Population Differences in the Schooling Behaviour of Newborn Guppies,Poecilia reticulata

Population differences in the schooling behaviour of adult guppies (Poecilia reticulata) from Trinidad have previously been well documented. This paper demonstrates that variation in schooling behaviour is also present in newborn fish. Guppies from the Aripo River of Trinidad display well-developed schooling behaviour from birth. In addition to forming cohesive and polarized groups, these newborn fish also exhibit predator inspection behaviour. Newborn guppies from the Paria River perform inspections but, unlike the Aripo fish, are poor schoolers. Population variation in behaviour at birth does not necessarily reflect the pattern observed in the adult fish. As adults, guppies from the Upper section of the Aripo River have a much lower schooling tendency and are less wary during inspection than the downstream Lower Aripo guppies. At birth, however, the schooling behaviour and inspection behaviour in the two populations is identical. These results suggest that different selective pressures operate on adult and newborn guppies in Trinidad.     

Genetic difference in female choice between two guppy populations

The pattern of mating preferences of female guppies, Poecilia reticulata, differs genetically between two Trinidadian populations. Males from the Aripo and Paria rivers of Trinidad differ in the extent and intensity of orange pigment in their colour patterns. The relative area of orange in Paria colour patterns was nearly twice that in Aripo colour patterns. To test the hypothesis that a difference in female mating preferences could have contributed to the difference in colour patterns, patterns of female choice between laboratory-reared Paria and Aripo females were compared. The frequency of sexual responses to male courtship displays was used to measure the average preference of females for individual males. Paria females discriminated significantly between Paria males based upon differences in the extent of orange in the colour pattern. Aripo females showed no evidence of discrimination between Paria males, and thus differed significantly from Paria females in choice behaviour. Neither group of females discriminated between Aripo males. These results are evidence that female choice behaviour can vary genetically within a species and suggest that differences in preferences may have contributed to divergence in colour patterns among guppy populations.     

Interpopulation Differences in Shoaling Behaviour in Guppies (Poecilia reticulata): Roles of Social Environment and Population Origin

In Trinidad, guppies (Poecilia reticulata) in high‐predation localities show more cohesive shoaling behaviour than those living with less dangerous predators in low‐predation sites. We evaluated the relative contributions of population origin (i.e. genetic and/or maternal effects) and social environment on the expression of shoaling by assessing the behaviour of juveniles reared in a range of social conditions. Focal individuals, offspring of guppies from populations from high‐ or low‐predation localities, were reared in a multifactorial experiment; we created four different social conditions by manipulating the source and demography of the conspecific residents with whom focal individuals interacted. We found that high‐predation fish displayed a stronger propensity to shoal than low‐predation ones. Our results also suggest a role for interactions between the source of the focal individuals, the demography of the group in which they were reared and the origin of the guppies with whom they were reared. Depending on their origin (high‐ vs. low‐ predation) and rearing density, our focal fish were more likely to shoal if they were reared with high‐predation residents. Learning from high‐predation residents, aggressive interactions with low‐predation residents and/or phenotype matching could have played a role in driving this effect of social environment. This effect of the phenotype of conspecifics on shoaling development would enhance heritable differences in shoaling propensity such that both could contribute to the well‐documented difference in shoaling behaviour of high‐ and low‐predation guppies in natural populations.     

The impact of parasites on the life history evolution of guppies (Poecilia reticulata): the effects of host size on parasite virulence

There is large spatial and temporal variation in the Gyrodactylus parasite fauna across natural guppy (Poecilia reticulata) populations in Trinidad. The life history evolution of these fish could be affected differently in the various habitats depending on the local parasite selection pressure. Here, we experimentally infected three guppy populations with three gyrodactylid strains in the laboratory and monitored the infection by recording the number of parasites and host mortality in a full factorial design. The origin of the guppy population and parasite strain, and the size of the hosts explained significant variation in the survival of hosts. Larger fish carried the highest parasite loads and experienced the highest mortality rates, which suggests that parasite-mediated selection may favour smaller phenotypes, possibly counter-balancing selection pressures by gape-limited predators, mate choice and female fecundity. We observed significant variation in virulence between parasite strains with the captive-bred experimental strain (Gt3) causing the highest mortality of hosts whilst reaching only relatively low maximum burdens. This suggests that adaptations to the captive environment and/or inbreeding depression may alter the virulence of such captive-bred parasites. There were significant differences in survival rate between guppy populations, with infected guppies from the large population of the Lower Aripo River showing a higher survival rate than the fish from the small and genetically less diverse Upper Aripo River population.     

Implications of multiple mating for offspring relatedness and shoaling behaviour in juvenile guppies

Polyandry (female multiple mating) can confer important benefits to females, but few studies have considered its potential costs. One such cost may arise through differences in the relatedness of offspring born to females with different mating histories; offspring born to monandrous females are always full siblings, while those produced by polyandrous females may be full or half siblings. These differences may have important consequences for social interactions among offspring. We used artificial insemination in the guppy (Poecilia reticulata), a promiscuous live-bearing fish, to evaluate shoaling behaviour in polyandrous and monandrous broods. We combined this information with known parentage data for the polyandrous broods to determine whether sibling relatedness influenced offspring shoaling behaviour. While we detected no effect of mating treatment (polyandry/monandry) on shoaling behaviour, we found that pairs of full siblings spent significantly more time shoaling (and in close proximity) than pairs of half siblings. This latter finding confirms the ability of newborn guppies to distinguish brood mates on the basis of kinship, but also suggests an important and hitherto unrealized potential cost of polyandry: a reduction in within-brood relatedness with potentially important implications for offspring social behaviour.     

Marked variation in parasite resistance between two wild populations of the Trinidadian guppy, Poecilia reticulata (Pisces: Poeciliidae)

This is the first study to demonstrate significant differences between two natural Trinidadian guppy populations in susceptibility to a pathogenic monogenean parasite, Gyrodactylus turnbulli . Following experimental infection with an isogenic laboratory culture of G. turnbulli , fish from the Upper Aripo (UA) lost parasites more slowly and carried up to three times as many parasites at peak infection than did those from the Lower Aripo (LA). The UA population appeared to be more susceptible than the LA fish, even though fish of both populations were naïve to this particular laboratory strain of G. turnbulli and had not encountered any gyrodactylid infection for at least 65 days. The parasite infection reduced the feeding response and feeding activity of UA and LA fish to a similar extent. Our findings suggest that this ectoparasite may have an important impact on the evolutionary biology of guppies (and possibly of other teleosts), particularly as the prevalence of Gyrodactylus infection in natural populations may be as high as 50%. We discuss the role of parasite infections on natural and sexual selection, the good genes model and the implications for immunogenetics in small genetically isolated host populations.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 79 , 645–651.     

Oviposition Behaviour and Reproductive Performance of Trichogramma australicum Girault (Hymenoptera: Trichogrammatidae) Reared in Artificial Diet

Biotypes of Trichogramma australicum were reared on artificial diet "A", Helicoverpa armigera (Hübner) (natural host) eggs and Sitotroga cerealella (Olivier) (factitious host) eggs. We evaluated the quality of these biotypes by comparing their oviposition behaviour and reproductive performance on H. armigera eggs. Female T. australicum reared in vitro accepted H. armigera eggs for oviposition and displayed similar behavioural components of oviposition to females reared on natural hosts. However, handling time during oviposition in H. armigera eggs by females from in vitro rearing was significantly longer than handling time of females reared on the natural host because the females needed a significantly longer time for host feeding. In vitro reared females produced significantly more progeny and parasitised more H. armigera eggs than the females reared on S. cerealella. Improvements to the artificial diet for T. australicum may reduce handling time of the in vitro reared females and increase the female population. These improvements may include changes in nutrient content and size of the artificial eggs.     

Pre-mating isolation is determined by larval rearing substrates in cactophilicDrosophila mojavensis. II. Effects of larval substrates on time to copulation,mate choice and mating propensity

Summary It has been hypothesized that reproductive character displacement has evolved in mainland Sonora, Mexico populations of cactophilicD. mojavensis due to the presence of a sympatric sibling speciesD. arizonae. In laboratory tests using ancestral Baja California populations and derived, sympatric mainland populations, asymmetrical sexual isolation has been observed among populations ofD. mojavensis where mainland females discriminate against Baja males. Effects of different pre-adult rearing environments on adult mating behaviour were assessed by comparing fermenting cactus tissues like those used in nature for breeding with laboratory media because previous studies have employed synthetic growth media for fly growth and development. Significant behavioural isolation was evident in all cases when larvae were reared on laboratory food, but was non-significant when flies were reared on fermenting cactus, except for the cactus used by most mainland populations, consistent with previous studies. Time to copulation of Baja females was greater than mainland females over all substrates, but male time to copulation did not differ between populations. Time to copulation for both sexes was significantly greater when flies were reared on laboratory food with one exception. The degree of behavioural isolation was weakly correlated with time to copulation across food types (Spearman rank correlation = 0.58,p = 0.099). Therefore, use of laboratory media in this and previous studies exaggerated adult pre-mating isolation and time to copulation in comparison to natural breeding substrates. These experiments suggest that a change in host substrates by saprophagous insects (where chemical differences exist between hosts) may have subtle effects on mating behaviour in a manner which promotes low levels of sexual isolation as a by-product of their utilization of a particular substrate during larval development. ForD. mojavensis, these results suggest that over evolutionary time, radiation into a new environment (from Baja to the mainland) allowed utilization of new host plants that may have incidentally promoted the sexual isolation patterns that have been observed within this species.See Etges (1992) for the first paper in this series.     

The role of innate and acquired resistance in two natural populations of guppies (Poecilia reticulata) infected with the ectoparasite Gyrodactylus turnbulli

Resource availability, predation, and sexual selection have all been shown to play an important role in the ecology and evolution of guppies, Poecilia reticulata , but the role of parasitism has received comparatively little attention. In the present study, we examined natural infection levels of wild-caught guppies from the Upper and Lower Aripo River in Trinidad (UA and LA, respectively) and experimentally infected a subsample of fish with an isogenic line of the ectoparasite Gyrodactylus turnbulli . LA fish showed a superior resistance compared to UA guppies during the primary, but not secondary infection 53 days later. Resistance of LA individuals was consistent across experiments, suggesting immunocompetence has a heritable genetic basis. The efficiency of the immune response of UA fish was not correlated across infections. During primary infections, UA fish were highly susceptible, but their resistance was significantly improved during a secondary infection, highlighting the importance of acquired resistance. We discuss the role of innate and acquired resistance, and place our findings in the context of natural gyrodactylid infections. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 647–655.     

The genetic and environmental basis of adaptive differences in shoaling behaviour among populations of Trinidadian guppies,Poecilia reticulata

The degree of plasticity an individual expresses when moving into a new environment is likely to influence the probability of colonization and potential for subsequent evolution. Yet few empirical examples exist where the ancestral and derived conditions suggest a role for plasticity in adaptive genetic divergence of populations. Here we explore the genetic and plastic components of shoaling behaviour in two pairs of populations of Poecilia reticulata (Trinidadian guppies). We contrast shoaling behaviour of guppies derived from high‐ and low‐predation populations from two separate drainages by measuring the shoaling response of second generation laboratory‐reared individuals in the presence and absence of predator induced alarm pheromones. We find persistent differences in mean shoaling cohesion that suggest a genetic basis; when measured under the same conditions high‐predation guppies form more cohesive shoals than low‐predation guppies. Both high and low‐predation guppies also exhibit plasticity in the response to alarm pheromones, by forming tighter, more cohesive shoals. These patterns suggest a conserved capacity for adaptive behavioural plasticity when moving between variable predation communities that are consistent with models of genetic accommodation.     

Parallel and nonparallel behavioural evolution in response to parasitism and predation in Trinidadian guppies

Natural enemies such as predators and parasites are known to shape intraspecific variability of behaviour and personality in natural populations, yet several key questions remain: (i) What is the relative importance of predation vs. parasitism in shaping intraspecific variation of behaviour across generations? (ii) What are the contributions of genetic and plastic effects to this behavioural divergence? (iii) And to what extent are responses to predation and parasitism repeatable across independent evolutionary lineages? We addressed these questions using Trinidadian guppies (Poecilia reticulata) (i) varying in their exposure to dangerous fish predators and Gyrodactylus ectoparasites for (ii) both wild‐caught F0 and laboratory‐reared F2 individuals and coming from (iii) multiple independent evolutionary lineages (i.e. independent drainages). Several key findings emerged. First, a population's history of predation and parasitism influenced behavioural profiles, but to different extent depending on the behaviour considered (activity, shoaling or boldness). Second, we had evidence for some genetic effects of predation regime on behaviour, with differences in activity of F2 laboratory‐reared individuals, but not for parasitism, which had only plastic effects on the boldness of wild‐caught F0 individuals. Third, the two lineages showed a mixture of parallel and nonparallel responses to predation/parasitism, with parallel responses being stronger for predation than for parasitism and for activity and boldness than for shoaling. These findings suggest that different sets of behaviours provide different pay‐offs in alternative predation/parasitism environments and that parasitism has more transient effects in shaping intraspecific variation of behaviour than does predation.     

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.     

Shoaling and mate choice of wild-type Tanichthys albonubes in the presence of the red fluorescent transgenic conspecifics

Shoaling and sexual behaviour of wild-type male and female white cloud mountain minnow Tanichthys albonubes were measured in the presence of the red fluorescent transgenic conspecifics under laboratory conditions. Wild-type female test fish showed no significant preference, whereas wild-type male test fish preferred to be near a shoal of red transgenic fish rather than wild-type fish. When placed in a potentially reproductive context, wild-type males had a higher competitive ability over transgenic males; wild-type females spent more time with wild-type males in visually mediated experiments, but wild-type males performed more courtship displays towards transgenic females. These results suggest that the red body colouration does not appear to disturb signal communication between wild-type and transgenic T. albonubes in shoaling behaviour; transgenic males have no mating advantage over wild-type males, but the red body colouration of transgenic females may affect mate choice of wild-type males.     

Oviposition behaviour of Bracon mellitor, a parasitoid of the boll weevil (Anthonomus grandis)

ABSTRACT. The parasitoid, Bracon mellitor , will probe with its ovipositor plant structures containing its host. The identification of methyl parahydroxy-benzoate (methyl parasept), an antimicrobial additive to the semi-synthetic diet used for rearing the host, as a releaser of this behaviour prompted an investigation of the parasitoid's response to this chemical. Its absence from field hosts suggested the response was learned. Female parasitoids reared in host-infested cotton plant buds from the fields or in methyl parasept-free hosts did not respond to methyl parasept alone until exposed to hosts contaminated with it. This is taken to imply associative learning by the females reared from the methyl parasept-free hosts. A few responses to methyl parasept were elicited from inexperienced females reared from methyl parasept-contaminated hosts, but their responsiveness increased after they had been exposed to methyl parasept-contaminated hosts as oviposition stimuli. These results point to the caution that must be exercised in the isolation and identification of kairomones.     

Spatial aspects of genetic differentiation of the European chub in the Rhone River basin

Starch-gel electrophoresis was used to examine genetic differentiation at four polymorphic loci in the European chub Leuciscus cephalus from 27 samples and three main areas of the Rhone River basin in France. The Upper Rhone samples appeared to be genetically distinct at locus PGM-2 * from the Lower Rhone and Saone-Grosne samples according to the constant row total-multiple correspondence analysis (CRT-MCA), which allowed the estimation of multivariate F_st equivalents. No difference between Lower Rhone and Saone-Grosne samples was revealed by the global analysis considering the three areas. However, distinct local analyses in the three areas showed that the spatial structure of genetic variability was dissimilar in these last two areas, suggesting a non-equilibrium process under the influence of dams in the Lower Rhone, and isolation by distance in Saone system. Isolation by distance was also suggested for the Upper Rhone samples.     

Sex reversal of the newt Triturus cristatus reared at extreme temperatures

Crested newt larvae were reared at defined temperatures, either from uncleaved eggs or from early feeding larvae, until metamorphosis when sexual differentiation had occurred. Trials at 18-24 degrees C showed a 1:1 sex ratio. A higher temperature trial produced more males than females, including some XX neomales. Lower temperatures resulted in a significant excess of females, including XY neofemales. Sex reversal only occurred in about half the possible cases on average. Extreme temperatures must perturb the normal XX/XY system of sex determination, to reveal either an ancestral ZZ/ZW system or a still more primitive environmental control. It is suggested that neofemales (but not neomales) could occur in nature.     

Genetic control of feeding preferences in the mosquitoes Aedes (Stegomyia) simpsoni and aegypti

ABSTRACT. The biting rate of a non-anthropophilic (Bwayise) population of Aedes simpsoni was found to be approximately 0.3 mosquitoes per catcher per hour, whereas that of an anthropophilic (Bwamba) population was approximately 101 per catcher per hour. Population density indices, as determined by the number of pupae per wet plant axil, were 0.70 in Bwayise and 1.00 in Bwamba. The big difference in anthropophilic behaviour between these populations was therefore unlikely to be derived from this small population difference. Larval density was higher at Bwamba than at Bwayise, but isolation or crowding of the larvae in the laboratory did not affect the biting behaviour of adult Ae. simpsoni. Laboratory studies also failed to confirm field observations that temperature might play a part in determining anthropophily and non-anthropophily in this species. In choice-chamber landing tests, using a rat and a human hand, Ae. simpsoni females derived from wild larvae and reared in the laboratory showed that 83% of the Bwamba strain landed on man, whereas only 38% of the Bwayise strain did so. In Aedes aegypti , 71% of a long-established laboratory strain (Ilobi) landed on man, whereas 47% of a relatively non-anthropophilic wild (Kampala) strain did so. These preferences persisted in culture. Selective breeding increased the preference for the rodent significantly in the Kampala strain of Ae. aegypti , but had no significant effect on the Ilobi strain. Crossbreeding showed that the F₁ and F₂ hybrids between the anthropophilic and non-anthropophilic strains were intermediate in their preference between the parental pure bred strains; the reciprocal crosses were not significantly different from each other. The behaviour of the backcross progenies, at least in Ae. aegypti , appeared to indicate that the genotype of the male parent might be the main determining factor.     

Inter and intra‐population variation in shoaling and boldness in the zebrafish (Danio rerio)

Population differences in anti‐predator behaviour have been demonstrated in several species, although less is known about the genetic basis of these traits. To determine the extent of genetic differences in boldness (defined as exploration of a novel object) and shoaling within and between zebrafish ( Danio rerio ) populations, and to examine the genetic basis of shoaling behaviour in general, we carried out a study that involved laboratory‐raised fish derived from four wild‐caught populations. Controlling for differences in rearing environment, significant inter‐population differences were found in boldness but not shoaling. A larger shoaling experiment was also performed using one of the populations as the basis of a North Carolina type II breeding design (174 fish in total) to estimate heritability of shoaling tendency. A narrow‐sense heritability estimate of 0·40 was obtained, with no apparent dominance effects.     

Comparative study of the molting cycle of wild and reared swimming crabs Callinectes danae (Crustacea: Portunidae)

Specimens of Callinectes danae Smith 1869 were caught in northeastern Brazil (2178 males, 2031 females); of these, 24 males and 24 females were reared for 6 months. Water temperature (T) and salinity (S) showed a significant effect on the average ecdysis in wild crab (μ), with a model obtained that was: μ = exp(?0.12268T + 0.06148S)/(1 + exp(?0.12268T + 0.06148S)). Size at morphometric maturity was significantly larger for wild males and females (9.45 and 8.38 cm, respectively) than for reared individuals (8.95 and 7.93 cm). Females of sizes above CW₅₀ (carapace width at maturation) showed an increased ecdysis activity, whereas males showed a decrease in ecdysis frequency in sizes over CW₅₀. Five and six molts were observed for females and males, respectively, in both wild and reared crabs; the modal classes of the reared crabs were shifted to smaller sizes. In reared females the terminal‐pubertal molt occurred at 107 days of age and at 148 days, on average, in males. The intermolt period varied from 8 to 41 days and increased with age.     

A test for conspecific cueing in two sympatric species of pupfish (<Emphasis Type="Italic">Cyprinodon beltrani</Emphasis>, <Emphasis Type="Italic">C. simus</Emphasis>)

In many fishes, individuals prefer to associate with phenotypically similar or conspecific individuals (conspecific cueing). Such phenotypic segregation can be an important evolutionary driver, for example, in intralacustric sympatric speciation processes. I examined conspecific cueing in two species of sympatric pupfish from Laguna Chichancanab in southern Mexico: the little shoaling and highly territorial Cyprinodon beltrani and the highly shoaling but non-territorial C. simus. Females were tested for shoal species preferences in two testing scenarios: (1) a sequential choice test where shoals of four conspecific or four heterospecific (Cyprinodon sp. or Poecilia reticulata) females were presented in succession, and (2) a simultaneous choice test where female shoals of both Cyprindon species were presented concurrently. Overall, higher shoaling in C. simus was corroborated in this study. In the sequential test, no effect of the type of stimulus shoal (con- or heterospecific) on shoaling behavior was detected. In the simultaneous tests, C. beltrani, but not C. simus females showed a preference for the conspecific shoal. It seems possible that C. simus females did not evolve species recognition mechanisms because no other Cyprinodon species in the Laguna Chichancanab shows equally high shoaling, which automatically leads to the formation of single-species (i.e., C. simus-) shoals. C. simus males do not establish long-term territories, but rather spawn within shoals, whereas C. beltrani females approach males in their breeding territories to spawn. I discuss that this behavioral difference still provides a powerful reproductive isolation mechanism even in the absence of conspecific cueing in C. simus.