Visual lateralization and development of spatial and social spacing behaviour of chicks (Gallus gallus domesticus)

We investigated whether the development of spatial behaviour of the domestic chicken is influenced by light exposure of the embryo, as is known to be the case for some other lateralized visual functions. Ninety-six chicks were incubated in the dark or exposed to light during the final days of incubation. Half of the chicks in each group had the experience of moving behind opaque screens from 10 to 12 days of age. The other half were given transparent screens as a control. Chicks were tested in a detour test and a rotated floor test and their dispersal in groups was observed in larger pens. In the rotated floor test, chicks that had had experience with opaque screens used distal cues significantly more often than chicks that had experience with transparent screens (P = 0.042), regardless of whether they had been exposed to light before hatching or incubated in the dark. There were no significant differences between treatments in the detour test or in the dispersal behaviour. Hence, visual lateralization has no influence on the development of the spatial behaviour that we tested, whereas the occlusion experience is quite specific and results in shifted attention to distal spatial cues.     

The occurrence of the second moult of Ascaris lumbricoides and Ascaris suum

Maung M. 1978. The occurrence of the second moult of Ascaris lumbricoides and Ascaris suum. International Journal for Parasitology 8: 371–378. Eggs of Ascaris lumbricoides and A. suum were cultured at 28°C and observed daily. Larvae were released by pressure, by artificial hatching with CO₂, and by natural hatching after infection of laboratory mice. The early stages of development in the egg were observed to comprise two moults, one occurring immediately after the other. Both moults were initiated within the egg, but the time of completion of the second moult varied considerably, and in some instances was not completed until the larvae reached the liver of experimentally infected animals.     

基于物理模型实验的光倒刺鲃生态行为学研究

建立了基于天然河道的物理模型,通过控制实验研究水环境因子对鱼类行为的影响。文中选取了金沙江下游2.6 km河段建立物理模型,以南方水系的经济鱼类光倒刺鲃为研究对象,进行了鱼的行为对底质和流速的响应实验。分析得出,光倒刺鲃对砂卵石底质的选择明显大于其它底质且差异极其显著(P<0.01),光倒刺鲃2龄幼鱼期的喜好流速范围为0.3-0.6 m/s;研究同时发现水流紊动强度对光倒刺鲃行为具有重要影响。该研究结果可以为光倒刺鲃栖息地模型提供参考。     

Preference for structured environment in zebrafish (Danio rerio) and checker barbs (Puntius oligolepis)

Information about the welfare and husbandry of pet and laboratory fish is scarce although millions of fish are sold in pet shops and used in laboratory research every year. Inadequate housing conditions can cause behavioural problems also in fish since they are complex animals with sophisticated behaviour. In this study, we investigated the influence of environmental complexity on compartment preference and behaviour in zebrafish (Danio rerio) and checker barbs (Puntius oligolepis). For the preference test, large aquaria were divided by two semi-transparent walls of Plexiglas into an empty compartment, a structured compartment enriched with plants and clay pots, and a smaller compartment in-between, where food was provided. For observation, the empty and structured compartments were divided into six zones of similar size by defining three vertical layers and two horizontal areas (back vs. front area). Seven groups of six to nine zebrafish and seven groups of seven or eight checker barbs were observed on four days each (within a time period of ten days) to assess compartment use and activity, and to assess behavioural diversity and use of zones within compartments. Both zebrafish and checker barbs showed a significant preference for the structured compartment. Nevertheless, in neither species did behavioural diversity differ between the empty and structured compartment. Zebrafish used all zones in both compartments to the same extent. Checker barbs, however, used the structured compartment more evenly than the empty compartment, where they mainly used the lower and middle zones. These results suggest that zebrafish and checker barbs have a preference for complex environments. Furthermore, they indicate that the behavioural and ecological needs of fish may vary depending on species, and recommendations for husbandry should be specified at species level.     

In the eye of the beholder: visual mate choice lateralization in a polymorphic songbird

Birds choose mates on the basis of colour, song and body size, but little is known about the mechanisms underlying these mating decisions. Reports that zebra finches prefer to view mates with the right eye during courtship, and that immediate early gene expression associated with courtship behaviour is lateralized in their left hemisphere suggest that visual mate choice itself may be lateralized. To test this hypothesis, we used the Gouldian finch, a polymorphic species in which individuals exhibit strong, adaptive visual preferences for mates of their own head colour. Black males were tested in a mate-choice apparatus under three eye conditions: left-monocular, right-monocular and binocular. We found that black male preference for black females is so strongly lateralized in the right-eye/left-hemisphere system that if the right eye is unavailable, males are unable to respond preferentially, not only to males and females of the same morph, but also to the strikingly dissimilar female morphs. Courtship singing is consistent with these lateralized mate preferences; more black males sing to black females when using their right eye than when using their left. Beauty, therefore, is in the right eye of the beholder for these songbirds, providing, to our knowledge, the first demonstration of visual mate choice lateralization.     

The settlement behaviour of planulae larvae of the hermatypic coral Favia fragum (Esper)

Experiments on the settlement behaviour of planulae larvae of the reef coral Favia fragum (Esper) are described. The larvae are positively phototaxic upon release but reverse this and become attracted to dark surfaces, corners, crevices, and the undersides of objects on the bottom. Clean glass surfaces were preferred to surfaces covered with biological slime but there was no preference for rough against smooth surfaces. There was clear evidence of gregarious settlement behaviour, the planulae being able to recognize both adult colonies and previously settled juveniles. A distinction was made between crawling and swimming larvae, and the consequences of their differences in behaviour on the spatial distribution of Favia on reef are discussed. Settlement behaviour of Favia is similar in many respects to that of the Pacific reef coral Pocillopora damicornis (Dana) but is distinguished by gregarious settlement and by a preference for clean surfaces over surfaces covered with biological slime.     

Bipedal tool use strengthens chimpanzee hand preferences

The degree to which non-human primate behavior is lateralized, at either individual or population levels, remains controversial. We investigated the relationship between hand preference and posture during tool use in chimpanzees (Pan troglodytes) during bipedal tool use. We experimentally induced tool use in a supported bipedal posture, an unsupported bipedal posture, and a seated posture. Neither bipedal tool use nor these supported conditions have been previously evaluated in apes. The hypotheses tested were 1) bipedal posture will increase the strength of hand preference, and 2) a bipedal stance, without the use of one hand for support, will elicit a right hand preference. Results supported the first, but not the second hypothesis: bipedalism induced the subjects to become more lateralized, but not in any particular direction. Instead, it appears that subtle pre-existing lateral biases, to either the right or left, were emphasized with increasing postural demands. This result has interesting implications for theories of the evolution of tool use and bipedalism, as the combination of bipedalism and tool use may have helped drive extreme lateralization in modern humans, but cannot alone account for the preponderance of right-handedness.     

Nematicidal activity of Haplophyllum tuberculatum and Plectranthus cylindraceus oils against Meloidogyne javanica

The potentials of Haplophyllum tuberculatum and Plectranthus cylindraceus oils to control Meloidogyne javanica were investigated in vitro and in a greenhouse. A mixture of Haplophyllum and Plectranthus oils (1:1) was highly toxic to M. javanica in vitro, as it killed all nematode juveniles and inhibited hatching of eggs at 12.5 μg/ml concentration after 24 h exposure time, as did carbofuran at the same concentration. In the green-house, tomatoes grown in soil treated with a combination (1:1) of the two oils developed fewer root galls than those grown in soil treated with higher doses of either oil. The oil mixture, at 2.5 and 5.0 μg/ml of soil, was not phytotoxic to tomato plants as evident from the appearance and height of plants after 12 weeks exposure time, compared to treatment over the same period at lower effective doses. The nematicidal activity of the combined essential oils was suggested by the presence of C₁₀ dienes, C₁₀ trienes and C₁₀ phenol.     

Factors controlling in vitro hatching of Vairimorpha plodiae (Microspora) spores and their infectivity to Plodia interpunctella,Heliothis virescens, and Pieris brassicae

Factors which influence the hatching of spores and proliferation of stages of the microsporidium Vairimorpha plodiae in two susceptible insects, Plodia interpunctella and Heliothis virescens, and one nonsusceptible insect, Pieris brassicae, were investigated. Spores hatched in 0.1 and 1 m KCl solutions when subjected to a change in pH, from pH 11 to pH 8. K⁺ was essential for hatching; NaCl solutions were not effective. Ca²⁺ and Mg²⁺ inhibited hatching, and calcium and magnesium chelating agents enhanced it. All three insect species had alkaline midgut contents and smooth, fragile peritrophic membranes. Spores hatched inside the midguts of all three insect species (P. interpunctella: maximum rate, 92.5%; H. virescens, 91.5%; P. brassicae, 82%). Sporoplasms were observed in the midgut epithelial and associated tracheole cells of P. brassicae. Both H. virescens and P. brassicae became infected when injected intrahemocoelically with spores.     

Variation in the hatching behaviour of Nematodirus battus: Polymorphic bet hedging?

Previous work on the transmission dynamics of Nematodirus battus, an important nematode parasite of farmed ruminants in temperate regions, suggests that it operates a bet-hedging strategy. Hatching of cold-sensitised eggs is concentrated in spring, while alternative hatching of non-cold-sensitised eggs in autumn mitigates the risk of poor conditions for hatching in spring or host absence during peak larval availability. Isolates from Scotland showed much less propensity to hatch without chilling than the previously characterised isolate from southern England. Nematodirus battus eggs from a hill farm in Scotland showed intermediate proportions of non-chilled hatching, perhaps related to unpredictability of climate at higher altitudes. Geographic polymorphism in larval behaviour appears to be present in the form of differing chilling requirements for egg hatching. Since bet-hedging through trait diversification is a plausible and demonstrated strategy for coping with environmental unpredictability, it is a likely target for adaptation to climate change. Predictions of disease epidemiology in a changing climate should incorporate parasite adaptation, but further theoretical and empirical characterisations of likely evolutionary responses are needed before this is possible for the most economically important systems.     

‘Handedness’ in snakes? Lateralization of coiling behaviour in a cottonmouth, Agkistrodon piscivorus leucostoma, population

Studies have documented the presence of behavioural lateralization in many groups of lower vertebrates, demonstrating that these behaviours are not limited to mammals and birds. These studies suggest that the evolution of brain lateralization, often linked to lateralized behaviours, may have occurred early in evolutionary history and may not have been the result of multiple independent evolutionary events as previously thought. The goal of this study was to further document behavioural lateralization in another group of lower vertebrates, snakes. Given the importance of the coiling posture to snakes, I examined the coiling behaviour of a cottonmouth population. Coiling asymmetries were found at both the individual and population levels. However, the adaptive significance and mechanisms influencing this behaviour remain undefined. Additional research is needed to explore these areas and to link the lateralized behaviours documented in this and other studies directly to brain asymmetries before the evolutionary history of brain lateralization can be further resolved. Copyright 2003 Published by Elsevier Ltd on behalf of The Association for the Study of Animal Behaviour.      

Prenatal light exposure affects early feather-pecking behaviour in the domestic chick

Recently we proposed that early feather pecking is a form of social exploration. Social recognition, important for exploration, is a lateralized function in the domestic chick. Lateralization of functions can be influenced by light exposure late in embryonic development. Therefore, we investigated whether this light exposure affected early posthatching feather-pecking behaviour in domestic chicks, Gallus gallus domesticus. White leghorn embryos either were exposed to light or remained in darkness in the last week of incubation. After hatching, they were housed in groups of two light-exposed and two dark-incubated chicks. Light-exposed chicks showed more feather pecking than did their dark-incubated cagemates. Dark-incubated chicks preferred to direct feather pecks to unfamiliar peers than to familiar peers; light-exposed chicks showed no preference. These effects were present in the first week after hatching and remained at least another 3 weeks. These results support the hypothesis that early gentle feather pecking is part of the normal behavioural repertoire of young chicks and influences social exploration. We discuss a possible mechanism underlying these results. We also suggest that it may be worthwhile not to expose embryos to light during the last week of incubation when housing hatchlings in commercial conditions, where feather pecking is a serious problem.     

Semi-monthly reproductive cycles in male and female fiddler crabs, Uca pugnax

In the fiddler crab, Uca pugnax, numbers of displaying males, numbers of burrows with half-dome superstructures (hoods), numbers of females with decalcified vulvar opercula, and numbers of females hatching their eggs, all follow a semi-monthly cycle with peaks near the time of the spring tides. These are all aspects of reproduction in Uca. Decalcification of female opercula, although necessary for mating and egg deposition, is neither necessary nor sufficient for behavioural response to courting males. In fact, behavioural responsiveness to males probably precedes decalcification in most cases. The different aspects of the reproductive cycle are coordinated so that females and males are ready to mate at about the same time near one spring tide, and the resulting eggs will be ready to hatch on the next spring tide. Two decalcified females which were kept isolated from males produced fertile clutches, suggesting that stored sperm from a previous mating may fertilize eggs in a later cycle. This may be one reason for the relative rarity of observed matings or precopulatory behaviour in Uca.     

Eclosion hormone activity in developing embryos of the silkworm, Bombyx mori

The ultimate timing of hatching in the silkworm, Bombyx mori, is controlled by a circadian oscillator. The presence of eclosion hormone in developing embryos of the silkworm is demonstrated. Eclosion hormone activity first becomes detectable in embryos which have developed almost to the stage of the differentiation of the neuroendocrine system. Hormonal activity increases sharply to a maximum level 1 day before hatching and falls by about a half in the newly hatched larvae. Eclosion hormone was partially purified from the pharate first-instar larvae and approx, a 2100-fold purification was achieved. The molecular weight of the embryo eclosion hormone is estimated to be 7000 ～ 9000 Daltons by gel-filtration on Sephadex G-50 (superfine). The role of eclosion hormone on hatching behaviour of the silkworm, Bombyx mori, is discussed.     

Effect of dietary history and algal traits on feeding rate and food preference in the green sea urchin Strongylocentrotus droebachiensis

Feeding behaviour is influenced by a variety of factors, including nutritional requirements, the quality of available foods, and environmental conditions. We examined the effect of two factors, food morphology and dietary history, on the feeding rate and preference of the sea urchin Strongylocentrotus droebachiensis. Standardizing food shape and structure did not alter urchins' expected preference for the native kelp Laminaria longicruris over the invasive alga Codium fragile ssp. tomentosoides. However, when foods containing L. longicuris were shaped to mimic the algae, the C. fragile mimic was consumed more rapidly than the kelp mimic. Dietary history had no effect on single diet feeding rate. Urchins feeding on C. fragile consistently consumed twice as much (by mass) as those fed kelp, regardless of their previous diet. Despite higher feeding rates on C. fragile, urchins feeding on this alga were unable to compensate for its low energetic content and ingested less energy. Dietary history had a short-term effect on food preference, with urchins tending to prefer less familiar foods. Our findings suggest that urchins feed on C. fragile at a high rate, due to ease of handling and/or compensatory feeding, and that they do not a have strict preference hierarchy. Rather, food choice appears to reflect active maintenance of a mixed diet.     

The life cycle of Anguina agrostis: Embryogenesis

Bpird A. F. and Sptynes B. A. 1981. The life cycle of Anguina agrostis: embryogenesis. International Journal for Parasitology11: 23–33. Egg development, from laying to hatching, of two widely separated populations of Anguina agrostis, has been followed over a range of temperatures. Development rates for these two populations have been shown to be identical with a thermal optimum between 18 and 20°C. The minimum time recorded for embryogenesis through to hatching was 9–10 days.Embryogenesis was inhibited by temperatures of 27°C and above and hatching by temperatures greater than 23°C.No significant differences were detected in the dimensions of eggs from either population. These eggs have an average length of 95 μm and an average width of 38 μm.Electron microscope studies of sections through eggs undergoing synchronous development show that the first and apparently only moult of the larva in the egg commences about 7 days after the start of embryogenesis under optimal conditions. The sequence of morphological events that occur throughout embryogenesis are described and recorded for whole specimens observed at low resolution and the moulting sequence is described from high resolution electron micrographs of the cuticles of synchronously developing embryos and larvae.     

A calibration method to generate seasonal hatching profiles for the fiddler crabs Uca pugnax (Smith, 1870) and Uca minax (LeConte, 1855) (Decapoda : Brachyura)

A statistical method for generating seasonal egg hatching profiles is applied to the brachyuran crabs Uca pugnax (Smith) and U. minax (LeConte) in New Jersey. Calibration experiments quantified the time course of egg development, using serial egg sampling at 1- to 2- day intervals from marked ovigerous females maintained in cages in the field. Egg stage was ranked from 1 to 10, based on morphological changes during development. Equations for predicting the number of days remaining until hatching from egg developmental stage were obtained from the calibration experiments, using stepwise polynomial regression. To cover the reproductive season, three consecutive calibration experiments using 15 or more females were run for U. pugnax; two for U. minax. Significant seasonal differences in the time course of egg development were detected. Weekly collections of females for each species were made; the date of larval release for each ovigerous female was predicted from the proximate calibration equation, yielding weekly hatching profiles. Weekly hatching profiles were summed to obtain seasonal hatching profiles. The average number of broods produced per female over the reproductive season was 1.9 for U. pugnax and 1.6 for U. minax. Hatching peaks for both species were associated with spring tides. The merits of this and other methods used to estimate daily variation in egg hatching of crabs are discussed.     

Burrowing behaviour in the crayfish, Cambarus diogenes diogenes girard

The crayfish, Cambarus diogenes diogenesGirard (1852), spends most of its life cycle in individually constructed underground burrows. The architectural behavioral patterns and sequences with which adult C. d. diogenes excavate an underground chamber were evaluated. Two motor patterns (Pushing and Carrying) and three burrow stages (shallow depression, angular pit, and burrow with two openings) were identified. During the development of burrowing behaviour in juveniles, a third motor pattern (Fanning) occurred. While the three motor patterns are functional soon after hatching, crayfish may learn to orient the Carrying motor pattern for the most efficient excavation of a stage-3 burrow with two openings. The ground-water level determined the final structure of a burrow.     

Near anoxia and sulfide as possible factors influencing the spatial distribution of Acartia tonsa and Acartia clausi: Comparative evaluation of egg tolerance

In many coastal and estuarine areas the planktonic copepods Acartia tonsa and Acartia clausi show a spatial separation with A. tonsa restricted to brackish waters and confined environments and A. clausi inhabiting areas more influenced by sea water. The hatching and viability of A. tonsa and A. clausi eggs exposed to anoxia and anoxia/sulfide (conditions that are frequent in bottom waters of the most confined areas) was evaluated to determine if these stress factors play a role in the distribution of these species. Subitaneous eggs, spawned by laboratory reared organisms, were incubated in near anoxia (< 7.59 × 10^− 3 mmol O₂ L^− 1) or anoxia/sulfide (∼ 1 mmol L^− 1) for different periods (1, 4, 8 and 15 days), then transferred to normoxic conditions. The exposure of the eggs to near anoxia and sulfide appears to induce the same response (quiescence) in both species. Exposure times ≤ 8 days to near anoxia or anoxia/sulfide did not affect egg viability, while 15 day exposure caused significant declines in hatching success of both species. A significant difference between the effects of near anoxia and anoxia/sulfide was observed when incubation lasted 15 days; hatching of eggs exposed to sulfide being higher than that of eggs exposed to near anoxia for both species. No significant differences were observed between the two species in hatching success of eggs exposed to both near anoxia and anoxia/sulfide (with the exception of eggs incubated in near anoxia for 4 days). The results indicate that the impact of anoxia and sulfide on the eggs of the two Acartia species cannot be a factor explaining the spatial distribution in coastal and brackish environments of these copepods.Feeding experiments on A. clausi were also performed. Suitability of different algal species to rear this copepod was evaluated and the results were compared with data previously obtained for A. tonsa. Differences in feeding needs between A. clausi and A. tonsa are discussed.