Context-dependent aggregation in Common Frog Rana temporaria tadpoles: influence of developmental stage, predation risk and social environment

1. This study examines the aggregation behaviour and activity of larvae of the Common Frog Rana temporaria in relation to the early social environment, ontogeny and the presence of chemical cues from a predatory fish to address three main questions: (i) Does previous social interaction influence aggregation behaviour in later developmental stages? (ii) To what extent does aggregation behaviour depend upon the risk level perceived by the individual? (iii) Does aggregation behaviour change through ontogeny?
2. Tadpoles were reared from eggs either in small groups or in complete isolation. In relatively early stages of development, tadpoles showed no preference for the side of the test container containing siblings over the side containing no larvae regardless of the social context experienced (isolation or contact with siblings).
3. The presence of chemical cues from a potential predator did not trigger the aggregation behaviour of tadpoles, but it had a remarkable effect on their activity and spatial distribution. Tadpoles exposed to water preconditioned by a predator spent significantly less time swimming and avoided the central area of the test container more frequently than did controls exposed to unconditioned water.
4. Tadpoles were more active, avoided the central section and associated preferentially with conspecifics (siblings) at later stages of development regardless of the social conditioning they had previously experienced.
5. Individuals reared in groups were twice as active as individuals reared in isolation. This suggests that the early social environment experienced by larvae can influence future behaviour and thereby growth and development rates.
6. The expression of conspecific attraction is probably linked to an ontogenetic shift in larval behaviour. However, reduced activity, rather than aggregation, appears to be the basic antipredator mechanism in larval Common Frog.     

The effect of social environment during ontogeny on life history expression in the guppy Poecilia reticulata

The effects of the social environment during development on life-history decisions and adult behaviour were assessed using male guppies Poecilia reticulata . Males raised with adults developed secondary sexual characteristics later than males raised either singly or with four of their siblings indicating social inhibition of maturation was evident in P. reticulata . There was no effect, however, of rearing environment on male behaviour. The results reveal that social environment during development can influence life-history decisions but is less important than immediate social context in determining male behavioural phenotype in P. reticulata .     

Physiological and social constraints on growth of Arctic charr, Salvelinus alpinus L.: an investigation of factors leading to stunting

When stunted (runt) Arctic charr, Salvelinus alpinus , were reared together in small groups growth rates were low. Contrary to expectation, there did not arise a rapidly growing despot within each group. It is suggested that the narrow size range offish within groups prevented the rapid formation of clear-cut dominance hierarchies. Fish reared in isolation had significantly higher and more variable rates of growth than those held in groups, demonstrating that social interactions between individuals were responsible for growth suppression of grouped-reared fish. There were no significant differences in growth rates between fish allowed visual contact with conspecifics and those held in visual isolation, indicating that visual contact is insufficient to cause growth depensation in Arctic charr. Despite the fact that growth rates of stunted (runt) Arctic charr improved when they were held in isolation, the growth rates recorded were substantially lower than those of normal individuals reared under hatchery conditions. It is concluded that physiological (genetic) factors are important in the determination of the slow growth rates of stunted (runt) Arctic charr and that this trend is exacerbated by social interactions with more rapidly growing siblings.     

Social control of neuronal soma size

Factors responsible for sexual maturation differ significantly among vertebrate species. In many, age is most important, whereas in others seasonal or social cues play a central role. Here we report that maturation in the African cichlid fish Haplochromis burtoni is socially controlled, and that this control includes regulation of soma growth in a population of preoptic neurons immunoreactive to gonadotropin-releasing hormone (irGnRH). Males reared in aquaria among fish of the same age mature sexually in about 3 months, whereas males reared in the presence of older, more aggressive conspecifics remain immature even at 5 months of age. Immature males display hypogonadism and have conspicuously undersized preoptic irGnRH neurons in comparison to those of mature siblings of the same age. This variable maturation rate increases the likelihood that individual males will survive to an age when they can successfully reproduce.     

Putative chemical inhibition of development by conspecifics in mosquitofish, Gambusia affinis

The objective of this study was to test for a chemical influence of adult Gambusia affinis on the development and maturation of juveniles. Sixty juveniles (<1 day old) were reared (from a total of 157 trials) individually up to 115d in 3liter containers that circulated water bathing either (1) two adult males, (2) two adult females, (3) an adult male and an adult female, or (4) conspecific-free tank water. Randomly chosen juveniles were sampled over time, sacrificed, sectioned, and measurements were taken of standard length and gonadal parameters such as gonad size, number of spermatogenic cysts, or number of oocytes. Measurements were regressed as functions of time, and analyzed for significant differences by ANCOVA. A total of 32 males and 28 females were examined. Males showed no significant differences in any of the parameters, but females showed reduced growth rate and smaller ovary size when reared in water bathing two adult females. Mortality rate in these young fish was high, but Chi-square analysis showed that mortality rate was significantly higher when they were raised in water bathing at least one adult female. Females are known to influence female development in other vertebrates; our findings suggest this may also be true for a fish, and that the interaction may be through chemical communication.     

The development of the Jamming Avoidance Response (JAR) in Eigenmannia: An innate behavior indeed

Summary In its Jamming Avoidance Response (JAR), the gymnotiform electric fish Eigenmannia shifts its electric organ discharge (EOD) frequency away from similar interfering frequencies. Continual behavioral measurements were carried out in 164 juvenile fish until a correct JAR emerged. Sixty-four of these fish were raised in complete isolation, the remainder in a community of their siblings. A correct JAR emerged in fish of 1.2–1.6 cm in body length, corresponding to a developmental age of 24–32 days. In 6 of 164 fish, the emergence of a correct JAR followed an interim appearance of an incorrect JAR, which involved frequency shifts in the direction opposite to those of a correct JAR. The fish raised in isolation developed the same forms of behavior and showed the same sequence in their appearance as did socially raised fish. This indicates that the JAR and its developmental schedule are innate. The appearance of an incorrect JAR suggests initial errors or incompleteness in the wiring of central nervous connections. A correct JAR ultimately emerged even if a stimulus regimen was offered that rewarded frequency shifts in the direction opposite to those of a correct JAR. This indicates that the development of the JAR is immune to experimental alterations of sensory experience.Abbreviations Df frequency difference between a jamming stimulus and fish's EOD - ELL electrosensory lateral line lobe - EO electric organ - EOD electric organ discharge - JAR Jamming Avoidance Response - nE nucleus electrosensorius - nE subnucleus of nE, causing drop of EOD frequency - nE subnucleus of nE, causing rise of EOD frequency - Pn pacemaker nucleus - PPn prepacemaker nucleus     

Kin recognition in Bufo scaber tadpoles: ontogenetic changes and mechanism

Ontogenetic changes in kin-recognition behavior, effect of social environment on kin-recognition ability, and use of visual and chemical cues in kin recognition have been studied in tadpoles of Bufo scaber after rearing them with kin, in mixed groups, or in isolation from Gosner stage 12 (gastrula). By use of a rectangular choice tank the tadpoles were tested for their ability to choose between (a) familiar siblings and unfamiliar non-siblings, (b) unfamiliar siblings and familiar non-siblings, and (c) unfamiliar siblings and unfamiliar non-siblings. When tested without any stimulus groups in the end compartments of the tank, random distribution was observed for the tadpoles and no bias for the apparatus or the procedure. In the presence of kin and non-kin in the end compartments, significantly more tadpoles spent most of their time near kin (familiar or unfamiliar) rather than near non-kin during early larval stages, up to stage 37. After stage 37 (characterized by the differentiation of toes), test tadpoles showed no preference to associate with kin, suggesting an ontogenetic shift in the kin-recognition ability in B. scaber. In experiments involving selective blockade of visual or chemical cues the test tadpoles preferentially associated near their kin on the basis of chemical rather than visual cues. These findings suggest that familiarity with siblings is not necessary for kin recognition and that kin-recognition ability is not modified after exposure to non-kin by mixed rearing. The findings for B. scaber indicate a self referent phenotype matching mechanism of kin recognition which is predominantly aided by chemical rather than visual cues.     

Social interactions and cortisol treatment increase the production of aggressive electrocommunication signals in male electric fish,Apteronotus leptorhynchus

Brown ghost knife fish, Apteronotus leptorhynchus, continually emit a weakly electric discharge that serves as a communication signal and is sensitive to sex steroids. Males modulate this signal during bouts of aggression by briefly (approximately 15 ms) increasing the discharge frequency in signals termed "chirps." The present study examined the effects of short-term (1-7 days) and long-term (6-35 days) male-male interaction on the continuous electric organ discharge (EOD), chirping behavior, and plasma levels of cortisol and two androgens, 11-ketotestosterone (11KT) and testosterone. Males housed in isolation or in pairs were tested for short-term and long-term changes in their EOD frequency and chirping rate to standardized sinusoidal electrical stimuli. Within 1 week, chirp rate was significantly higher in paired fish than in isolated fish, but EOD frequency was equivalent in these two groups of fish. Plasma cortisol levels were significantly higher in paired fish than in isolated fish, but there was no difference between groups in plasma 11KT levels. Among paired fish, cortisol levels correlated positively with chirp rate. To determine whether elevated cortisol can cause changes in chirping behavior, isolated fish were implanted with cortisol-filled or empty Silastic tubes and tested for short-term and long-term changes in electrocommunication signals and steroid levels. After 2 weeks, fish that received cortisol implants showed higher chirp rates than blank-implanted fish; there were no difference between groups in EOD frequency. Cortisol implants significantly elevated plasma cortisol levels compared to blank implants but had no effect on plasma 11KT levels. These results suggest that male-male interaction increases chirp rate by elevating levels of plasma cortisol, which, in turn, acts to modify neural activity though an 11KT-independent mechanism.     

Life history of captive gray-cheeked mangabeys: Physical and sexual development

Ontogeny refers to every aspect of the development of an individual. In this respect growth and sexual maturation are useful life-history parameters that can be correlated with developmental features of social behavior. In this paper, I analyze body-weight growth and sexual maturation in captive gray-cheeked mangabeys (Cercocebus albigena). I also describe the development of external morphological characteristics, used as “physical markers.” Body-weight growth is analyzed in 15 males and 7 females. Individual weight velocity curves for animals of both sexes showed an, early peak around 2 years of age. Males had a later growth spurt, peaking between 4 and 6 years of age. Females showed no clear second growth acceleration (spurt), but they experienced an interruption of their weight growth deceleration between 3 and 5 years of age, which is generally coincident with puberty. In females there is a close relationship between weight and the occurrence of the first swelling of their sexual skin. These developmental parameters are compared to those described in baboons and macaques.     

Ontogeny of numerical abilities in fish

Background

It has been hypothesised that human adults, infants, and non-human primates share two non-verbal systems for enumerating objects, one for representing precisely small quantities (up to 3–4 items) and one for representing approximately larger quantities. Recent studies exploiting fish''s spontaneous tendency to join the larger group showed that their ability in numerical discrimination closely resembles that of primates but little is known as to whether these capacities are innate or acquired.

Methodology/Principal Findings

We used the spontaneous tendency to join the larger shoal to study the limits of the quantity discrimination of newborn and juvenile guppies. One-day old fish chose the larger shoal when the choice was between numbers in the small quantity range, 2 vs. 3 fish, but not when they had to choose between large numbers, 4 vs. 8 or 4 vs. 12, although the numerical ratio was larger in the latter case. To investigate the relative role of maturation and experience in large number discrimination, fish were raised in pairs (with no numerical experience) or in large social groups and tested at three ages. Forty-day old guppies from both treatments were able to discriminate 4 vs. 8 fish while at 20 days this was only observed in fish grown in groups. Control experiments showed that these capacities were maintained after guppies were prevented from using non numerical perceptual variables that co-vary with numerosity.

Conclusions/Significance

Overall, our results suggest the ability of guppies to discriminate small numbers is innate and is displayed immediately at birth while discrimination of large numbers emerges later as a result of both maturation and social experience. This developmental dissociation suggests that fish like primates might have separate systems for small and large number representation.     

Collapse of the reproductive process of two migratory fish (Prochilodus argenteus and Prochilodus costatus) in the Três Marias Reservoir,São Francisco River,Brazil

Generally, migratory fish can complete vitellogenesis even when the migration process is interrupted; however, final oocyte maturation does not occur and therefore there is no spawning. To evaluate the reproductive process of migratory fish inside the reservoir of the Três Marias Dam (a lentic environment), 90 female and 81 male Prochilodus argenteus and 172 female and 115 male Prochilodus costatus were captured in this environment. Males and females from both species in the resting stage were pre‐dominant, and the highest frequency of specimens in advanced maturation stages occurred in November, December and January. According to histological analysis, ovarian regression was frequent and vitellogenic oocytes undergoing atresia were intensely observed, moreover, no fish with ovaries and testes with characteristics of spawning and spermiation, respectively, were captured. This indicated that both species were preparing for reproduction and reaching advanced gonad maturation, but were unable to complete the process of reproduction in this environment. The data from this study indicate that the modification of portions of rivers to lentic environments can have a negative impact on the reproductive process of migratory fish in freshwater.     

The role of visual cues in the facilitation of growth in a schooling fish

Synopsis This study tested the hypothesis that visual contact between fish may result in enhanced rates of growth in a schooling fish. Juvenile chum salmon, Oncorhynchus keta, were held singly and reared in isolation or in visual contact with conspecifics. Fish were fed at either a low (6% body weight d^–1) or high (20% body weight d^–1) ration for 42d. Specific rates of weight gain were 18% greater at low ration and 38% greater at high ration for fish in visual contract with conspecifics than for those held in isolation. The results demonstrate a selective advantage of visual cues associated with schooling behavior and suggest that the efficacy of growth models for schooling fishes may be enhanced by the consideration of social interactions which may facilitate growth.     

The Importance of Egg Size and Social Effects for Behaviour of Arctic Charr Juveniles

Early behaviour can determine food intake and growth rate with important consequences for life history and survival in fishes. Egg size is known to affect growth rate of young Arctic charr but its influence on the development of behaviour is poorly documented. It is believed that egg size influence on growth and potentially on the behaviour of young fish decreases over time, minimized by the effects of social factors. Shortly after first feeding, we examined differences in mobility and foraging of Arctic charr in relation to egg size and social environment. The behaviour of juveniles from small and large eggs was compared five times over the course of development and in three different experimental settings: long‐term isolation (isolation before hatching), short‐term isolation vs. group rearing and mixed size group vs. homogeneous size groups. Egg size affected foraging behaviour and mobility of fish: fish coming from large eggs were more mobile and foraged more than fish coming from small eggs. Social environment affected foraging behaviour, mobility and space use: fish in a group were more mobile, foraged more and responded faster to food delivery than isolated fish. The interaction of egg size and social effects was seen primarily in foraging activities but did not affect mobility or space use. Large fish in groups foraged more than the three other groups: large fish in isolation, small fish in groups and small fish in isolation. Agonistic behaviour was rarely observed and there was no significant effect of group composition on agonistic behaviour. We discuss the importance of egg size and social effects at early stages of development with a focus on the evolutionary ecology of Arctic charr.     

Sperm transfer is affected by mating history in the simultaneously hermaphroditic snail Lymnaea stagnalis

Abstract. Males are predicted to strategically allocate sperm across mating partners in order to maximize their chances of paternity. This requires that males have the ability to detect aspects of their partner's mating history or the number of potential mates. We investigated whether simultaneous hermaphrodites mating in the male role strategically adjust sperm transfer depending on rearing conditions. The pond snail Lymnaea stagnalis (Basommatophora) is known to donate sperm repeatedly to different partners during a breeding season and store received sperm for >3 months. The rearing conditions of the donor as well as the recipient affect the amount of sperm transferred. Sperm donors raised in isolation transfer more sperm than those raised in groups. Furthermore, isolated sperm donors transfer less sperm to partners that were raised in groups than to those raised in isolation, i.e., virgins. These findings suggest that snails raised in isolation shift their sex allocation toward the male function and indicate that they can somehow assess the mating status of their partner.     

Transgenic Medaka Fish Bearing the Mouse Tyrosinase Gene: Expression and Transmission of the Transgene Following Electroporation of the Orange-Colored Variant

Transgenic fish bearing the mouse tyrosinase gene (mg-Tyrs-J) were produced by transfection into fertilized eggs of the homozygous normal orange-colored variant of medaka fish, Oryzias latipes, by means of electroporation. Of 589 eggs transfected, 38 fish (6%) exhibited brownish wild-type skin pigmentation, which was discernible from control siblings. Light microscopy of the skin from the founders thus generated disclosed that 1) melanization occurred and was restricted to melanophores formed presumably from preexisting amelanotic melanophores, 2) there was a wide variation in the degree of melanization observed among melanophores, and 3) no melanin deposition was recognized in xanthophores or leucophores. Immunofluorescence using an antibody raised against mouse tyrosinase disclosed that melanophores at varying stages of maturation were reactive. Thus, it was shown that the transgene in medaka fish expressed its action in a cell type-specific manner. Crossing of transgenic founders with homozygous orange-colored variant fish yielded two groups of offspring expressing either the wild-type or the orange-colored skin pigmentation at an approximate ratio of 1:1. Crossing between founders exhibiting wild-type pigmentation yielded only offspring with melanized skin. Skin melanophores in these offspring formed vertical stripes, which are rare in this species. The hereditary basis of melanized skin was demonstrated in matings of Fl progenies, which resulted in similar degrees of melanization over whole skin melanophores. The sum of these findings implied that the transgene is expressed as a dominant character gene and is transmitted through germ cell lines according to the Mendelian law. PCR analysis combined with nested PCR technique strongly suggested that the transgene was integrated into the medaka genome, even though the copy number deduced from gel banding was largely diminished, possibly as a result of fragmentation or instability within the medaka genome.     

Effects of social isolation on growth,stress response,and immunity of zebrafish

Stressful housing conditions like social isolation have been shown to profoundly affect the physiology and health of various organisms which is rarely addressed in fish species. In the present study, we used a shoaling species, zebrafish, to investigate the stress reactivity of grouped and individually housed fish. We also hypothesized if isolation is a stressful condition may disrupt growth performance and innate immune response of individuals. To this end, fish were housed individually (social isolated treatment) or in groups of five fish (control treatment) for 60 days. Growth indices of fish were not affected by social isolation. Sixty-day social isolation did insignificant effect on baseline cortisol levels of specimens; however, individually housed zebrafish showed lower plasma cortisol to chasing stress than the control grouped fish. On the contrary, exposure to predator caused higher cortisol levels in social isolated fish. Serum lysozyme activity of isolated individuals was significantly lower than control fish, but activity of serum complement remained unchanged. Our results represent evidences that zebrafish experienced social isolation showed broad changes in physiological and immunological functions which may affect the quality of life.     

Age and growth of Far Eastern staghorn sculpin <Emphasis Type="Italic">Ggymnocanthus herzensteini</Emphasis> (Cottidae) in peter the Great Bay (the Sea of Japan)

In a sample of Far Eastern staghorn sculpin Gymnocanthus herzensteini with a length up to 40 cm, age and growth were assessed from the results of analysis of thin longitudinal sections of otolith (sagitta). Males attained to an age not less than 13 years and females attained to an age not less than 17 years. Maximum length of males is much smaller than that of females. The absolute gains of females are greater than those of males; however, there are no considerable differences in the specific rate of growth. The most intensive growth is observed in the first two to three years of life. During sexual maturation, its rate decreases. The next noticeable decrease in the rate of growth occurs in fish of elder age groups. In catches of Far Eastern staghorn sculpin in Peter the Great Bay, females dominate; however, in groups of small and medium-sized individuals, the proportion of males increases, which is related to their smaller, as compared to females, absolute gains. The subsequent decrease in the proportion of large-sized males is determined by their greater natural mortality, as compared to similar-sized females.     

EVALUATING KINSHIP OF NEWLY SETTLED JUVENILES WITHIN SOCIAL GROUPS OF THE CORAL REEF FISH ANTHIAS SQUAMIPINNIS

It is conventionally assumed that eggs and/or larvae of most coral reef fishes are thoroughly mixed during a pelagic phase, so that juvenile recruits at any particular reef site represent a random sample of the reproductive products entering the local gene pool. However, a recent review of biological factors that might limit mixing raised the testable hypothesis that groups of genetically related individuals may sometimes persist through the pelagic phase and settle as sibling cohorts (Shapiro, 1983). Here we provide a critical genetic test of this hypothesis by examining allozyme variation in juvenile aggregations of the serranid reef fish, Anthias squamipinnis. Results demonstrate that juvenile cohorts within large social groups in Anthias are not composed exclusively or predominantly of siblings, but rather represent a random sample of progeny from many matings. Also included are considerations of allelic and genotypic criteria by which hypotheses about sibling assemblages might generally be evaluated.     

Social and reproductive behavior of a captive group of walleye pollock,Theragra chalcogramma

Synopsis The social and reproductive behavior of a group of four male and seven female walleye pollock,Theragra chalcogramma, were observed in a large tank. Pollock spent most of their time swimming in a loose aggregation near the surface. Males descended from the aggregation more often than females to follow and make physical contact with other males as well as with females. The difference between males and females in the frequency of diving in our tank is consistent with the reported pattern of depth segregation of the sexes in natural pollock spawning aggregations. The frequency of social interactions increased when pollock became reproductively active and was higher at night and during twilight when most of the spawning occurred. Male interactions with females most frequently involved physical contact, while male interactions with other males were more often limited to following. There was no indication that male-male interactions result in the formation of stable social dominance relationships that determine priority of access to mates, as has been suggested previously for walleye pollock. Rather, following and contact interactions appear to promote male identification of potential mates and encounters with ripe females. The possible functional significance of male social interactions is discussed in relation to reports on natural walleye pollock spawning aggregations.