The effect of shoal size on patterns of body colour segregation in mollies

Individual white and black mollies Poecilia latipinna spent significantly more time near the larger group when given the choice between two shoals of similar colouration to themselves. When given the choice between a large and a small shoal of dissimilar colouration to themselves, black test fish spent significantly more time with the larger shoal while white test fish showed no preference for either group. Both white and black mollies chose the smaller of two shoals when given the choice between a large dissimilarly coloured shoal and a small similarly coloured shoal. The results indicate that mollies actively discriminate between shoals on the basis of both body colour and shoal size. However, body colour segregation appears to have a stronger influence on shoal choice.     

Nymphal Development and Reproduction of Podisus nigrispinus (Heteroptera: Pentatomidae) Fed With Combinations of Tenebrio molitor (Coleoptera: Tenebrionidae) Pupae and Musca domestica (Diptera: Muscidae) Larvae

The development and reproduction of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) fed on Tenebrio molitor L. (Coleoptera: Tenebrionidae) and Musca domestica L. (Diptera: Muscidae) were studied in four treatments. P. nigrispinus was permitted to feed on: (1) T. molitor pupae (T 1 ); (2) Musca domestica larvae (T 2 ); (3) both prey supplied simultaneously (T 3 ); (4) both prey supplied on alternate days (T 4 ). Duration of the nymphal period of P. nigrispinus was similar in all diets studied with nymphal viability of approximately 75%. Heavier females were obtained in T 1 and T 4 , but no correlation between this factor and the reproductive rate of the predator was found. Therefore, the use of body weight as a parameter to evaluate rearing quality should be approached with caution. However, females of this predator showed higher egg and nymph production when they received both prey. For this reason P. nigrispinus should be reared with T. molitor and M. domestica simultaneously or on alternate days.     

Laboratory rearing of <Emphasis Type="Italic">Theileria annulata</Emphasis>-free <Emphasis Type="Italic">Hyalomma anatolicum anatolicum</Emphasis> ticks

Hyalomma anatolicum anatolicum is a three-host tick which transmits Theileria annulata infection in Indian cattle. Laboratory rearing of ixodid ticks is an essential requirement of any laboratory engaged with research on ticks and tick borne diseases. The Entomology laboratory of Indian Veterinary Research Institute is fully equipped with all the facilities and skilled manpower to maintain a homogenous H. a. anatolicum population throughout the year. The continuous supply of eggs, larvae and adults of H. a. anatolicum is maintained to meet out the demand of different experiments viz., preparation of tick antigens for immunization of animals, experimental challenge, isolation of genomic DNA and RNA. Maintenance of a H. a. anatolicum colony free of T. annulata infection is imperative for the experimental challenge infestation on cross-bred (Bos indicus × B. taurus) calves, in order to prevent the transmission of T. annulata infection to the experimental animals. A system has been developed in the laboratory in which the larvae of H. a. anatolicum were fed on New Zealand white rabbits and the dropped fed nymphs molted to adults are fed on cross-bred calves free of T. annulata infection. This synthetic cycle prevents the transstadial transmission of T. annulata as the rabbits are unsusceptible to T. annulata infection and only the adults were fed on cross-bred animals. Moreover, absence of transovarial transmission of T. annulata prevents the chance of carry over infection to experimental animals in the next cycle. Declaration: The experiments have been conducted in accordance with the approved guidelines of Committee for the Purpose of Control and Supervision of Experimentation on Animals (CPCSEA). Besides, the institute animal ethics committee continuously monitored the animal experimentation.     

Functional Consequences of Iron Overload in Catecholaminergic Interactions: the Youdim Factor

The influence of postnatal iron overload upon implications of the functional and interactive role of dopaminergic and noradrenergic pathways that contribute to the expressions of movement disorder and psychotic behaviours in mice was studied in a series of experiments. (1) Postnatal iron overload at doses of 7.5 mg/kg (administered on Days 10–12 post partum) and above, invariably induced a behavioural syndrome consisting of an initial (1st 20–40 min of a 60-min test session) hypoactivity followed by a later (final 20 min of a 60-min test session) hyperactivity, when the mice were tested at adult ages (age 60 days or more). (2) Following postnatal iron overload, subchronic treatment with the neuroleptic compounds, clozapine and haloperidol, dose-dependently reversed the initial hypoactivity and later hyperactivity induced by the metal. Furthermore, DA D₂ receptor supersensitivity (as assessed using the apomorphine-induced behaviour test) was directly and positively correlated with iron concentrations in the basal ganglia. (3) Brain noradrenaline (NA) denervation, using the selective NA neurotoxin, DSP4, prior to administration of the selective DA neurotoxin, MPTP, exacerbated both the functional (hypokinesia) and neurochemical (DA depletion) effects of the latter neurotoxin. Treatment with L-Dopa restored motor activity only in the animals that had not undergone NA denervation. These findings suggest an essential neonatal iron overload, termed “the Youdim factor”, directing a DA–NA interactive component in co-morbid disorders of nigrostriatal-limbic brain regions. Special issue dedicated to Dr. Moussa Youdim.     

活跃性和社会性对中华倒刺鲃集群行为的影响

为考察群体中不同的个性组成对鱼类集群行为的影响及其内在机制,选取中华倒刺鲃(Spinibarbus sinensis)幼鱼为实验对象,依次测定其活跃性和社会性,随后分别根据活跃性和社会性的高低分为高、低和混合活跃性(或社会性)鱼群,考察鱼群中不同个性组成对集群时的整体运动特征以及每尾鱼的个体运动特征的影响。研究发现：(1)中华倒刺鲃的个性特征稳定且个体间变异较大;(2)高活跃性鱼群的运动时间比和速度同步性均大于低活跃性鱼群,而混合鱼群位于二者之间且与两个同质性鱼群均无显著差异;高社会性鱼群速度同步性显著小于低社会性和混合社会性鱼群,而后两者之间没有显著差异。(3)活跃性特征与集群运动时每尾鱼的运动特征(速度及其同步性等)相关,社会性特征不仅与上述运动特征关联,还与凝聚力大小(距鱼群质心距离)相关。研究表明：(1)鱼群的活跃性和社会性组成均对集群行为产生重要影响,但其内在机制截然不同。主要表现为：就活跃性而言,群体的运动状态是由群体中所有成员共同决定(平均决定机制);就社会性而言,少数低社会性成员对鱼群的运动水平表现有着主导作用(少数决定机制);(2)实验鱼的活跃性在集群行为中得到了较大...     

Hatching sex ratio and sex specific chick mortality in common terns Sterna hirundo

Bias in sex ratios at hatching and sex specific post hatching mortality in size dimorphic species has been frequently detected, and is usually skewed towards the production and survival of the smaller sex. Since common terns Sterna hirundo show a limited sexual size dimorphism, with males being only about 1–6% larger than females in a few measurements, we would expect to find small or no differences in production and survival of sons and daughters. To test this prediction, we carried out a 2-year observational study on sex ratio variation in common terns at hatching and on sex specific post hatching mortality. Sons and daughters hatched from eggs of similar volume. Post hatching mortality was heavily influenced by hatching sequence. In addition, we detected a sex specific mortality bias towards sons. Overall, hatching sex ratio and sex specific mortality resulted in fledging sex ratios 8% biased towards females. Thus, other reasons than body size may be influencing the costs of rearing sons. Son mortality was not homogeneous between brood sizes, but greater for two-chick broods. Since adults rearing two-chick broods were younger, lighter and bred consistently later than those rearing three-chick broods, it is suggested that lower capacity of two-chick brood parents adversely affected offspring survival of sons. Though not significantly, two-chick broods tended to be female biased at hatching, perhaps to counteract the greater male-biased nestling mortality. Thus, population bias in secondary sex ratio is not limited to strongly size dimorphic species, but species with a slight sexual size dimorphism can also show sex ratio bias through a combination of differential production and mortality of sons and daughters.     

Dissecting chill coma recovery as a measure of cold resistance: evidence for a biphasic response in Drosophila melanogaster

Cold resistance in insects has traditionally been measured in terms of survival following a stress, but alternative methods are increasingly being used because of their relevance to the ecology of organisms and their utility in characterizing variation among species, populations and individuals. One such method capable of discriminating among Drosophila species and conspecific Drosophila populations from different environments is adult chill coma recovery time, the time taken for adults to become active again after being knocked down by a cold stress. Here we characterized the chill coma response of D.melanogaster in detail. Adults were exposed to a range of temperatures and stressful periods prior to measuring recovery. Recovery from chill coma in D.melanogaster was biphasic; as flies were stressed under cooler temperatures, recovery times leveled off and then decreased before sharply increasing again as mortality starts to occur. This biphasic response has previously been observed in D.subobscura where it has a somewhat different shape. A second mechanism therefore acts at relatively lower temperatures to ameliorate the effects of the cold stress. When D.melanogaster were reared at 19 and 25 °C for two generations, the shape of the curve relating temperature to recovery time was similar, but flies from the warmer temperature had longer recovery times and showed responses that leveled off and then decreased at relatively higher temperatures. As exposure time to cold stress was increased, recovery times also increased except at mild stress levels. Chill coma recovery in D.melanogaster is a complex trait and likely to reflect multiple underlying components.     

Sedimentary and poroperm anatomy of shoal-water carbonates (Muschelkalk,South-German Basin): an outcrop-analogue study of inter-well spacing scale

Outcrop-analogue studies are rarely carried out on a very detailed scale of just several hundred metres, which represents a common inter-well spacing. Superb outcrop conditions in south Germany for Upper Muschelkalk shoal-water carbonates located on a carbonate ramp allowed us to perform a detailed analysis of their sedimentary and poroperm organisation. The cyclic structure of the carbonates is evident in three types of genetic sequences 1–3 m thick, which in turn build larger-scale sequences. Lateral variations of microfacies in the study area are restricted to a few percent of individual components, leading to an excellent degree of correlation of sequences. Microfacies do not correlate well with porosity and permeability. Therefore, in order to characterise reservoir properties of the carbonate-sand shoal it is necessary to integrate rock fabric and pore type. The cyclic framework outlined in this outcrop analogue provides a predictive tool for subsurface reservoir characterisation. The stratigraphic sequences correspond to fluid-flow units showing the thickest (up to 2 m) and best reservoir qualities ( up to 20%, k up to 53 md) towards the overall regressive maximum.     

Body size and shoaling in fish

Shoaling behaviour is generally described as a trade-off between the anti-predator benefits of living in groups and the costs of increased foraging competition. An individual's fitness varies as a function of shoal size and shoal composition, and this relationship is potentially body length dependent. As teleost fishes show indeterminate growth, many populations exhibit a broad range of individual body lengths. The latter is used as a criterion in active choice of shoaling companions, and shoals are often size-assorted. This reduces predation risk through minimizing phenotypic oddity, and may reduce competition between size-classes. There is some evidence for a positive relationship between shoal size and the body length of shoal members, although it remains unclear whether this is a result of active shoal-size choice or a by-product of the body length distribution of the population. Shoal membership is highly dynamic and individuals may maximize their fitness by switching frequently between groups of varying size and composition in response to changes in their physiological stage and the external environment. Fish shoals provide an excellent opportunity to investigate the functions and mechanisms of group living, and future studies should aim to take an integrated view of individual behaviours, group size and phenotypic composition when investigating group choice decisions.