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Mechanical cues are widely used for regulating cell behavior because of their overarching, extensive, and non‐invasive advantages. However, unlike chemical cues, mechanical cues are not efficient enough to determine cell fate independently and improving the mechanosensitivity of cells is rather challenging. In this study, the combined effect of chemical and mechanical cues on the osteogenic differentiation of human mesenchymal stem cells is examined. These results show that chemical cues such as the presence of an osteogenic medium, induce cells to secrete more collagen, and induce integrin for recruiting focal adhesion proteins that mature and cascade a series of events with the help of the mechanical force of the scaffold material. High‐resolution, highly ordered hollow‐micro‐frustum‐arrays using double‐layer lithography, combined with modified methacrylate gelatin loaded with pre‐defined soluble chemicals to provide both chemical and mechanical cues to cells. This approach ultimately facilitates the achievement of cellular osteodifferentiation and enhances bone repair efficiency in a model of femoral fracture in vivo in mice. Moreover, the results also reveal these pivotal roles of Integrin α2/Focal adhesion kinase/Ras homolog gene family member A/Large Tumor Suppressor 1/Yes‐associated protein in human mesenchymal stem cells osteogenic differentiation both in vitro and in vivo. Overall, these results show that chemical cues enhance the microtopographical sensitivity of cells. [ABSTRACT FROM AUTHOR]

The mechanisms causing native species displacement by invasive species can be challenging to identify. We used survey data to demonstrate a local extinction of a native gastropod (Pomacea paludosa) from a Florida wetland coincident with invasion of a non-native gastropod (Pomacea maculata). We then examined the potential for P. maculata to displace P. paludosa. Two field experiments examined effects of densities and heterospecific interactions on juvenile P. paludosa growth in situ and lab and mesocosm experiments explored chemically-mediated interactions between the species. Field experiments produced variable results; evidence for reduced P. paludosa growth in the presence of P. maculata was found under higher nutrient conditions with fast snail growth rates, but growth inhibition disappeared under oligotrophic conditions. Resource reduction was not seen in the field experiments. Juvenile P. paludosa did not avoid mucus of P. maculata and did not reduce feeding in response to chemical cues. Nevertheless, exposure to mucus and waterborne cues of P. maculata reduced P. paludosa growth by 53% relative to conspecific cue exposure. In mesocosms juvenile P. paludosa growth was significantly negatively correlated with exposure to adult P. maculata waterborne cues. Stronger effects were evident when waterborne cues were combined with mucus at low exposure (20%). We documented the first apparent local extinction of P. paludosa by P. maculata. We found no evidence for competition, but the results collectively pointed to an effect of direct chemical inhibition that could be important at field scales and at low invasive densities. [ABSTRACT FROM AUTHOR]

Abstract Females must choose among potential mates with different phenotypes in a variety of social contexts. Many male traits are inherent and unchanging, but others are labile to social context. Competition, for example, can cause physiological changes that reflect recent wins and losses that fluctuate throughout time. We may expect females to respond differently to males depending on the outcome of their most recent fight. In Bolitotherus cornutus (forked fungus beetles), males compete for access to females, but copulation requires female cooperation. In this study, we use behavioral trials to determine whether females use chemical cues to differentiate between males and whether the outcome of recent male competition alters female preference. We measured female association time with chemical cues of two size‐matched males both before and after male–male competition. Females in our study preferred to associate with future losers before males interacted, but changed their preference for realized winners following male competitive interactions. Our study provides the first evidence of change in female preference based solely on the outcome of male–male competition.

The mechanism of food detection in tadpoles of Polypedates maculatus was experimentally tested. We used a rectangular glass test tank with stimulus zones in opposite ends to provide visual and/or chemical food. For visual cues, boiled spinach was placed inside a glass container, and for chemical cues boiled spinach was placed in a mesh cage. Each tadpole of P. maculatus (either at an early or medium developmental stage) was held at the center of the test tank for acclimation. The tadpole was released, and we recorded whether it approached or did not approach the caged food. Tadpoles of all stages failed to detect food using visual cues. Tadpoles of all stages detected food using chemical cues. In tests using chemical cues, they spent the majority of their time (69.3% by early stage tadpoles and 87.3% by medium-stage tadpoles) near the container with food than in the end with no containers or with only visual food cues. Tadpoles in medium stages spent more time near food (18.1% of total time) than tadpoles in early stages. These findings indicate that tadpoles of P. maculatus detect food by chemical sensory mechanisms rather than visual ones. Tadpoles in medium stages spent more time near food than tadpoles in early stages indicating that time spent foraging increases as tadpoles grow.

Phoresy, the use of another organism for dispersal, is one of the most intriguing commensalistic interactions. The selection of a correct host is fundamental for phoretic organisms to ensure arrival to suitable habitats and to encounter potential mates. This study focuses on a group of phoretic mites in the genus Lasioseius (Acari: Blattisociidae). In La Selva Biological Station, a tropical wet forest in Costa Rica, Lasioseius mites feed on nematodes inside the scrolls formed by the young leaves of their hosts, plants in the order Zingiberales. When leaves expand and unfurl, mites disperse to another rolled leaf by clinging onto 'rolled‐leaf beetles', a group of insect herbivores specialized on Zingiberales (genera Cephaloleia and Chelobasis; Coleoptera: Chrysomelidae). In this study, we determined whether Lasioseius mites associated with Cephaloleia belti Baly are specialized on this beetle species as a phoretic host. Mites may also be attracted to Chelobasis perplexa Baly, sharing the same host plant. Another possibility is that Lasioseius mites are opportunistic generalists and attach to rolled‐leaf beetle species (e.g., Cephaloleia dorsalis Baly) that never share host plants with either C. belti or Ch. perplexa. In a laboratory setting, we tested whether mites preferred scents from and/or attached to particular beetle species. Scent attraction experiments showed that Lasioseius mites collected from C. belti were attracted to scents from C. belti and Ch. perplexa, but were not attracted to scents from C. dorsalis. Mites collected from C. belti attached to both C. belti and Ch. perplexa, but never to C. dorsalis. In conclusion, Lasioseius mites are not strict specialists, but are able to detect and attach to beetle species that inhabit their host plant. [ABSTRACT FROM AUTHOR]

Recent range expansion of many species northward and upward in elevation suggests that the expanding species are able to cope with new biotic interactions in the leading edge. To test this hypothesis, we used a common garden experiment expanding the elevation range of an obligatorily univoltine dragonfly (Sympetrum striolatum) to investigate whether the growth, behavioral (food intake), and morphological (8th and 9th abdominal lateral spine) responses differed when confronted with dragonfly predators that dominate low-elevation (Aeshna cyanea) and high-elevation (A. juncea) lentic freshwater systems under two temperature treatments (20 °C and 24 °C). Growth rate and growth efficiency increased at higher temperature. Overall, low- and high-elevation predators induced a similar increase in growth rate and growth efficiency but a decrease in food intake at 24 °C. Lateral abdominal spines were longer only in low-elevation dragonflies at 18 °C. Our study suggests that range-expanding species may have been successful in colonizing new areas at higher elevations because they respond to dominant high-elevation predators in a similar way to the more familiar low-elevation predators. [ABSTRACT FROM AUTHOR]

In this paper we hypothesize that the attraction of the cashew whitefly, Aleurodicus cocois, depends on volatile emissions from cashew plants. To test this hypothesis, we determined the degree of A. cocois infestation in dwarf-cashew clones: CCP 76, EMBRAPA 51 and PRO 143/7 under field conditions, we evaluated the behavioral response of A. cocois adult females to plant volatiles of these clones in a 4-way olfactometer, and we characterized the volatile organic compounds released by each dwarf cashew clone by solid-phase microextraction and coupled gas chromatography-mass spectrometry (GC-MS). Under field conditions, the highest degree of A. cocois infestation was found in EMBRAPA 51 while PRO 143/7 was the least infested clone. Bioassays revealed that volatile compounds of CCP 76 were attractive to A. cocois over clean air, while EMBRAPA 51 and PRO 143/7 volatiles were not attractive to whiteflies. The dwarf cashew clones released common volatile compounds that differed in quantity. According to the principal component analysis the compounds α-pinene, myrcene, carene δ-2, limonene, α-copaene, β-caryophyllene, β-ocimene, allo-ocimene and neo-allo-ocimene were emitted at intermediate levels by clone CCP 76 compared to EMBRAPA 51 and PRO 143/7. Additionally, some compounds (o- cymene and 2,6-dimethyl-1,3,5,7-octatetraene, (E, E)-) were found exclusively in the samples of CCP 76. The results suggest that cashew volatile compounds may be determining factors in A. cocois choice of host plants and that the susceptibility of clone CCP 76 to this insect may be associated with the release of appropriate proportions of attractive volatile compounds. [ABSTRACT FROM AUTHOR]

The invasive brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), has disrupted integrated pest management programs in agroecosystems including tree fruit in North America and several other regions worldwide. While the toolbox for managing the pest continues to grow, it has not yet been determined if feeding or oviposition by H. halys onto orchard or forest trees induces changes in volatiles emitted from trees that could be exploited by foraging egg parasitoids or other insects. The goal of this study was to investigate differences in volatile compound emissions from branches of potted peach and tree of heaven exposed directly and systemically to H. halys feeding and oviposition. Analyses indicate that H. halys feeding and oviposition induced changes in both the blend and specific amounts of volatile compounds emitted from both tree species. Tree of heaven branches directly exposed to H. halys oviposition and feeding emitted nerolidol at a higher rate than those exposed to feeding alone and control trees. Tree of heaven compound leaves systemically exposed to H. halys feeding alone emitted higher rates of (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) than trees exposed to oviposition and feeding or control trees. Conversely, for peach, both branches exposed directly or systemically resulted in a decrease in cis-3-hexenyl acetate when exposed to H. halys oviposition. Such changes in plant volatile compounds, or blends of compounds, have the potential to be used by foraging natural enemies of H. halys. [ABSTRACT FROM AUTHOR]

Mate choice in frogs depends heavily on acoustic communication, and females in many species possess an inherent preference for longer and/or more complex calls. Recently, it has become clear that conspecific chemical cues can also be useful in attracting potential mates in anuran species. However, how conspecific chemical cues influence mate choice decisions when paired with acoustic signals remains less clear. In the present study, we conducted three experiments to investigate whether and how male odor cues affect female choice decisions in the absence or presence of acoustic signals in serrate-legged small treefrogs (Kurixalus odontotarsus). We found that disturbance odors alone can trigger avoidance behavior of females, suggesting that the odors of disturbed K. odontotarsus can act as an alarm cue for conspecifics. Females also avoided disturbance odors in the presence of advertisement calls, except for calls with five notes. In addition, females preferred calls with two notes to calls with four notes when the latter was paired with disturbance odors. In contrast, female choice decisions were not affected by the odors of undisturbed males, either in the absence or the presence of advertisement calls. Our results indicate that disturbance odors can influence, or even reverse, mate choice by females for acoustic signals. Significance statement: In addition to acoustic signals, chemical cues can also be used in close-range communication in some anuran species. In the present study, we investigated how female Kurixalus odontotarsus use male chemical cues and/or acoustic signals during the mate choice process. We demonstrate that male disturbance odors can act as an alarm cue to trigger the avoidance behavior of females. Furthermore, this alarm cue can even reverse mate choice by females for acoustic signals. Our study highlights the importance of integrating multisensory signals and cues in mate choice decisions and has important implications for understanding chemical communication in anurans. [ABSTRACT FROM AUTHOR]

Abstract Laboratory experiments have shown that the viability of embryos of the invasive cane toad (Rhinella marina) can be reduced by exposure to chemical cues from older conspecific larvae. These effects (very strong in laboratory trials) may offer an exciting new approach to controlling this problematic invasive species in Australia. However, the degree to which the method works in natural environments has yet to be assessed. Our experiments in the laboratory and in seminatural outdoor waterbodies show that chemical cues from tadpoles do indeed suppress the growth, development, and survival of conspecific larvae that are exposed as embryos and do so in a dose‐dependent manner; higher tadpole densities cause greater suppression of embryos. In seminatural outdoor waterbodies, suppressor‐exposed tadpoles were less than half as likely to survive to metamorphosis as were controls, and were much smaller when they did so and hence, less likely to survive the metamorph stage. Additionally, female cane toads were less likely to oviposit in a waterbody containing free‐ranging (but not cage‐enclosed) tadpoles, suggesting that the presence of tadpoles (rather than the chemical cues they produce) may discourage oviposition. Broadly, our results suggest that the suppression effect documented in laboratory studies does indeed occur in the field also, and hence that we may be able to translate that approach to develop new and more effective ways to reduce rates of recruitment of peri‐urban populations of cane toads in their invasive range.

The ability to detect predators at a distance through chemical cues is often essential for prey, but spatial variation in predator presence and species may promote variability in the reactions of prey subpopulations. We collected isopods (Caecidotea communis) from three ponds: two with fish (sunfish in one, shiners in the other), and one without. We exposed individuals from these three subpopulations to kairomones and diet cues released by sunfish (Lepomis spp.) or golden shiners (Notemigonus crysoleucas). We used time-lapse photography to calculate the rate of movement and proportion of time isopods spent moving, both soon after cue introduction and twenty-five minutes later. Thus, we tested for reactions to cues, for rapid cue degradation or short-term habituation, and for effects of natal pond. The isopods from all subpopulations did not alter their rate of movement nor their percent of time moving when exposed to dechlorinated tap water or cues from sunfish. The isopods from the pond containing shiners significantly increased their proportion of time moving, and showed a not significant tendency to move more rapidly, when exposed to cues from shiners as opposed to dechlorinated tap water. Our results are the first to demonstrate that isopods may lack a behavioral response to chemicals indicating likely imminent danger from the same species of fish as occur in their natal pond. [ABSTRACT FROM AUTHOR]

Although self-recognition or self-awareness has been studied with the visually-based mirror test, passed by several species, primarily apes, the possibility of a chemically-based analogue is controversial. Prior studies suggested that chemical self-recognition may occur in some squamate reptiles. To evaluate this possibility, we studied 24 individually housed gartersnakes, Thamnophis sirtalis , raised from birth on either earthworm or fish diets and tested 12 male and 12 female snakes with cage liners that were either clean, their own, or from same-sex siblings fed their own or the opposite diet. Tongue flicking and activity were recorded in 30-minute video-recorded trials in a balanced design. After initial habituation to the stimuli, male, but not female, snakes discriminated between their own stimuli and those from littermates fed the same diet. Combined with other data and studies, the possibility that a chemical 'mirror' form of self-recognition exists in squamate reptiles is supported. [ABSTRACT FROM AUTHOR]

The ability of shoaling fish to recognise and differentiate between potential groupmates may affect their fitness and survival. Fish are capable of social recognition and multiple sensory cues mediate the recognition mechanisms. This has been comprehensively studied for juvenile and adult freshwater species. However, the recognition ability and mechanisms intervening during the larval phase of marine species are yet poorly understood. Fish larvae are capable of discriminating conspecifics from heterospecifics based on chemical and/or visual cues, but whether this recognition occurs at finer scales, such as discerning among conspecifics of different reefs, is yet understudied. Here, we tested the hypothesis that larvae of a marine fish species, the sand smelt (Atherina presbyter Cuvier, 1829), are able to recognise and associate with conspecifics of their natal reef versus conspecifics of a non-natal reef based on three sensory modalities—chemical, visual, and chemical and visual simultaneously. Results do not support our hypothesis, but still provide evidence of group cohesion and indicate large differences in the relative importance of the different senses when associating with conspecifics, with visual cues playing a more important role than chemical cues alone. [ABSTRACT FROM AUTHOR]

Our changing climate is affecting predator-prey interactions in different ways. Increasing atmospheric CO2 is acidifying the ocean and disrupting the chemosensation of several species. Here, we evaluated a risk-induced trait response to a potential predator under an acidified scenario. Using planktonic crab larvae as a prey model, we first analysed their swimming avoidance response to different potential fish predators and conspecific odours. Prey intensified their avoidance response to conspecific and predator odours, but not to all predators, with no maternal effect. Then, larvae were exposed to a responsive predator odour under a predicted acidified scenario. A similar response was observed for both saltwater and predator odour under low pH conditions. Thus, acidification seems to affect the chemosensation of planktonic larvae, leading them to not distinguish between a non-harmful stimulus and a potential predator and potentially bringing a cascade of ecological impairments.

In aquatic systems, olfaction plays an important role in acquiring information about the social environment and influences important behaviours in various contexts, including predator avoidance, foraging, aggressive and reproductive behaviour and mate selection. As the presence of diseases might modify individual odour, fish may use the variability in conspecifics' odours as an indicator of the health status and infectious load of potential mates. Here, female Nile tilapia were tested for their ability to detect infected males and discriminate between bacterial infected and uninfected individuals by means of chemical cues. Females were allowed to choose between the odours of males infected by Aeromonas hydrophila bacteria and uninfected males. The findings show that female Nile tilapia initially showed a preference for infected males in terms of their first choice in a dichotomous choice test, but the total duration of time spent with the stimulus from infected males was not longer than that for the uninfected males. This may indicate that males at early stages of infection, i.e., without advanced clinical signs of infection, emit odours that allow them to enjoy the benefits of socialization when the infection is not yet detected by conspecifics. Thus, in the context of reproduction, males might attract female partners and have some chance of reproducing, before being avoided. [ABSTRACT FROM AUTHOR]

Large-scale losses of spat are commonplace during the early stages of mussel aquaculture costing the industry millions in lost production. The dominant cause of this poor spat retention is thought to be secondary settlement behavior, whereby spat detach from farming substrata in an effort to relocate to another site. One approach that could be used to reduce these spat losses is to use natural substrates, such as macroalgae, to which wild mussel spat commonly attach. These natural substrates are often associated with chemical and morphological settlement cues. In New Zealand, the majority of mussel spat used by the aquaculture industry are harvested from the wild while attached to a range of species of macroalgae and other general debris (referred to as Kaitaia spat material). The filamentous morphology and chemicals released by some of these macroalgal species, including the rhodophyte Pterocladia lucida, have been shown to improve mussel settlement. Therefore, in this study, the spat of the green-lipped mussel, Perna canaliculus, were seeded onto aquaculture grow ropes with and without P. lucida to determine whether the presence of the macroalgae would improve the retention of the mussel spat. The presence of P. lucida increased spat retention by 33% relative to a control over 12 weeks and also increased the proportion of spat (by 16%) that successfully migrated away from biodegradable seeding substrata onto the permanent structure of the grow rope. The timing of spat losses relative to the breakdown of seeding substrata is consistent with the macroalga producing chemical cues that encourage spat settlement. In contrast, no spat attached directly to the P. lucida suggesting morphology of the macroalga was not playing a role in the observed increase in spat retention. These results suggest that there may be chemical cues present in P. lucida that may have the potential to be used to help resolve the problem of poor spat retention in green-lipped mussel aquaculture. [ABSTRACT FROM AUTHOR]

In scramble competition mating systems, males do not guard females and females usually mate polyandrously, leading to high levels of sperm competition. Mathematical models predict that males facing sperm competition can either decrease or increase their reproductive effort. To test how male reproductive responses vary according to sperm competition risk, we ran two experiments using the polyandrous gift‐giving spider Paratrechalea ornata. First, we tested whether males prefer substrates containing silk of unmated females than substrates containing silk of once‐mated females, competitor males or without silk. Males spent more time on substrates containing silk of females but showed no preference for unmated females, which indicates that males may optimize mate search by prioritizing substrates containing cues of potential mating partners. The lack of preference for unmated females suggests that males cannot detect female mating status from silk or that the costs of searching preferentially for unmated females are high in the field. Second, we tested whether males adjust prey‐gift construction when facing sperm competition risk. Experimental groups (substrate containing silk of an unmated female and silk of another male vs. substrate containing only silk of an unmated female) did not differ in the frequency of gift construction, latency to gift construction and number of flies added to the gift. However, males facing sperm competition risk constructed gifts with less silk, suggesting the occurrence of a less evident form of male mate choice based on differential allocation of resources to prey‐gift. Additionally, given the trade‐off between investing in prey‐gifts quantity or quality, a lower silk investment should enable males to increase the number of gifts constructed and the number of courted females. Taken together, our results indicate that males detect female and male pheromones on substrate and adjust the construction of prey‐gifts in response to apparent sperm competition risk. [ABSTRACT FROM AUTHOR]

Social insects have the ability to perform tasks in an organized way. Communication plays a key role in controlling these processes, and throughout evolution, these organisms developed a complex system for transferring information. Different stingless bee species use the same resource during foraging that could lead to an eventual competition. It is important for organisms to access the costs of confrontation with rival individuals and the energetic gain from foraging when exploiting a food source. Thus, the present work aimed to investigate behavioral responses in the foraging activity of Plebeia droryana Friese, 1900 in the presence of chemical and visual cues of Trigona spinipes Fabricius, 1793. Foragers of P. droryana were trained to visit artificial feeders with two different sugar concentrations and were exposed to chemical and visual cues of T. spinipes at different setups, but always separately. We also identified the cuticular hydrocarbons (CHCs) of T. spinipes foragers. Both visual and chemical cues from T. spinipes did not cause P. droryana to decrease its foraging activity at 50% sucrose concentration. We found that 40% concentration caused bees to reduce the foraging effort when faced with visual cues from T. spinipes. Thus, similar to other species, we found that P. droryana was attracted to the food source containing a 50% sugar solution regardless of the presence of T. spinipes chemical cues. Based on our results, we infer that food quality is the most important factor when P. droryana foragers are exploiting a food source. [ABSTRACT FROM AUTHOR]

To assess whether amphipods' habitat choice and feeding preference for a specific seaweed species are based on nutritional value or structural complexity, and to evaluate the role of chemical cues in the amphipod choice, we carried out laboratory experiments using amphipods (Ampithoe marcuzzii) and seaweeds from different divisions (Chlorophyta, Ochrophyta, and Rhodophyta). To evaluate feeding preference, we carried out a multiple‐choice experiment offering six species of seaweeds to amphipods. To assess whether habitat choice by amphipods is guided exclusively by seaweed complexity, we conducted an assay offering seaweeds and complexity‐like mimics (artificial plants) to amphipods, quantifying their choices. To evaluate whether seaweeds' secondary metabolites acted as chemical cues affecting seaweed choice by the amphipods, we used the same plastic mimics, one of which was brushed with crude extracts from the most‐consumed seaweeds and a control. The consumption of Gracilaria cervicornis by amphipods was around three times higher than that of the other offered species, likely due to its paucity of chemical and physical defenses. The highest contents of nitrogen and crude proteins in this species may have contributed to its high consumption. Amphipods also used G. cervicornis as a shelter more than its mimic, but exhibited no preference between other seaweeds and their mimics, indicating that a more palatable refuge is preferred. This idea was corroborated when amphipods were able to detect chemical cues of G. cervicornis painted over a plastic mimic of similar structure and preferred it over the control mimic, which had the same complexity but no chemicals. Our results suggest that amphipods use chemical cues to identify high‐quality habitat regarding refuge (complexity) and food source (nutritional value). [ABSTRACT FROM AUTHOR]

Varroa destructor Anderson & Trueman (Acari: Varroidae) is one of the major contributors to the significant losses of western honey bee, Apis mellifera L. (Hymenoptera: Apidae), colonies worldwide. Hygienic behavior, in which individual workers detect, uncap, and remove unhealthy brood, is a type of social immunity that reduces pathogen and parasite loads in the colony. Previous evidence suggests that hygienic worker bees identify diseased brood through olfactory cues. The aims of the present work were (1) to study the hygienic behavior of worker bees toward V. destructor‐infested cells at different stages of brood development, (2) to explore changes in brood volatile profiles associated with the progression of mite infestation, and (3) to analyze the role of specific volatile compounds in triggering the hygienic behavior. Results showed that the removal rate of infested brood changed along its development and the progression of mite reproduction. Two compounds, ethyl hexanoate and α‐pinene, were present in volatile collections from mite‐infested pupae but absent from uninfested pupae. Field bioassays showed that these volatiles are relevant to elicit the hygienic behavior. A third compound, β‐ocimene, was present in infested and uninfested brood but its abundance pattern varied according to the infestation status throughout brood development. Specifically, for uninfested brood, the abundance of β‐ocimene showed a reduction in black‐eyed pupae, whereas for infested brood, its abundance decreased drastically in light‐pink‐eyed pupae and remained constant in black‐eyed pupae. Our results revealed that olfactory signals associated with V. destructor infestation change as the reproductive cycle of V. destructor progresses inside the cell. These changes can be mimicked to some extent by adding specific volatile compounds to the cell to induce hygienic removal. These findings shed light on the chemical basis of hygienic behavior against V. destructor and could facilitate the development of improved hygienic selection tools to breed mite‐resistant honey bee colonies. [ABSTRACT FROM AUTHOR]

Sexual pheromones are chemical molecules responsible for mediating sex recognition and mating events. Long- and close-range sexual pheromones act differently. The first type is released to attract potential partners, whereas the second coordinates the interactions after potential mating partners encounter each other. Cuticular hydrocarbons (CHCs) have been suggested to be important cues in the mating systems of several Hymenoptera species, although empirical data are still lacking for many species. Here, we evaluated whether males of the model species Polistes dominula can differentiate the sex of individuals based on their CHC composition. In August 2019, several post-worker emergent nests (n = 19) were collected in the vicinity of Leuven (Belgium) and taken to the lab (KU Leuven), where newly emerged females and males were sampled, marked individually, and kept in plastic boxes for at least a week before being used in the mating trials. Focal males were paired with females and males from different nests and subjected to five different conditions: (I) alive, (II) dead, (III) CHCs washed, (IV) CHCs partially returned, and (V) CHCs from the opposite sex. We videotaped the interactions for 10 min and analysed the duration and different behavioural interactions of the focal male. Our results indicate that CHCs may be used by males as cues to recognise a potential mating partner in P. dominula, since the focal males displayed specific courtship behaviours exclusively toward females. Although we cannot exclude that visual cues could also be used in combination with the chemical ones, we empirically demonstrate that CHCs may be important to convey sexual information at close range in mating systems, allowing fast decisions toward potential sexual partners or rivals. [ABSTRACT FROM AUTHOR]

Females must choose among potential mates with different phenotypes in a variety of social contexts. Many male traits are inherent and unchanging, but others are labile to social context. Competition, for example, can cause physiological changes that reflect recent wins and losses that fluctuate throughout time. We may expect females to respond differently to males depending on the outcome of their most recent fight. In Bolitotherus cornutus (forked fungus beetles), males compete for access to females, but copulation requires female cooperation. In this study, we use behavioral trials to determine whether females use chemical cues to differentiate between males and whether the outcome of recent male competition alters female preference. We measured female association time with chemical cues of two size‐matched males both before and after male–male competition. Females in our study preferred to associate with future losers before males interacted, but changed their preference for realized winners following male competitive interactions. Our study provides the first evidence of change in female preference based solely on the outcome of male–male competition. [ABSTRACT FROM AUTHOR]

During foraging, organisms need to assess the costs and benefits related to resources wanted. An energy‐efficient way of locating and deciding among new food sources is to use cues left by other organisms in the environment (i.e., social information). In the present study, manipulative bioassays were conducted to evaluate the role of intra‐ and interspecific chemical cues in the selection of food resource by Nasutitermes corniger (Termitidae: Nasutitermitinae). For this, we tested the hypothesis that individuals of N. corniger are able to perceive and use chemical cues by either colonies of the same species or from different species. Linear trail bioassays were conducted to verify whether N. corniger workers perceive and accept intra‐ and interspecific chemical cues. Then, resource bioassays were performed with a binary and multiple choices to evaluate whether the termite group's decision of food resources was based on intra‐ and/or interspecific chemical cues. In general, groups of N. corniger preferred baits with chemical cues of other intraspecific colonies or with undetectable cues (hexane solvent or interspecific cues) than those with their own chemical signals. These results suggest that intraspecific chemical cues seem to modulate the food resource selection in N. corniger, which may help researchers to better understand the use of habitat by termites. [ABSTRACT FROM AUTHOR]

The acanthocephalan parasite, Polymorphus minutus, manipulates its intermediate hosts' (gammarids) behaviour, presumably to facilitate its transmission to the definitive hosts. A fundamental question is whether this capability has evolved to target gammarids in general, or specifically sympatric gammarids. We assessed the responses to chemical cues from a non-host predator (the three-spined sticklebacks Gasterosteus aculeatus) in infected and non-infected gammarids; two native (Gammarus pulex and Gammarus fossarum), and one invasive (Echinogammarus berilloni) species, all sampled in the Paderborn Plateau (Germany). The level of predator avoidance was assessed by subjecting gammarids to choice experiments with the presence or absence of predator chemical cues. We did not detect any behavioural differences between uninfected and infected G. pulex and E. berilloni, but an elevated degree of predator avoidance in infected G. fossarum. Avoiding non-host predators may ultimately increase the probability of P. minutus' of predation by the definitive host. Our results suggested that P. minutus' ability to alter the host's behaviour may have evolved to specifically target sympatric gammarid host species. Uninfected gammarids did not appear to avoid the non-host predator chemical cues. Overall the results also opened the possibility that parasites may play a critical role in the success or failure of invasive species. [ABSTRACT FROM AUTHOR]

In social bees, the choice of food sources is based on several factors, including scent marks, color, and location of flowers. Here, we used similar setups, in which two stingless bee species, Melipona subnitida and Plebeia flavocincta, and the Western honeybee, Apis mellifera, were tested regarding the importance of chemical cues, color cues, and location-dependent cues for foraging behavior. It was determined whether workers chose food sources according to (1) scent marks deposited by conspecifics, (2) the color hue of a food source, (3) the trained location or the proximity of a food source to the hive. All three species preferred the scent-marked over an unmarked feeder that was presented simultaneously, but M. subnitida showed a weaker preference compared to the other species. When trained to blue feeders all three bee species preferred blue, but A. mellifera showed the strongest fidelity. The training to yellow feeders led to less distinct color choices. Only workers of M. subnitida mostly orientated at the training position and the close proximity to the nest. Whether the distance of a feeding site influenced the choice was dependent on the tested parameter (color or scent marks) and the species. Workers of M. subnitida preferably visited the feeder closer to the nest during the scent mark trials, but choose randomly when tested for color learning. Worker honeybees preferred the closer feeding site if trained to yellow, but not if trained to blue, and preferred the more distant feeder during the scent mark trials. Workers of P. flavocincta preferred the closer feeder if trained to blue or yellow, and preferred the more distant feeder during the scent mark trials. The disparity among the species corresponds to differences in body size. Smaller bees are known for reduced visual capabilities and might rely less on visual parameters of the target such as color hue, saturation, or brightness but use scent cues instead. Moreover, the dim-light conditions in forest habitats might reduce the reliability of visual orientation as compared to olfactory orientation. Honeybees showed the most pronounced orientation at floral color cues.

Females use a variety of physical and behavioral features to locate potential mates and assess their quality. These male signals can be transmitted across one or multiple signaling modalities and, recently, the roles of silk-related signaling by males has received more attention. In the wolf spider, Pardosa milvina (Hentz, 1844), males use a visual courtship display to attract female attention and encourage sexual receptivity. We hypothesized that male chemotactile cues, including silk, feces, excretions and secretions, help females find prospective mates. We also suspected that females could use those cues to discriminate between males that differed in body condition. We monitored female reactions to isolated male chemotactile cues and to those same cues combined with visual signals provided by a sequestered male. Females did not change their activity in the presence of isolated male chemotactile cues. When males were included in the design, we verified that the courtship display was key to attracting the females and that males in good condition performed with more intensity. Surprisingly, the presence of male chemotactile cues repelled females; females approached males less often and tended to spend less time near courting males. This research verified that the visually conspicuous male courtship displays are condition-dependent and important in attracting a female. The chemotactile cues that were produced by isolated males caused females to move away from courting males, thus it is likely that any communication through chemical or tactile modalities is a more specific and individualized dialog that occurs during each courtship exchange. [ABSTRACT FROM AUTHOR]

The ubiquitous oceanic copepod Calanus finmarchicus is the major link between primary producers and important fish stocks in the North Atlantic Ocean and adjacent seas. Despite over a century of research on growth and development of this key species, the effect of predation risk on these processes remains elusive. We tested how food level and chemical cues from a fish predator influence growth and development of C. finmarchicus, using a predator naïve laboratory population. Copepods reached adult stage earlier both in response to high food and to predator cues in our experiment. High food also increased growth and lipid accumulation. In contrast, perceived predation risk triggered reduced size and lipid fullness, indicating a decoupling of growth and development rates. Our results demonstrate that chemical predator cues can influence life history strategies in C. finmarchicus, and suggest that present and future patterns in oceanic zooplankton size and population dynamics may also reflect differences in predation risk. [ABSTRACT FROM AUTHOR]

Biological control research often focuses on the ability of predators to reduce pest densities and protect crops through consumption. Less studied is their ability to protect crops by altering pest behaviour (non‐consumptive effects). Lab experiments were conducted to test predation rates of striped cucumber beetles (Acalymma vittatum; Coleoptera: Chrysomelidae) and spotted cucumber beetles (Diabrotica undecimpunctata howardi; Coleoptera: Chrysomelidae) by large (>10 mm) wolf spiders (Araneae: Lycosidae). Field experiments were conducted to examine how the physical presence and/or cues of spiders impact the behaviour and mortality of A. vittatum (specialist) and D. undecimpunctata (generalist) cucumber beetles as well as growth and damage of cucumber plants (Cucumis sativus; Cucurbitaceae). A. vittatum and D. undecimpunctata adults were added to caged cucumber plants without a spider, with spider cues only (spider removed before beetle inclusion), with spider only (spider introduced to plants immediately before beetle inclusion), and with spiders and their cues present (spiders introduced 24 hr in advance of beetle inclusion). A. vittatum responded to spider cues primarily by emigrating from plants. Contrarily, D. undecimpunctata did not display obvious responses, such as reduced feeding or increased emigration, to spider foraging and/or cues. Actively foraging lycosids increased A. vittatum mortality and reduced densities of D. undecimpunctata in the field when cucumber plants were flowering. This study highlights how non‐consumptive and consumptive effects can play a role in modifying pest populations, and how these effects can vary across species and plant growth stages. [ABSTRACT FROM AUTHOR]

The prey naiveté hypothesis (PNH) posits that prey will often fail to recognize and respond to introduced predators with whom they do not share a co-evolutionary history. We tested this hypothesis by examining anti-predator behaviour in the native characid fish Astyanax ruberrimus in response to its main native (Hoplias microlepis) and introduced (Cichla monoculus) fish predators in Panama. We observed the behaviour of wild-caught A. ruberrimus from an invaded and uninvaded site following exposure to chemical stimuli from: (1) injured conspecifics, (2) the native predator, and (3) the introduced predator. We found, first, that A. ruberrimus consistently responded to cues from injured conspecifics, suggesting that this species possesses an alarm signaling mechanism similar to that observed across Ostariophysan fishes. Second, A. ruberrimus responded to cues from their native predator, but only in one population, suggesting responses may be threat-sensitive. Third, A. ruberrimus lacking prior exposure to C. monoculus did not respond to cues from this predator, consistent with the PNH. In contrast, A. ruberrimus that have co-occurred with C. monoculus for several decades did respond to cues from this predator, suggesting that prior exposure to C. monoculus has led (either via local adaptation or learning) to acquired predator recognition. Overall, our findings are consistent with the PNH, although we cannot conclusively rule out alternate explanations for the observed differences between populations. Our work represents a first step towards understanding the role that behavioural naiveté may have played in the initial stages of this important tropical freshwater introduction. [ABSTRACT FROM AUTHOR]

Group-living prey rely on social information such as alarm signals and other social cues to avoid predation. By definition, "signals" imply that a message is voluntarily directed at receivers (i.e., the audience), whereas "cues" are released incidentally regardless of the audience composition. Thus, audience effects can be used to differentiate between signals and cues when communication is difficult to observe or quantify. In at least two fish species, chemical disturbance cues are released during a predator attack to signal to familiar audiences about predation risk. Here, we examined whether audience composition affects disturbance cue release in wood frog (Lithobates sylvaticus) tadpoles to better understand the function of disturbance cues across aquatic prey. Groups of tadpoles underwent simulated predator attacks to obtain disturbance cues. The groups were either familiar and related, unfamiliar and related, familiar and unrelated, or unfamiliar and unrelated. To assess the relative potency of each cue, we used a behavioral bioassay design involving activity changes in independent tadpole receivers (unfamiliar and unrelated to the donors). If tadpoles use disturbance cues to signal related and/or familiar individuals, we predicted increased fright responses in receivers to cues obtained from those groups. However, we detected no effect of audience composition, indicating that tadpoles release similar disturbance cues regardless of audience kinship or familiarity. Nevertheless, disturbance cues evoked a consistent antipredator response in receivers indicating that these chemicals still act as reliable risk cues. Further comparative studies using audience effects are necessary to understand how disturbance cues have evolved across aquatic prey. Significance statement: When aquatic prey encounter predators and are frightened, they release chemicals known as "disturbance cues" into the water. These chemicals alert other prey nearby of potential danger. For example, wood frog tadpoles release disturbance cues when they are being chased by a predator. Tadpoles that smell the disturbance cues of other tadpoles are less likely to be eaten by predators. Since wood frog tadpoles are often found in shallow ponds filled with both familiar siblings as well as other tadpoles that are unfamiliar and unrelated, we wondered if tadpoles would produce more disturbance cues when familiar or related tadpoles were nearby. Here, we show that no matter who the audience members are, familiar siblings or not, tadpoles release disturbance cues that cause similar fright. This suggests that disturbance cues are not released differently depending on the audience in this species. [ABSTRACT FROM AUTHOR]

Signal divergence and sensory preferences may lead to sexual isolation and eventually promote speciation between animal populations. However, few studies have quantified the degree of chemical signal divergence and scent-mediated sexual isolation in lizard populations. Geographic and ecological variations among populations of the whiptail lizard Aspidoscelis lineattissimus suggest that there might be chemical signal divergence among these populations. Here, we used gas chromatography-mass spectrometry to characterize and compare the chemical composition of the femoral gland secretions of male whiptail lizards of four populations from a western region of Mexico and, through behavioral experiments, explored the effects of lizard scents on precopulatory behaviors and intrasexual male-male chemical recognition among populations. Our results showed that males of each population contain a divergent mixture of compounds in their femoral gland secretions. Differential chemosensory behavior indicated that male and female lizards discriminated and were more attracted to scents of lizards from their same population. Although females also seem to discriminate male scents between populations, their associated preference to territories scent-marked by males of their own population is different between regions (eastern vs western) and not between populations. We suggest that between some populations of A. lineattissimus there may be partial premating isolation mediated by chemical signals and behavioral divergence. Significance statement: Geographic variation in sexual signals can strongly affect discrimination and recognition abilities among reproductive individuals from divergent populations, resulting in sexual isolation and speciation. Studies suggest that reproductive isolation and speciation in lizard systems may be mediated by chemical signals, male mate preferences, and male-male interactions but not by female mate preferences. Using gas chromatography-mass spectrometry techniques and behavioral experiments, we found that chemical divergence in femoral gland secretions of male Aspidoscelis lineattissimus influences behavioral discrimination among four distinct populations. Males and females recognized and responded more toward lizard scents from their own population. In addition, some female populations were able to discriminate between territories scent-marked by males from different populations. We suggest that chemical and behavioral differences between populations may influence partial premating isolation, which can be mediated by inter and intrasexual interactions. [ABSTRACT FROM AUTHOR]

Frankliniella occidentalis causes significant damage to berry crops in Mexico. Traps may be used for monitoring or mass‐trapping thrips populations. Generally, colour traps are used for monitoring thrips, but sometimes a chemical stimulus can be added to the traps. However, there is conflicting information about what colour is the most attractive and efficient for capturing F. occidentalis. In this study, we first evaluated six colours of adhesive traps for catching F. occidentalis in blackberries grown in tunnels or in an open field. Subsequently, using the most attractive trap colour, we assessed the biological activity of neryl (S)‐2‐methylbutanoate and (R)‐lavandulyl acetate, components of the pheromone aggregation of F. occidentalis. Finally, we examined the effect of neryl (S)‐2‐methylbutanoate dosage rates on the number of captured thrips. We found that blue (tunnel) and yellow (open field) followed by violet traps captured a significantly greater number of F. occidentalis compared with the white, black and green traps. Our results confirm that neryl (S)‐2‐methylbutanoate is the only component necessary for enhancing the performance of coloured traps. Blue and yellow traps baited with 200–400 µg of neryl (S)‐2‐methylbutanoate increased the capture 2.5–3 times compared to unbaited traps. In all experiments, traps captured more females than males in blackberries grown in tunnels, whereas the opposite was found in blackberries cultivated in the open field. These results constitute the first step in the development of a monitoring system for F. occidentalis in soft fruit crops in Mexico. [ABSTRACT FROM AUTHOR]

Laboratory experiments have shown that the viability of embryos of the invasive cane toad (Rhinella marina) can be reduced by exposure to chemical cues from older conspecific larvae. These effects (very strong in laboratory trials) may offer an exciting new approach to controlling this problematic invasive species in Australia. However, the degree to which the method works in natural environments has yet to be assessed.Our experiments in the laboratory and in seminatural outdoor waterbodies show that chemical cues from tadpoles do indeed suppress the growth, development, and survival of conspecific larvae that are exposed as embryos and do so in a dose‐dependent manner; higher tadpole densities cause greater suppression of embryos.In seminatural outdoor waterbodies, suppressor‐exposed tadpoles were less than half as likely to survive to metamorphosis as were controls, and were much smaller when they did so and hence, less likely to survive the metamorph stage. Additionally, female cane toads were less likely to oviposit in a waterbody containing free‐ranging (but not cage‐enclosed) tadpoles, suggesting that the presence of tadpoles (rather than the chemical cues they produce) may discourage oviposition.Broadly, our results suggest that the suppression effect documented in laboratory studies does indeed occur in the field also, and hence that we may be able to translate that approach to develop new and more effective ways to reduce rates of recruitment of peri‐urban populations of cane toads in their invasive range. [ABSTRACT FROM AUTHOR]

Many animals have evolved mechanisms to detect and avoid parasitized conspecifics, primarily through odour cues, but whether birds are capable of odour-mediated parasite avoidance is unknown. Recently, we showed that exposing song sparrows (Melospiza melodia) to avian malaria parasites (Plasmodium sp.) alters the chemical composition of their preen oil, which is the major source of body odour in birds. Here, we presented song sparrows with preen oil from uninfected (sham-inoculated) and malaria-infected conspecifics, predicting that birds would spend more time with odour cues from uninfected than infected birds. Birds without detectable malarial infections spent about 50% more time with preen oil from uninfected than infected conspecifics, and females spent nearly twice as much time with preen oil from uninfected than infected conspecifics. However, neither difference was statistically significant. Song sparrows may be able to detect odour cues of infection, but further experiments are needed to confirm or refute this. [ABSTRACT FROM AUTHOR]

Nesting mortality in birds is caused primarily by predation. The ability to use different predator cues to assess the level of predation risk could be essential to minimize the predation risk during the breeding period. Previous studies show that birds modified their parental behavior when they detected chemical or visual cues of predators in the surrounding of the nest. However, according to the threat sensitivity hypothesis, birds may use more than one predator cue in order to accurately assess the level of predation risk. In this assessment, the behavior of predators can provide important information to evaluate the motivation of the predator to launch an attack. However, there are no studies that examined the importance of chemical, visual and behavioral cues of predators on the antipredatory behavior of birds. We examined the antipredatory behavior of blue tit Cyanistes caeruleus parents when they were exposed to live predators or stuffed models of predators that also had predator chemical cues. Blue tits were able to detect the behavioral cues of predators and exhibited greater antipredatory behaviors when exposed to a live predator than to a stuffed model with chemical cues. The results suggest that birds use the chemical, visual and behavioral cues of the predators to assess the level of predation risk and adjust their antipredatory behavior accordingly. [ABSTRACT FROM AUTHOR]

Gnathiid isopods are common crustacean parasites that inhabit all oceans from shorelines to depths of over 3000 m and use chemical cues to find their marine fish hosts. While gnathiids are host-generalists, hosts vary in their susceptibility to infestation. However, the mechanisms that mediate differential susceptibility are unknown. Here we used a combination of field and laboratory experiments to investigate if the chemical attractiveness of hosts explains differences in susceptibility of Caribbean reef fishes to infestation by a common Caribbean gnathiid isopod, Gnathia marleyi. We showed that while G. marleyi can detect and locate hosts using only chemical cues, they do not exhibit a preference for chemical cues produced by more susceptible fish species. We conclude that species-specific chemical cues are not the main mechanism driving differences in host susceptibility to gnathiid isopod infestation and that visual or post-attachment factors such as ease of obtaining a blood meal are likely mediators. [ABSTRACT FROM AUTHOR]

Group living often requires strong levels of communication between individuals. This communication is usually studied in the context of visual or auditory communication. However, chemical communication is the most widely used form of communication. We examined the role of chemical communication in mediating social decisions in a group‐living lizard, Egernia stokesii. Specifically, we examined the extent to which scat‐piling, a behaviour by which individuals deposit scat in a communal area, affected the refuge choice of individual E. stokesii. To achieve this, we examined individual refuge choice in response to scat piles or single scats and against two types of scat stimuli, one being their own scat and the other being scat belonging to an unrelated and unfamiliar conspecific. We show that lizards behave differently when presented with a scat pile compared with a single scat, and whether the scat stimulus was their own or sourced from an unfamiliar conspecific. When scats were in piles, individuals spent more time inspecting, more time in, and more often chose the treatment refuge as their final refuge choice, at a trial's end, when the treatment was their own scat compared with when the treatment was the refuge with the unfamiliar scat. In contrast, for individual scat treatments, individuals spent more time inspecting and more often ended up in the treatment refuge with an unfamiliar scat compared with when the treatment was their own scat. These results suggest that individuals are responding to information contained within multiple components of the scats – both their volume and their source. These results have implications for understanding how social aggregations are maintained within squamates, where sociality has evolved independently from other vertebrate lineages. [ABSTRACT FROM AUTHOR]

The European eel Anguilla anguilla Linnaeus 1758 is critically endangered with recruitment estimated at 5–10% of historical levels. Enhancing survival of recruits is pivotal for conservation, and restoration should consider habitat choice of elvers ascending river systems. We experimentally show that newly ascended elvers choose small pebble habitat over finer and larger substrates, regardless of the presence or absence of piscivore chemical cues, indicating no predator‐induced change in substrate choice. Enriching habitats with this substrate fraction should enhance eel recruitment as well as biodiversity at large. [ABSTRACT FROM AUTHOR]

Intraspecific communication is essential for agonistic and mating behaviours. Agonistic strategy of males must change according to the sex of opponents and that of females is also dependent on their physiological state as to whether they are brooding or not. We have analysed here the agonistic encounters between pairs of male and female crayfish in various combinations to reveal the interaction between agonistic and mating behaviours. After male crayfish became dominant, they aggressively chased subordinate males with attacks, while they did not attack female opponents. Furthermore, the agonistic behaviour of males changed depending on whether females were ovigerous or not. On the other hand, two females showed intense combats despite being ovigerous or not. Crayfish discriminated the sex of opponents via chemical signals in the urine. However, the dominant and subordinate social order of crayfish had no effect on selecting mating partners. [ABSTRACT FROM AUTHOR]

In social bees, the choice of food sources is based on several factors, including scent marks, color, and location of flowers. Here, we used similar setups, in which two stingless bee species, Melipona subnitida and Plebeia flavocincta , and the Western honeybee, Apis mellifera , were tested regarding the importance of chemical cues, color cues, and location-dependent cues for foraging behavior. It was determined whether workers chose food sources according to (1) scent marks deposited by conspecifics, (2) the color hue of a food source, (3) the trained location or the proximity of a food source to the hive. All three species preferred the scent-marked over an unmarked feeder that was presented simultaneously, but M. subnitida showed a weaker preference compared to the other species. When trained to blue feeders all three bee species preferred blue, but A. mellifera showed the strongest fidelity. The training to yellow feeders led to less distinct color choices. Only workers of M. subnitida mostly orientated at the training position and the close proximity to the nest. Whether the distance of a feeding site influenced the choice was dependent on the tested parameter (color or scent marks) and the species. Workers of M. subnitida preferably visited the feeder closer to the nest during the scent mark trials, but choose randomly when tested for color learning. Worker honeybees preferred the closer feeding site if trained to yellow, but not if trained to blue, and preferred the more distant feeder during the scent mark trials. Workers of P. flavocincta preferred the closer feeder if trained to blue or yellow, and preferred the more distant feeder during the scent mark trials. The disparity among the species corresponds to differences in body size. Smaller bees are known for reduced visual capabilities and might rely less on visual parameters of the target such as color hue, saturation, or brightness but use scent cues instead. Moreover, the dim-light conditions in forest habitats might reduce the reliability of visual orientation as compared to olfactory orientation. Honeybees showed the most pronounced orientation at floral color cues. [ABSTRACT FROM AUTHOR]

Foraging is key for most animals, because their energy and matter income depend on food ingestion. However, animals may respond adaptively to perceived competitor and/or predator proximity by modifying their foraging rates. Increased foraging activity is expected to improve the chances of succeeding in competition. However, the benefits of increased foraging activity could be offset by the risks of increased conspicuousness to predators. Plus, starvation may have counteracting or additive effects on foraging behaviour. Here, we test these hypotheses in larval Iberian ribbed newts (Pleurodeles waltl). We estimated foraging rates of individuals haphazardly assigned to either a restricted or an unrestricted-feeding regime, in water with (1) self-odour as control, (2) predator Dytiscus sp. chemical cues, and (3) competitor conspecific larva chemical cues. Treatments were presented in a random sequence. Newt larvae responded to either predator or conspecific chemical cues by increasing foraging rates relative to the control. Conspecific chemical cues increased foraging rates over the other two treatments. Feeding regime did not modify larva response to perceived predator and competitor proximity. Increased foraging rates in the presence of conspecific chemical cues could simultaneously improve larval energetic status to face competition and reduce prey available for the competitor. Intermediate foraging rates in the presence of predator chemical cues suggest a trade-off between the benefits (likely improved energetic status or accelerated metamorphosis) and the costs (likely increased conspicuousness) of increased food ingestion. These results prove that larval newts adjust foraging rates to perceived predator and competitor proximity. [ABSTRACT FROM AUTHOR]

Epidermal club cells (ECCs) are present in many species of teleost fish. In an attempt to justify their presence in the epidermis of fish, they have been associated with numerous functions. One proposed function is communication with conspecifics during a predation event, as these cells may passively release substances upon rupture, which may occur during predation. We identified the presence and distribution of ECCs in the body skin of adult cardinal tetra, Paracheirodon axelrodi (Schultz, 1956) and analyzed the animal's behavioral response to conspecific skin extract in a laboratory setting. The identification and distribution of ECCs in the epidermis of the animals were confirmed by conventional histology and immunohistochemistry. Our results demonstrated that: ECCs are present in the skin of the entire body; a high density is observed in the dorsal side from head to tail, in the insertion of the fins and in the epidermis covering them; and ventral distribution is less extensive and more dispersed than dorsal distribution. Treatment of P. axelrodi specimens with skin preparations of conspecifics resulted in behavioral changes in the animals: they showed erratic swimming movements, they showed avoidance of the area of stimulus application and they decreased the time spent moving. Overall, these results allow us to conclude that P. axelrodi possesses ECCs throughout the body, with a greater presence in areas of high exposure to predation events (dorsal area and fins). Animals exposed to conspecific skin extract showed a significant increase in behaviors described as anti-predatory in other species. This supports the hypothesis that ECCs may be the origin of chemical alarm cues that are passively released when skin damage occurs, alerting the rest of the group to the risk of predation. • Epithelial club cells of the fish Paracheirodon axelrodi are mainly localized in areas of high predation exposure. • Epithelial club cells of P. axelrodi are similar to those described in Cypriniformes. • P. axelrodi responds to conspecific skin extracts with antipredator behavior. [ABSTRACT FROM AUTHOR]

Aquatic invertebrates utilize multiple forms of sensory perception including chemical signaling, to evaluate their surrounding environment. The hermit crab Calcinus latens is able to detect external chemical cues within the complex coral rubble habitat. These discrete chemicals whether emanated from a potential predator, competitor or conspecific are received through chemosensory structures and elicit a specific behavioral response. This study examines the effect of four chemical treatments (control-ambient sea water, predator-Octopus bocki, potential competitor-Saron marmoratus and conspecific-Calcinus latens) on the number of times an individual Calcinus latens is observed in active, exploratory behavior verses stationary, defensive behavior. The results demonstrate a significant difference in the amount of time observed in defensive behaviors by the hermit crabs exposed to the treatment containing octopus chemical cues when compared to the other treatments. Across the four chemical treatments, there was a significant difference in the observed use of six specific behaviors, indicating a patterned behavioral response, unique for each treatment. Additionally, an experiment testing the response of Calcinus latens individuals to artificially introduced treatment species, (octopus Octopus bocki, shrimp Saron marmoratus as well as conspecifics) in which tested individuals could utilize all modes of sensory perception, was compared to the chemically stimulated behaviors. Analysis of the response behavior to chemical cues verses multimodal sensory assessment of actual treatment species demonstrated a statistically significant similarity in elicited behavior which underlines the importance of chemical signaling in modulating the behavior of Calcinus latens within the coral rubble microhabitat.

Several species of entomopathogenic nematodes have different host-seeking methods, and could be considered as "ambusher" or "cruiser". These differences may depend on how the nematodes detect the volatile signals used as cues for foraging. This study aimed to evaluate the locomotor response of Heterorhabditis amazonensis RSC5 to the compounds from root exudates of different plants, as well as to stimulants produced by the presence of insects or to the feeding activity of insects on plants. Arenas with agar-water substrates, containing root exudates from corn, bean, soybean, cucumber, garlic and tomato seedlings, were assembled to determine the substrates possibly preferred by H. amazonensis.Arenas with sand were also constructed to include, besides the seedling root exudates, treatments containing Spodoptera frugiperda, garlic seedlings and S. frugiperda feeding on garlic seedlings. The H. amazonensis species was attracted to the volatile chemicals emitted by all the root exudates tested, especially the exudate from garlic seedlings. However, it showed the greatest attraction to the combination of garlic seedlings and S. frugiperda, indicating that the search of H. amazonensis for its host is enhanced by the association between the insect and the volatile chemical compounds produced by plants, when attacked by insects.

The introduction of invasive species leading to decline of freshwater fauna is a major concern for conservation biologists. In this study we examined the effect of introduced Tilapia on the survival of the loach Lepidocephalichthys thermalis via predation experiments with Tilapia and a native predator, the Snakehead fish Channa gachua. Examining the chemoecology of prey-predator interactions, we found that L. thermalis failed to detect water-borne cues from Tilapia but did recognize cues from C. gachua, indicating innate predator recognition. We also observed that L. thermalis can learn to associate kairomones with Tilapia when conditioned with kairomones and injured conspecific cues. Trained L. thermalis showed higher survival during Tilapia predation trials. Thus under experimental conditions the vulnerability of L. thermalis to Tilapia predation due to failure to detect chemical cues can be reduced via associative training. It remains to be determined how useful this behavioral plasticity can be in wild L. thermalis populations exposed to introduced Tilapia.

Ant nests and their surrounding territories represent a hoard of trophic resources, as well as of stable and protected environments for many arthropods involved in commensal, mutualistic, or parasitic associations. Among these organisms, called myrmecophiles, several are butterflies. Here, we explore the amazing diversity of strategies developed by myrmecophilous butterflies to “cheat” or manipulate ants and to elude the tough defenses of the colony. During oviposition, female butterflies use visual or plant volatile signals to identify the presence of ants, whereas chemical and vibroacoustic cues, either isolated or combined, are used by larvae and pupae to attract, deceive, or appease workers. Examples of mimicry and eavesdropping on both intraspecific and interspecific signals are discussed, primarily referring to the obligate-parasitic interactions involving Maculinea butterflies and Myrmica ants. Multimodal communication is crucial to maintaining the strong cohesion and social structure of ant societies, but its corruption is at the base of the evolution and persistence of interspecific associations, which can be beneficial or detrimental for the colony's fitness. In this framework, the remarkable complexity of signaling could have prompted the evolution of specialized life cycles enhancing the extraordinary butterfly diversity.