Biomedical subjects

A Bisazza

Publications and source records attributed to A Bisazza.

At least 19 recordsLinked to original sources

PubMed2001

Consistency among different tasks of left-right asymmetries in lines of fish originally selected for opposite direction of lateralization in a detour task.

Lines of fish, Girardinus falcatus preferentially turning rightward (RD) or leftward (LD) when facing a dummy predator visible behind a barrier have been obtained through selective breeding. To check whether lateralization was maintained in other behavioral responses, five different tests were carried out. They comprised measures of (1) turning direction in a T-maze; (2) proportion of clockwise and anticlockwise direction of rotation in a circular arena; (3) preferential eye use by females during shoaling behavior (i.e. while looking at their own mirror image reflection); (4) preferential eye use by males during sexual behavior (i.e. while turning around a barrier to join a group of females); and (5) preferential eye use by males during agonistic behavior (i.e. while attacking a rival visible in a mirror). In all five tests the two selected lines showed opposite direction of lateralization. Results thus indicate that behavioral asymmetries in the detour test are predictive of lateralization in other types of behavioral tests. Moreover, results show that RD and LD fish have a similar but left-right reversed pattern of subdivision of cognitive/ behavioral functions, which is suggestive of a similarly left-right reversed (mirror image) brain organization.

Agonistic Behavior↗

PubMed2001

Lateralization of ventral fins use during object exploration in the blue gourami (Trichogaster trichopterus).

Blue gourami fish have a pair of modified ventral fins that are used to obtain tactile information about surrounding objects. Use of ventral fins by blue gourami was investigated during initial exploration of novel objects. When exposed to a sequence of novel plastic objects, varying in shape and colour, the blue gourami showed preferential use of the left fin during initial contacts. Laterality apparently depends on the nature of the stimulus: Fish exposed to a randomized series of natural objects showed preferential use of the left fin for inanimate mineral objects, but no asymmetry was apparent for investigating animate objects. This would suggest that some form of 'handedness' may have been present prior to the appearance of tetrapods. On the other hand, measurements of fish monocular viewing revealed that the fin use was strongly associated with preferential use of the ipsilateral eye before the touching of the stimulus took place, thus, suggesting that the asymmetry in fin use may also be related to lateralization of the visual system.

Animals↗

PubMed2000

Heritability of lateralization in fish: concordance of right-left asymmetry between parents and offspring.

The poeciliid fish Girardinus falcatus shows a consistent population bias to detour a vertical-bar barrier preferentially leftwise when approaching a dummy predator to inspect it; the asymmetry seems to be due to a preferential use of the lateral field of the right eye during fixation of biologically relevant stimuli such as a predator. In order to unravel the origins of this lateral bias, we took advantage of the individual variability present in the natural population to perform artificial selection experiments. Males and females that scored similarly at the detour test were mated together and their progeny were tested in the same task. Results showed that there was a striking similarity in the strength and in the direction of the asymmetries between parents and offspring. Correlation was highly significant and the estimate of heritability was greater than 0.5. This represents the first demonstration of heritability of the direction of a behavioural asymmetry outside the primate order. The finding paves the way to the use of a novel and suitable animal model for the neuro-genetics of lateralization and to the possible identification of homologous and/or analogous genes underlying brain asymmetry among vertebrates.

Animals↗

PubMed2000

Variation of female preference for male coloration in the eastern mosquitofish Gambusia holbrooki.

The preference for melanistic males was studied in two populations of eastern mosquitofish (Gambusia holbrooki, Pisces: Poeciliidae), one from Florida and one from northern Italy. Melanism in the eastern mosquitofish is a Y--linked character, expressed in males only. Melanistic males have black spots varying in size and number. In the Florida population, melanistic males are common, whereas in the Italian population they have never been observed. Females were male-deprived for at least 2 months before being tested in a dichotomous choice chamber. Italian females showed a significant preference for unpigmented males from their own population, whereas Florida females preferred melanistic males. When given the choice between males with few (< 10% of the body surface) and males with many (> 50%) black spots, Italian females preferred males with few black spots and Florida females those with many black spots. The preference of the Italian females for unpigmented males was confirmed in females reared from birth to maturity in the presence of only melanistic males. The preference of Florida females for melanistic males was also confirmed in females reared from birth to maturity in the presence of only unpigmented males. Altogether, these results demonstrate that in the eastern mosquitofish there is polymorphism in female preference and that this preference does not have an environmental basis.

Animals↗

PubMed2000

Population lateralisation and social behaviour: a study with 16 species of fish.

We investigated turning responses in 16 species of fish faced with a vertical-bar barrier through which a learned dummy predator was visible. Ten of these species showed a consistent lateral bias to turn preferentially to the right or to the left. Species belonging to the same family showed similar directions of lateral biases. We performed an independent test of shoaling tendency and found that all gregarious species showed population lateralisation, whereas only 40% of the non-gregarious species did so. The results provide some support to the Rogers (1989) hypothesis that population lateralisation might have been developed in relation to the need to maintain coordination among individuals in behaviours associated with social life.

Journal Article↗

PubMed1999

Laterality and cooperation: mosquitofish move closer to a predator when the companion is on their left side.

Mirror images simulating social partners that cooperated or defected have been used as an experimental method to test the hypothesis that, while inspecting a predator, pairs of fish play a conditional strategy, Tit for Tat, in an iterated version of the Prisoner's Dilemma game. Using this method, we found that predator inspection was more likely to occur when the mirror image was visible on the left rather than on the right side of mosquitofish, Gambusia holbrooki. The same occurred even when a videorecorded stimulus presentation was used, in which sequences of the predator were mixed with their mirror-image equivalents, thus showing that the asymmetry was not due to behavioural or morphological asymmetries of the predator itself. Moreover, irrespective of whether they were tested with a cooperative (parallel mirror) or a defecting (angled mirror) partner, mosquitofish drew closer to the predator when the mirror was on their left side. These findings suggest that the images seen on the right and left sides by a fish may evoke different types of social behaviour, probably because of differing modes of analysis of perceptual information carried out by the left and right sides of the brain; accurate control and balancing of the side of presentation of visual stimuli during behavioural experiments thus appears to be crucial. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1999

Possible evolutionary origins of cognitive brain lateralization.

Despite the substantial literature on the functional architecture of the asymmetries of the human brain, which has been accumulating for more than 130 years since Dax and Broca's early reports, the biological foundations of cerebral asymmetries are still poorly understood. Recent advances in comparative cognitive neurosciences have made available new animal models that have started to provide unexpected insights into the evolutionary origins and neuronal mechanisms of cerebral asymmetries. Animal model-systems, particularly those provided by the avian brain, highlight the interrelations of genetic, hormonal and environmental events to produce neural and behavioural asymmetries. Novel evidences showing that functional and structural lateralization of the brain is widespread among vertebrates (including fish, reptiles and amphibians) have accumulated rapidly. Perceptual asymmetries, in particular, seem to be ubiquitous in everyday behaviour of most species of animals with laterally placed eyes; in organisms with wider binocular overlap (e.g., amphibians), they appear to be retained for initial detection of stimuli in the extreme lateral fields. We speculate that adjustment of head position and eye movements may play a similar role in mammals with frontal vision as does the choice for right or left lateral visual fields in animals with laterally placed eyes. A first attempt to trace back the origins of brain asymmetry to early vertebrates is presented, based on the hypothesis that functional incompatibility between the logical demands associated with very basic cognitive functions is central to the phenomenon of cerebral lateralization.

Animals↗

PubMed1999

What causes lateralization of detour behavior in fish? Evidence for asymmetries in eye use.

A consistent population bias to detour a vertical-bar barrier preferentially leftwise during approach to inspect a dummy predator was demonstrated in the poeciliid fish Girardinus falcatus. The asymmetry seems to be due to a preferential use of the lateral visual field of the right eye during fixation of biologically relevant stimuli such as a predator. Viewing tests revealed in fact that fish which tended to detour the barrier on the left side used the right eye to scrutiny a dummy predator and the left eye to scrutiny a neutral stimulus, whereas fish which tended to detour the barrier on the right side showed the reverse pattern of eye use; fish that did not show any consistent bias in the detour test did not reveal any significant preference in the viewing test.

Animals↗

PubMed1999

Roots of brain specializations: preferential left-eye use during mirror-image inspection in six species of teleost fish.

It has recently been reported that predator inspection is more likely to occur when a companion (i.e. the mirror image of the test animal) is visible on the left rather than on the right side of mosquitofish Gambusia holbrooki. This very unexpected outcome could be consistent with the hypothesis of a preferential use of the right eye during sustained fixation of a predator as well as of a preferential use of the left eye during fixation of conspecifics. We measured the time spent in monocular viewing during inspection of their own mirror images in females of six species of fish, belonging to different families-G. holbrooki, Xenotoca eiseni, Phoxinus phoxinus, Pterophyllum scalare, Xenopoecilus sarasinorun, and Trichogaster trichopterus. Results revealed a consistent left-eye preference during sustained fixation in all of the five species. Males of G. holbrooki, which do not normally show any social behaviour, did not exhibit any eye preferences during mirror-image inspection. We found, however, that they could be induced to manifest a left-eye preference, likewise females, if tested soon after capture, when some affiliative tendencies can be observed. These findings add to current evidence in a variety of vertebrate species for preferential involvement of structures located in the right side of the brain in response to the viewing of conspecifics.

Animals↗

PubMed1998

Complementary right and left hemifield use for predatory and agonistic behaviour in toads.

Cerebral lateralization, the differing specializations of the right and left sides of the brain once thought to be unique of humans, is now well known to occur in both birds and mammals. Here we report that in toads the right hemisfield of vision guides predatory tongue-striking responses towards moving prey and the left hemisfield guides agnostic tongue-striking responses towards conspecifics. This indicates, for the first time, complementary cerebral specializations for visual processing in anurans, and strongly supports the hypothesis that lateralized brain functions in birds and mammals may have arisen from a common lateralized ancestor. Complementary specializations in visual processing may have originally evolved to avoid problem of response competition during control of medial organs such as the tongue in organisms with laterally placed eyes and, in organisms with wider binocular overlap, it appears to be retained for initial detection of stimuli in the extreme lateral fields.

Agonistic Behavior↗

PubMed1998

Lateralized agonistic responses and hindlimb use in toads.

The recent discovery of forepaw preferences (handedness) in toad species has provided some insight into the evolution of brain lateralization. We tested the prediction that, as in higher vertebrates, visual lateralization and other motor preferences (footedness) also exists in toad species. During feeding periods, South American cane toads, Bufo marinus, showed a population bias to strike with the tongue at other toads occupying their left visual field. This is the first demonstration of lateralized visual behaviour in an amphibian species. Tongue striking at an individual's eyes or head may sometimes delay its approach to prey already seen by the attacker, or may dislodge prey from its mouth. In addition, we report hindlimb preferences (footedness) for contact righting in three species of toad (B. marinus, the European green toad, B. viridis, and the European common toad, B. bufo). After being fully overturned on to their back on a horizontal surface, toads initiated and completed righting using the hindlimbs and with only perfunctory use of the forepaws. Together, the findings of visual lateralization and footedness demonstrate that in toads, as in higher vertebrates, behavioural lateralization is not restricted to handedness. The hypothesis that lateralized brain functions in birds and mammals might have arisen from a common lateralized ancestor is therefore supported. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1998

The origins of cerebral asymmetry: a review of evidence of behavioural and brain lateralization in fishes, reptiles and amphibians.

Early evidence for lateralization at a population and/or individual level in 'lower' vertebrates is reviewed. The lateralities include structural asymmetries in the epithalamus of several species of fish and amphibians, asymmetries in the location of both eyes on the same side of the head and of the dorsal/ventral crossing at optic-chiasma in flatfish, asymmetries in copulatory organs of several species of fishes, asymmetries in lung size and direction of coiling in reptiles, and asymmetrical distribution of scarring in whitefish. More recent data on functional lateralization at population level in lower vertebrates are also reviewed. These include: lateral asymmetries in the direction of turning during escape behaviour and in eye use in poeciliid fish; lateralization of pectoral stridulation sounds in catfish; neural lateralization for control of vocalization in the frogs; pawedness in toads; lateralization of courtship behaviour in newts; and lateralization of aggressive responses in lizards. Several cases of behavioural asymmetries at the individual level are also described, and possible relationships between lateralization at the individual level and fluctuating asymmetries arising from reduced heterozygosity are discussed. It is argued that the overall evidence now available supports the hypothesis of an early origin of brain lateralization in vertebrates.

Amphibians↗

PubMed1998

Lateralization of detour behaviour in poeciliid fish: the effect of species, gender and sexual motivation.

We studied detour responses of two species of poeciliid fish (Gambusia hoolbroki and Girardinus falcatus) faced with a vertical-bar barrier, through which conspecifics of the same or different sex or a simulated-predator (which induced detour behaviour for predator-inspection responses) were visible. Both species showed a consistent bias to turn leftward when faced with the predator, and a consistent bias to turn rightward when faced with an opaque barrier. Sexual stimuli (conspecifics of different sex) elicited a leftward bias in females that had been deprived of the presence of males for 2 months, whilst no bias was apparent in non-deprived females. Social stimuli (conspecifics of the same sex) elicited a consistent rightward bias in females but not in males in both species. Results suggest that males and females of both species show basically the same pattern of laterality and that sex differences, when present, can be accounted for in terms of differences in sexual and/or social motivation.

Animals↗

PubMed1997

Laterality in detour behaviour: interspecific variation in poeciliid fish

We measured whether males of five species of poeciliid fish made detours to the right or left of a vertical-bar obstacle in order to approach a group of females. Three of these species, Gambusia holbrookiGambusia nicaraguensis and Poecilia reticulata showed a significant bias to the left, whereas Brachyrhaphis roseni and Girardinus falcatus showed a significant bias to the right. When tested for direction of turning in front of an opaque barrier, or when a dummy predator was used as a target in a detour test, G. holbrooki and G. falcatus showed similar biases to the right (opaque barrier) and left (predator), thus suggesting that the difference observed when females were used as a target could arise from species differences in the degree of sexual motivation in a novel environment. The two species that showed bias to the right with the females were less likely to exhibit sexual behaviour when placed in a novel environment. Moreover, manipulation of the factors affecting the relative strength of sexual motivation and of fear of a novel environment, such as how long fish were maintained in captivity or in the test apparatus before being tested, caused shifts in the direction of the lateral asymmetries. These results suggest that the presence of functional asymmetries in behaviour could be widespread among vertebrates and that the direction of such asymmetries tends to be strikingly similar in closely related species, thus supporting the hypothesis of an early evolution of laterality in brain and behaviour.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour

Journal Article↗

PubMed1997

Sexual selection constrained by internal fertilization in the livebearing fish Xenotoca eiseni

Fish of the family Goodeidae have an advanced form of viviparity but males lack a specialized copulatory organ. Goodeids show reduced sexual-size dimorphism compared with the other livebearing families of the order Cyprinodontiformes. I investigated some mechanisms of sexual selection acting on body size in the goodeid fish Xenotoca eiseni. Both males and females strongly prefer mates of their own size. Comparison of mating activities in pairs with various degrees of size difference between males and females showed that matched pairs copulated more successfully. Similar mate preference in the two sexes thus appears to be the consequence of the primitive method of internal fertilization that requires the partners to be exactly synchronized during sperm transfer. Competition for access to a female was intense and body size determined the hierarchy in a small group. However, unless the size of the female was close to that of the dominant male, assortative mate preferences prevailed and the large-male advantage in competition was offset. Reduced size dimorphism in X. eiseni and in other goodeids may be explained by constraints on the action of sexual selection imposed by the need for effective fertilization.Copyright 1997 The Association for the Study of Animal BehaviourCopyright 1997The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1997

Lateral asymmetries during escape behavior in a species of teleost fish (Jenynsia lineata).

Lateral asymmetries in the direction of turning during escape behavior in a species of teleost fish, Jenynsia lineata, are reported. When faced with the visual image of a simulated predator, approximately half of the individuals exhibited a significant bias to turn rightwards or leftwards, and the asymmetry tended to be retained when the same fish were retested 1 month later. Some morphological characters (pectoral fin rays, scales in natural row, supraorbital, preopercular, and postotic pores) were measured to check whether the degree of behavioral asymmetry was correlated with morphological fluctuating asymmetries associated with environmental stress or reduced heterozygosis. The results showed that it was not. The implications of these results for the interpretation of behavioral lateralization at the individual and population level are discussed.

Animals↗

PubMed1997

Rotational swimming preferences in mosquitofish: evidence for brain lateralization?

Rotational preferences of mosquitofish (Gambusia holbrooki) were investigated in circular tanks with a group of females or a group of predators located at the centre, or during spontaneous swimming in absence of any particular target. Mosquitofish swam preferentially clockwise in presence of the predators, whilst no significant preferences appeared with the females or during spontaneous swimming. Similar rotational biases have been reported previously only for rodents and marine mammals: the present findings suggest that even teleost fish may possess lateralized brains.

Animals↗

PubMed1997

Detour tests reveal task- and stimulus-specific behavioral lateralization in mosquitofish (Gambusia holbrooki).

We studied detour responses of male mosquitofish faced with a vertical-bar barrier through which a group of females was visible. Mosquitofish showed a consistent population bias to detour the barrier preferentially leftwise when a straight barrier was used, whilst the asymmetry disappeared if a U-shaped barrier was used. The leftward bias was apparent even when using a simulated-predator as a target (which induced detour behaviour for predatory-inspection responses), but not when using an empty environment or a group of males as a target. Moreover, when faced with an opaque barrier, mosquitofish tended to turn on their right side. These lateral biases could be accounted for in terms of a right eye preference during lateral (monocular) fixation of any stimulus of interest, suggesting functional lateralization in a teleost species for the analysis of visual information.

Animals↗