Tracking larval insect movement within soil using high resolution X-ray microtomography

1. In contrast to above-ground insects, comparatively little is known about the behaviour of subterranean insects, due largely to the difficulty of studying them in situ. 2. The movement of newly hatched (neonate) clover root weevil (Sitona lepidus L. Coleoptera: Curculinidae) larvae was studied non-invasively using recently developed high resolution X-ray microtomography. 3. The movement and final position of S. lepidus larvae in the soil was reliably established using X-ray microtomography, when compared with larval positions that were determined by destructively sectioning the soil column. 4. Newly hatched S. lepidus larvae were seen to attack the root rhizobial nodules of their host plant, white clover (Trifolium repens L.). Sitona lepidus larvae travelled between 9 and 27 mm in 9 h at a mean speed of 1.8 mm h(-1). 5. Sitona lepidus larvae did not move through the soil in a linear manner, but changed trajectory in both the lateral and vertical planes.

Why are some handaxes symmetrical? Testing the influence of handaxe morphology on butchery effectiveness

The morphology of Acheulean handaxes continues to be a subject of debate amongst Lower Palaeolithic archaeologists, with some arguing that many handaxes are over-engineered for a subsistence function alone. This study aims to provide an empirical foundation for these debates by testing the relationship between a range of morphological variables, including symmetry, and the effectiveness of handaxes for butchery. Sixty handaxes were used to butcher 30 fallow deer by both a professional and a non-professional butcher. Regression analysis on the resultant data set indicates that while frontal symmetry may explain a small amount of variance in the effectiveness of handaxes for butchery, a large percentage of variance remains unexplained by symmetry or any of the other morphological variables under consideration.

Morphology, biomass and nutrient status of fine roots of Scots pine (Pinus sylvestris) as influenced by seasonal fluctuations in soil moisture and soil solution chemistry

A field monitoring study was carried out to follow the changes of fine root morphology, biomass and nutrient status in relation to seasonal changes in soil solution chemistry and moisture regime in a mature Scots pine stand on acid soil. Seasonal and yearly fluctuations in soil moisture and soil solution chemistry have been observed. Changes in soil moisture accounted for some of the changes in the soil solution chemistry. The results showed that when natural acidification in the soil occurs with low pH (3.5-4.2) and high aluminium concentration in the soil solution (> 3-10 mg l(-1)), fine root longevity and distribution could be affected. However, fine root growth of Scots pine may not be negatively influenced by adverse soil chemical conditions if soil moisture is not a limiting factor for root growth. In contrast, dry soil conditions increase Scots pine susceptibility to soil acidification and this could significantly reduce fine root growth and increase root mortality. It is therefore important to study seasonal fluctuations of the environmental variables when investigating and modelling cause-effect relationships.

Morphology and myofiber composition of skeletal musculature of the forelimb in young and aged wild type and myostatin null mice

Most current research into therapeutic approaches to muscle diseases involves the use of the mouse as an experimental model. Furthermore, a major strategy to alleviate myopathic symptoms through enhancing muscle growth and regeneration is to inhibit the action of myostatin (Mstn), a transforming growth factor-beta (TGF-beta) family member that inhibits muscle growth. Presently, however, no study has expanded the morphological analysis of mouse skeletal muscle beyond a few individual muscles of the distal hindlimb, through which broad conclusions have been based. Therefore, we have initially undertaken an expansive analysis of the skeletal musculature of the mouse forelimb and highlighted the species-specific differences between equivalent muscles of the rat, another prominently used experimental model. Subsequently, we examined the musculature of the forelimb in both young and old adult wild-type (mstn(+/+)) and myostatin null (mstn(-/-)) mice and assessed the potential beneficial and detrimental effects of myostatin deletion on muscle morphology and composition during the aging process. We showed that: (1) the forelimb muscles of the mouse display a more glycolytic phenotype than those of the rat; (2) in the absence of myostatin, the induced myofiber hyperplasia, hypertrophy, and glycolytic conversion all occur in a muscle-specific manner; and, importantly, (3) the loss of myostatin significantly alters the dynamics of postnatal muscle growth and impairs age-related oxidative myofiber conversion.

Male morphology and dishonest signalling in a fig wasp

Despite theoretical predictions, dishonest signalling has rarely been observed in aggressive interactions. We present evidence of such signalling in the nonpollinating. g wasp Philotrypesis sp. A ex Ficus rubiginosa. First, morphometric data indicated that an alternative 'atypical' male morph (17.8% of individuals) exists that tends to be larger in body size and has longer mandibles for a given body size than other 'typical' males. Second, behavioural observations suggested that males use mandible gape width (which depends on mandible length) as a cue to assess opponents before fights and retreat without escalating if they are unlikely to win, and, probably because their greater mandible gape width causes more opponents to retreat without escalating, that atypical males engaged in fewer fights than typical males for a given body size but had higher mating success. Third, atypical males were less likely to win fights than typical males of similar mandible length relative to opponents. In addition, we found that atypical males incur more injuries (greater receiver-dependent signal costs) than typical males of similar body size relative to rivals. We discuss the implications of our findings for future work on dishonest signalling. (C) 2009 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Floral morphology and development in quillajaceae and surianaceae (Fabales), the species-poor relatives of leguminosae and polygalaceae

Background and Aims: Molecular phylogenies have suggested a new circumscription for Fabales to include Leguminosae, Quillajaceae, Surianaceae and Polygalaceae. However, recent attempts to reconstruct the interfamilial relationships of the order have resulted in several alternative hypotheses, including a sister relationship between Quillajaceae and Surianaceae, the two species-poor families of Fabales. Here, floral morphology and ontogeny of these two families are investigated to explore evidence of a potential relationship between them. Floral traits are discussed with respect to early radiation in the order. Methods: Floral buds of representatives of Quillajaceae and Surianaceae were dissected and observed using light microscopy and scanning electron microscopy. Key Results Quillajaceae and Surianaceae possess some common traits, such as inflorescence morphology and perianth initiation, but development and organization of their reproductive whorls differ. In Quillaja, initiation of the diplostemonous androecium is unidirectional, overlapping with the petal primordia. In contrast, Suriana is obdiplostemonous, and floral organ initiation is simultaneous. Independent initiation of five carpels is common to both Quillaja and Suriana, but subsequent development differs; the antesepalous carpels of Quillaja become fused proximally and exhibit two rows of ovules, and in Suriana the gynoecium is apocarpous, gynobasic, with antepetalous biovulate carpels. Conclusions: Differences in the reproductive development and organization of Quillajaceae and Surianaceae cast doubt on their potential sister relationship. Instead, Quillaja resembles Leguminosae in some floral traits, a hypothesis not suggested by molecular-based phylogenies. Despite implicit associations of zygomorphy with species-rich clades and actinomorphy with species-poor families in Fabales, this correlation sometimes fails due to high variation in floral symmetry. Studies considering specific derived clades and reproductive biology could address more precise hypotheses of key innovation and differential diversification in the order.

Influence of gut morphology on passive transport of freshwater bryozoans by waterfowl in Donana (southwestern Spain)

Waterbirds have been proposed as important vectors for the passive dispersal of those aquatic invertebrates and plants that lack a capacity for active dispersal between isolated water bodies. We analysed the frequency of internal transport of bryozoan propagules (statoblasts) by waterbirds in Donana, Spain, by examining their presence in the intestines and ceca of dead birds and analysing the role of different aspects of gut characteristics in explaining variation in the presence/absence and abundance of statoblasts. Of the 228 samples examined, 7.9% presented intact statoblasts of Plumatella fungosa (Pallas, 1768), Plumatella emarginata Allman, 1844, and two unidentified Plumatella species. For a given bird species, individuals with heavier gizzards and shorter ceca had a lower incidence and abundance of statoblasts in the lower gut. Grit mass and intestine length were unrelated to the presence or abundance of statoblasts. Our results suggest that waterbirds frequently transport bryozoans on a local scale, with lighter gizzards and longer ceca favouring such transport. Lighter gizzards are likely to destroy fewer propagules before they reach the lower gut. Species and individuals with longer ceca are particularly good candidates for long-distance dispersal of bryozoans, given the longer passage time of propagules that enter the ceca.

The joint effects of larval density and C-14-cypermethrin on the life history and population growth rate of the midge Chironomus riparius

1. Chemical effects on organisms are typically assessed using individual-level endpoints or sometimes population growth rate (PGR), but such measurements are generally made at low population densities. In contrast most natural populations are subject to density dependence and fluctuate around the environmental carrying capacity as a result of individual competition for resources. As ecotoxicology aims to make reliable population projections of chemical impacts in the field, an understanding of how high-density or resource-limited populations respond to environmental chemicals is essential. 2. Our objective was to determine the joint effects of population density and chemical stress on the life history and PGR of an important ecotoxicological indicator species, Chironomus riparius, under controlled laboratory conditions. Populations were fed the same ration but initiated at different densities and exposed to a solvent control and three concentrations of C-14-cypermethrin in a sediment-water test system for 67 days at 20 +/- 1 degreesC. 3. Density had a negative effect on all the measured life-history traits, and PGR declined with increasing density in the controls. Exposure to C-14-cypermethrin had a direct negative effect on juvenile survival, presumably within the first 24 h because the chemical rapidly dissipated from the water column. Reductions in the initial larval densities resulted in an increase in the available resources for the survivors. Subsequently, exposed populations emerged sooner and started producing offspring earlier than the controls. C-14-cypermethrin had no effect on estimated fecundity and adult body weight but interacted with density to reduce the time to first emergence and first reproduction. As a result, PGR increased with cypermethrin concentration when populations were initiated at high densities. 4. Synthesis and applications. The results showed that the effects of C-14-cypermethrin were buffered at high density, so that the joint effects of density and chemical stress on PGR were less than additive. Low levels of chemical stressors may increase carrying capacity by reducing juvenile competition for resources. More and perhaps fitter adults may be produced, similar to the effects of predators and culling; however, toxicant exposure may result in survivors that are less tolerant to changing conditions. If less than additive effects are typical in the field, standard regulatory tests carried out at low density may overestimate the effects of environmental chemicals. Further studies over a wide range of chemical stressors and organisms with contrasting life histories are needed to make general recommendations.

The influence of larval density, food availability and habitat longevity on the life history and population growth rate of the midge Chironomus riparius

Despite long-standing interest in the forms and mechanisms of density dependence, these are still imperfectly understood. However, in a constant environment an increase in density must reduce per capita resource availability, which in turn leads to reduced survival, fecundity and somatic growth rate. Here we report two population experiments examining the density dependent responses under controlled conditions of an important indicator species, Chironomus riparius. The first experiment was run for 35 weeks and was started at low density with replicate populations being fed three different rations. Increased ration reduced generation time and increased population growth rate (pgr) but had no effect on survival, fecundity and female body weight in the first generation. In the second generation there was a six-fold increase in generation time, presumably due to the greatly reduced per capita resource availability as the estimated initial densities of the second generation were 300 times greater than the first. Juvenile survival to emergence, fecundity, adult body weight and pgr declined by 90%, 75%, 35% and 99%, respectively. These large between-generation effects may have obscured the effects of the threefold variation in ration, as only survival to emergence significantly increased with ration in the second generation. These results suggest that some chironomid larvae survive a reduction in resource availability by growing more slowly. In the ephemeral habitats sometimes occupied by C. riparius, the effects of population density may depend crucially on the longevity of the environment. A second experiment was therefore performed to measure pgr from six different starting densities over an eight-week period. The relationship between pgr and density was concave, viewed from above. At densities above 16 larvae per cm(2), less than 1% of the population emerged and no offspring were produced. Under the conditions of experiment 2 - an 8-week habitat lifespan carrying capacity was estimated as 8 larvae per cm(2).

The effect of PEG crystallization on the morphology of PEG/peptide block copolymers containing amyloid beta-peptide fragments

Ordered nanostructures are observed in the melt and solid state for a series of three peptide/PEG conjugates containing fragments of amyloid beta-peptides. These are conjugated to PEG with (M) over bar (n) = 3 300 g.mol(-1) and a melting temperature T-m = 45-50 degrees C. The morphology at room temperature is examined by AFM and POM. This shows spherulite formation for the weakly fibrillizing KLVFF-PEG sample but fibril formation for FFKLVFF-PEG. The fibrillization tendency of the latter is enhanced by multiple phenylalanine residues. Simultaneous SAXS and WAXS was used to investigate the morphology as a function of temperature. The secondary structure is probed by FTIR.