Unpredictable Feeding Research Articles

Feeding predictability as a cognitive enrichment protects brain function and physiological status in rainbow trout: a multidisciplinary approach to assess fish welfare

Cognitive enrichment is a promising but understudied type of environmental enrichment that aims to stimulate the cognitive abilities of animals by providing them with more opportunities to interact with (namely, to predict events than can occur) and to control their environment. In a previous study, we highlighted that farmed rainbow trout can predict daily feedings after two weeks of conditioning, the highest conditioned response being elicited by the combination of both temporal and signalled predictability. In the present study, we tested the feeding predictability that elicited the highest conditioned response in rainbow trout (both temporal and signalled by bubbles, BUBBLE + TIME treatment) as a cognitive enrichment strategy to improve their welfare. We thus analysed the long-term effects of this feeding predictability condition as compared with an unpredictable feeding condition (RANDOM treatment) on the welfare of rainbow trout, including the markers in the modulation of brain function, through a multidisciplinary approach. To reveal the brain regulatory pathways and networks involved in the long-term effects of feeding predictability, we measured gene markers of cerebral activity and plasticity, neurotransmitter pathways and physiological status of fish (oxidative stress, inflammatory status, cell type and stress status). After almost three months under these predictability conditions of feeding, we found clear evidence of improved welfare in fish from BUBBLE + TIME treatment. Feeding predictability allowed for a food anticipatory activity and resulted in fewer aggressive behaviours, burst of accelerations, and jumps before mealtime. BUBBLE + TIME fish were also less active between meals, which is in line with the observed decreased expression of transcripts related to the dopaminergic system. BUBBLE + TIME fish tented to present fewer eroded dorsal fin and infections to the pathogen Flavobacterium psychrophilum. Decreased expression of most of the studied mRNA involved in oxidative stress and immune responses confirm these tendencies else suggesting a strong role of feeding predictability on fish health status and that RANDOM fish may have undergone chronic stress. Fish emotional reactivity while isolated in a novel-tank as measured by fear behaviour and plasma cortisol levels were similar between the two treatments, as well as fish weight and size. To conclude, signalled combined with temporal predictability of feeding appears to be a promising approach of cognitive enrichment to protect brain function via the physiological status of farmed rainbow trout in the long term.

Skill Acquisition and Development Issues with Predictable Badminton Feeding Routines

Badminton practice designs contain feeding routines that allow players to practice technical skills. Optimal skill acquisition and development is gained through practice simulating competitive match play rather than approaches centred around mass repetition with low levels of uncertainty. This study aimed to evaluate the biomechanical differences in twelve youth elite UK badminton players in activities with varying levels of predictability. The three experimental trials were handfeed, multifeed and match play trials. Motion capture cameras were used to record participant biomechanical data. Data analysis revealed several significant biomechanical differences between trials. Results showed that an increase in trial unpredictability led to increased depth of the forward lunge shot and a lower racket shuttlecock strike position with greater forward trunk bend. This study showed that visual search behaviour in badminton is a key component of the forward lunge shot. Predictable practice feeding routines may cause poor skill acquisition and development through maladaptive learning behaviours. Coaches are recommended to implement unpredictable feeding practice routines to simulate the visual search behaviour of competitive badminton match play to enhance skill acquisition and development in youth elite badminton players.

Winter mortality of young mudskipper fish: Effects of size, temperature and energy depletion

Winter mortality can be a strong selective pressure on animals living in temperate regions, especially for young and small individuals. Therefore, understanding the mechanism for its size-dependence is important to predict population dynamics of the species in a fluctuating environment. In this study, we experimentally investigated the effects of body size, temperature and energy reserve depletion on the overwinter mortality of young mudskipper fish (Boleophthalmus pectinirostris). Small size-class fish (<44 mm in SL) died earlier than large size-class fish (≥44 mm) under both heated and unheated temperature conditions. Relatively higher energy and lipid content in live compared to dead fish and suspended mortality during the warm period under unheated conditions suggested the effects of both energy depletion and low temperature on overwinter mortality. Small size-class fish showed a relatively higher energy depletion rate under both temperature conditions probably due to their higher mass-specific metabolic rate. Since small size-class fish died earlier than large size-class fish, the body size difference in energy depletion rate may be one of the factors affecting the size-dependence of overwinter mortality. The energy depletion rate gradually decreased with the progress of experiment, suggesting that fasting-induced metabolic depression occurred. The estimated relative lipid mass decreased with the progress of experiment. The lipid depletion rate with elapsed days significantly reduced in small size-class fish under unheated conditions comparing with large size-class fish, while the rate in large size-class fish was significantly larger than that of small size-class fish in heated conditions. The difference suggests the possibility that small size-class fish switches metabolic fuels at a relatively lower temperature condition to maintain a minimum activity level for unpredictable feeding opportunities during the pre-winter season.

Seasonal changes in yolk hormone concentrations carry-over to offspring traits

Yolk hormones are substances which transmit non-genetic factors from the mother to the next generation. The systematic changes of yolk hormone concentrations within asynchronously hatching clutches have been interpreted as a means to adaptively shape the offspring’s phenotype. However, in synchronously hatching clutches the role of yolk hormones is less understood. We investigated whether seasonal changes between eggs in the yolk hormones testosterone (Testo), progesterone (Prog) and corticosterone (Cort) also occur in the grey partridge, a synchronously hatching precocial species without direct food competition between siblings. Specifically we asked whether yolk hormone concentrations systematically vary with season and whether they affect the offspring’s hatching mass, mass gain, circulating baseline and stress-induced Cort. Additionally, we investigated the effect of genetic background and food availability on yolk hormone concentrations by subjecting grey partridge hens of two strains (wild and domesticated) to two different feeding regimes (predictable vs. unpredictable feeding) during egg laying. We hypothesized that egg hormone concentrations change over the season, but breeding in captivity over many generations and ad libitum food access could have resulted in domestication effects which abolished potential seasonal effects. Results showed that progressing season had a strong positive effect on yolk Prog and yolk Testo, but not on yolk Cort. Feeding regimes and strain had no effect on yolk hormones. Offspring mass and mass gain increased and baseline Cort decreased with progressing season. In addition, yolk Testo correlated positively with offspring mass gain and negatively with baseline Cort, while yolk Prog had a positive correlation with baseline Cort. Strain and feeding regimes of the mother had no effect on offspring traits. In conclusion, grey partridge chicks hatching late in the season might benefit from the increased concentrations of the growth-stimulating yolk Testo and by this catch-up in development. Hence, yolk hormone concentration could adaptively shape the offspring phenotype in a precocial species.

Fluctuations in nutrient composition affect male reproductive output in Drosophila melanogaster

Insects are known to selectively balance their intake of protein and carbohydrate to optimize reproduction and survival. For insects who feed on decomposing fruit, fluctuations in macronutrient composition occur as fruits ripe and decomposition progresses which may challenge optimal resource allocation. Using Drosophila melanogaster, we tested the effect of macronutrient fluctuations and the variability of these fluctuations on starvation resistance and components of reproductive output; traits known to be sensitive to different protein to carbohydrate (P:C) ratios in the diet. For 8 days, flies were fed the same protein to carbohydrate (P:C) ratio (constant feeding), or fed diets with fluctuations in P:C ratio on each day; these fluctuations being regular (predictably fluctuating) or irregular (unpredictably fluctuating). The three feeding regimes yielded the same average P:C ratio across the duration of the experiment. We found no difference in starvation resistance across the feeding regimes. Interestingly, there was a sexual dimorphism in the effect on reproductive output with males performing worst in the unpredictable feeding regime, and with no effect of feeding regime on female performance. Our study provides evidence for means of adapting to fluctuating macronutrient composition and suggests females are more tactful than males in storing and allocating resources for reproduction.

The development of fault bars in domestic chickens (Gallus gallus domesticus) increases with acute stressors and individual propensity: implications for animal welfare

AbstractNegative experiences during feather growth can result in fault bar formation. Fault bars are malformations perpendicular to the rachis of the feather caused by stressful experiences during feather growth. However, there are little data on the causal effect of psychological stress on the formation of fault bars in chickens. The objective of this study was to examine the effect of acute stress in domestic chickens (Gallus gallus domesticus) on fault bar formation to validate this measure as a welfare indicator. Thirty broiler breeder pullets were housed in six cages at 21 days of age. Three cages were exposed to an acute stress protocol while the other three were the unstressed control. Feathers were marked as close as possible to the growing follicle at 21 (wing feathers) and 60 (all feathers) days of age. Acute stress came in the form of three procedures (unpredictable feed delivery, induction of tonic immobility, and crowding) repeated twice, 3-8 days apart and randomly, from 28 to 60 days of age. Wing, tail, and cover feathers were removed and measured at 60 days of age for weight, length, and number of fault bars. Exposure to acute, unpredictable stress increased the number of fault bars in wing feathers of chicks with a high number of initial fault bars. Feather growth decreased for the stressed group compared to the control. These results suggest that feather traits, including fault bars and feather growth, can be used as indicators of negative welfare in chickens.

Meeting in the middle: Hybrid clay three-dimensional fabrication processes for bio-reef structures

Despite the relative accessibility of clay, its low cost and reputation as a robust and sustainable building material, clay three-dimensional printing remains an under-utilized digital fabrication technique in the production of architectural artefacts. Given this, numerous research projects have sought to extend the viability of clay three-dimensional digital fabrication by streamlining and automating workflows through computational methods and robotic technologies in ways that afford agency to the digital and machinic processes over human bodily skill. Three-dimensional printed clay has also gained prominence as a resilient material well suited to the design and fabrication of artificial reef and habitat-enhancing seawall structures for coastal marine environments depleted and disrupted by human activity, climate change and pollution. Still, these projects face similar challenges when three-dimensional printing complex forms from the highly plastic and somewhat unpredictable feed material of clay. In response, this article outlines a research project that seeks to improve the translation of complex geometries into physical clay artefacts through additive three-dimensional printing processes by drawing on the notion of digital craft and giving focus to human–machine interaction as a collaborative practice. Through the case study of the 1:1 scale fabrication of a computationally generated bio-reef structure using clay as a feed material and a readily available Delta Potterbot XLS-2 ceramic printer, the research project documents how, by exploiting the human ability to intuitively handle clay and adapt, and the machine’s ability to work efficiently and with precision, humans and machines can fabricate together. With the urgent need to develop more sustainable building practices and materials, this research contributes valuable knowledge of hybrid fabrication processes towards extending the accessibility and viability of clay three-dimensional printing as a resilient material and fabrication system.

Feeding ecology and sexual dimorphism in a speciose flower beetle clade (Hopliini: Scarabaeidae).

The relationship between feeding ecology and sexual dimorphism is examined in a speciose South African monkey beetle clade. We test whether feeding and mating at a fixed site (embedding guild) is associated with greater levels of sexual dimorphism and possibly sexual selection than species using unpredictable feeding resources (non-embedding guild). Sexual dimorphism was measured using a point scoring system for hind leg and colour across the two feeding guilds for >50% of the regional fauna. Quantification of hind leg dimorphism using a scoring system and allometric scaling were used to identify traits subject to sexual selection. Feeding guild had a significant effect on hind leg dimorphism, with embedders having high and non-embedders low scores. The sessile and defendable distribution of females on stable platform flowers may favour contests and associated hind leg weaponry. In contrast, degree of colour dimorphism between the sexes was not associated with any particular feeding guild, and may serve to reduce male conflict and combat. Embedder males had high proportions (∼76%) of species with positive allometric slopes for almost all hind leg traits. For male non-embedders, only ∼37% of species showed positive scaling relationships. Phylogenetic data, in conjunction with behavioural data on the function of leg weaponry and visual signalling among males is needed to better understand the link between sexual dimorphism and sexual selection in the radiation of the monkey beetles.

Assessment of Body Condition in African (Loxodonta africana) and Asian (Elephas maximus) Elephants in North American Zoos and Management Practices Associated with High Body Condition Scores.

Obesity has a negative effect on health and welfare of many species, and has been speculated to be a problem for zoo elephants. To address this concern, we assessed the body condition of 240 elephants housed in North American zoos based on a set of standardized photographs using a 5-point Body Condition Score index (1 = thinnest; 5 = fattest). A multi-variable regression analysis was then used to determine how demographic, management, housing, and social factors were associated with an elevated body condition score in 132 African (Loxodonta africana) and 108 Asian (Elephas maximus) elephants. The highest BCS of 5, suggestive of obesity, was observed in 34% of zoo elephants. In both species, the majority of elephants had elevated BCS, with 74% in the BCS 4 (40%) and 5 (34%) categories. Only 22% of elephants had BCS 3, and less than 5% of the population was assigned the lowest BCS categories (BCS 1 and 2). The strongest multi-variable model demonstrated that staff-directed walking exercise of 14 hours or more per week and highly unpredictable feeding schedules were associated with decreased risk of BCS 4 or 5, while increased diversity in feeding methods and being female was associated with increased risk of BCS 4 or 5. Our data suggest that high body condition is prevalent among North American zoo elephants, and management strategies that help prevent and mitigate obesity may lead to improvements in welfare of zoo elephants.

Walking Behavior of Zoo Elephants: Associations between GPS-Measured Daily Walking Distances and Environmental Factors, Social Factors, and Welfare Indicators.

Research with humans and other animals suggests that walking benefits physical health. Perhaps because these links have been demonstrated in other species, it has been suggested that walking is important to elephant welfare, and that zoo elephant exhibits should be designed to allow for more walking. Our study is the first to address this suggestion empirically by measuring the mean daily walking distance of elephants in North American zoos, determining the factors that are associated with variations in walking distance, and testing for associations between walking and welfare indicators. We used anklets equipped with GPS data loggers to measure outdoor daily walking distance in 56 adult female African (n = 33) and Asian (n = 23) elephants housed in 30 North American zoos. We collected 259 days of data and determined associations between distance walked and social, housing, management, and demographic factors. Elephants walked an average of 5.3 km/day with no significant difference between species. In our multivariable model, more diverse feeding regimens were correlated with increased walking, and elephants who were fed on a temporally unpredictable feeding schedule walked 1.29 km/day more than elephants fed on a predictable schedule. Distance walked was also positively correlated with an increase in the number of social groupings and negatively correlated with age. We found a small but significant negative correlation between distance walked and nighttime Space Experience, but no other associations between walking distances and exhibit size were found. Finally, distance walked was not related to health or behavioral outcomes including foot health, joint health, body condition, and the performance of stereotypic behavior, suggesting that more research is necessary to determine explicitly how differences in walking may impact elephant welfare.

Early experiences matter: a review of the effects of prenatal environment on offspring characteristics in poultry

Early life experiences can be important in determining offspring phenotypes and may influence interaction with the environment and hence health, welfare, and productivity. The prenatal environment of poultry can be divided into the pre-lay environment and the egg storage/incubation environment, both of which can affect offspring outcomes. The ability to separate maternal and egg/incubation effects makes birds well suited to this type of research. There are many factors, including feeding and nutrition, environmental conditions, husbandry practices, housing system, social environment, infectious environment, and maternal health status, that can influence both the health and performance and behavior and cognition of the offspring. There are some aspects of the environments that can be changed to produce beneficial effects in the offspring, like addition of certain additives to feed or short changes in incubation temperatures, while other aspects should be avoided to reduce negative effects, such as unpredictable feeding and lighting regimens. Measures of offspring characteristics may prove to be a useful method of assessing parent stock welfare if known stressors result in predictable offspring outcomes. This has the advantage of assessing the parent environment without interfering with the animals and possibly affecting their responses and could lead to improved welfare for the animals.

STEREOTYPIC BEHAVIORS IN BEARS

Confined bears are deprived of natural stimulus, such as large roaming domains, active foraging and enriched habitats, making them vulnerable to develop stereotypic behaviors. Motivation drives and neuro-pathological imbalance are the causes. Various stereotypic behavior types have been reported, including oral, head and locomotory related behaviors, and pacing are the most commonly seen. Stereotypic behavior level could be monitored using an observation-reporting system or fecal corticoid. Environmental and feeding enrichment are the proposed solutions; however, habituation could be developed. Parallel intermittent and consecutive environmental enrichment and unpredictable feeding schedule would be beneficial. Medication, especially long-term and low-dosage fluoxetine, was found to be effective in alleviating bear stereotypic behaviors.

Male-Biased Sex-Ratio of DunlinsCalidris alpinain the Gulf Of Gdańsk (Southern Baltic) During Autumn Migration

This long-term study (10 years) aimed to check if the sex-ratio of dunlins Calidris alpina at a stopover site in the southern Baltic region was biased. Two age classes among non-juvenile dunlins were recognised: immatures (2nd calendar year) and adults (> 2nd calendar year). There was a significant male bias in the sample of 4,406 non-juvenile dunlins captured during their southward migration. Overall, 60.3% of immatures and 59.4% of adults were males. Particularly among adults, the proportion of males increased significantly after the start of autumn migration. The annual sex-ratios were consistently male biased, but varied somewhat and fluctuated in parallel for adults and immatures. One plausible explanation for the male bias is that males and females differ in migration strategy. Females may make longer flights and avoid stopover sites with unpredictable feeding conditions, such as the southern Baltic coasts, which provide low quality habitat. Assuming a balanced non-juvenile population sex ratio, the ‘missing’ females could stopover elsewhere in the Baltic or fly directly to the tidal areas of the Wadden Sea. The sex ratio in the study area may depend on wind conditions during the early phase of autumn migration. In some years, adverse weather may force more females than usual to stopover in the study area.

Response of green hydra (Hydra viridissima) to variability and directional changes in food availability

AbstractNatural environments tend to be variable resulting in alternating periods of high and low food availability. Therefore, animals have to be able to accommodate to sudden environmental changes by adjusting their physiology and behaviour to new conditions. We investigated how simulated food variability affects life history traits (asexual reproduction and stress tolerance) and response to environmental change in laboratory experiments with green hydra (Hydra viridissima). We assigned hydra into four groups differing in feeding frequency (high or low) and food regularity (random or stable). After 21 days of accommodation, feeding frequency was changed (increased or decreased) in half of each group, the other half was kept as a control group. Hydra showed a delayed response to environmental change (increased or decreased feeding frequency). This delay in response was greater under an unpredictable feeding scheme. Animals on a random scheme had lower budding rates and lower stress tolerance. Follow-up experiments suggest that this might be due to receiving food on subsequent days, since we found that animals fed daily have lower budding rates than those fed on alternate days. We hypothesize that frequent feeding might cause high levels of oxidative/xenobiotic stress which could overwhelm the defence system of these animals.

CLOUD AND ONTOLOGY BASED KNOWLEDGE COLLABORATION - A DIGITAL OIL FIELD INITIATIVE

Continuous increase in oil pricing is not only causing difficulties to consumer but the imbalance in demand and supply is impacting the producer and refineries also. Consumer may adjust the demand dynamically as per the price fluctuation but oil major cannot change the production so dynamically. The recommended solution is the latest technology which could optimize the production, meeting the increasing but fluctuating demand at reasonable production price. Continuous increasing in oil prices and demand for crude, the hydrocarbon industry is serious in reaching to its full potential for value creation unless it is not developing the technological innovation. The emerging solution is Cloud based intelligent energy solution. Cloud based smart oil filed engineering is one of the initiative where the oil fields are mathematically modelled as a process industry with unpredictable feed (production). Real time engineering visualization and geospatial scientific computing integration on mobile system is major challenge. Cloud technology has opened an unrestricted universe for Hydrocarbon industry. Cloud Computing led Digital Oil Field is business-centric engineering solutions which has empowered the oil majors to optimize the resources, decreased infrastructure cost, ubiquitous access to business-centric integrated solution, easy engineering visualization and flexible business modelling, ultimately resulting reduction in the production cost of oil & gas. The cloud based solution is hired on demand service provides robust security, business, modelling, engineering solution, real time visualization, market analytics and management controls on smart mobile device. This paper talks about the case study of a cloud based application (name EICEbox) helping oil companies solving the complex engineering problem and providing the knowledge collaboration platform to oil and gas companies. Keywords— Cloud Computing, Cloud Ontology, Digital Oil field, Engineering Knowledge Management ---------------------------------------------------------------------***--------------------------------------------------------------------

The Effects of Feeding Unpredictability and Classical Conditioning on Pre-Release Training of White-Lipped Peccary (Mammalia, Tayassuidae)

Some authors have suggested that environmental unpredictability, accompanied by some sort of signal for behavioral conditioning, can boost activity or foster exploratory behavior, which may increase post-release success in re-introduction programs. Thus, using white-lipped peccary (Tayassu pecari), a vulnerable Neotropical species, as a model, we evaluated an unpredictable feeding schedule. Associating this with the effect of classical conditioning on behavioral activities, we assessed the inclusion of this approach in pre-release training protocols. The experimental design comprised predictable feeding phases (control phases: C1, C2 and C3) and unpredictable feeding phases (U1- signaled and U2- non-signaled). The animals explored more during the signaled and non-signaled unpredictable phases and during the second control phase (C2) than during the other two predictable phases (C1 and C3). The peccaries also spent less time feeding during the signaled unpredictable phase (U1) and the following control phase (C2) than during the other phases. Moreover, they spent more time in aggressive encounters during U1 than the other experimental phases. However, the animals did not show differences in the time they spent on affiliative interactions or in the body weight change during the different phases. The signaled unpredictability, besides improving foraging behavior, showing a prolonged effect on the next control phase (C2), also increased the competition for food. The signaled feeding unpredictability schedule, mimicking wild conditions by eliciting the expression of naturalistic behaviors in pre-release training, may be essential to fully prepare them for survival in the wild.

The adaptive function of hatching asynchrony: an experimental study in great tits

In many bird species offspring hatch over hours or days, which leads to an age and size hierarchy within broods. The function of hatching asynchrony is much debated, and it has been suggested that the induced size hierarchy among offspring may be an adaptive maternal mechanism for maximizing reproductive output under variable environmental conditions. The best known hypothesis to explain the adaptive value of hatching asynchrony, the ‘brood reduction’ hypothesis, holds that a size hierarchy among offspring allows for a quick adaptive adjustment of brood size to unpredictable feeding conditions and thus benefits parents. To test the consequences of hatching asynchrony on offspring growth and food provisioning we experimentally manipulated the onset of incubation of eggs within broods of great tits, Parus major , to induce either synchronous or asynchronous hatching, and then manipulated brood size after hatching to simulate favourable, control or harsh conditions. We did not find a difference in offspring mortality between asynchronous and synchronous broods under any of these conditions. In harsh conditions, nestling mass and size were reduced in asynchronous broods compared to synchronous ones. The opposite pattern occurred under control conditions. Although our results showed that induced hatching asynchrony alters offspring phenotype, they do not provide strong support for the brood reduction hypothesis as a mechanism to explain hatching asynchrony. • We tested the adaptive value of hatching asynchrony in great tits. • We induced either synchronous or asynchronous hatching. • We simultaneously manipulated the rearing conditions by changing brood size. • Nestling mortality did not differ between asynchronous and synchronous broods. • In enlarged broods, nestlings in asynchronous broods were lighter and smaller. • Our results do not support the brood reduction hypothesis.

Unpredictable Feeding Impairs Glucose Tolerance in Growing Lambs

Irregular eating is associated with insulin resistance and metabolic disease in adults but may affect young, growing children differently. We investigated the metabolic effects of unpredictable feeding in female juvenile lambs randomly assigned to receive, for six weeks, maintenance feed given twice daily in equal portions (Control Group, C; n = 24) or the same weekly feed amount in aliquots of variable size at unpredictable times (Unpredictable Group, U; n = 21). Intravenous glucose tolerance tests (IVGTT), insulin tolerance tests (ITT), and measurement of diurnal plasma cortisol concentrations were performed pre and post the dietary intervention. Groups were compared using t test and RM ANOVA. Weight gain was similar in both groups (C 18±2%; U 16±2% of initial body weight). Glucose area under the curve (AUC) was unchanged in C (AUC pre 818±34, post 801±33 mmol.min.l−1), but increased by 20% in U (pre 830±25, post 1010±19 mmol.min.l−1; p<0.0001), with an inadequate insulin response to glucose load (log(AUC insulin first 40 minutes) post intervention C 1.49±0.04 vs U 1.36±0.04 ng.min.ml−1; p = 0.03). Insulin tolerance and diurnal variation of plasma cortisol concentrations were not different between groups. Unpredictable feeding impairs insulin response to glucose in growing lambs despite high quality food and normal weight gain. Irregular eating warrants investigation as a potentially remediable risk factor for disordered glucose metabolism.

Investigating the influence of predictable and unpredictable feed delivery schedules upon the behaviour and welfare of Atlantic salmon parr (Salmo salar) using social network analysis and fin damage

Social network analysis was utilised to quantify the effect of short-term predictable (PD) and unpredictable (UD) feed delivery schedules of 10 days on behavioural interactions and the frequency and severity of fin damage in Atlantic salmon. Fin damage was only observed on the dorsal fin and its frequency and severity was significantly higher in UD compared to PD groups. Social networks analysis based on aggressive interactions showed a higher group degree-centrality, clustering coefficient, in-degree centrality and out-degree centrality in UD compared to PD groups. These results suggested a specific separation of roles in fish into initiators of aggression and receivers of aggression only in UD groups. Initiators were highly aggressive individuals and received very little aggression. Conversely, receivers were non hostile individuals and acted mainly as recipient of aggression. Also, initiators of aggressive interactions had less fin erosion and were heavier and longer than receivers of aggression. However, overall fish in PD were significantly more aggressive than fish in UD groups. The weight, length and condition factor did not differ significantly between fish subjected to predictable and unpredictable feed delivery. The higher level of and more severe dorsal fin erosion in the UD group is evidence of poorer welfare status in fish receiving unpredictable feeding schedules due to the development of an organised robust network where individual members attained distinct roles according to their aggressive behaviour.

Evolution of the Arctic Calanus complex: an Arctic marine avocado?

Before man hunted the large baleen whales to near extinction by the end of the nineteenth century, Arctic ecosystems were strongly influenced by these large predators. Their main prey were zooplankton, among which the calanoid copepod species of the genus Calanus, long considered key elements of polar marine ecosystems, are particularly abundant. These herbivorous zooplankters display a range of adaptations to the highly seasonal environments of the polar oceans, most notably extensive energy reserves and seasonal migrations to deep waters where the non-feeding season is spent in diapause. Classical work in marine ecology has suggested that slow growth, long lifespan and large body size in zooplankton are specific adaptations to life in cold waters with short and unpredictable feeding seasons. Here, we challenge this understanding and, by using an analogy from the evolutionary and contemporary history of the avocado, argue that predation pressure by the now nearly extinct baleen whales was an important driving force in the evolution of life history diversity in the Arctic Calanus complex.