Microarchitecture and function of the lophophore in the bryozoan Cryptosula pallasiana

The architecture and function of the lophophore of the marine bryozoan Cryptosula pallasiana (Moll) are described, including some new features not previously discovered in bryozoans. The nature of fluid movements within the lophophoral coelom during feeding activities is postulated on the basis of the arrangements of epithelia and muscles. Epithelial cells at the tentacle bases are blastemic in nature, and there is a ciliated pit of unknown function in the angle between every pair of tentacles. There are 6 nerves in each tentacle, including a pair of single-axon subperitoneal nerves. Neurosecretory-like vesicles and glycogen occur in some neurons of the ganglion. The basal lamina collagen has a diameter smaller than that previously recorded for an invertebrate. Filament dimensions are given for several different muscles. Tentacle muscles and lophophore retractor muscles are smooth. Thick paramyosin-like filaments up to 75 nm diameter occur in two muscle types. A new set of muscles is described: the basal transverse muscles of the tentacles.     

Zinc phosphate granules in tissue surrounding the midgut of the barnacle Balanus balanoides

The chemical composition of inorganic granules found in parenchyma cells surrounding the midgut of adult Balanus balanoides (L.) was determined. X-ray microanalysis indicated the presence of magnesium, phosphorus, potassium, calcium, iron and zinc in the granules. A quantitative analysis of granule-rich pellets isolated from the midguts of adult barnacles showed that the granules were composed mainly of zinc phosphate, the remaining elements being minor constituents only.     

Arsenic in groundwaters of the Lower Mekong

Increasing incidence and awareness of arsenic in many alluvial aquifers of South-east Asia has raised concern over possible arsenic in the Lower Mekong Basin. Here, we have undertaken new research and reviewed many previous small-scale studies to provide a comprehensive overview of the status of arsenic in aquifers of Cambodia and the Cuu Long Delta of Vietnam. In general natural arsenic originates from the Upper Mekong basin, rather than from the local geology, and is widespread in soils at typical concentrations of between 8 and 16 ppm; (dry weight). Industrial and agricultural arsenic is localised and relatively unimportant compared to the natural alluvial arsenic. Aquifers most typically contain groundwaters of no more than 10 μg L⁻¹, although scattered anomalous areas of 10 to 30 μg L⁻¹ are also quite common. The most serious, but possibly ephemeral arsenic anomalies, of up to 600 μg L⁻¹, are associated with iron and organic-rich flood-plain sediments subject to very large flood-related fluctuations in water level, resulting in transient arsenopyrite dissolution under oxidizing conditions. In general, however, high-arsenic groundwaters result from the competing interaction between sorption and dissolution processes, in which arsenic is only released under reducing and slightly alkaline conditions. High arsenic groundwaters are found both in shallow water-tables, and in deeper aquifers of between 100 and 120 m depth. There is no evidence of widespread arsenicosis, but there are serious localised health-hazards, and some risk of low-level arsenic ingestion through indirect pathways, such as through contaminated rice and aquaculture. An almost ubiquitous presence of arsenic in soils, together with the likelihood of greatly increased groundwater extraction in the future, will require continuing caution in water resources development throughout the region.     

Distribution of salmon-habitat potential relative to landscape characteristics and implications for conservation.

The geographic distribution of stream reaches with potential to support high-quality habitat for salmonids has bearing on the actual status of habitats and populations over broad spatial extents. As part of the Coastal Landscape Analysis and Modeling Study (CLAMS), we examined how salmon-habitat potential was distributed relative to current and future (+100 years) landscape characteristics in the Coastal Province of Oregon, USA. The intrinsic potential to provide high-quality rearing habitat was modeled for juvenile coho salmon (Oncorhynchus kisutch) and juvenile steelhead (O. mykiss) based on stream flow, valley constraint, and stream gradient. Land ownership, use, and cover were summarized for 100-m analysis buffers on either side of stream reaches with high intrinsic potential and in the overall area encompassing the buffers. Past management seems to have concentrated nonindustrial private ownership, agriculture, and developed uses adjacent to reaches with high intrinsic potential for coho salmon. Thus, of the area in coho salmon buffers, 45% is either nonforested or recently logged, but only 10% is in larger-diameter forests. For the area in steelhead buffers, 21% is either non-forested or recently logged while 20% is in larger-diameter forests. Older forests are most extensive on federal lands but are rare on private lands, highlighting the critical role for public lands in near-term salmon conservation. Agriculture and development are projected to remain focused near high-intrinsic-potential reaches for coho salmon, increasing the importance of effectively addressing nonpoint source pollution from these uses. Percentages of larger-diameter forests are expected to increase throughout the province, but the increase will be only half as much in coho salmon buffers as in steelhead buffers. Most of the increase is projected for public lands, where policies emphasize biodiversity protection. Results suggest that widespread recovery of coho salmon is unlikely unless habitat can be improved in high-intrinsic-potential reaches on private lands. Knowing where high-intrinsic-potential stream reaches occur relative to landscape characteristics can help in evaluating the current and future condition of freshwater habitat, explaining differences between species in population status and risk, and assessing the need for and feasibility of restoration.     

Territoriality among male red-winged blackbirds

Summary To test theories recently proposed to explain territorial dominance in animals, we performed several versions of experiments in which male red-winged blackbirds were removed from their territories, held in captivity for varying periods, and then released to challenge their replacements. Males removed for 7 to 49 h recovered their territories from replacement males, either when released or over the following few days or weeks. The duration males were held off territory, the duration replacement males occupied territories, and the original owners' awareness before fighting that they had been replaced, apparently did not influence contest outcomes, but whether the new owner was a neighbor or a previously non-territorial male had some effect. The pattern of territory recovery observed most closely supports the hypothesis that territorial dominance in redwings arises from asymmetries in local knowledge and experience between owners and challengers, although another hypothesis, the Resource Holding Potential hypothesis, was not entirely ruled out. We discuss design of removal experiments to test territoral dominance, and propose that ecologies of particular species may powerfully influence outcomes of these experiments.     

A comment on linear control problems in the theory of renewable resource exploitation

Optimal steady state yields from a renewable resource are identified using capital theory and the notion of a most rapid approach path. The optimal stock level determined in this fashion is seen to be identical to that implied by Green's Theorem and Pontryagin's Maximum Principle.     

Biodegradation of Injection Molded Starch-Poly (3-hydroxybutyrate-co-3-hydroxyvalerate) Blends in a Natural Compost Environment

Injection molded specimens were prepared by blending poly (hydroxybutyrate-co-valerate) (PHBV) with cornstarch. Blended formulations incorporated 30% or 50% starch in the presence or absence of poly-(ethylene oxide) (PEO), which enhances the adherence of starch granules to PHBV. These formulations were evaluated for their biodegradability in natural compost by measuring changes in physical and chemical properties over a period of 125 days. The degradation of plastic material, as evidenced by weight loss and deterioration in tensile properties, correlated with the amount of starch present in the blends (neat PHBV < 30% starch < 50% starch). Incorporation of PEO into starch-PHBV blends had little or no effect on the rate of weight loss. Starch in blends degraded faster than PHBV and it accelerated PHBV degradation. Also, PHBV did not retard starch degradation. After 125 days of exposure to compost, neat PHBV lost 7% of its weight (0.056% weight loss/day), while the PHBV component of a 50% starch blend lost 41% of its weight (0.328% weight loss/day). PHB and PHV moieties within the copolymer degraded at similar rates, regardless of the presence of starch, as determined by ¹H-NMR spectroscopy. GPC analyses revealed that, while the number average molecular weight (Mn) of PHBV in all exposed samples decreased, there was no significant difference in this decrease between neat PHBV as opposed to PHBV blended with starch. SEM showed homogeneously distributed starch granules embedded in a PHBV matrix, typical of a filler material. Starch granules were rapidly depleted during exposure to compost, increasing the surface area of the PHBV matrix.     

Mathematical model for the microbial metabolism of glucose induced enhanced biological phosphorus removal in an anaerobic/aerobic sequential batch reactor

Glucose plays a significant role in enhanced biological phosphorus removal (EBPR). Previous experimental studies have shown that in addition to acetate, glucose can induce and maintain a successful EBPR performance under certain operating procedures. Mathematical modeling of the EBPR metabolism is an important consideration that is necessary to produce a deeper insight into this process. In this study, four anaerobic reactions plus four aerobic reactions with fourteen kinetic constants are structured to describe the dynamic behavior of the key metabolic components in the glucose induced EBPR system. The development of the stoichiometric coefficients for the reactions is based on fundamental biochemical principles. The model describes the dynamics of the important storage compounds, which are considered separately from the active biomass. Sequential batch experiments were performed to find the optimum model parameters using sludges exhibiting stable EBPR from glucose fed system. The maximum specific substrate conversion rate in the glucose model is composed of two factors: the maximum specific rates of glucose direct conversion to PHV (q _gv ^max ) and glucose conversion to glycogen q _gl ^max , which are 14.1 and 699.7 C-mmol/C-mmol·h, respectively. The maximum specific rate of polyphosphate synthesis k _pp ^max is 0.2 P-mmol/C-mmol·h. The model with the best-fit parameters satisfactorily simulates the dynamic behavior of the key components during both anaerobic and aerobic conditions.