide) effects, with their direction and magnitude depending on the cue origin, pesticide identity, and test species. With the present study we assessed the impact of alarm cues alone and in combination with the neonicotinoid insecticide thiacloprid on leaf consumption, predation on Baetis nymphs, and dry weight of the amphipod Gammarus fossarum. Alarm cues (ground gammarids) and thiacloprid alone decreased gammarid leaf consumption with increasing intensities. At a defined alarm cue intensity, which alone did not cause a significant reduction in gammarid feeding, thiacloprid-induced feeding effects were additive. During an experiment targeting gammarid predation on Baetis nymphs (120 h), thiacloprid and alarm cues alone did increase and reduce predation significantly, respectively. Moreover, alarm cues led to a lower final gammarid dry weight. However, alarm cues did not affect response variables during a second predation experiment performed at a higher thiacloprid concentration (2 vs 0.75 µg/L). This discrepancy in alarm cue effects highlights either a varying susceptibility of the test species to these cues among experiments or that cue quality is fluctuating. Thus, the present study highlights a considerable variability in the individual and interactive effects of infochemicals and chemical stressors on aquatic biota, an insight relevant in the assessment of multiple stressors. Environ Toxicol Chem 2020;39:1755-1764. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Morphology and life history divergence in cave and surface populations of Gammarus lacustris (L.)

Cave animals provide a unique opportunity to study contrasts in phenotype and life history in strikingly different environments when compared to surface populations, potentially related to natural selection. As such, we compared a permanent cave-living Gammarus lacustris (L.) population with two lake-resident surface populations analyzing morphology (eye- and antennal characters) and life-history (size at maturity, fecundity and egg-size). A part of the cytochrome c oxidase subunit I gene in the mitochondrion (COI) was analyzed to contrast genetic relationship of populations and was compared to sequences in GenBank to assess phylogeography and colonization scenarios. In the cave, a longer life cycle was implied, while surface populations seemed to have a shorter life cycle. Egg size, and size at maturity for both sexes, were larger in the cave than in surface populations, while fecundity was lower in the cave than in surface populations. The cave population had longer first- and second antennae with more articles, longer first- and second peduncles, and fewer ommatidia than surface populations. The cold low-productive cave environment may facilitate different phenotypic and life-history traits than in the warmer and more productive surface lake environments. The trait divergences among cave and surface populations resembles other cave-surface organism comparisons and may support a hypothesis of selection on sensory traits. The cave and Lake Ulvenvann populations grouped together with a sequence from Slovenia (comprising one genetic cluster), while Lake Lille Lauarvann grouped with a sequence from Ukraine (comprising another cluster), which are already recognized phylogenetic clusters. One evolutionary scenario is that the cave and surface populations were colonized postglacially around 9 000–10 000 years ago. We evaluate that an alternative scenario is that the cave was colonized during an interstadial during the last glaciation or earlier during the warm period before onset of the last glaciation.

Managing the risks and rewards of death in eusocial insects

Eusocial insects frequently face death of colony members as a consequence of living in large groups where the success of the colony is not dependent on the fate of the individual. Whereas death of conspecifics commonly triggers aversion in many group-living species due to risk of pathogens, eusocial insects perform cooperative corpse management. The causes and social context of the death, as well as feeding and nesting ecology of the species, influence the way that corpses are treated. The corpse itself releases cues that dictate the colony's response. As a result, social insects exhibit behavioural responses that promote disease resistance, colony defence and nutrient recycling. Corpse management represents a unique adaption that enhances colony success, and is another factor that has enabled eusocial insects to be so successful. In this review, we summarize the causes of death, the sensory detection of death and corpse management strategies of social insects. In addition, we provide insights into the evolution of behavioural response to the dead and the ecological relevance of corpse management.This article is part of the theme issue 'Evolutionary thanatology: impacts of the dead on the living in humans and other animals'.

Effects of sublethal cadmium exposure on antipredator behavioural and antitoxic responses in the invasive amphipod Dikerogammarus villosus

Amphipods are recognised as an important component of freshwater ecosystems and are frequently used as an ecotoxicological test species. Despite this double interest, there is still a lack of information concerning toxic impacts on ecologically relevant behaviours. The present study investigated the influence of cadmium (Cd), a non-essential heavy metal, on both antipredator behaviours and antitoxic responses in the invasive amphipod Dikerogammarus villosus under laboratory conditions. Amphipod behaviour (i.e. refuge use, aggregation with conspecifics, exploration and mobility) was recorded following a 4-min test-exposure to 500 µg Cd/L with or without a 24-h Cd pre-exposure and in the presence or absence of a high perceived risk of predation (i.e. water scented by fish predators and injured conspecifics). Following behavioural tests, malondialdehyde (MDA) levels, a biomarker for toxic effect, and energy reserves (i.e. lipid and glycogen contents) were assessed. Cd exposures induced (1) cell damage reflected by high MDA levels, (2) erratic behaviour quantified by decreasing refuge use and exploration, and increasing mobility, and (3) a depletion in energy reserves. No significant differences were observed between 4-min test-exposed and 24-h pre-exposed individuals. Gammarids exposed to Cd had a disturbed perception of the alarm stimuli, reflected by increased time spent outside of refuges and higher mobility compared to gammarids exposed to unpolluted water. Our results suggest that Cd exposure rapidly disrupts the normal behavioural responses of gammarids to alarm substances and alters predator-avoidance strategies, which could have potential impacts on aquatic communities.

Chemical ecology of predator–prey interactions in aquatic ecosystems: a review and prospectusThe present review is one in the special series of reviews on animal–plant interactions

The interaction between predator and prey is an evolutionary arms race, for which early detection by either party is often the key to success. In aquatic ecosystems, olfaction is an essential source of information for many prey and predators and a number of cues have been shown to play a key role in trait-mediated indirect interactions in aquatic communities. Here, we review the nature and role of predator kairomones, chemical alarm cues, disturbance cues, and diet cues on the behaviour, morphology, life history, and survival of aquatic prey, focusing primarily on the discoveries from the last decade. Many advances in the field have been accomplished: testing the survival value of those chemicals, providing field validation of laboratory results, understanding the extent to which chemically mediated learning may benefit the prey, understanding the role of these chemicals in mediating morphological and life-history adaptations, and most importantly, the selection pressures leading to the evolution of chemical alarm cues. Although considerable advances have been made, several key questions remain, the most urgent of which is to understand the chemistry behind these interactions.

Gammarus spp. in aquatic ecotoxicology and water quality assessment: toward integrated multilevel tests

The amphipod genus Gammarus is widespread and is structurally and functionally important in epigean freshwaters of the Northern Hemisphere. Its presence is crucial, because macroinvertebrate feeding is a major rate-limiting step in the processing of stream detrius. In addition, Gammarus interacts with multiple trophic levels bu functioning as prey, predator, herbivore, detritivore, and shredder. Such a broad span of ecosystem participation underlines the importance of Gammarus to pollutants and other disturbances may render it a valuable indicator for ecosystem health. This review summarizes the vast number of studies conducted with Gammarus spp. for evaluating aquatic ecotoxicology endpoints and examines the suitability of this native invertabrate species for the assessment of stream ecosystem health in the Northern Hemisphere. Numerous papers have been published on how pollutants affect gammarind behavior (i.e., mating, predator avoidance), reproduction, development, feeding activity, population structure, as well as the consequences of pollution on host-parasite, predator-prey, or native-invasive species interactions. Some biochemical and molecular biomarkers have already been established, such as the measurement of vitellogenin-like proteins, metallothioneins, alkali-labile phosphates (in proteins), and lipogenic enzyme activities for assessing endocrine distribution and detoxification mechanisms.

Spiny lobsters detect conspecific blood-borne alarm cues exclusively through olfactory sensilla

When attacked by predators, diverse animals actively or passively release molecules that evoke alarm and related anti-predatory behavior by nearby conspecifics. The actively released molecules are alarm pheromones, whereas the passively released molecules are alarm cues. For example, many insects have alarm-signaling systems that involve active release of alarm pheromones from specialized glands and detection of these signals using specific sensors. Many crustaceans passively release alarm cues, but the nature of the cues,sensors and responses is poorly characterized. Here we show in laboratory and field experiments that injured Caribbean spiny lobsters, Panulirus argus, passively release alarm cues via blood (hemolymph) that induce alarm responses in the form of avoidance and suppression of feeding. These cues are detected exclusively through specific olfactory chemosensors,the aesthetasc sensilla. The alarm cues for Caribbean spiny lobsters are not unique to the species but do show some phylogenetic specificity: P. argus responds primarily with alarm behavior to conspecific blood, but with mixed alarm and appetitive behaviors to blood from the congener Panulirus interruptus, or with appetitive behaviors to blood from the blue crab Callinectes sapidus. This study lays the foundation for future neuroethological studies of alarm cue systems in this and other decapod crustaceans.

Behavioural responses of Gammarus pulex (Crustacea, Amphipoda) to low concentrations of pharmaceuticals

The continuous discharge of pharmaceuticals and personal care products into the environment results in a chronic exposure of aquatic organisms to these substances and their metabolites. As concentrations in surface waters are in the ng/L range, and sometimes in the low microg/L range, they are not likely to result in lethal toxicity. However, prolonged exposure to low concentrations of anthropogenic chemicals may lead to sublethal effects, including changes in behaviour. The aim of this study was to assess the effect of three pharmaceuticals, the antidepressant fluoxetine, the analgesic ibuprofen and the anti-epileptic carbamazepine, and one cationic surfactant, cetyltrimethylammonium bromide (CTAB), on the activity of the benthic invertebrate Gammarus pulex (Crustacea: Amphipoda: Gammaridae). We used the multispecies freshwater biomonitor to assess changes in activity of G. pulex in a quantitative manner. Exposure to low concentrations (10-100ng/L) of fluoxetine and ibuprofen resulted in a significant decrease in activity, whereas the activity of G. pulex at higher concentrations (1microg/L-1mg/L) was similar to the control. Response to carbamazepine showed a similar pattern, however, differences were not significant. The tested surfactant CTAB evoked a decrease in activity at increasing concentration. These behavioural effect concentrations were 10(4) to 10(7) times lower than previously reported LOECs and in the range of environmentally occurring concentrations. The potential consequences of this decreased activity for G. pulex population growth and benthic community structure and the exposure to mixtures of pharmaceuticals deserves further attention.