Mixed Size Groups Research Articles

Application of digital colorimeter for preliminary characterization of gold nanoparticle swarms produced by Termitomyces heimii using a novel Bioinspired Microfluidics assay

In our laboratory work extending over several years we have successfully studied the biogeochemical role of termite mounds and their occupants the termites and the exosymbiont fungus-Termitomyces. Fungi appear to be promising for large scale production of nanoparticles (NPs) as these are simpler to grow both in laboratory and at industrial scale. This paper reports a novel microfluidics based assay system to detect Gold bioreduction capacity of different tissues in tissue based and cell free environment. Using sterile microtest well, different tissues such as umbo, pileus, lamellae, stipe context, stipe epicutis, pseudorrhiza context, pseudorrhiza epicutis of Termitomyces heimii mature fruitbodies were tested with 200μl chloroauric acid (one mM) and after an interval of 5,10, 15, 30, 45, 60, 120 min and 12, 24 and 48 hours. The results in terms production of distinct nanoparticles were directly visualized microscopically and using mobile based digital colorimeter. Membrane filtered sterile water soluble extracts (SWSE) from the same tissues were similarly screened. The results manifested by mono and polydisperse GNPs and microparticles of mixed size groups demonstrated that cell free system can be potentially useful for bioinspired fabrication of GNPs. Further work in this direction is in progress using several termitomyces cultures.

The non-additive effects of body size on nest architecture in a polymorphic ant.

Like traditional organisms, eusocial insect societies express traits that are the target of natural selection. Variation at the colony level emerges from the combined attributes of thousands of workers and may yield characteristics not predicted from individual phenotypes. By manipulating the ratios of worker types, the basis of complex, colony-level traits can be reduced to the additive and non-additive interactions of their component parts. In this study, we investigated the independent and synergistic effects of body size on nest architecture in a seasonally polymorphic harvester ant, Veromessor pergandei Using network analysis, we compared wax casts of nests, and found that mixed-size groups built longer nests, excavated more sand and produced greater architectural complexity than single-sized worker groups. The nests built by polymorphic groups were not only larger in absolute terms, but larger than expected based on the combined contributions of both size classes in isolation. In effect, the interactions of different worker types yielded a colony-level trait that was not predicted from the sum of its parts. In nature, V. pergandei colonies with fewer fathers produce smaller workers each summer, and produce more workers annually. Because body size is linked to multiple colony-level traits, our findings demonstrate how selection acting on one characteristic, like mating frequency, could also shape unrelated characteristics, like nest architecture.This article is part of the theme issue 'Interdisciplinary approaches for uncovering the impacts of architecture on collective behaviour'.

The role of density and relatedness in wild juvenile A tlantic salmon growth

Growth is a key life-history trait in fish that is influenced by both abiotic (such as temperature and water chemistry) and biotic factors (such as density and food availability). Investigating how growth performance is influenced by such factors in the wild is important for understanding how population processes influence animals in natural environments and for predicting the response to conservation and management strategies that manipulate these conditions. The theory of kin selection predicts that significant growth and survival benefits are conferred upon animals associating with close relatives. However, resource competition may be more intense among close relatives, and little is known about the trade-off between these two processes under different ecological conditions. Here, we examine the correlation between naturally occurring densities and kin-biased growth rate using a species where kin recognition has a strong impact on behaviour in laboratory studies, but where, paradoxically, field investigations have failed to document predicted kin-biased growth or survival. Intra- and inter-family differences in growth rate of juvenile Atlantic salmon Salmo salar were studied to examine how relatedness (groups of full-sibling fish and groups of mixed-sibling fish) and sibling group (family/genotype) affect salmon parr growth, and the correlation of growth rate under a range of naturally occurring densities. Parentage and relatedness of neighbouring fish were assigned using microsatellite and passive integrated transponder tags, which allowed the growth estimation of individual fish. The results show that growth rate was significantly influenced by both sibling group (family of origin) and also by an interaction between relatedness and density. The latter finding indicates that at higher densities, full-sibling groups achieved higher growth rates in comparison to mixed-sibling groups. Thus, the growth benefits of associating with relatives are not conferred under all ecological conditions, but it becomes most apparent at high density when resource competition is greatest.

CONTEXT-DEPENDENT KIN DISCRIMINATION IN LARVAL FOUR-TOED SALAMANDERS HEMIDACTYLIUM SCUTATUM (CAUDATA: PLETHODONTIDAE)

We studied kin discrimination in the larvae of the four-toed salamander Hemidactylium scutatum. The results of a spatial affinity assay supported the hypothesis that larvae can recognize kin and do so whether they have been raised alone or with siblings. Larvae were attracted to siblings and did not avoid non-siblings. Two additional experiments tested the hypothesis that kin discrimination is a function of predator density. The consistent predator avoidance pattern of larval H. scutatum was to lower activity level. In the experiment characterized by a higher predator density, sibling groups of larvae exposed to a predator lowered their amount of swimming more than larvae in mixed sibling groups. These results are consistent with the hypothesis of context-dependent kin discrimination and suggest that individuals can balance costs and benefits of behaviors as a function of ecological and social factors. This study is the first to demonstrate kin recognition in the larval stage of any species in the family Plethodontidae.

Factors which affect the occurrence of cannibalism and the broad-headed "cannibal" morph in larvae of the salamander Hynobius retardatus

Cannibalism in amphibian larvae may be suppressed among siblings in comparison to distant relatives or nonkin, even when a "cannibal" morph that can consume conspecifics shows adaptive advantages. Two experimental studies were undertaken to analyze factors which affect the frequency of cannibalism and the occurrence of the broad-headed "cannibal" morph in larvae of the salamander Hynobius retardatus. The first experiment investigated whether or not the broad-headed "cannibal" morph is only induced after performing cannibalism. Because the broad-headed "cannibal" morph was observed in larval populations that showed no cannibalism, it was concluded that the "cannibal" morph could be induced without actual cannibalism. Second, possible factors affecting the occurrence of the broad-headed "cannibal" morph were analyzed with respect to the density of larvae, level of food supply, and kinship among larvae, alone or in combination. Appearance of the broad-headed "cannibal" morph was affected by interactive effects of density×kinship: although the morph was induced significantly more often at a higher density if the conspecifics were distantly or not related, it was strongly suppressed even at high density if larval kinship was very close or among siblings. In contrast, the frequency of cannibalism was independently affected by larval density, level of food supply, and kinship among larvae: it was significantly larger at high than at low larval densities, at low than at high food supply, and in mixed-sibling groups than in pure sibships. These results suggest that the "cannibal" morphs in H. retardatus are induced even without cannibalism at a high density of conspecifics in mixed-sibling groups, but the occurrence of this morph, which continuously consumes conspecifics, is suppressed among siblings.

Cannibalism and the Resulting Dimorphism in Larvae of a Salamander Hynobius retardatus, Inhabited in Hokkaido, Japan

Abstract A cannibalism in the larvae of a salamander (Hynobius retardatus) and a resultant dimorphism were firstly described in laboratory-raised population. The cannibalistic larva develops to a “broad-headed” morph which has a wider head and grows faster compared with a non-cannibalistic “typical” morph. Laboratory experiments were conducted to examine a possible relationship between the dimorphism and cannibalism. Level of food supply and kinship of larvae affected the frequency of cannibalism. Low level of the food supply resulted in higher incidence of the cannibalism. The frequency of cannibalism in siblings was significantly lower than in the mixed-sibling groups. Possible biological significance of the cannibalism in this species was discussed.

Effect of size-sorting on biomass gain and individual growth rates in Arctic charr, Salvelinus alpinus L.

The rearing of Arctic charr in size-sorted groups did not result in any increase in biomass gain over that obtained in mixed-size groups. On the contrary, fish reared in size-sorted groups suffered a growth disadvantage when compared with fish of similar initial size reared in mixed groups. It is suggested that high levels of interactions between fish of similar size may be a major factor influencing growth of fish in size-sorted groups.

An Observational Study of Small-Group Mathematics Instruction in Elementary Schools

This article reports a naturalistic study of small-group instruction in elementary school mathematics classes. Three school districts from three cities (a small suburban city, a large urban city, and a middle-sized city) in three midwestern states were studied. Observations (N = 206) of entire mathematics periods were made in the classrooms of 33 teachers (primarily fourth-, fifth-, and sixth-grade) in 21 schools. This article describes the types of small-group formats observed, the variation in teachers’ use of time in 12 teaching functions, and the extent to which group structure and use of teaching functions affected the task climate in which students learned mathematics. Six types of small-group formats were found: whole-class ad hoc, two groups, three groups, four groups or more (mixed-size groups), heterogeneous work groups (cooperative learning), and individualized grouping.

EFFECTS OF SIZE AT STOCKING ON COMPETITION AND GROWTH OF ALL‐MALE TILAPIA HYBRIDS

ABSTRACTTriplicate ponds (0.07‐ha) were stocked with either a single size group (11–12 cm) or mixed size groups (either smalls 7–8 cm, mediums 11–12 cm or larges 15–16 cm) of all‐male tilapia hybrids of female Tilapia nilotica x male T. hornorum. After 140 days, smalls, mediums and larges gained 1.89, 3.10 and 2.59 g/day in mixed stocking, respectively, while mediums in single stocking gained 2.59 g/day. In mixed stocking, growth of smalls was depressed due to competition with mediums, larges, or both. Larges apparently expended mre energy on nest building and guarding, thus allowing mediums to maximize their food intake and growth. Lack of a predetermined hierarchy under single stocking resulted in depressed growth.

The respiratory metabolism of selected lumbricidae

Open-system infra red gas analysis was used to measure the CO2 output throughout a year of four species of earthworm. The respiratory quotients (R.Q.s) of the four species were determined by means of a Warburg apparatus and it was found that they varied with season. In some instances R.Q.s did not fall within the expected range of 0.7 to 1.0 and the low values were attributed to calciferous gland activity and the fixation of metabolic CO2.The results from CO2 output measurements at 10°C and R.Q.s were used to calculate oxygen uptake, this varied seasonally but the mean annual values at 10°C for adult, large immature and small immature A. rosea were 64.17, 72.66 and 78.56 μl O2 g-1 fresh wt h-1 respectively. Mixed size groups of L. castaneus had a mean annual oxygen consumption at 10°C of 155.83 μl O2 g-1 fresh wt h-1 and equivalent values for D. rubida and O. cyaneum were 112.02 and 69.35 μl O2 g-1 fresh wt h-1. The apparent relationship between a high respiratory rate per unit weight and a litter dwelling habit (e.g. L. castaneus and D. rubida) disappeared when allowance was made for the weight of gut contents. Mean annual values for oxygen uptake in μl O2 g-1 gut free fresh wt h-1 at 10°C were L. castaneus (194.79), D. rubida (142.22), A. rosea (95.70) and O. cyaneum (139.28). No size specific metabolism could be demonstrated either within or between species, this is believed to be correlated with the different levels of activity shown by different species and their life stages.Rates of oxygen consumption per unit weight for A. rosea were shown to be proportional to ambient temperature. Q 10 slopes of this relation, between 6 and 15°C, were higher for large immature A. rosea (2.42) and small immatures (1.96) than for adult clitellate worms (1.42). The mean Q 10 relationship for all size classes of A. rosea was 1.93 over the same temperature range and the equivalent value for cocoons was 1.63. The relationship between the oxygen consumption rate of all size classes of A. rosea and ambient temperature was not significantly affected by acclimatisation at 5 and 10° C prior to measurements being made at 6, 10 and 15° C.