A central simplifying assumption in evolutionary behavioral ecology has been that optimal behavior is unaffected by genetic or proximate constraints. Observations and experiments show otherwise, so that attention to decision architecture and mechanisms is needed. In psychology, the proximate constraints on decision making and the processes from perception to behavior are collectively described as the emotion system. We specify a model of the emotion system in fish that includes sensory input, neuronal computation, developmental modulation, and a global organismic state and restricts attention during decision making for behavioral outcomes. The model further includes food competition, safety in numbers, and a fluctuating environment. We find that emergent strategies in evolved populations include common emotional appraisal of sensory input related to fear and hunger and also include frequency-dependent rules for behavioral responses. Focused attention is at times more important than spatial behavior for growth and survival. Spatial segregation of the population is driven by personality differences. By coupling proximate and immediate influences on behavior with ultimate fitness consequences through the emotion system, this approach contributes to a unified perspective on the phenotype, by integrating effects of the environment, genetics, development, physiology, behavior, life history, and evolution.

Diel vertical migration of a natural population of Daphnia longispina was investigated experimentally in enclosures twice in 1985. The amount of available food was manipulated and vertical distributions were recorded at times of low (night) and high (day) risk of predation from fish. In the first experiment, the large D. longispina displayed diel migrations. When food was depleted experimentally, however, the large animals were near the surface during both day and night. In the second experiment, large D. longispina first began to migrate after being provided with ingestionrate-saturating concentrations of food. Vertical migrations in D. longispina seemed to reflect a trade off between two conflicting interests: avoiding predation and risking starvation. This trade off was balanced by the overall amount of available food, restricting migrations of the large animals when food was scarce.

BackgroundIn host-parasite evolutionary arms races, parasites are generally expected to adapt more rapidly, due to their large population sizes and short generation times. There exist systems, though, where parasites cannot outpace their hosts because of similar generation times in both antagonists. In those cases concomitant adaptation is expected.MethodsWe tested this hypothesis in the three-spined stickleback-Schistocephalus solidus tapeworm system, where generation times are comparable in both organisms. We chose two populations of sticklebacks which differ prominently in the prevalence of S. solidus and consequently in its level of selective pressure. We performed a full factorial common garden experiment. Particularly, Norwegian (NO) and German (DE) sticklebacks, as well as hybrids between both stickleback populations and in both parental combinations, were exposed each to a single S. solidus originating from the same two host populations.ResultsWe found the infection phenotype to depend on the host population, the parasite population, but not their interaction. NO-parasites showed higher infectivity than DE-parasites, with NO-sticklebacks also being more resistant to DE-parasites than to the sympatric NO-parasite. Reciprocally, DE-hosts were more susceptible to the allopatric NO-parasite while DE-parasites grew less than NO-parasites in all stickleback groups. Despite this asymmetry, the ratio of worm to host weight, an indicator of parasite virulence, was identical in both sympatric combinations, suggesting an optimal virulence as a common outcome of parallel coevolved systems. In hybrid sticklebacks, intermediate infection rates and growth of S. solidus from either origin suggests a simple genetic basis of resistance. However, comparison of infection phenotypes in NO-maternal and DE-maternal hybrid sticklebacks indicates local adaptation to the sympatric counterpart in both the host and the parasite.ConclusionsHost-parasite systems with similar generation time show evidence for concomitant reciprocal adaptation resulting in parasite optimal virulence and host parasite specific resistance.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1419-3) contains supplementary material, which is available to authorized users.

Captive birds and mammals reared in enriched rearing environments have been shown to behave more flexibly compared to animals reared in impoverished or plain environments. Recent evidence has shown that this is also true for fish; enrichment promotes faster recovery after a stressful experience, a higher propensity for exploration of novel areas and the development of more sophisticated social behaviour. Here we report how enrichment influences social learning in juvenile cod Gadus morhua that were reared in either spatially enriched or plain tanks. Naïve juvenile cod were allowed to repeatedly observe experienced tutors as they foraged on gammarid or mysid prey, or control tutors that acted as social stimuli but did not forage. The naïve fish then received a mixture of mysid and gammarid prey. Enriched-reared fish improved their ability to consume live prey in the presence of foraging tutors, but plain-reared fish did not. Although gammarids were consumed more often and more quickly than mysids, both among tutors and naïve fish, social learning from tutors demonstrating mysid hunting and consumption had its greatest effect on social learning in the enriched fish.

The physiological effects of salmon lice infections on post-smolt of Atlantic salmon were examined by experimentally infecting hatchery reared post-smolts with infective copepodids. Even at high infection intensities, ranging from 30-250 lice per fish, early chalimus stages did not have severe, physiological effects on the fish. There was a sudden increase in fish mortality after the appearance of preadult I stages. Infected fish were then suffering due to lesions and osmoregulatory failure. Plasma chloride level increased significantly and total protein, albumin and haematocrit decreased significantly in infected compared to uninfected fish. All infected fish became moribund before adult lice appeared. Infection intensities above 30 salmon lice larvae per fish thus appear to cause death of Atlantic salmon post-smolt soon after the lice reach their pre-adult stage. 1996 The Fisheries Society of the British Isles

Sea trout did not develop symptoms or gross clinical signs of infectious salmon anaemia (ISA) when injected with ascites from salmon, but ISA virus was propagated and haematocrit values dropped. The virus was transmitted from trout to salmon.1995 The Fisheries Society of the British Isles

No abstract

No abstract