Flight physiology of migrating Urania fulgens (Uraniidae) moths: kinematics and aerodynamics of natural free flight

Summary Air speeds and wing kinematics were determined for the Neotropical moth Urania fulgens in natural migratory flight over Lake Gatun, Republic of Panama. Morphological parameters are presented for the same insects filmed in free flight. A quasi-steady aerodynamic analysis was used to show that unsteady mechanisms of lift generation are probably not necessary to produce the forces necessary for fast forward flight. Mechanical power requirements of forward flight were estimated from the biomechanical and morphological data. Over an airspeed range of 1.5 to 4.5 m/s, the mechanical power required to fly is predicted to increase dramatically with forward speed. A comparison of estimated metabolic rates with endogenous lipid reserves suggests that U. fulgens feeds extensively on flower nectar during migration from Central into South America.     

Potential use of sulfite as a supplemental electron donor for wastewater denitrification

Biological denitrification typically requires the addition of a supplemental electron donor, which can add a significant operating expense to wastewater treatment facilities. Most common electron donors are organic, but reduced inorganic sulfur compounds (RISCs), such as sulfide (HS^?) and elemental sulfur (S⁰), may be more cost-effective. S⁰ is an inexpensive and well characterized electron donor, but it provides slow denitrification rates due to its low solubility. A lesser-known RISC is sulfite (\({\text{SO}}_{3}^{2 - }\)), which can be easily produced from S⁰ by a simple combustion process. Unlike S⁰, \({\text{SO}}_{3}^{2 - }\) is highly soluble, and therefore may provide higher denitrification rates. However, very little is known about microbial denitrification with \({\text{SO}}_{3}^{2 - }\). Also, \({\text{SO}}_{3}^{2 - }\) is a strong reductant that reacts abiotically with oxygen and has toxic effects on microorganisms. This paper reviews \({\text{SO}}_{3}^{2 - }\) in the environment, \({\text{SO}}_{3}^{2 - }\) chemistry, microbiology, toxicity, and its potential use for denitrification. Since \({\text{SO}}_{3}^{2 - }\) is an intermediate in the sulfur oxidation pathway of most sulfur-oxidizing microorganisms, it is an energetic electron donor and it should select for a \({\text{SO}}_{3}^{2 - }\)-oxidizing community. Our review of the literature, as well as our own lab experience, suggests that \({\text{SO}}_{3}^{2 - }\) can effectively serve as an electron donor for denitrification. Further research is needed to determine the kinetics of \({\text{SO}}_{3}^{2 - }\)-based denitrification, its toxic threshold for sulfur-oxidizing microorganisms, and its potential inhibition of sensitive species such as nitrifying microorganisms and potential formation of nitrous oxide. Its effect on sludge settling efficiency also should be explored.     

Characterizing Forest Change Using Community-Based Monitoring Data and Landsat Time Series

Increasing awareness of the issue of deforestation and degradation in the tropics has resulted in efforts to monitor forest resources in tropical countries. Advances in satellite-based remote sensing and ground-based technologies have allowed for monitoring of forests with high spatial, temporal and thematic detail. Despite these advances, there is a need to engage communities in monitoring activities and include these stakeholders in national forest monitoring systems. In this study, we analyzed activity data (deforestation and forest degradation) collected by local forest experts over a 3-year period in an Afro-montane forest area in southwestern Ethiopia and corresponding Landsat Time Series (LTS). Local expert data included forest change attributes, geo-location and photo evidence recorded using mobile phones with integrated GPS and photo capabilities. We also assembled LTS using all available data from all spectral bands and a suite of additional indices and temporal metrics based on time series trajectory analysis. We predicted deforestation, degradation or stable forests using random forest models trained with data from local experts and LTS spectral-temporal metrics as model covariates. Resulting models predicted deforestation and degradation with an out of bag (OOB) error estimate of 29% overall, and 26% and 31% for the deforestation and degradation classes, respectively. By dividing the local expert data into training and operational phases corresponding to local monitoring activities, we found that forest change models improved as more local expert data were used. Finally, we produced maps of deforestation and degradation using the most important spectral bands. The results in this study represent some of the first to combine local expert based forest change data and dense LTS, demonstrating the complementary value of both continuous data streams. Our results underpin the utility of both datasets and provide a useful foundation for integrated forest monitoring systems relying on data streams from diverse sources.     

Electrical coupling between mammalian cones

BACKGROUND: Cone photoreceptors are noisy because of random fluctuations of photon absorption, signaling molecules, and ion channels. However, each cone's noise is independent of the others, whereas their signals are partially shared. Therefore, electrically coupling the synaptic terminals prior to forward transmission and subsequent nonlinear processing can appreciably reduce noise relative to the signal. This signal-processing strategy has been demonstrated in lower vertebrates with rather coarse vision, but its occurrence in mammals with fine acuity has been doubted (even though gap junctions are present) because coupling would blur the neural image. RESULTS: In ground squirrel retina, whose triangular cone lattice resembles the human fovea, paired electrical recordings from adjacent cones demonstrated electrical coupling with an average conductance of approximately 320 pS. Blur caused by this degree of coupling had a space constant of approximately 0.5 cone diameters. Psychophysical measurements employing laser interferometry to bypass the eye's optics suggest that human foveal cones experience a similar degree of neural blur and that it is invariant with light intensity. This neural blur is narrower than the eye's optical blur, and we calculate that it should improve the signal-to-noise ratio at the cone terminal by about 77%. CONCLUSIONS: We conclude that the gap junctions observed between mammalian cones, including those in the human fovea, represent genuine electrical coupling. Because the space constant of the resulting neural blur is less than that of the optical blur, the signal-to-noise ratio can be markedly improved before the nonlinear stages with little compromise to visual acuity.     

Mechanisms driving the specificity of a myrmecophyte–ant association

In the understory of pristine Guianese forests, the myrmecophyte Hirtella physophora almost exclusively shelters colonies of the plant-ant Allomerus decemarticulatus in its leaf pouches. We experimentally tested three non-mutually exclusive hypotheses concerning phenomena that can determine the species specificity of this association throughout the foundation stage of the colonies: (1) interspecific competition results in the overwhelming presence of A. decemarticulatus queens or incipient colonies; (2) exclusion filters prevent other ant species from entering the leaf pouches; and (3) host-recognition influences the choice of founding queens, especially A. decemarticulatus . Neither interspecific competition, nor the purported exclusion filters that we examined play a major role in maintaining the specificity of this association. Unexpectedly, the plant trichomes lining the domatia appear to serve as construction material during claustral foundation rather than as a filter. Finally, A. decemarticulatus queens are able to identify their host plant from a distance through chemical and/or visual cues, which is rarely demonstrated in studies on obligatory ant–plant associations. We discuss the possibility that this specific host-recognition ability could participate in shaping a compartmentalized plant-ant community where direct competition between ant symbionts is limited.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 90–97.     

The Iberian Peninsula: ancient history of a hot spot of mite harvestmen (Arachnida: Opiliones: Cyphophthalmi: Sironidae) diversity

The Iberian Peninsula represents a hot spot of cyphophthalmid (mite harvestman) disparity, with four of the eight genera currently recognized in the family Sironidae represented in the region – a generic diversity and morphological disparity not found in any other region of the World so far. From these, two genera (Iberosiro and Odontosiro) are monotypic, and are restricted to the western side of the peninsula. Parasiro is restricted to the north‐east region, from the Catalonian Coastal Ranges and both sides of the Eastern Pyrenees, in areas where the annual rainfall surpasses 1000 mm, and mostly restricted to areas with Paleozoic and Variscan rocks, with other species of the genus extending to Corsica, Sardinia, and the Italian Peninsula. A second species of the genus Paramiopsalis, Paramiopsalis eduardoi sp. nov. from Fragas do Eume, is described here along with a re‐diagnosis of the genus. Paramiopsalis species, together with Odontosiro, inhabit the north‐west corner of the Iberian Peninsula, an area with some of the highest recorded annual rainfall, and with Paleozoic rocks from the Iberian Massif or Variscan granitoid rocks. A phylogenetic analysis of the members of the family Sironidae using four molecular markers, despite not including all of the Iberian genera, clearly shows the non‐monophyly of the Iberian Cyphophthalmi, indicating that the Iberian Peninsula is home to multiple ancient lineages of mite harvestmen. The two Paramiopsalis species form a sister clade to the Balkan genus Cyphophthalmus, whereas Parasiro constitutes the first lineage of the sironids represented.     

Localization of Rheb to the endomembrane is critical for its signaling function

Rheb, a small GTPase, has emerged as a key molecular switch that directly regulates the activity of the mammalian target of rapamycin (mTOR). Similar to other members of the Ras superfamily, Rheb has a C-terminal CaaX box that is subject to farnesylation. This study reports that farnesylation is a key determinant of Rheb's subcellular localization and directs its association with the endomembrane. Timed imaging of live cells expressing EGFP-Rheb reveals that following brief association with the ER, Rheb localizes to highly ordered, distinct structures within the cytoplasm that display characteristics of Golgi membranes. Failure of Rheb to localize to the endomembrane impairs its ability to interact with mTOR and activate downstream targets. Consistent with the notion that the endomembrane may serve as a platform for the assembly of a functional Rheb/mTOR complex, treatment of cells with brefeldin A interferes with transmission of Rheb signals to p70S6K.     

Metabolic energy utilization during development of Antarctic naked dragonfish (Gymnodraco acuticeps)

We have capitalised on the availability of eggs and adults of the naked dragonfish Gymnodraco acuticeps (Sub-order Notothenioidei, F. Bathydraconidae) near McMurdo Station, Antarctica to examine metabolic energy utilization at different stages of its life cycle. Average egg respiration rates were found to increase from 2.17±1.02 nmol O₂ h⁻¹ ind⁻¹ at about 17 h post-fertilization (hpf) to 5.72±0.56 nmol h⁻¹ ind⁻¹ at about 24 hpf, during which time the eggs underwent first cleavage. The respiration rates of embryos from 2–20 days post-fertilization (dpf) averaged 4.11±1.47 nmol O₂ h⁻¹ ind⁻¹. About 10 months post-fertilization, oxygen consumption rates of 27.14±3.92 nmol O₂ h⁻¹ ind⁻¹ were recorded immediately prior to hatching, with a peak of 112.41±31.38 nmol O₂ h⁻¹ ind⁻¹ at the time of hatch. Larvae aged 46–63 days post-hatch had an average respiration rate of 64.4±15.11 nmol O₂ h⁻¹ ind⁻¹. Mass-specific respiration rates of hatched larvae (approximately 1–2 months old) were calculated using dry weights (DW) and averaged 16.1±3.4 nmol O₂ h⁻¹ mg⁻¹ DW. Adult dragonfish respiration rates (corrected for a 100 g fish and using a 0.8 scaling exponent) averaged 0.91±0.36 mmol O₂ kg⁻¹ h⁻¹ after a 48 h acclimatization period, which is not indicative of significant metabolic cold adaptation. The energy contents of dragonfish eggs and larvae were also measured by microbomb calorimetry and used, along with the respiration data, in an initial approach to estimate an energy budget. In order to balance the budget, the bulk of the available post-gastrulation respiratory energy (during 213 days of embryonic incubation) must be consumed at a relatively low average rate (7.1 nmol O₂ h⁻¹ ind⁻¹), which supports the possibility that advanced dragonfish embryos overwinter in a relatively quiescent metabolic state while awaiting a suitable stimulus (such as the return of the sun) to initiate hatching.