High costs of female choice in a lekking lizard

Although the cost of mate choice is an essential component of the evolution and maintenance of sexual selection, the energetic cost of female choice has not previously been assessed directly. Here we report that females can incur high energetic costs as a result of discriminating among potential mates. We used heart rate biologging to quantify energetic expenditure in lek-mating female Galápagos marine iguanas (Amblyrhynchus cristatus). Receptive females spent 78.9+/-23.2 kJ of energy on mate choice over a 30-day period, which is equivalent to approximately (3/4) of one day's energy budget. Females that spent more time on the territories of high-quality, high-activity males displayed greater energetic expenditure on mate choice, lost more mass, and showed a trend towards producing smaller follicles. Choosy females also appear to face a reduced probability of survival if El Ni?o conditions occur in the year following breeding. These findings indicate that female choice can carry significant costs, and suggest that the benefits that lek-mating females gain through mating with a preferred male may be higher than previously predicted.     

Phytoplankton exudates provide full nutrition to a subset of accompanying heterotrophic bacteria via carbon,nitrogen and phosphorus allocation

Marine bacteria rely on phytoplankton exudates as carbon sources (DOCp). Yet, it is unclear to what extent phytoplankton exudates also provide nutrients such as phytoplankton-derived N and P (DONp, DOPp). We address these questions by mesocosm exudate addition experiments with spent media from the ubiquitous pico-cyanobacterium Prochlorococcus to bacterial communities in contrasting ecosystems in the Eastern Mediterranean – a coastal and an open-ocean, oligotrophic station with and without on-top additions of inorganic nutrients. Inorganic nutrient addition did not lower the incorporation of exudate DONp, nor did it reduce alkaline phosphatase activity, suggesting that bacterial communities are able to exclusively cover their nitrogen and phosphorus demands with organic forms provided by phytoplankton exudates. Approximately half of the cells in each ecosystem took up detectable amounts of Prochlorococcus-derived C and N, yet based on 16S rRNA sequencing different bacterial genera were responsible for the observed exudate utilization patterns. In the coastal community, several phylotypes of Aureimarina, Psychrosphaera and Glaciecola responded positively to the addition of phytoplankton exudates, whereas phylotypes of Pseudoalteromonas increased and dominated the open-ocean communities. Together, our results strongly indicate that phytoplankton exudates provide coastal and open-ocean bacterial communities with organic carbon, nitrogen and phosphorus, and that phytoplankton exudate serve a full-fledged meal for the accompanying bacterial community in the nutrient-poor eastern Mediterranean.     

Proximate mechanisms of reproductive monopolization in male moustached tamarins (Saguinus mystax)

In moustached tamarin (Saguinus mystax) groups, the single breeding female mates polyandrously with most or all nonrelated adult males. Nonetheless, paternity is monopolized in many groups by a single male. No evidence for male endocrine suppression has been found in this species. The proximate mechanisms of monopolization thus remain poorly understood. The aim of this study was to investigate the possible impact of agonistic interactions and mate-guarding on the monopolization of paternity in male moustached tamarins. Furthermore, we evaluated the likely costs of these behaviors, and whether olfactory cues might be used for its timing. We used behavioral data on proximity, agonistic interactions, time budgets, and scent-marking behavior to answer these questions. While direct agonistic competition does not play a prominent role, fertile females were consorted in some periods by one male, the sire of the previous and next litter. Consorting was instigated nearly exclusively by the male. It probably occurred during the female's periods of highest fertility, and thus likely functions as mate-guarding. The timing of the consortship was probably guided by olfactory cues in the female's scent marks. While we did not obtain direct evidence for energy costs in terms of increased energy expenditure or decreased food intake, we found that consorting males are more conspicuous and therefore may be more vulnerable to predators.     

The immunoglobulin-superfamily molecule basigin is a binding protein for oligomannosidic carbohydrates: an anti-idiotypic approach

Recognition molecules that carry carbohydrate structures regulate cell interactions during development and play important roles in synaptic plasticity and regeneration in the adult. Glycans appear to be involved in these interactions. We have searched for binding proteins for oligomannosidic structures using the L3 antibody directed against high mannose-type glycans in an anti-idiotypic approach. A selected monoclonal anti-idiotype antibody was used for affinity chromatography and identified basigin as a binding protein from mouse brain detergent lysates. Basigin was found to bind to high mannose-carrying cell recognition molecules, such as myelin-associated glycoprotein, L1, the beta2-subunit of Na+/K+-ATPase and an oligomannosidic neoglycolipid. Furthermore, basigin was involved in outgrowth of astrocytic processes in vitro. A striking homology between the first immunoglobulin (Ig)-like domain of basigin and the fourth Ig-like domain of NCAM, previously shown to bind to oligomannosidic glycans, and the lectin domain of the mannose receptor confirms that basigin is an oligomannose binding lectin. To our knowledge this is the first report that anti-idiotypic antibodies can be used to identify binding partners for carbohydrates.     

Essential role of the apolipoprotein E receptor-2 in sperm development

The apolipoprotein (apo) E receptor-2 (apoER2) is a member of the low density lipoprotein receptor gene family and an important regulator of neuronal migration. It acts as a receptor for the signaling factor Reelin and provides positional cues to neurons that migrate to their proper position in the developing brain. Besides brain formation defects, apoER2-deficient mice also exhibit male infertility. The role of the receptor in male reproduction, however, remained unclear. Here we demonstrate that apoER2 is highly expressed in the initial segment of the epididymis, where it affects the functional expression of clusterin and phospholipid hydroperoxide glutathione peroxidase (PHGPx), two proteins required for sperm maturation. Reduced PHGPx expression in apoER2 knockout mice results in the inability of the sperm to regulate the cell volume and in abnormal sperm morphology and immotility. Because insufficient expression of PHGPx is a major cause of infertility in men, these findings not only highlight an important new function for apoER2 that is unrelated to neuronal migration, but they also suggest a possible role for apoER2 in human infertility.     

Competition strategies for the decolorization of a textile-reactive dye with the white-rot fungi Trametes versicolor under non-sterile conditions

A variety of white-rot fungi can oxidize textile dyes under sterile conditions; however, an important consideration for their use in treating wastewater containing textile dyes is whether similar degrees of treatment can be achieved under non-sterile conditions. Four strategies were investigated for their potential in optimizing the use of the fungus Trametes versicolor in non-sterile culture for treating wastewater containing the diazo textile dye C.I. Reactive Black 5 (RB5). Three strategies with suspended culture were designed to increase the decolorization activity in suspended culture from a given amount of T. versicolor inoculum based on its tolerance of low pH (pH reduction in medium), production of extracellular enzymes (use of suspended enzymes alone), and its ability to produce enzymes independent of growth (nitrogen limitation in medium). The results showed that reduction of the medium pH to 3 did not suppress bacterial growth, while enzyme production by T. versicolor ceased. The use of the extracellular enzymes alone would allow the decoupling of the process of fungal growth from wastewater treatment; however, the enzyme activity of an enzyme suspension decreased rapidly under non-sterile conditions. The strategy of limiting nitrogen in the medium to suppress bacterial growth has potential together with the fourth strategy, the cultivation of fungi on organic solids to produce inocula for a decolorization process under non-sterile conditions. A high degree of decolorization of RB5 under non-sterile conditions was achieved with T. versicolor grown on grains as sole substrate. The rate of decolorization was dependent on the amount of fungal inoculum used.     

A novel conus peptide ligand for K+ channels

Voltage-gated ion channels determine the membrane excitability of cells. Although many Conus peptides that interact with voltage-gated Na(+) and Ca(2+) channels have been characterized, relatively few have been identified that interact with K(+) channels. We describe a novel Conus peptide that interacts with the Shaker K(+) channel, kappaM-conotoxin RIIIK from Conus radiatus. The peptide was chemically synthesized. Although kappaM-conotoxin RIIIK is structurally similar to the mu-conotoxins that are sodium channel blockers, it does not affect any of the sodium channels tested, but blocks Shaker K(+) channels. Studies using Shaker K(+) channel mutants with single residue substitutions reveal that the peptide interacts with the pore region of the channel. Introduction of a negative charge at residue 427 (K427D) greatly increases the affinity of the toxin, whereas the substitutions at two other residues, Phe(425) and Thr(449), drastically reduced toxin affinity. Based on the Shaker results, a teleost homolog of the Shaker K(+) channel, TSha1 was identified as a kappaM-conotoxin RIIIK target. Binding of kappaM-conotoxin RIIIK is state-dependent, with an IC(50) of 20 nm for the closed state and 60 nm at 0 mV for the open state of TSha1 channels.     

Nitric oxide synthase II in rat skeletal muscles

Constitutive expression of nitric oxide synthase (NOS) II was found in rat hindlimb muscles by immunohistochemistry and western blotting during development from embryonic day 21 to the adult stage of 75 days. The immunohistochemical NOS II expression pattern was related to the physiological metabolic fibre types SO (slow-oxidative), FOG I, II (fast-oxidative glycolytic; I more glycolytic, II more oxidative) and FG (fast-glycolytic) and to the myosin-based fibre types I and IIA, IIB (IIX not separated) identified in serial sections by enzyme histochemistry and immunohistochemistry. In adult muscles only the small population of FOG II fibres, which is a part of both IIA and IIB fibre population, showed NOS II immunoreactivity. This is the reason that only weak NOS II expression in adult hindlimb muscles has been detected by western blotting. Hindlimb muscles of embryonic, neonatal and young rats of 8 days expressed more NOS II as compared with adult rat hindlimb muscles. This can be explained by the findings that before the age of 21 days fast fibres were metabolically undifferentiated, all of them were NOS II positive and contribute to the NOS II expression of the muscle. In muscles of diabetic rats the NOS II expression was elevated indicating an inhibition of glucose uptake into the muscle fibres of diabetic muscles. Our findings suggest that the NOS II may be designated both as constitutive and inducible.