Multispectral Sorting Based on Visibly High-Risk Kernels Sourced from Another Country Reduces Fumonisin and Toxigenic Fusarium on Maize Kernels.

Fusarium species infect maize crops leading to the production of fumonisin by their toxigenic members. Elimination of microbes is critical in mitigating further postharvest spoilage and toxin accumulation. The current study investigates the efficacy of a previously described multispectral sorting technique to analyze the reduction of fumonisin and toxigenic Fusarium species found contaminating maize kernels in Kenya. Maize samples (n = 99) were collected from six mycotoxin hotspot counties in Kenya (Embu, Meru, Tharaka Nithi, Machakos, Makueni, and Kitui County) and analyzed for aflatoxin and fumonisin using commercial ELISA kits. Aflatoxin levels in majority (91%) of the samples were below the 10 ng/g threshold set by the Kenya Bureau of Standards and therefore not studied further. The 23/99 samples that had >2,000 ng/g of fumonisin were selected for sorting. The sorter was calibrated using kernels sourced from Ghana to reject visibly high-risk kernels for fumonisin contamination using reflectance at nine distinct wavelengths (470-1,550 nm). Accepted and rejected streams were tested for fumonisin using ELISA, and the presence of toxigenic Fusarium using qPCR. After sorting, there was a significant (p < 0.001) reduction of fumonisin, by an average of 1.8 log ng/g (98%) and ranging between 0.14 and 2.7 log ng/g reduction (28-99.8%) with a median mass rejection rate of 1.9% (ranged 0% to 48%). The fumonisin rejection rate ranged between 0 and 99.8% with a median of 77%. There was also a significant reduction (p = 0.005) in the proportion of DNA represented by toxigenic Fusarium, from a mean of 30-1.4%. This study demonstrates the use of multispectral sorting as a potential postharvest intervention tool for the reduction of Fusarium species and preformed fumonisin. The spectral sorting approach of this study suggests that classification algorithms based on high-risk visual features associated with mycotoxin can be applied across different sources of maize to reduce fumonisin.

Efficacy of electron beam irradiation in reduction of mycotoxin-producing fungi, aflatoxin, and fumonisin, in naturally contaminated maize slurry.

Maize is a staple food in Kenya. However, maize is prone to fungal infestation, which may result in production of harmful aflatoxins and fumonisins. Electron beam (eBeam) food processing is a proven post-harvest technology, but published literature is rare on the ability of eBeam to reduce mycotoxins in naturally contaminated maize samples. This study evaluated the efficacy of eBeam doses in reducing viable fungal populations and the destruction of aflatoxins and fumonisins in naturally highly contaminated maize samples from eastern Kenya. Ninety-seven maize samples were analyzed for total aflatoxins and fumonisins using commercial ELISA kits. Then, 24 samples with >100 ng/g of total aflatoxins and >1000 ng/g of total fumonisins were chosen for eBeam toxin degradation studies. Prior to eBeam exposure studies, the samples were made into a slurry using sterile de-ionized water. These slurry samples were exposed to target doses of 5 kGy, 10 kGy, and 20 kGy, with 0 kGy (untreated) samples as controls. Samples were analyzed for total fungal load using culture methods, the quantity of total aflatoxins and fumonisins using ELISA, and the presence of Aspergillus and Fusarium spp. nucleic acids using qPCR for just control samples. There was a significant positive correlation in the control samples between total Aspergillus and aflatoxin levels (r = 0.54; p = 0.007) and total Fusarium and fumonisin levels (r = 0.68; p < 0.001). Exposure to eBeam doses 5 kGy and greater reduced fungal loads to below limits of detection by plating (<1.9 log(CFU/g)). There was also a significant (p = 0.03) average reduction of 0.3 log (ng/g) in aflatoxin at 20 kGy (range from -0.9 to 1.4 log (ng/g)). There was no significant reduction in fumonisin even at 20 kGy. eBeam doses below 20 kGy did not reduce mycotoxins. These results confirm the sensitivity of fungi to eBeam doses in a naturally contaminated maize slurry and that 20 kGy is effective at degrading some pre-formed aflatoxin in such maize preparations.

Status and challenges for sustainable billfish fisheries in the Western Indian Ocean.

Billfish species (families Istiophoridae and Xiphiidae) are caught in artisanal, recreational, and commercial fisheries throughout the Western Indian Ocean region. However, data and information on the interactions among these fisheries and the ecology of billfish in the WIO are not well understood. Using an in-depth analysis of peer-reviewed articles, grey literature, observation studies, and authors' insider knowledge, we summarize the current state of knowledge on billfish fisheries in 10 countries. To describe historical and current trends, we examined fisheries statistics from governmental and non-governmental agencies, sportfishing clubs' reports, diaries of sportfishing captains, and the catch and effort databases of the Indian Ocean Tuna Commission. We highlight two key points. First, billfish fisheries in the Western Indian Ocean are highly diverse, comprising two distinct segments-coastal and oceanic. However, data are poor for most countries with significant gaps in information especially for sport and artisanal fisheries. Second, the evidence assembled showed that billfish species have immense social, cultural, and economic value. Swordfish are targeted by both large-scale and semi-industrial fisheries, while other billfish species, particularly marlin, are highly sought after by sport fisheries in most countries. Our paper provides a comprehensive review of billfish fisheries and available information in the context of the WIO underscoring the need to strengthen data collection and reporting, citizen science, and collaborative sustainable development and management of billfish. Supplementary Information: The online version contains supplementary material available at 10.1007/s11160-022-09725-8.

Bone density and asymmetry are not related to DDT in House Sparrows: Insights from micro-focus X-ray computed tomography.

In organisms, DDT (Dichlorodiphenyltrichloroethane) and its metabolites, DDE (Dichlorodiphenyldichloroethylene) and DDD (Dichlorobischlorophenylethane) are endocrine mimics. They can influence bone density and other bone structural features. This study was conducted on House Sparrows (Passer domesticus) caught from the Free State - and the Limpopo Provinces of South Africa (SA). The sites were chosen based on spraying patterns of DDT for malaria control or non-spraying. The bone mineral densities of the femurs as well as the lengths of the left- and right leg bones were determined using micro-focus X-ray computed tomography (µ-XCT). The concentrations of DDT and its metabolites in the liver were determined with gas-chromatography mass-spectrometry to provide baseline concentrations of DDT in the body, allowing comparison of the various groups of birds. There was no asymmetry between the lengths of the bones of the left- and the right legs. DDT concentrations in the liver did not correlate with bone lengths. In addition, there were no significant differences between the relative densities of the left- and right leg bones with increase of concentrations of DDT. The concentrations of DDT and its metabolites did not have a significant effect on the measured bone parameters of House Sparrows. It is possible that the concentrations of DDT and its metabolites in the environments were too low to be injurious to the birds and/or tolerance to the insecticide has developed in the birds over more than six decades of almost continuous application of DDT.

Variability in distribution and use of tuberculosis diagnostic tests in Kenya: a cross-sectional survey.

BACKGROUND: Globally, 40% of all tuberculosis (TB) cases, 65% paediatric cases and 75% multi-drug resistant TB (MDR-TB) cases are missed due to underreporting and/or under diagnosis. A recent Kenyan TB prevalence survey found that a significant number of TB cases are being missed here. Understanding spatial distribution and patterns of use of TB diagnostic tests as per the guidelines could potentially help improve TB case detection by identifying diagnostic gaps. METHODS: We used 2015 Kenya National TB programme data to map TB case notification rates (CNR) in different counties, linked with their capacity to perform diagnostic tests (chest x-rays, smear microscopy, Xpert MTB/RIF®, culture and line probe assay). We then ran hierarchical regression models for adults and children to specifically establish determinants of use of Xpert® (as per Kenyan guidelines) with county and facility as random effects. RESULTS: In 2015, 82,313 TB cases were notified and 7.8% were children. The median CNR/100,000 amongst 0-14yr olds was 37.2 (IQR 20.6, 41.0) and 267.4 (IQR 202.6, 338.1) for ≥15yr olds respectively. 4.8% of child TB cases and 12.2% of adult TB cases had an Xpert® test done, with gaps in guideline adherence. There were 2,072 microscopy sites (mean microscopy density 4.46/100,000); 129 Xpert® sites (mean 0.31/100,000); two TB culture laboratories and 304 chest X-ray facilities (mean 0.74/100,000) with variability in spatial distribution across the 47 counties. Retreatment cases (i.e. failures, relapses/recurrences, defaulters) had the highest odds of getting an Xpert® test compared to new/transfer-in patients (AOR 7.81, 95% CI 7.33-8.33). Children had reduced odds of getting an Xpert® (AOR 0.41, CI 0.36-0.47). HIV-positive individuals had nearly twice the odds of getting an Xpert® test (AOR 1.82, CI 1.73-1.92). Private sector and higher-level hospitals had a tendency towards lower odds of use of Xpert®. CONCLUSIONS: We noted under-use and gaps in guideline adherence for Xpert® especially in children. The under-use despite considerable investment undermines cost-effectiveness of Xpert®. Further research is needed to develop strategies enhancing use of diagnostics, including innovations to improve access (e.g. specimen referral) and overcoming local barriers to adoption of guidelines and technologies.

Associations between DDT and egg parameters of the House Sparrow Passer domesticus from the Thohoyandou area of South Africa.

This study investigated whether the pesticide DDT (Dichlorodiphenyltrichloroethane) and its metabolites, DDE (Dichlorodiphenyldichloroethylene) and DDD (Dichlorobischlorophenylethane) were associated with adverse effects on multiple endpoints of the eggs of House Sparrows from the Thohoyandou area in South Africa, where DDT is used for malaria control. Eggshell thickness, pore numbers, pore shapes, and volume densities of the pores were measured to test possible adverse effects. Analysis was done using a scanning electron microscope and the concentrations of the pesticides were determined with the aid of gas chromatography-mass spectrometry. The highest concentrations recorded was p,p'-DDE at 0.84 µg/g wm (wet mass) in the eggs collected from Mangondi (a site last sprayed five years before sampling). Overall, the concentrations of total DDT recorded in this study were lower than reported by most other studies conducted in the same area. The association between DDT concentrations and House Sparrows eggshells were noticeable in the eggshell thicknesses, with significant differences between the eggs collected from Muledane (a site last sprayed 30 years before sampling) and Makula (a site sprayed both years of sampling) (P < 0.0022). Limited differences were found between the pore numbers and pore density of eggshells from the various sites. It may be that the limited effect on the pore numbers and volume densities of the pores are associated with low concentrations of DDT in the House Sparrow eggs.

Scaling metabolism from individuals to reef-fish communities at broad spatial scales.

Fishes contribute substantially to energy and nutrient fluxes in reef ecosystems, but quantifying these roles is challenging. Here, we do so by synthesising a large compilation of fish metabolic-rate data with a comprehensive database on reef-fish community abundance and biomass. Individual-level analyses support predictions of Metabolic Theory after accounting for significant family-level variation, and indicate that some tropical reef fishes may already be experiencing thermal regimes at or near their temperature optima. Community-level analyses indicate that total estimated respiratory fluxes of reef-fish communities increase on average ~2-fold from 22 to 28 °C. Comparisons of estimated fluxes among trophic groups highlight striking differences in resource use by communities in different regions, perhaps partly reflecting distinct evolutionary histories, and support the hypothesis that piscivores receive substantial energy subsidies from outside reefs. Our study demonstrates one approach to synthesising individual- and community-level data to establish broad-scale trends in contributions of biota to ecosystem dynamics.

Air breathing in Magadi tilapia Alcolapia grahami, under normoxic and hyperoxic conditions, and the association with sunlight and reactive oxygen species.

Observations of the Magadi tilapia Alcolapia grahami in hot, highly alkaline Lake Magadi revealed that they air breathe not only during hypoxia, as described previously, but also during normoxia and hyperoxia. Air breathing under these latter conditions occurred within distinct groupings of fish (pods) and involved only a small proportion of the population. Air breathing properties (duration and frequency) were quantified from video footage. Air breathing within the population followed a diel pattern with the maximum extent of pod formation occurring in early afternoon. High levels of reactive oxygen species (ROS) in the water may be an irritant that encourages the air-breathing behaviour. The diel pattern of air breathing in the field and in experiments followed the diel pattern of ROS concentrations in the water which are amongst the highest reported in the literature (maximum daytime values of 2.53 ­ 8.10 µM H2O2). Interlamellar cell masses (ILCM) occurred between the gill lamellae of fish from the lagoon with highest ROS and highest oxygen levels, while fish from a normoxic lagoon with one third the ROS had little or no ILCM. This is the first record of air breathing in a facultative air-breathing fish in hyperoxic conditions and the first record of an ILCM in a cichlid species.

Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): a fish living on the edge.

Spermatogenesis in Lake Magadi tilapia (Alcolapia grahami), a cichlid fish endemic to the highly alkaline and saline Lake Magadi in Kenya, was evaluated using light and transmission electron microscopy. Spermatogenesis, typified by its three major phases (spermatocytogenesis, meiosis and spermiogenesis), was demonstrated by the presence of maturational spermatogenic cells namely spermatogonia, spermatocytes, spermatids and spermatozoa. Primary spermatogonia, the largest of all the germ cells, underwent a series of mitotic divisions producing primary spermatocytes, which then entered two consecutive meiotic divisions to produce secondary spermatocytes and spermatids. Spermatids, in turn, passed through three structurally distinct developmental stages typical of type-I spermiogenesis to yield typical primitive anacrosomal spermatozoa of the externally fertilizing type (aquasperm). The spermatozoon of this fish exhibited a spheroidal head with the nucleus containing highly electron-dense chromatin globules, a midpiece containing ten ovoid mitochondria arranged in two rows and a flagellum formed by the typical 9 + 2 microtubule axoneme. In addition, the midpiece, with no cytoplasmic sheath, appeared to end blindly distally in a lobe-like pattern around the flagellum; a feature that was unique and considered adaptive for the spermatozoon of this species to the harsh external environment. These observations show that the testis of A. grahami often undergoes active spermatogenesis despite the harsh environmental conditions to which it is exposed on a daily basis within the lake. Further, the spermiogenic features and spermatozoal ultrastructure appear to be characteristic of Cichlidae and, therefore, may be of phylogenetic significance.

Immuno-localization of type-IV collagen in the blood-gas barrier and the epithelial-epithelial cell connections of the avian lung.

The terminal respiratory units of the gas exchange tissue of the avian lung, the air capillaries (ACs) and the blood capillaries (BCs), are small and rigid: the basis of this mechanical feature has been highly contentious. Because the strength of the blood-gas barrier (BGB) of the mammalian lung has been attributed to the presence of type-IV collagen (T-IVc), localization of T-IVc in the basement membranes (BM) of the BGB and the epithelial-epithelial cell connections (E-ECCs) of the exchange tissue of the lung of the avian (chicken) lung was performed in order to determine whether it may likewise contribute to the strength of the BGB. T-IVc was localized in both the BM and the E-ECCs. As part of an integrated fibroskeletal scaffold on the lung, T-IVc may directly contribute to the strengths of the ACs and the BCs.

Recent advances into understanding some aspects of the structure and function of mammalian and avian lungs.

Recent findings are reported about certain aspects of the structure and function of the mammalian and avian lungs that include (a) the architecture of the air capillaries (ACs) and the blood capillaries (BCs); (b) the pulmonary blood capillary circulatory dynamics; (c) the adaptive molecular, cellular, biochemical, compositional, and developmental characteristics of the surfactant system; (d) the mechanisms of the translocation of fine and ultrafine particles across the airway epithelial barrier; and (e) the particle-cell interactions in the pulmonary airways. In the lung of the Muscovy duck Cairina moschata, at least, the ACs are rotund structures that are interconnected by narrow cylindrical sections, while the BCs comprise segments that are almost as long as they are wide. In contrast to the mammalian pulmonary BCs, which are highly compliant, those of birds practically behave like rigid tubes. Diving pressure has been a very powerful directional selection force that has influenced phenotypic changes in surfactant composition and function in lungs of marine mammals. After nanosized particulates are deposited on the respiratory tract of healthy human subjects, some reach organs such as the brain with potentially serious health implications. Finally, in the mammalian lung, dendritic cells of the pulmonary airways are powerful agents in engulfing deposited particles, and in birds, macrophages and erythrocytes are ardent phagocytizing cellular agents. The morphology of the lung that allows it to perform different functions-including gas exchange, ventilation of the lung by being compliant, defense, and secretion of important pharmacological factors-is reflected in its "compromise design."

West Indian Ocean variability and East African fish catch.

We describe marine climate variability off the east coast of Africa in the context of fish catch statistics for Tanzania and Kenya. The time series exhibits quasi-decadal cycles over the period 1964-2007. Fish catch is up when sea surface temperature (SST) and atmospheric humidity are below normal in the tropical West Indian Ocean. This pattern relates to an ocean Rossby wave in one phase of its east-west oscillation. Coastal-scale analyses indicate that northward currents and uplift on the shelf edge enhance productivity of East African shelf waters. Some of the changes are regulated by the south equatorial current that swings northward from Madagascar. The weather is drier and a salty layer develops in high catch years. While the large-scale West Indian Ocean has some impact on East African fish catch, coastal dynamics play a more significant role. Climatic changes are reviewed using 200 years of past and projected data. The observed warming trend continues to increase such that predicted SST may reach 30 degrees C by 2100 while SW monsoon winds gradually increase, according to a coupled general circulation model simulation with a gradual doubling of CO(2).

Inspiratory aerodynamic valving occurs in the ostrich, Struthio camelus lung: a computational fluid dynamics study under resting unsteady state inhalation.

In the avian lung, inhaled air is shunted past the openings of the medioventral secondary bronchi (MVSB) by a mechanism termed 'inspiratory aerodynamic valving' (IAV). Sizes and orientations of the trachea (Tr), syrinx (Sx), extrapulmonary primary bronchus (EPPB), intrapulmonary primary bronchus (IPPB), MVSB, mediodorsal secondary bronchi (MDSB), lateroventral secondary bronchi (LVSB) and the ostium (Ot) were determined in the ostrich, Struthio camelus. Air flow was simulated through computationally generated models and its dynamics analysed. The 'truncated normal model' (TNM) consisted of the Tr, Sx, EPPB, IPPB, MVSB and the Ot. For the 'inclusive normal model' (INM), the MDSB and the LDSB were added. Variations of these models included the 'truncated MVSB1 rotated model' (T(MVSB1)RM), the 'truncated constriction fitted model' (TCFM) and the 'inclusive MVSB1 rotated model' (I(MVSB1)RM). In the TNM, the T(MVSB1)RM and the TCFM, the air flow exited through the MVSB while for the INM and the I(MVSB1)RM, very little of it did: IAV did not occur in the partial models. In the I(MVSB1)RM, rotating the MVSB1 clockwise did not affect IAV. The incomplete models may be faulty because the velocity/pressure profiles in different parts of the interconnected airways form an integrated functional continuum in which different parts of the system considerably impact on each other.

Identifying reefs of hope and hopeful actions: contextualizing environmental, ecological, and social parameters to respond effectively to climate change.

Priorities for conservation, management, and associated activities will differ based on the interplay between nearness of ecosystems to full recovery from a disturbance (pristineness), susceptibility to climate change (environmental susceptibility [ES]), and capacity of human communities to cope with and adapt to change (social adaptive capacity [AC]). We studied 24 human communities and adjacent coral reef ecosystems in 5 countries of the southwestern Indian Ocean. We used ecological measures of abundance and diversity of fishes and corals, estimated reef pristineness, and conducted socioeconomic household surveys to determine the AC of communities adjacent to selected coral reefs. We also used Web-based oceanographic and coral mortality data to predict each site's ES to climate warming. Coral reefs of Mauritius and eastern Madagascar had low ES and consequently were not predicted to be affected strongly by warm water, although these sites were differentiated by the AC of the human community. The higher AC in Mauritius may increase the chances for successful self-initiated recovery and protective management of reefs of this island. In contrast, Madagascar may require donor support to build AC as a prerequisite to preservation efforts. The Seychelles and Kenya had high ES, but their levels of AC and disturbance differed. The high AC in the Seychelles could be used to develop alternatives to dependence on coral reef resources and reduce the effects of climate change. Pristineness weighted toward measures of fish recovery was greatest for Kenya's marine protected areas; however, most protected areas in the region were far from pristine. Conservation priorities and actions with realistic chances for success require knowledge of where socioecological systems lie among the 3 axes of environment, ecology, and society.

Comparative in vitro study of interactions between particles and respiratory surface macrophages, erythrocytes, and epithelial cells of the chicken and the rat.

In mammals, surface macrophages (SMs) play a foremost role in protecting the respiratory system by engulfing and destroying inhaled pathogens and harmful particulates. However, in birds, the direct defense role(s) that SMs perform remains ambiguous. Paucity and even lack of SMs have been reported in the avian respiratory system. It has been speculated that the pulmonary defenses in birds are inadequate and that birds are exceptionally susceptible to pulmonary diseases. In an endeavour to resolve the existing controversy, the phagocytic capacities of the respiratory SMs of the domestic fowl and the rat were compared under similar experimental conditions by exposure to polystyrene particles. In cells of equivalent diameters (8.5 microm in the chicken and 9.0 microm in the rat) and hence volumes, with the volume density of the engulfed polystyrene particles, i.e. the volume of the particles per unit volume of the cell (SM) of 23% in the chicken and 5% in the rat cells, the avian cells engulfed substantially more particles. Furthermore, the avian SMs phagocytized the particles more efficiently, i.e. at a faster rate. The chicken erythrocytes and the epithelial cells of the airways showed noteworthy phagocytic activity. In contrast to the rat cells that did not, 22% of the chicken erythrocytes phagocytized one to six particles. In birds, the phagocytic efficiencies of the SMs, erythrocytes, and epithelial cells may consolidate pulmonary defense. The assorted cellular defenses may explain how and why scarcity of SMs may not directly lead to a weak pulmonary defense. The perceived susceptibility of birds to respiratory diseases may stem from the human interventions that have included extreme genetic manipulation and intensive management for maximum productivity. The stress involved and the structural-functional disequilibria that have occurred from a 'directed evolutionary process', rather than weak immunological and cellular immunity, may explain the alleged vulnerability of the avian gas exchanger to diseases.

Study of the structure of the air and blood capillaries of the gas exchange tissue of the avian lung by serial section three-dimensional reconstruction.

We have previously reconstructed the gas exchange tissue of the adult muscovy duck, Cairina moschata using a method of manually aligning sections and tracing the contours of the components of the gas exchange tissue. This reconstruction method demonstrated that the air capillaries are comprised of an expanded globular part interconnected by narrow air channels. The blood capillaries completely surround the air capillaries forming an anastomosing meshwork of short segments. However, the resulting reconstruction was limited in scope because of the laborious process of tracing the profiles of each component through the sequence of micrographs. We have now reconstructed a larger proportion of the exchange tissue by using a cross-correlation based alignment strategy and have demonstrated that the staining intensity of each of the exchange tissue components is sufficiently different to allow them to be identified by simple filtering and thresholding. The resulting reconstructions sample a much larger proportion of the exchange tissue and demonstrate the heterogeneity of structures from different locations in the parabronchus. We have shown that a sheet-flow-type arrangement of blood capillaries surrounds the infundibulum; this represents an unexpected functional convergence with the arrangement of blood capillaries surrounding the mammalian alveoli. It is feasible, using this reconstruction strategy, to analyse the exchange tissue of a large number of avian species in order to determine structural correlates of function. The resulting reconstructions could be analysed in order to determine the basis of the functional efficiency and rigidity of the avian lung.

National scale-up of HIV testing and provision of HIV care to tuberculosis patients in Kenya.

SETTING: Kenya, one of the 22 tuberculosis (TB) high-burden countries, whose TB burden is fuelled by the human immunodeficiency virus (HIV). OBJECTIVE: To monitor and evaluate the implementation of HIV testing and provision of HIV care to TB patients in Kenya through the establishment of a routine TB-HIV integrated surveillance system. DESIGN: A descriptive report of the status of implementation of HIV testing and provision of HIV interventions to TB patients one year after the introduction of the revised TB case recording and reporting system. RESULTS: From July 2005 to June 2006, 88% of 112835 TB patients were reported to the National Leprosy and TB Control Programme, 98773 (87.9%) of whom were reported using a revised recording and reporting system that included TB-HIV indicators. HIV testing of TB patients increased from 31.5% at the beginning of this period to 59% at the end. Of the 46428 patients tested for HIV, 25558 (55%) were found to be HIV-positive, 85% of whom were provided with cotrimoxazole preventive treatment and 28% with antiretroviral treatment. CONCLUSION: A country-wide integrated TB-HIV surveillance system in TB patients can be implemented and provides essential data to monitor and evaluate TB-HIV related interventions.

Spectacularly robust! Tensegrity principle explains the mechanical strength of the avian lung.

Among the air-breathing vertebrates, the respiratory system of birds, the lung-air sac system, is remarkably complex and singularly efficient. The most perplexing structural property of the avian lung pertains to its exceptional mechanical strength, especially that of the minuscule terminal respiratory units, the air- and the blood capillaries. In different species of birds, the air capillaries range in diameter from 3 to 20 micro m: the blood capillaries are in all cases relatively smaller. Over and above their capacity to withstand enormous surface tension forces at the air-tissue interface, the air capillaries resist mechanical compression (parabronchial distending pressure) as high as 20 cm H(2)O (2 kPa). The blood capillaries tolerate a pulmonary arterial vascular pressure of 24.1 mmHg (3.2 kPa) and vascular resistance of 22.5 mmHg (3 kPa) without distending. The design of the avian respiratory system fundamentally stems from the rigidity (strength) of the lung. The gas exchanger (the lung) is uncoupled from the ventilator (the air sacs), allowing the lung (the paleopulmonic parabronchi) to be ventilated continuously and unidirectionally by synchronized bellows like action of the air sacs. Since during the ventilation of the lung the air capillaries do not have to be distended (dilated), i.e., surface tension force does not have to be overcome (as would be the case if the lung was compliant), extremely intense subdivision of the exchange tissue was possible. Minuscule terminal respiratory units developed, producing a vast respiratory surface area in a limited lung volume. I make a case that a firm (rigid) rib cage, a lung tightly held by the ribs and the horizontal septum, a lung directly attached to the trunk, specially formed and compactly arranged parabronchi, intertwined atrial muscles, and tightly set air capillaries and blood capillaries form an integrated hierarchy of discrete network system of tension and compression, a tensegrity (tensional integrity) array, which absorbs, transmits, and dissipates stress, stabilizing (strengthening) the lung and its various structural components.

The morphology of the pecten oculi of the ostrich, Struthio camelus.

The pecten oculi is a structure peculiar to the avian eye. Three morphological types of pecten oculi are recognized: conical type, vaned type and pleated type. The pleated type has been well studied. However, there exists only scanty data on the morphology of the latter two types of pectens. The structure of the vaned type of pecten of the ostrich, Struthio camelus was investigated with light and electron microscope. The pecten of this species consists of a vertical primary lamella that arises from the optic disc and supports 16-19 laterally located secondary lamellae, which run from the base and confluence at the apex. Some of the secondary lamellae give rise to 2 or 3 tertiary lamellae. The lamellae provide a wide surface, which supports 2-3 Layers of blood capillaries. Pigmentation is highest at the distal ends of the secondary and tertiary Lamella where blood capillaries are concentrated and very scanty on the primary and the proximal ends of the secondary lamella where the presence of capillaries is much reduced. In contrast to the capillaries of the pleated pecten, the endothelium of the capillaries in the pecten of the ostrich exhibits very few microvilli. These observations suggest that the morphology of the pecten of the ostrich, a flightless ratite bird is unique to the pleated pecten and is designed to meet the balance between optimal vision and large surface area for blood supply and yet ensuring it is kept firmly erect within the vitreous.