Kleptoparasitic prey competition in shoaling fish: effects of familiarity and prey distribution

Familiarity is thought to stabilize dominance hierarchies andreduce aggressive interactions within groups of socially livinganimals. Though familiarity has been widely studied in shoalingfish, few studies have investigated changes in prey competitionas a function of time spent together within groups of initiallyunfamiliar individuals. In this study, we created shoals ofthree-spined stickleback (Gasterosteus aculeatus) and monitoredchanges in foraging rates and related competitive behaviorswithin shoals over a 4-week period in experimental series whereprey was spatially and temporally concentrated or dispersed.Prey share was unequal under both prey distribution modes, anddisparity in prey share was not seen to change as trials progressed.Interestingly, the contest rate for prey items fell over timewhen individuals were competing for dispersed prey but not whenprey were concentrated. We found no evidence that fish showedassociation preferences for either group members that had consumeda greater or lesser proportion of prey during trials. Thoughthe intensity of competition may be reduced by increased groupstability in nature, this is likely to be strongly dependenton the way prey resources are distributed through space andtime.     

Avian prey-dropping behavior. I. The effects of prey characteristics and prey loss

Numerous species of birds break hard-shelled prey items by droppingthemfrom a height. This intriguing prey-extraction method providesan excellentopportunity for studying foraging behavior becausea single, easily measurablequantity—height of drop—maybe influenced by a wide variety ofidentifiable characteristicsof the prey (e.g., breakability, weight) andsocial environment(e.g., alone or in the presence of kleptoparasites). Usingadynamic, state variable modeling approach, this paper presentsthe firsttheoretical framework for avian prey-dropping systemsthat incorporates thediversity of prey characteristics andsocial situations. The model yielded aseries of qualitativepredictions about prey-dropping behavior that can betestedreadily in any prey-dropping system. In particular, the resultsindicatedthat quantitative and qualitative differences in item breakabilityandpotential kleptoparasitism should have a significant effecton the heightand pattern of prey dropping.     

Predatory behavior of the praying mantis,Tenodera aridifolia II. Combined effect of prey size and predator size on the prey recognition

Predatory behavior of the praying mantis,Tenodera aridifolia, as a function of the combined effect of its size and the size of the prey was investigated by using prey models. Behavioral responses were almost identical through the nymphal development in the predator. As the mantis grew, it attacked larger prey models, suggesting that it recognizes the prey's size in accordance with its own body size. Regression analyses demonstrate that the ratio of the prey's volume to the cube and the square of the predator's length is a more important parameter for prey recognition than are the one-dimensional parameters of the prey's and the predator's sizes.     

The dynamics of prey choice in fish: the importance of prey size and satiation

Over a number of decades the process of prey choice has been investigated using fishes as model predators. Using fishes for the model has allowed the proximate factors that determine how a mobile predator finds and chooses to eat the prey encountered within a variable 3‐D environment to be estimated. During prey choice a number of constraints exist, in particular most fish predators will eat their prey whole thus their jaws and gut create functional limitations once a prey has been attacked. By considering the relationship between the size of the prey and the predator's feeding apparatus and feeding motivation this study explores the link between mechanistic studies and theoretical, optimal foraging based predictions. How the prediction of prey choices made by the fish following prey encounter can be reconciled with what is likely to be found in the fish's stomach is discussed. This study uses a progression of empirical examples to illustrate how the limits of functional constraints and prey choice at different stages of motivation to feed can be taken into account to improve predictions of predator prey choice.     

Implications of a fluctuating fish predator guild on behavior, distribution, and abundance of a shared prey species: the grass shrimp Palaemonetes pugio

In some systems, the identity of a prey species' dominant predator(s) may not be constant over time. In cases in which a prey species exhibits different responses to various predator species, such changes in predator identity may have population-wide consequences. Our goals were to determine (1) whether mortality of and refuge use by the grass shrimp, Palaemonetes pugio, were predator-specific, and (2) how effects of prey size and habitat interacted with predator type. Striped bass (Morone saxatilis) exerted twice as much predation pressure as mummichog (Fundulus heteroclitus), although not equally as great on large (female) and small (male) shrimp. Mummichog, which fed preferentially on large shrimp, forced a partitioning of habitat between the two shrimp size classes. In contrast, large and small shrimp occupied similar habitats when subjected to striped bass, which fed on both size classes equally. Refuge use of grass shrimp depended on predator type. In the presence of mummichog, which occupied shallower depths in the water column than striped bass, shrimp stayed deep and close to structural habitat. Striped bass, which were deeper, caused shrimp to move high in the water column away from structural habitat. When both predators were present, shrimp distribution was similar to that when only striped bass were present, striped bass predation rate was enhanced, and overall mortality was higher than with either predator alone. Results suggest that at times when mummichogs are the dominant predators, large (female) shrimp experience higher predation than small (male) shrimp and are physically separated from their potential mates. When striped bass are more abundant, male and female shrimp may share a similar, shallow, less structure-oriented distribution and be subjected to higher mortality. When both predators are present, mortality rates may be higher still. This predator-, size-, and habitat-specificity of grass shrimp behavior suggests significant population and distribution consequences of fluctuating predator guilds and fluctuating cover of structural habitats in the field.     

The effect of adrenalectomy upon the absorption,distribution and metabolism of ethanol in the rat

There was an increase in blood ethanol levels following the intraperitoneal or intravenous administration of ethanol to rats 8 days after adrenalectomy, compared to control animals. This was due to a 20% decrease in total body water and an increased rate of absorption following intraperitoneal administration. There was no change in the rate of ethanol metabolism.     

The effect of denervation upon the functional properties of myosin and its fragments.

A study has been made of some structural and enzymatic properties of myosin and its fragments from denervated white muscles of rabbit in the course of atrophy using different methods: UV-luminiscence, flow birefringence, electromicroscopy, viscosimetry and enzymatic measurements. All the studied parameters had a tendency to decrease; at prolonged observation some properties were partially restored. Considerable changes of structural properties of LMM were revealed: the ability of LMM from denervated muscle to form high-ordered structures which is characteristic of LMM from normal muscle decreased considerably.     

The functional response ofTyphlodromus pyri to its prey,Panonychus ulmi: the effect of pollen

We looked at the effect of the presence of pollen (Typha latifolia) on the functional response ofTyphlodromus pyri (Phytoseiidae) toPanonychus ulmi (Tetranychidae) in the laboratory. We found that pollen significantly reduced the predation rate but that the magnitude of the effect was not large. Over the lower range of prey densities the effect appeared to be due to a decrease in search efficiency.     

Predatory behavior of the praying mantis,Tenodera aridifolia I. Effect of prey size on prey recognition

Predatory behavior and effect of prey size of the praying mantis,Tenodera aridifolia, was investigated using three-dimensional prey models. Parameters of prey such as width, length, shape (length/width), area (width×length) and volume were investigated for effects on Watch and Attack responses. Regression analyses suggest that volume is the most important variable in prey recognition. This behavioral trait is considered adaptive, since prey volume is the most reliable measurement for the energy content of the prey.     

The functional response of Typhlodromus pyri to its prey, Panonychus ulmi: the effect of pollen

We looked at the effect of the presence of pollen (Typha latifolia) on the functional response of Typhlodromus pyri (Phytoseiidae) to Panonychus ulmi (Tetranychidae) in the laboratory. We found that pollen significantly reduced the predation rate but that the magnitude of the effect was not large. Over the lower range of prey densities the effect appeared to be due to a decrease in search efficiency.     

Wasp uses venom cocktail to manipulate the behavior of its cockroach prey

The sting of the parasitoid wasp Ampulex compressa is unusual, as it induces a transient paralysis of the front legs followed by grooming behavior and then by a long-term hypokinesia of its cockroach prey. Because the wasp's goal is to provide a living meal for its newborn larva, the behavioral changes in the prey are brought about by manipulating the host behavior in a way beneficial to the wasp and its offspring. To this end, the wasp injects its venom cocktail with two consecutive stings directly into the host's central nervous system. The first sting in the thorax causes a transient front leg paralysis lasting a few minutes. This paralysis is due to the presence of a venom component that induces a postsynaptic block of central cholinergic synaptic transmission. Following the head sting, dopamine identified in the venom appears to induce 30 min of intense grooming. During the long-term hypokinesia that follows the grooming, specific behaviors of the prey are inhibited while others are unaffected. We propose that the venom represses the activity of head ganglia neurons thereby removing the descending excitatory drive to the thoracic neurons.Abbreviations CNS central nervous system - DA dopamine - GI giant interneuron - PSP postsynaptic potential - SEG sub-esophageal ganglion - TI thoracic interneuron     

The relationship between fish assemblages and the helminth communities of a prey fish, in a group of small shallow lakes

Galaxias maculatus (small puyen) is an abundant native fish distributed in lakes and rivers of the Patagonia, and it is the frequent prey of other fishes, fish-eating birds, and mammals. Previous studies have shown that it is parasitized by 33 metazoan species and that the richness and composition of the parasite communities vary between lakes. The aim of the present work was to analyze the relationship between the composition of fish assemblages and the helminth component community structure of G. maculatus . Ten environmentally similar, small, shallow lakes, belonging to the Nahuel Huapi Lake basin, were chosen because of the differences in the native fish assemblages. Parasite community structure in G. maculatus varied according to the fish assemblage of each lake. The presence of the piscivorous fish Percichthys trucha regularly produced variations in the composition and richness at the component and infracommunity levels, as well as the percentage of autogenic parasite species in G. maculatus .     

Uptake and distribution of radioiodine, and the effect of ambient nitrate, in some fish species

125I uptake by the thyroid was most pronounced in the smelt (Osmerus eperlanus), perch (Perca fluviatilis), rainbow trout (Salmo gairdneri), roach (Rutilus rutilus) and bleak (Alburnus alburnus). Unlike other tissues, only the muscle in the species studied no relative accumulation of 125I as compared to the ambient water. The Crusian carp (Cyprinus carassius) indicated the lowest levels of accumulation of 125I among the species tested. Thyroid radioiodine concentration was independent of the length of the fish in the rainbow trout and perch. In the rainbow trout, however, the liver and muscle radioiodine concentrations decreased significantly with increasing length of the fish. Exposure of rainbow trout to water containing supranormal concentration of nitrate (1500 micrograms/l) resulted in lowered 125I uptake. The same phenomenon was observed for the perch and Crusian carp, with low nitrate concentrations, while with higher nitrate concentrations, the uptake levels were again increased. Thyroid function, as judged from the conversion ratio and T/S ratio, was not affected by nitrate.     

Species composition,distribution, and behavior of fish on the Vavilov Underwater Ridge (the Atlantic Ocean)

From the data of commercial landings and underwater observations on the Vavilov Ridge (the eastern part of the Atlantic Ocean), approximately 50 bottom, near bottom, and near bottom-pelagic fish species of 38 families are recorded. The following species have the highest commercial importance: mackerel scads Decapterus longimanus,and D. macarellus,,mackerel Scomner japonicus, Beryx splendens, Allocyttus guineensis, Epigonus affinis,,etc.     

The bottlenose dolphin Tursiops truncatus foraging around a fish farm：Effects of prey abundance on dolphins＇ behavior

The extent to which prey abundance influences both bottlenose dolphin foraging behavior and group size in the presence of human activities has not previously been studied.The primary aim of this study was to identify and quantify how wild bottlenose dolphins respond,individually and as groups,to the relative abundance of prey around a fish farm.Detailed views of dolphins＇ behavior were obtained by focal following individual animals whilst simultaneously collecting surface and underwater behavioral data.A total of 2150 dive intervals were analyzed,corresponding to 342 focal samples,lasting over 34 hours.Bottlenose dolphins remained submerged for a mean duration of 46.4 seconds and a maximum of 249 seconds.This study provides the first quantified data on bottlenose dolphin diving behavior in a marine fin-fish farm area.This study＇s results indicate that within a fish farm area used intensively by bottlenose dolphins for feeding,dolphins did not modify dive duration.Additionally,underwater observations confirmed that dolphins find it easier to exploit a concentrated food source and it appears that hunting tactic and not group size plays an important role during feeding activities.Thus,bottlenose dolphins appear capable of modifying their hunting tactics according to the abundance of prey.When top predators display behavioral responses to activities not directed at them,the task of studying all possible effects of human activities can become even more challenging.