Total Suspended Solids Effects on Freshwater Lake Biota Other than Fish.

Protective benchmarks for the effects of total suspended solids (TSS) on freshwater aquatic biota primarily focus on fish; whether these benchmarks will also protect their prey or co-existing lower trophic level aquatic biota was uncertain. We conducted an extensive literature review of TSS effects on those organisms comprising the food webs upon which fish living in lakes depend: phytoplankton, zooplankton, periphyton, and benthic invertebrates. The available literature indicates that TSS benchmarks that protect sensitive life stages of lake fish will also protect their supporting food webs; in other words, the function of lake aquatic communities will be protected and maintained.

Explaining differences in the lifespan and replicative capacity of cells: a general model and comparative analysis of vertebrates.

A better understanding of the factors that govern individual cell lifespan and the replicative capacity of cells (i.e. Hayflick's limit) is important for addressing disease progression and ageing. Estimates of cell lifespan in vivo and the replicative capacity of cell lines in culture vary substantially both within and across species, but the underlying reasons for this variability remain unclear. Here, we address this issue by presenting a quantitative model of cell lifespan and cell replicative capacity. The model is based on the relationship between cell mortality and metabolic rate, which is supported with data for different cell types from ectotherms and endotherms. These data indicate that much of the observed variation in cell lifespan and cell replicative capacity is explained by differences in cellular metabolic rate, and thus by the three primary factors that control metabolic rate: organism size, organism temperature and cell size. Individual cell lifespan increases as a power law with both body mass and cell mass, and decreases exponentially with increasing temperature. The replicative capacity of cells also increases with body mass, but is independent of temperature. These results provide a point of departure for future comparative studies of cell lifespan and replicative capacity in the laboratory and in the field.

Engaging persons with dementia in advance care planning: Challenges and opportunities.

This study reports findings from a series of focus groups with persons with dementia and family caregivers intended to explore: (1) perceptions of and experiences with advance care planning (ACP); (2) concerns related to future care including, but not limited to, end-of-life care; and (3) practices that may support positive engagement with ACP. A total of 18 participants including 10 persons with dementia and eight family caregivers participated in five focus groups held in two urban cities in Canada. All focus group deliberations were audio recorded, transcribed verbatim, and analyzed in five stages using a semantic thematic approach. All participants expressed some form of engagement in ACP, but understandings were limited and divergence was expressed regarding the timing of more expansive conversations about future care. Although some persons with dementia were ready to engage in future care discussions, most preferred focusing on the present and suggested their families did not require direction. This placed families in the complex dilemma of protecting their loved ones while compromising their own needs for dialogue. Although individually focused models of ACP engagement hold promise for those persons with dementia ready to engage in future planning, our findings suggest that early engagement of families in the reflective process may go a long way in supporting ACP activation. Our findings further suggest that persons with dementia who do not have close family/friends may require extensive ACP encouragement and support from service providers.

Common metabolic constraints on dive duration in endothermic and ectothermic vertebrates.

Dive duration in air-breathing vertebrates is thought to be constrained by the volume of oxygen stored in the body and the rate at which it is consumed (i.e., "oxygen store/usage hypothesis"). The body mass-dependence of dive duration among endothermic vertebrates is largely supportive of this model, but previous analyses of ectothermic vertebrates show no such body mass-dependence. Here we show that dive duration in both endotherms and ectotherms largely support the oxygen store/usage hypothesis after accounting for the well-established effects of temperature on oxygen consumption rates. Analyses of the body mass and temperature dependence of dive duration in 181 species of endothermic vertebrates and 29 species of ectothermic vertebrates show that dive duration increases as a power law with body mass, and decreases exponentially with increasing temperature. Thus, in the case of ectothermic vertebrates, changes in environmental temperature will likely impact the foraging ecology of divers.

The cost of sex: quantifying energetic investment in gamete production by males and females.

The relative energetic investment in reproduction between the sexes forms the basis of sexual selection and life history theories in evolutionary biology. It is often assumed that males invest considerably less in gametes than females, but quantifying the energetic cost of gamete production in both sexes has remained a difficult challenge. For a broad diversity of species (invertebrates, reptiles, amphibians, fishes, birds, and mammals), we compared the cost of gamete production between the sexes in terms of the investment in gonad tissue and the rate of gamete biomass production. Investment in gonad biomass was nearly proportional to body mass in both sexes, but gamete biomass production rate was approximately two to four orders of magnitude higher in females. In both males and females, gamete biomass production rate increased with organism mass as a power law, much like individual metabolic rate. This suggests that whole-organism energetics may act as a primary constraint on gamete production among species. Residual variation in sperm production rate was positively correlated with relative testes size. Together, these results suggest that understanding the heterogeneity in rates of gamete production among species requires joint consideration of the effects of gonad mass and metabolism.