Wild social behavior differs following experimental loss of vision in social hermit crabs

Even for animals with multiple senses at their disposal, there may be a strong reliance on a single sense, like vision, for social behavior. Experimentally blocking or eliminating vision offers a powerful means of testing impacts on social behavior, though few studies have followed experimentally blinded individuals in the wild to test potential changes in social behavior in natural settings. Here we conducted experiments with social hermit crabs (Coenobita compressus), applying opaque material overtop their eyes to temporarily blind individuals. We then released these experimentally blinded individuals and non-blinded control individuals into the wild as well as into captive social settings. Compared to control individuals, experimentally blinded individuals initiated significantly fewer social contacts with conspecifics in the wild. These experimentally blinded individuals were not, however, differentially targeted by conspecifics. Interestingly, unlike the wild experiments, the captive experiments showed no differences in social behavior between experimentally blinded and non-blinded control individuals, suggesting that experiments in natural settings in the wild may be essential to fully unraveling impacts of blindness on social behavior. Broadly, for social animals that are highly reliant on the visual modality, social behavior may change dramatically if they lose their vision.

Are you scared yet? Variations to cue indices elicit differential prey behavioral responses even when gape-limited predators are relatively small

Anti-predator behavior is often evoked based on measurements of risk calculated from sensory cues emanating from predators independent of physical attack. Yet, the exact sensory indices of cues utilized in risk assessment remain largely unknown. To examine how different predatory cue indices of information are used in risk assessment, we presented prey with various cues from sub-lethal gape-limited predators. Rusty crayfish (<i>Faxonius rusticus</i> (Girard, 1852)) were exposed to predatory odors from sub-lethal sized largemouth bass (<i>Micropterus salmoides</i> (Lacepѐde, 1802)) to test effects of changing predator abundance, relative size relationships, and total predator length in flow through mesocosms. Foraging, shelter use, and movement behavior were used to measure cue effects. Foraging time depended jointly upon predator abundance and total predator size (p = 0.030). Specifically, high predator abundance resulted in decreased foraging efforts as gape ratio increased. Similarly, sheltering time depended on the interaction between predator abundance and gape ratio when predator abundance was highest (p = 0.020). Crayfish significantly increased exploration time when gape ratio increased (p = 0.010). Thus, this study shows crayfish can utilize different indices of predatory cues, namely total predator abundance and relative size ratios, in risk assessment but do so in context specific ways.

Clothianidin interferes with recognition of a previous encounter in rusty crayfish (Faxonius rusticus) due to a chemosensory impairment

Clothianidin, a neonicotinoid insecticide that binds to arthropod nicotinic acetylcholine receptors, is widely used to protect plants against a wide variety of agricultural pests. Little is known about how this insecticide affects non-target invertebrate species in aquatic environments. In this study, we explored the effects of aqueous exposures of clothianidin on locomotion, chemosensory-based responses, and agonistic encounters of rusty crayfish (Faxonius rusticus). Clothianidin exposures at a concentration of 1.0 μg/L (i.e., 1.0 ppb) did not alter initiations and retreats, but did increase the amount of time the crayfish interacted per interaction. In a subsequent food cue experiment with crayfish exposed to clothianidin concentrations of 0.4 μg/L and 1.0 μg/L, the test organisms demonstrated chemosensory dysfunction, but no decrease in locomotory movement. As chemosensation is essential for recognizing previous rivals in crayfish, the loss of this sense likely resulted in the exposed crayfish being unable to detect cues used to recognize a previous competitor. An inability to recognize a previous competitor (and who won or lost the previous interaction) could result in crayfish spending more time fighting and less time on foraging and reproduction. This study demonstrates that exposures of crayfish to clothianidin at concentrations found in the environment affects the behavioural ecology of these aquatic invertebrates.

Winner and loser effects influence subsequent mating interactions in crayfish

In species whose social structure includes dominance relationships, individuals are likely to engage in frequent agonistic interactions with conspecifics, and these interactions can have substantial effects on participants. For example, 'winner' and 'loser' effects, whereby winning or losing a contest increases the probability of winning or losing subsequent encounters, have been described in many species. However, a smaller body of research has shown that winning or losing a contest can lead to additional behavioral changes that affect other domains of an individual's social experiences. Here, we report on an experiment designed to evaluate the effects of prior contests on subsequent mating interactions in the crayfish (Faxonius virilis). We presented males with mating opportunities either immediately following or 7 days after a contest with a conspecific male. We predicted that winners would be more likely to mate than losers, because of either or both winner/loser effects and differences in male competitiveness. We found that, when presented with a mating opportunity immediately following a contest, winning males were more likely to mate than were losing males. We also found that these differences had eroded within 7 days, such that there was no significant difference in the proportions of winners and losers that mated after that period. We concluded that the changes in mating behavior that we observed immediately after a contest were likely due to relatively short-term winner and loser effects, rather than any differences in the males' competitiveness, which would presumably be of longer duration.

Outcomes of agonistic interactions alter sheltering behavior in crayfish

'Winner' and 'loser' effects have been demonstrated in a broad range of species, but such investigations are often limited to the effects of prior contest outcomes on future agonistic interactions. Much less is known about the impacts of winning or losing contests on other aspects of individual behavior, like courtship interactions and sheltering behavior. In this investigation, I examined the effect of prior contest outcomes on sheltering behavior in the crayfish Faxonius virilis. I predicted that winners of contests would spend less time inside shelters and more time exploring, while losers of contests would spend more time inside shelters and less time exploring. I compared individual sheltering behavior before and after staged dyadic encounters between competitively mismatched individuals. This experiment revealed strong effects on the behavior of contest losers, which showed significant increases in the amount of time spent inside the shelter immediately after the contest. However, there was no significant change in the sheltering behavior of contest winners. These results reinforce the idea that contest outcomes can affect individual behaviors other than agonistic behavior, and suggest that losing a contest may motivate individual crayfish to engage in less-risky behavior, at least for a brief period after the contest.

Discrete modulation of anti-predatory and agonistic behaviors by sensory communication signals in juvenile crayfish

We investigated how the exchange of sensory signals modulates the individual behaviors of juvenile crayfish in an anti-predatory context as well as during intraspecific agonistic encounters. We first compared crayfish housed in total sensory isolation or in pairs with access to chemical and visual cues. After 1 week of housing, we analysed their individual responses to a visual danger signal while they were foraging. We found that crayfish previously housed in pairs with exchange of sensory signals responded to a simulated predator attack predominantly with freezing behavior, whereas animals deprived of all sensory communication mostly responded by performing escape tail-flips. Next, we used the same housing conditions in between repeated fights in pairs of crayfish. Aggressive and submissive behaviors increased in subsequent fights both after total isolation and after exchange of olfactory and visual signals. Thus, unlike responses to simulated predator attacks, intraspecific agonistic behavior was not modulated by exposure to the same sensory signals. However, when we tested the effects of olfactory or visual communication independently, aggression increased dramatically after the exchange of olfactory signals, which also led to a high number of rank reversals in second fights, suggesting a destabilization of the original dominance relationship. Exposure to visual cues during the 1-week separation, however, produced the opposite effect, reducing agonistic behaviors and rank reversals. These findings demonstrate that exchange of sensory signals modulates future anti-predatory decision-making and intraspecific agonistic behaviors discretely, suggesting that the effect of these signals on shared neural circuitry is context dependent.

The role of sensory modalities in producing nonconsumptive effects for a crayfish–bass predator–prey system

The impact of nonconsumptive effects (NCEs) in structuring predator–prey interactions and trophic cascades is a prominent area of ecological research. For NCEs to occur, prey need to be able to detect the presence of predators through sensory mechanisms. The investigation of the role of different sensory modalities in predator detection has lagged behind the development of NCE-based theories. This study aimed to determine whether a hierarchy in the reliance upon sensory modalities exists in the rusty crayfish (Orconectes rusticus (Girard, 1852) = Faxonius rusticus (Girard, 1852)) for predator detection and if this hierarchy is altered across different sensory environments (flowing and nonflowing environments). Rusty crayfish were exposed to largemouth bass (Micropterus salmoides (Lacépède, 1802)) odor in either a flowing or nonflowing arena where behavior was recorded under different sensory lesions. Linear mixed models were conducted to determine the impact of lesions, flowing environments, and the interactive effects of lesions and flowing environments on the rusty crayfish ability to respond to predatory stimuli. Results from this study support the significance of sensory multimodality in the rusty crayfish for accurately detecting and assessing predatory threats. Results from this study also suggest a hierarchy in the reliance upon sensory modalities in the rusty crayfish that is dependent upon the environment and the location of rusty crayfish within an environment.

Information depends on context: behavioural response to chemical signals depends on sex and size in crayfish contests

Securing information about oneself or an opponent can be crucial to update the likelihood of winning a contest and the relative costs of continuing or escalating. This information can subsequently reduce costly errors. However, information encoded in signals exchanged by opponents can differ based on context. We sought to unravel these differences by pairing male and female crayfish (Orconectes rusticus) under varying sex and size conditions. A pre-optimized technique was used to visualize a well-studied contest signal in crayfish (i.e., urine). Behavioural responses were quantified prior to and after the release of that signal. There was a characteristic de-escalation of behavioural intensity after an opponent released urine. However, behavioural changes after the release event were dependent on the sex and the relative size of the opponents. Urine also significantly altered both sender and receiver behaviour, but lack of behavioural differences suggests urine plays a role in both opponent and auto-communication.

Effects of sertraline on behavioral indices of crayfish Orconectes virilis

Sertraline, a selective serotonin re-uptake inhibitor, is a widely prescribed antidepressant in North America. Though sertraline is continuously released from wastewater treatment plant discharge to surface water, effects of aqueous exposure of sertraline on behavioral responses of aquatic animals are largely unknown. Our study explored the effects of aqueous exposures of sertraline on antagonistic bouts and predator response behavior of virile crayfish (Orconectes virilis). Crayfish were either exposed or not exposed to waterborne sertraline and then size-matched for paired antagonistic bouts to determine if sertraline affects the aggression of each crayfish. We investigated the effect of sertraline on responses to visual predator cues and determined whether sertraline acts as an olfactory cue. Our results demonstrate that crayfish exposed to sertraline are more aggressive when paired with control crayfish but, when sertraline crayfish are paired, there is no change in aggression. Attraction response to sertraline in behavioral mazes was also observed, which may represent a maladaptive behavior, and in an ecological context may result in crayfish moving to areas with elevated levels of sertraline. However, aqueous exposure to sertraline had no effect on predator responses of crayfish. Future research is warranted to determine whether such medicine released in wastewater treatment plant effluents produces long-term ecologically important consequences for aquatic animals residing in urbanized aquatic ecosystems.

Evidence for assessment disappears in mixed-sex contests of the crayfish, Orconectes virilis

During agonistic interactions, decisions about contest persistence can be informed by assessment of one’s own energy or time expenditure (self-assessment), one’s own expenditure combined with opponent inflicted costs (cumulative assessment), or through information exchange with an opponent (mutual assessment). Females and males can be expected to exhibit different strategies for contest resolution due to contrasting energetic requirements and resource valuation. We examined the assessment strategies crayfish employ during same-sex and mixed-sex fights. Two individuals interacted for 15 min, and fight duration and times spent at various intensity levels were quantified. Results indicated that both sexes employ a self-assessment strategy during same-sex fights. Evidence for assessment during mixed-sex fights was notably weaker, suggesting the resolution of mixed-sex fights involves different behavioural elements and/or sources of information. In species where mixed-sex fights are common year-round, the lack of common rules can lead to greater energy expenditure for both sexes.