Spatial and temporal variations of the ectoparasites of seven reef fish species from Lizard Island and Heron Island, Australia

Spatial and temporal variations in abundance of ectoparasites from 7 coral reef" fish species Illernigymnus melapterus (Labridae), Siganus doliatus (Siganidae), Scolopsis bilineatus (Nemipteridae), Thalassoma lunare (Labridae), Scants sordidus (Scaridae), Ctenochaetus striatus (Acanthuridae), and Acanthochromis polyacanthus (Pomacentridae)I at 2 locations, Lizard Island and Heron Island in the Great Barrier Reef, were investigated. The study demonstrates that there is a significant species-specific parasite fauna which is conserved over space and time. Host identity explained most of the variation in parasite composition and abundance while host size explained a smaller proportion of the variation. For each species the parasite assemblage showed little variation among local, but physically varied, sites. Species-specific patterns of parasite abundance were similar between widely separated locations, although there were more categories of parasites at the northern location, Lizard Island. Parasite numbers and species composition among fish species at Lizard Island did not vary among collection times except for S. doliatus, which had a 7-fold increase between May 1992 and January 1993, mainly due to dactylogyridean monogeneans. Parasite abundance was positively correlated with fish standard length for 3 fish species

Image scoring and cooperation in a cleaner fish mutualism

Humans are highly social animals and often help unrelated individuals that may never reciprocate the altruist's favour. This apparent evolutionary puzzle may be explained by the altruist's gain in social image: image-scoring bystanders, also known as eavesdroppers, notice the altruistic act and therefore are more likely to help the altruist in the future. Such complex indirect reciprocity based on altruistic acts may evolve only after simple indirect reciprocity has been established, which requires two steps. First, image scoring evolves when bystanders gain personal benefits from information gathered, for example, by finding cooperative partners. Second, altruistic behaviour in the presence of such bystanders may evolve if altruists benefit from access to the bystanders. Here, we provide experimental evidence for both of the requirements in a cleaning mutualism involving the cleaner fish Labroides dimidiatus. These cleaners may cooperate and remove ectoparasites from clients or they may cheat by feeding on client mucus. As mucus may be preferred over typical client ectoparasites, clients must make cleaners feed against their preference to obtain a cooperative service. We found that eavesdropping clients spent more time next to 'cooperative' than 'unknown cooperative level' cleaners, which shows that clients engage in image-scoring behaviour. Furthermore, trained cleaners learned to feed more cooperatively when in an 'image-scoring' than in a 'non-image-scoring' situation

Cleaner fish cause predators to reduce aggression toward bystanders at cleaning stations

Mutualisms, in which both participants gain a net benefit, are ubiquitous in all ecosystems, and the importance of understanding their broader ecological context has been demonstrated many times. Indirect effects of mutualisms may have important implications for surrounding ecosystems through changes in density, species composition, or behavior; however, the latter has been difficult to quantify. In fish cleaning mutualisms, cleaners benefit by removing and consuming ectoparasites from clients, whereas clients benefit from a reduction in parasite load. Cleaner fish are also thought to benefit from immunity to predation and use tactile stimulation as a preconflict management strategy to manipulate partners' decisions and to avoid being eaten by piscivorous client fish. Here we show, using a laboratory experiment, that the presence of cleaner fish resulted in nearby fish not involved in the cleaner-client mutualism experiencing less aggression (chases) from predatory clients. In addition, the rate that piscivorous clients chased prey was negatively correlated with the amount of tactile stimulation given to the predator by the cleaner. These data suggest that, in the laboratory, the risk of aggression from predators toward nearby prey fish was greatly reduced as a by-product of cleaner fish presence and tactile stimulation of predators by cleaner fish. These results raise the question of whether cleaning stations act as safe havens from predator aggressio

The role of serotonin in the modulation of cooperative behavior

We examined the modulatory role of serotonin in cooperation between unrelated individuals. The identification of the neurohormonal candidates that may modulate levels of cooperation in marine cleaning mutualisms has been a major aim in recent years. Our results provide evidence that serotonin is a driver of cooperative behavioral activities and contribute to the understanding of neural pathways of cooperation, which aim to unravel the basic drive of animal tendencies to cooperate with other

Cortisol mediates cleaner wrasse switch from cooperation to cheating and tactical deception

Recent empirical research, mostly done on humans, recognizes that individuals' physiological state affects levels of cooperation. An individual's internal state may affect the payoffs of behavioural alternatives, which in turn could influence the decision to either cooperate or to defect. However, little is known about the physiology underlying condition dependent cooperation. Here, we demonstrate that shifts in cortisol levels affect levels of cooperation in wild cleaner wrasse Labroides dimidiatus. These cleaners cooperate by removing ectoparasites from visiting 'client' reef fishes but prefer to eat client mucus, which constitutes cheating. We exogenously administrated one of three different compounds to adults, that is, (a) cortisol, (b) glucocorticoid receptor antagonist mifepristone RU486 or (c) sham (saline), and observed their cleaning behaviour during the following 45. min. The effects of cortisol match an earlier observational study that first described the existence of "cheating" cleaners: such cleaners provide small clients with more tactile stimulation with their pectoral and pelvic fins, a behaviour that attracts larger clients that are then bitten to obtain mucus. Blocking glucocorticoid receptors led to more tactile stimulation to large clients. As energy demands and associated cortisol concentration level shifts affect cleaner wrasse behavioural patterns, cortisol potentially offers a general mechanism for condition dependent cooperation in vertebrates

Dopamine disruption increases negotiation for cooperative interactions in a fish

Humans and other animals use previous experiences to make behavioural decisions, balancing the probabilities of receiving rewards or punishments with alternative actions. The dopaminergic system plays a key role in this assessment: for instance, a decrease in dopamine transmission, which is signalled by the failure of an expected reward, may elicit a distinct behavioural response. Here, we tested the effect of exogenously administered dopaminergic compounds on a cooperative vertebrate's decision-making process, in a natural setting. We show, in the Indo-Pacific bluestreak cleaner wrasse Labroides dimidiatus, that blocking dopamine receptors in the wild induces cleaners to initiate more interactions with and to provide greater amounts of physical contact to their client fish partners. This costly form of tactile stimulation using their fins is typically used to prolong interactions and to reconcile with clients after cheating. Interestingly, client jolt rate, a correlate of cheating by cleaners, remained unaffected. Thus, in low effective dopaminergic transmission conditions cleaners may renegotiate the occurrence and duration of the interaction with a costly offer. Our results provide first evidence for a prominent role of the dopaminergic system in decision-making in the context of cooperation in fish.info:eu-repo/semantics/publishedVersio

Cue-based decision rules of cleaner fish in a biological market task

To develop an evolutionary theory of social decision making, we require an understanding of how individuals utilize environmental cues to form decision rules. We exposed ‘cleaner’ fish (bluestreak cleaner wrasse, Labroides dimidiatus) to a biological market task, where giving priority to an ephemeral (i.e. ‘visitor’ client) food plate, over a permanent (i.e. ‘resident’ client) plate, doubled the food reward. Previously published experiments revealed that adult cleaners from a complex social environment regularly solved this task and outperformed adult cleaners from a simple social environment as well as juveniles from both habitat types. In these studies, plates were differentiated by colour and/or colour pattern. However, client size is another potentially useful cue that may be used by cleaners to solve the biological market task in nature, as visitor clients are typically larger than resident clients. Here, we tested cleaners in a setting where plates differed only in size and not colour/pattern: the majority of cleaners exhibited a spontaneous preference for inspecting larger plates or were more likely to reach the task-solving criterion if the visitor plate was larger. All cleaners were able to solve the task when we incorporated both size and colour/pattern cues; however, only cleaners from the complex social environment settled on the more precise colour/pattern cue. In contrast, cleaners from the simple social environment relied on size as the primary, yet less precise, cue to solve the task. In conclusion, our results strongly suggest that intraspecific variation in the performance of cleaners in the biological market task is based on variation in the relative salience of available cues and correlates with variation in a cleaner's natural social environment. Variation in the relative salience of available cues may therefore explain a portion of the intra- and interspecific variance in cognitive performance and social behaviour documented in other animal species

Cleaner shrimp remove parasite eggs on fish cages

Benthic stages of cultured fishes' ectoparasites are a major contributor to persistent reinfections in aquaculture. These stages are resistant to chemical therapies and are costly to manage in terms of time and labour. Cleaner shrimp, unlike cleaner fishes, prey on benthic stages, suggesting they have the potential to reduce parasite reinfection pressure without having to be in direct contact with the client fish. Cleaner shrimp have never been used as biocontrols in commercial aquaculture, but offer an advantage over cleaner fishes in that they are not susceptible to the ectoparasites of their clients. We present the first investigation of a cultured cleaner shrimp, Lysmata vittata, as a biocontrol agent against the eggs of the economically important cosmo politan ectoparasite Neobenedenia girellae infecting cultured juvenile grouper, Epinephelus lanceolatus, under simulated recirculating aquaculture conditions. L. vittata removed the eggs of N. girellae entangled on the mesh of the culture cages and significantly reduced N. girellae recruitment to fish by similar to 87%. Our results demonstrate the value of cleaner shrimp in addressing ectoparasite problems and highlight the importance of investigating novel biocontrol strategies in aquaculture