Body Condition Indices Predict Reproductive Success but Not Survival in a Sedentary,Tropical Bird

Body condition may predict individual fitness because those in better condition have more resources to allocate towards improving their fitness. However, the hypothesis that condition indices are meaningful proxies for fitness has been questioned. Here, we ask if intraspecific variation in condition indices predicts annual reproductive success and survival. We monitored a population of Neochmia phaeton (crimson finch), a sedentary, tropical passerine, for reproductive success and survival over four breeding seasons, and sampled them for commonly used condition indices: mass adjusted for body size, muscle and fat scores, packed cell volume, hemoglobin concentration, total plasma protein, and heterophil to lymphocyte ratio. Our study population is well suited for this research because individuals forage in common areas and do not hold territories such that variation in condition between individuals is not confounded by differences in habitat quality. Furthermore, we controlled for factors that are known to impact condition indices in our study population (e.g., breeding stage) such that we assessed individual condition relative to others in the same context. Condition indices that reflect energy reserves predicted both the probability of an individual fledging young and the number of young produced that survived to independence, but only during some years. Those that were relatively heavy for their body size produced about three times more independent young compared to light individuals. That energy reserves are a meaningful predictor of reproductive success in a sedentary passerine supports the idea that energy reserves are at least sometimes predictors of fitness. However, hematological indices failed to predict reproductive success and none of the indices predicted survival. Therefore, some but not all condition indices may be informative, but because we found that most indices did not predict any component of fitness, we question the ubiquitous interpretation of condition indices as surrogates for individual quality and fitness.     

From Models to Measurements: Comparing Downed Dead Wood Carbon Stock Estimates in the U.S. Forest Inventory

The inventory and monitoring of coarse woody debris (CWD) carbon (C) stocks is an essential component of any comprehensive National Greenhouse Gas Inventory (NGHGI). Due to the expense and difficulty associated with conducting field inventories of CWD pools, CWD C stocks are often modeled as a function of more commonly measured stand attributes such as live tree C density. In order to assess potential benefits of adopting a field-based inventory of CWD C stocks in lieu of the current model-based approach, a national inventory of downed dead wood C across the U.S. was compared to estimates calculated from models associated with the U.S.’s NGHGI and used in the USDA Forest Service, Forest Inventory and Analysis program. The model-based population estimate of C stocks for CWD (i.e., pieces and slash piles) in the conterminous U.S. was 9 percent (145.1 Tg) greater than the field-based estimate. The relatively small absolute difference was driven by contrasting results for each CWD component. The model-based population estimate of C stocks from CWD pieces was 17 percent (230.3 Tg) greater than the field-based estimate, while the model-based estimate of C stocks from CWD slash piles was 27 percent (85.2 Tg) smaller than the field-based estimate. In general, models overestimated the C density per-unit-area from slash piles early in stand development and underestimated the C density from CWD pieces in young stands. This resulted in significant differences in CWD C stocks by region and ownership. The disparity in estimates across spatial scales illustrates the complexity in estimating CWD C in a NGHGI. Based on the results of this study, it is suggested that the U.S. adopt field-based estimates of CWD C stocks as a component of its NGHGI to both reduce the uncertainty within the inventory and improve the sensitivity to potential management and climate change events.     

Glutathione activation of a cysteine proteinase from Schistosoma mansoni

A cysteine proteinase isolated from Schistosoma mansoni adults requires reduction by thiols for activation. The proteinase is located in the parasite digestive tract where it degrades hemoglobin released from host red blood cells. Reduced glutathione (GSH) has been shown to be effective in activation. Total glutathione concentration and the GSH/oxidized glutathione (GSSG) ratio were measured in whole blood lysate (3.2 mM, 284), serum (24 microM, 9.8) and material collected from the parasite digestive tract (4.2 mM, 137). The ratio of GSH/GSSG at which the enzyme displays half-maximal activity (Kox) is 1.0. Proteinase activation as a function of glutathione concentration and time was determined. The first-order reaction yielded a half-time of activation of 13 min at 5 mM. The second-order rate constant was 12.7 M-1 X min-1. The function of the proteinase and its possible regulation by glutathione activation are discussed.     

Functional heterogeneity of murine macrophage precursor cells from spleen and bone marrow

We previously reported that highly purified bone marrow-derived macrophage precursors can exert strong spontaneous cytotoxicity against YAC-1 tumor cells, Candida albicans, and protozoa of the genus Leishmania. In the present paper, evidence is shown that macrophage precursors in normal untreated mice are not confined to the bone marrow compartment but can also be found in the spleen. These organ-associated cells, which have the same buoyant density as large granular lymphocytes, have been positively sorted by means of an indirect rosetting technique employing the macrophage-specific monoclonal antibodies F4/80 and M143. The rosetting fractions represented an extremely homogeneous population of macrophage precursors characterized by high candidacidal and natural killer activity and by a strong proliferative response to the macrophage-specific colony-stimulating factor CSF-1. Spleen- and bone marrow-derived macrophage precursors differed in their target selectivity. In addition, the mature macrophages derived in vitro from these two precursor populations displayed striking differences in their candidacidal activity. The implications of these findings in relationship to heterogeneity in the macrophage differentiation line are discussed.     

Environmental stress and bacterial infection in channel catfish, Ictalurus punctatus Rafinesque

Channel catfish, Ictalurus punctatus , were injected intraperitoneally with a sublethal dose of Aerornonas hydrophila and then stressed for 144 h by being maintained either in a dissolved oxygen concentration of 1·5 mg/1, 1·2 mg/1 total ammonia, and/or 6·5 mg/1 free CO₂ with a continuous inflow of water. A significant difference in percentage of mortality was noted between treatments ( P < 0·05). The trunk kidneys of surviving stressed fish had significantly higher total bacterial counts than non-stressed controls. A. hydrophila was isolated from 67% of the stressed fish and 9% of the control fish. Edwardsiella tarda , apparently endemic in the population, was isolated from 43% of the stressed fish and 7% of the control fish. Histopathological lesions were in the gills, liver, spleen, trunk kidney, and head kidney of stressed fish, but not control fish.