Bold female zebrafish (Danio rerio) have physiological advantages in reproductive performance.

Simple SummaryBoldness is a widely studied personality trait that is positively related to an individual’s willingness to fight. To explore the agonistic behavior between female and male crabs with different degrees of boldness, we quantified the boldness of females and males using a behavior observation system and used the experimentally determined boldness and classification. The results showed that boldness affected the agonistic behavior between female and male swimming crabs, the fighting willingness and capacity of male crabs is higher than that of female individuals and is higher in bold crabs than in shy individuals. Energy reserves and metabolic rates may be one of the factors affecting the agonistic behavior in crabs and that the agonistic behavior resulted in significant changes in key energy metabolites.Individual differences in metabolism and agonistic behavior have been a key research area in evolution and ecology recently. In this study, we investigated the boldness of swimming crabs Portunus trituberculatus and explored the agonistic behavior between female and male crabs, specifically examining competitions between bold females vs. bold males (BF–BM), bold females vs. shy males (BF–SM), shy females vs. shy males (SF–SM), and shy females vs. bold males (SF_BM) and its relationship with energy metabolism. The main results revealed the following: There was no significant difference in boldness between females and males, while there were more bold individuals than shy in both females and males. Bold individuals initiated significantly more fights than shy individuals, and male initiators won significantly more fights than female initiators. The duration and intensity of fight between bold individuals was significantly higher than fights between shy individuals. For males, the concentration of glucose in the hemolymph was significantly higher in shy crabs than bold crabs, while there was no significant difference between shy and bold individuals in females. After fighting, the concentration of glycogen in claws was lower than that before fighting, and the concentrations of glucose and lactate in hemolymph were significantly higher after fighting than before. We found that the fighting willingness and ability were higher in male crabs than females and higher in bold crabs than shy. Fighting ability varied between sexes and was influenced by boldness and energy state.

Mirror-image stimulation (MIS) was used to determine the individual behavioral phenotypes of 90 adult, 132 yearling, and 135 young yellow-bellied marmots (Marmota flaviventris). Linear typal analysis (LTA) was used to group individuals based on similarities in their MIS scores. Principal component analysis (PCA) was used to evaluate the patterns of variation in behaviors and discriminant function analysis (DFA) was used to determine if there were consistent differences in marmot behavior. LTA produced two interpretable groups that were significantly and negatively correlated. Marmots in each group formed a shy-bold continuum. Bold animals were those that approached the mirror early and made nose contact with the image whereas shy animals approached the mirror late in the run, spent time in the back half of the arena, and frequently chirped at the image. Behaviors shifted with age; young were predominantly bold and adults were predominantly shy. This shift appears to be developmental and not genetically determined. Reliability and predictability analyses indicated that there is a 75% probability that a MIS run correctly identifies an individual's behavioral phenotype. The probability increases to 90% for those individuals with high loading scores. Play, agonistic, and amicable behaviors of female yearlings recorded in the field were significantly correlated with their MIS behavioral phenotypes whereas only play of male yearlings was so correlated. Correlations among eight life-history traits of adult females were independent of behavioral phenotypes. Shy females were more likely to be associated with female non-kin, produced more daughters, and were more likely to be immigrants. Among female yearlings, shy phenotypes were likely to become recruits and bold phenotypes were more likely to disperse. Bold adult females recruited yearlings regardless of their behavioral phenotype whereas shy adult females recruited primarily shy yearlings and the majority of bold yearlings dispersed. Among adult males, shy phenotypes were more likely to be territorial-colonial and to produce more young. Lifetime reproductive success (LRS) of females was strongly related to the number of years of residency, which was strongly correlated with the frequency of reproduction and the production and recruitment of offspring. The demographic patterns were independent of behavioral phenotype. Behavioral phenotype impacts demographic trends mainly by increasing the recruitment of daughters by bold females. LRS of males depends on the length of residency. Shy males have a higher LRS because they are territorial-colonial for a longer time and produce more young. Bold individuals appear to be those that are sub- ordinate and attempt to affiliate with other marmots whereas shy individuals appear to be dominant and less likely to be affiliative. By being more aggressive, the shy marmot is more likely to achieve residency as a yearling or adult whereas the more affiliative adult is more likely to recruit offspring, but affiliative yearlings are less likely to become recruits, especially when the adults are the dominant, “shy” individuals.

Sex differences in a shoaling-boldness behavioral syndrome, but no link with aggression

Behavioural Biology: Fortune Favours Bold and Shy Personalities

Hypoxia often occurs in aquatic environments as dissolved oxygen (DO) concentration decrease to a level where it is detrimental to aquatic organisms. To investigate the effects of hypoxia on the physiology of zebrafishes (Danio rerio), the organisms were kept at normoxic conditions (DO: 8±0.3mgL(-1): control group) or were subjected to mild (DO: 3±0.3mgL(-1)) or severe hypoxia (DO: 1±0.2mgL(-1)) for 48h and a subsequent restoration of oxygen concentrations (DO: 8±0.3mgL(-1)) for another 96h at 25°C. We found that the enzyme activities show different initial responses, acclimation and recovery to severe hypoxia relative to normoxic conditions, but no significant difference was observed between normoxic conditions and mild hypoxia. The results suggest that zebrafishes can acclimate to the mild hypoxia (3mgL(-1)) quickly but oxidative damage would occur when DO decreased below 1mgL(-1). Our findings could be useful for water resource managers to set protection limits of DO for aquatic organisms.

Personality and behavioral syndromes are of significant interest to a wide range of biological disciplines. Recent research using network analysis techniques has revealed widespread variation among individuals in sociability, which is a major axis of personality that creates the social microenvironment in which individuals express all other behaviors. We investigated the relationship between sociability and boldness, another fundamental personality axis, using a wild population of eastern grey kangaroos ( Macropus giganteus ) tested in their natural environment. We studied 2 dimensions of sociability (grouping behavior and association patterns). Over 2 years we found significant within-individual consistency and interindividual variation in the foraging group sizes of 171 females. Network analysis comparisons of 103 females between the years, using HWIG (an association index that controls for gregariousness), showed that individuals were also highly consistent in their social network measures. We tested the boldness of 51 of these females 6–21 times each over 18 months, using flight initiation distance tests; individuals were also highly consistent in this measure of personality. Shy females had significantly larger mean foraging group sizes. After controlling for gregariousness and space use, shy females had fewer preferred associates than bolder females. Therefore, boldness can have an important influence on the size and composition of foraging groups and thus social networks, in wild mammals.

Animal space use is affected by spatio-temporal variation in food availability and/or population density and varies among individuals. This inter-individual variation in spacing behaviour can be further influenced by sex, body condition, social dominance, and by the animal’s personality. We used capture-mark-recapture and radio-tracking to examine the relationship between space use and personality in Eurasian red squirrels (Sciurus vulgaris) in three conifer forests in the Italian Alps. We further explored to what extent this was influenced by changes in food abundance and/or population density. Measures of an individual’s trappability and trap diversity had high repeatability and were used in a Principal Component Analysis to obtain a single personality score representing a boldness-exploration tendency. Males increased home-range size with low food abundance and low female density, independent of their personality. However, bolder males used larger core-areas that overlapped less with other males than shy ones, suggesting different resource (food, partners) utilization strategies among personality types. For females, space use-personality relationships varied with food abundance, and bolder females used larger home ranges than shy ones at low female density, but the trend was opposite at high female density. Females’ intrasexual core-area overlap was negatively related to body mass, with no effect of personality. We conclude that relationships between personality traits and space use in free-ranging squirrels varied with sex, and were further influenced by spatio-temporal fluctuations in food availability. Moreover, different personality types (bold-explorative vs. shy) seemed to adopt different space-use strategies to increase access to food and/or partners.

The present study aimed to investigate the reversibility of endocrine disruption in zebrafish (Danio rerio) at different effect levels. For this purpose, three different endocrine disrupting chemicals (EDCs) were chosen according to their different modes of action. 17!- Ethinylestradiol (EE2), a semi-synthetic estrogen is the most popular substance in oral contraceptives and is regularly measured in surface waters. 17s-trenbolone is an anabolic steroid, which binds with high affinity to the androgen receptor. The substance is used in industrial animal farming and sports as muscle growth promoter. Prochloraz is a popular fungicide with multiple modes of action. Its main effect on the endocrine system is that it inhibits the enzyme aromatase, which is essential for the conversion of androgens into estrogens. The effects of those three EDCs were assessed by performance of exposure experiments with developing zebrafish. After exposure of 60 days (from fertilized egg to sexual differentiation), half of the fish were continuously exposed until 100 days post hatch and the other half was held in clean water. In addition, this project focuses on assessing the correlation between different levels of biological organization. For this purpose, five effect levels with different ecological relevance were investigated: (1) population level: sex ratio; (2) individual level: growth; (3) organ/cell level: histology of gonads; (4) protein level: vitellogenin (VTG) induction and (5) mRNA level: aromatase (cyp19b) expression in brain. The three different EDCs investigated in this study showed strong impact on the sexual development of zebrafish at all effect levels at environmentally relevant concentrations. For trenbolone and prochloraz we could only find tendencies of reversibility, most effects remained unchanged after 40 days of depuration in clean water. Despite different underlying mechanisms, these substances produce an irreversible and considerable drift of the sex ratio towards males, as well as permanent effects on growth, VTG and aromatase levels. A clear reversibility of those effects could only be shown for EE2. Even at population level the impact of the semi-synthetic estrogen was reversible. These results show that the sexual development of zebrafish is a fragile process that can easily be disrupted permanently by substances that are found in the environment. Moreover, the results indicate that even a periodic exposure to those EDCs can cause severe impairment for wildlife and humans.

Triterpene betulin may be involved in the acute effects of pulp and paper mill effluent on testis physiology in zebrafish

Effects of UV filters (benzophenones and octocrylene) and mifepristone on different life stages of zebrafish (Danio rerio)

Developmental exposure of zebrafish (Danio rerio) to bisphenol-S impairs subsequent reproduction potential and hormonal balance in adults

Waves of follicle development, growth and degeneration in adult ovary of zebrafish (Danio rerio) on chronic exposure to environmental estrogens in laboratory

Effects of butachlor on reproduction and hormone levels in adult zebrafish (Danio rerio)

In a number of animal species, individuals differ in their ability to solve cognitive tasks. However, the mechanisms underlying this variability remain unclear. It has been proposed that individual differences in cognition may be related to individual differences in behavior (i.e., personality); a hypothesis that has received mixed support. In this study, we investigated whether personality correlates with the cognitive ability that allows inhibiting behavior in 2 teleost fish species, the zebrafish Danio rerio and the guppy Poecilia reticulata. In both species, individuals that were bolder in a standard personality assay, the open-field test, showed greater inhibitory abilities in the tube task, which required them to inhibit foraging behavior toward live prey sealed into a transparent tube. This finding reveals a relationship between boldness and inhibitory abilities in fish and lends support to the hypothesis of a link between personality and cognition. Moreover, this study suggests that species separated by a relatively large phylogenetic distance may show the same link between personality and cognition, when tested on the same tasks.

Long term exposure to tris (2-chloroethyl) phosphate (TCEP) causes alterations in reproductive hormones, vitellogenin, antioxidant enzymes, and histology of gonads in zebrafish (Danio rerio): In vivo and computational analysis