Sperm design and variation in the New World blackbirds (Icteridae)

Post-copulatory sexual selection (PCSS) is thought to be one of the evolutionary forces responsible for the rapid and divergent evolution of sperm design. However, whereas in some taxa particular sperm traits are positively associated with PCSS, in other taxa, these relationships are negative, and the causes of these different patterns across taxa are poorly understood. In a comparative study using New World blackbirds (Icteridae), we tested whether sperm design was influenced by the level of PCSS and found significant positive associations with the level of PCSS for all sperm components but head length. Additionally, whereas the absolute length of sperm components increased, their variation declined with the intensity of PCSS, indicating stabilizing selection around an optimal sperm design. Given the diversity of, and strong selection on, sperm design, it seems likely that sperm phenotype may influence sperm velocity within species. However, in contrast to other recent studies of passerine birds, but consistent with several other studies, we found no significant link between sperm design and velocity, using four different species that vary both in sperm design and PCSS. Potential reasons for this discrepancy between studies are discussed

Postcopulatory Sexual Selection Is Associated with Reduced Variation in Sperm Morphology

The evolutionary role of postcopulatory sexual selection in shaping male reproductive traits, including sperm morphology, is well documented in several taxa. However, previous studies have focused almost exclusively on the influence of sperm competition on variation among species. In this study we tested the hypothesis that intraspecific variation in sperm morphology is driven by the level of postcopulatory sexual selection in passerine birds.Using two proxy measures of sperm competition level, (i) relative testes size and (ii) extrapair paternity level, we found strong evidence that intermale variation in sperm morphology is negatively associated with the degree of postcopulatory sexual selection, independently of phylogeny.Our results show that the role of postcopulatory sexual selection in the evolution of sperm morphology extends to an intraspecific level, reducing the variation towards what might be a species-specific 'optimum' sperm phenotype. This finding suggests that while postcopulatory selection is generally directional (e.g., favouring longer sperm) across avian species, it also acts as a stabilising evolutionary force within species under intense selection, resulting in reduced variation in sperm morphology traits. We discuss some potential evolutionary mechanisms for this pattern

Hydraulic characterization and design of a full-scale biocurtain

This paper describes the design and hydraulic characterization of a cost-effective biocurtain that is currently being used to remove carbon tetrachloride from an aquifer in Schoolcraft, Michigan, Novel aspects of the design are the use of closely spaced wells to recirculate solutes through a biocurtain, well screens spanning the vertical extent of contamination, and a semipassive mode of operation, with only six hours of low-level pumping per meek. This design was developed by coupling now and transport simulations with a cost optimization algorithm, based on initial hydraulic conductivity data and system design constraints from a previous pilot-scale experiment adjacent to the current site. The hydraulic conductivity of the site was characterized using permeameter analysis on more than 200 samples from continuous well cores that were collected during well installation. The subset of available conductivity data was used to predict tracer transport through the biocurtain during system operation. Observed tracer concentration arrival histol ies during initial system operation confirmed model predictions. Modeling also established that closely spaced wells operated for brief periods each week could effectively deliver the agents needed for remediation across the biocurtain, This was confirmed during long-term operation of the system, which has resulted in highly efficient contamination degradation. The delivery well design methodology is expected to be broadly applicable at other sites where flow can be recirculated between a series of delivery wells

Piracy and limited liability

Piracy, Limited liability, Income distribution, L12, O34,

Variation in soft tissue chemistry among scyphozoan and cubozoan jellyfishes from the Great Barrier Reef, Australia

Bioaccumulation of trace elements in jellyfish has so far received little attention, despite their being prey for many animals from multiple trophic levels and targeted by commercial jellyfish fisheries. Scyphozoan and cubozoan jellyfish were collected over a three year period from across-shelf and along the northern and central Great Barrier Reef, Australia. To test the hypotheses that jellyfishes were able to accumulate elements above ambient background levels, and if there were spatial or temporal variations among species, soft tissue concentrations of 14 trace elements were compared with ambient seawater concentrations. Most elements, including aluminium, arsenic, barium, cadmium, chromium, copper, iron, manganese and zinc were measured at concentrations above ambient seawater levels indicating bioaccumulative capacity. Results showed some regulation of lithium in Cassiopea sp., Cyanea sp. and Mastigias sp., while calcium, magnesium and strontium reflected ambient conditions for all species. Accumulation varied significantly among species and sampling locations. For Mastigias sp. and Netrostoma sp., tissue concentrations of Al, As, Cu, Fe and Zn decreased with distance from the mainland. The hypothesis that jellyfishes are capable of accumulating trace elements was accepted, and their use as biomonitors should be investigated further