Grouped sequential exploitation of food patches in a flock feeder,the feral pigeon

Feral and laboratory flocks of rock doves ($\text{Columba}$$\text{livia}$) show a pattern of grouped sequential exploitation when simultaneously presented with two dispersed, depleting patches of seed. This behavior contrasts with the ideal free distribution pattern shown when patches are small and concentrated. Grouped sequential exploitation consists of two phases: all pigeons first land together and feed at one patch, then leave one by one for the other patch. Departure times of individuals for the second patch are correlated with feeding rate at patch 1, which is in turn correlated with position in the dominance hierarchy. The decision to switch from patch 1 to patch 2 improves individual feeding rates in all cases, but is done slightly later than it should according to optimal foraging theory.     

Cardiolipin biosynthesis and remodeling enzymes are altered during development of heart failure

Cardiolipin (CL) is responsible for modulation of activities of various enzymes involved in oxidative phosphorylation. Although energy production decreases in heart failure (HF), regulation of cardiolipin during HF development is unknown. Enzymes involved in cardiac cardiolipin synthesis and remodeling were studied in spontaneously hypertensive HF (SHHF) rats, explanted hearts from human HF patients, and nonfailing Sprague Dawley (SD) rats. The biosynthetic enzymes cytidinediphosphatediacylglycerol synthetase (CDS), phosphatidylglycerolphosphate synthase (PGPS) and cardiolipin synthase (CLS) were investigated. Mitochondrial CDS activity and CDS-1 mRNA increased in HF whereas CDS-2 mRNA in SHHF and humans, not in SD rats, decreased. PGPS activity, but not mRNA, increased in SHHF. CLS activity and mRNA decreased in SHHF, but mRNA was not significantly altered in humans. Cardiolipin remodeling enzymes, monolysocardiolipin acyltransferase (MLCL AT) and tafazzin, showed variable changes during HF. MLCL AT activity increased in SHHF. Tafazzin mRNA decreased in SHHF and human HF, but not in SD rats. The gene expression of acyl-CoA: lysocardiolipin acyltransferase-1, an endoplasmic reticulum MLCL AT, remained unaltered in SHHF rats. The results provide mechanisms whereby both cardiolipin biosynthesis and remodeling are altered during HF. Increases in CDS-1, PGPS, and MLCL AT suggest compensatory mechanisms during the development of HF. Human and SD data imply that similar trends may occur in human HF, but not during nonpathological aging, consistent with previous cardiolipin studies.     

Trophic interactions in soils as they affect energy and nutrient dynamics. IV. Flows of metabolic and biomass carbon

Flows of biomass and respiratory carbon were studied in a series of propylene-oxide sterilized soil microcosms. One-half of the microcosms received three pulsed additions of 200 ppm glucose-carbon to mimic rhizosphere carbon inputs. Biotic variables were: bacteria (Pseudomonas) alone, or amoebae (Acanthamoeba) and nematodes (Mesodiplogaster) singly, or both combined in the presence of bacteria.Over the 24-day experiment, respiration was significantly higher in the microcosms containing the bacterial grazers. Biomass accumulation by amoebae was significantly higher than that by nematodes. The nematodes respired up to 30-fold more CO₂ per unit biomass than did amoebae. Similar amounts of carbon flowed into both respiratory and biomass carbon in microcosms with fauna, compared with the bacteria-alone microcosms. However, partitioning of available carbon by the microfauna varied considerably, with little biomass production and relatively more CO₂-C produced in the nematode-containing microcosms. The amoebae, in contrast, allocated more carbon to tissue production (about 40% assimilation efficiency) and correspondingly less to CO₂.