The burrows and physiological adaptations to a burrowing lifestyle of Natatolana borealis (Isopoda: Cirolanidae)

The isopod Natatolana borealis Lilljeborg constructs U-shaped burrows in soft mud, the bore of which closely approximates the width of the occupant. Within artificial burrows, the isopods are largely quiescent and often adopt a position close to one of the burrow openings. Conditions within burrows constructed in the laboratory are moderately hypoxic [11.7 to 14.9 kPa (88 to 112 torr)], with isopods showing discontinuous irrigation behaviour (pleopod beating). Rates of oxygen consumption (measured at 10°C) are maintained approximately constant over a wide range of oxygen partial pressure (P_{O 2}) due, in part, to a pronounced increase in pleopod beat rate. Values for the critical partial pressure of oxygen (P_c), the P_{O 2} at which can no longer be maintained independent of P_{O 2}, were 2.0 to 3.3 kPa (15 to 25 torr). N. borealis can survive lengthy periods (65 h at 5°C) of anoxia, during which there is a significant reduction in the carbohydrate concentration and an increase in the l-lactate concentration of the tissues. The oxygencarrying capacity of the haemolymph of N. borealis was low. The haemocyanin showed a relatively high oxygen affinity [P₅₀=0.39 kPa (2.99 torr) at 10°C at the in vivo pH of 7.80] and a pronounced Bohr effect (-1.22). These characteristics may be advantageous to a burrowing mode of life and also for the conditions likely to be encountered in fish carcasses into which they burrow en masse to feed.     

Mating strategies and mating success of fallow (Dama dama) bucks in a non-lekking population

The rutting behaviour of bucks in an enclosed population was investigated between 1988 and 1990. A substantial proportion of the matings were observed. After preliminary observations in the 1987 rut we categorised bucks into one of four rutting strategies based mainly on their degree of territoriality. We investigate the effects of age, dominance and mating strategy on mating success. Territories were aggregated in an area of oak woods and mating success was highly skewed. Bucks of between 5 and 7 years old achieved the majority (over 90%) of observed matings. Mating success was highly correlated with dominance but only weakly related to fighting success. The possession of a territory was crucial to achieving high reproductive success, with a 38-fold difference between the most and least successful strategies. Bucks pursuing the different strategies also differed in the time they commenced groaning, timing of matings, mating interference and the locations where they achieved their matings. Although high-ranking males devoted considerable effort to obtaining and defending a territory only 36% of each buck's matings were achieved on his territory and males tended to abandon these sites when the tendency of females to visit them decreased.     

Significance of ammonia in determining the N:P ratio of the sea water off Barbados,West Indies

N:P atomic ratios calculated on NO₃-N alone for the upper waters of the tropical Atlantic Ocean off Barbados are very low, being only 9.8:1. Absolute values are also low, the integrated values between O and 100 m for NO₃-N and PO₄-P being 0.59 and 0.06 g-at l^-1, respectively. However, when ammonia is included as a nitrogen source the ratio becomes 28.8:1. This is the average value obtained from 42 samples taken over a 21-month period, and suggests that phosphorus, and not nitrogen, is the more critical nutrient in phytoplankton growth off Barbados.     

Responses of Mytilus edulis on exposure to the water-accommodated fraction of North Sea oil

Individuals of Mytilus edulis L., collected from the Erme estuary (S.W. England) in 1978, were exposed to low concentrations (7 to 68 g l^-1) of the water-accommodated fraction (WAF) of North Sea crude oil. The pattern of accumulation of petroleum hydrocarbons in the body tissues was affected by the presence of algal food cells, the period of exposure, the hydrocarbon concentration in seawater, the type of body tissue and the nature of the hydrocarbon. Many physiological responses (e.g. rates of oxygen consumption, feeding, excretion, and scope for growth), cellular responses (e.g. lysosomal latency and digestive cell size) and biochemical responses (e.g. specific activities of several enzymes) were significantly altered by short-term (4 wk) and/or long-term (5 mo) exposure to WAF. Stress indices such as scope for growth and lysosomal latency were negatively correlated with tissue aromatic hydrocarbons.     

Methylalkylpyrazines in aposematic insects,their hostplants and mimics

Summary Adults of forty-five aposematic insect species from four orders, and/or, in eight cases, their early stages, were examined for the presence of 2-methoxy-3-alkylpyrazines by coupled gas chromatography/mass spectrometry. The survey also included eight cryptic and related species and six unrelated mimics, twelve selected hostplants of those herbivores that had proved positive for such pyrazines, and nine well known toxic plants. Positive results were as follows: aposematic adult species, 26 (58 %); obscurely coloured species, 1 (12.5%); mimics, 2 (33%); host-plants, 5 (42%); well-known toxic plants, 4 (44%). Among the taxonomic groups, these pyrazines were found in the lepidopteran families and subfamilies Papilionidae, Danainae, Heliconiinae, Acraeinae, Zygaenidae and Arctiidae, and among the Coleoptera, in the Lycidae, Cantharidae, Endomychidae, Coccinellidae, Oedemeridae and Meloidae. Single cases of the occurrence of these pyrazines were also detected in the Hemiptera (Cercopidae) and Orthoptera (Pyrgomorphidae). Mimics were found with and without the pyrazines. Among the plants they were detected in Aristolochiaceae, Asclepiadaceae, Asteraceae, Papaveraceae, Passifloraceae, Solanaceae and Urticaceae. Some aposematic and phytophagous insects apparently sequester pyrazines from their hostplants whereas others, particularly the predatory species, manufacture these substancesde novo. Alerting signals in general are discussed.     

An estimate of carbonate production by macrobenthos in some tropical,soft-bottom communities

Productivity figures are available for most of the species comprising a few soft-bottom communities in the Miami area, USA. These are in the form of the ratio of annual somatic production to standing crop, both being measured as drytissue weight. These values have been converted to carbonate productivity ratios, and from these the carbonate production per square metre per year calculated. The values range from less than 1 g to nearly 400 g for sublittoral communities, and about 1 kg for one intertidal area.Contribution No. 1559 from the University of Miami, Rosenstiel School of Marine and Atmospheric Science, 10 Rickenbacker Causeway, Miami, Florida 33149, USA.     

Social,environmental and genetic factors in the ontogeny of phenotypic differentiation in a lizard with alternative male reproductive strategies

Summary Adult male tree lizards, Urosaurus ornatus, practise alternative (territorial or sneaker/satellite) reproductive strategies that are correlated with differences in throat color and body size. In this study we raised tree lizards from hatching in the laboratory to examine the question of whether the phenotypic expression of secondary sex coloration and body size can be facultatively influenced by social or abiotic environmental factors. We compared males reared in the laboratory under different social and environmental conditions to males in the field and found no effect of different conditions on phenotypic differentiation (Figs. 2–4). Thus, phenotypic differences between morphs probably result largely from nonfacultative expression of different genotypes. This suggests that alternative male morphs practise a mixed evolutionary stable strategy (ESS) rather than one morph making the best of a bad situation. However, in the context of ESS theory it is difficult to explain our further result that the nonterritorial morph in this species grows faster and reaches a larger adult body size than the territorial morph (Fig. 5).     

Regional estimation of current and future forest biomass

The 90,674 wildland fires that burned 2.9 million ha at an estimated suppression cost of $1.6 billion in the United States during the 2000 fire season demonstrated that forest fuel loading has become a hazard to life, property, and ecosystem health as a result of past fire exclusion policies and practices. The fire regime at any given location in these regions is a result of complex interactions between forest biomass, topography, ignitions, and weather. Forest structure and biomass are important aspects in determining current and future fire regimes. Efforts to quantify live and dead forest biomass at the local to regional scale has been hindered by the uncertainty surrounding the measurement and modeling of forest ecosystem processes and fluxes. The interaction of elevated CO2 with climate, soil nutrients, and other forest management factors that affect forest growth and fuel loading will play a major role in determining future forest stand growth and the distribution of species across the southern United States. The use of satellite image analysis has been tested for timely and accurate measurement of spatially explicit land use change and is well suited for use in inventory and monitoring of forest carbon. The incorporation of Landsat Thematic Mapper data coupled with a physiologically based productivity model (PnET), soil water holding capacity, and historic and projected climatic data provides an opportunity to enhance field plot based forest inventory and monitoring methodologies. We use periodic forest inventory data from the USDA Forest Service's Forest Inventory and Analysis (FIA) project to obtain estimates of forest area and type to generate estimates of carbon storage for evergreen, deciduous, and mixed forest classes for use in an assessment of remotely sensed forest cover at the regional scale for the southern United States. The displays of net primary productivity (NPP) generated from the PnET model show areas of high and low forest carbon storage potential and their spatial relationship to other landscape features for the southern United States. At the regional scale, predicted annual NPP in 1992 ranged from 836 to 2181 g/m2/year for evergreen forests and 769-2634 g/m2/year for deciduous forests with a regional mean for all forest land of 1448 g/m2/year. Prediction of annual NPP in 2050 ranged from 913 to 2076 g/m2/year for evergreen forest types to 1214-2376 g/m2/year for deciduous forest types with a regional mean for all forest land of 1659 g/m2/year. The changes in forest productivity from 1992 to 2050 are shown to display potential areas of increased or decreased forest biomass. This methodology addresses the need for spatially quantifying forest carbon in the terrestrial biosphere to assess forest productivity and wildland fire fuels.     

Exploring the Relationship Between Hydrologic Parameters and Nutrient Loads Using Digital Elevation Model and GIS – A Case Study from Sugarcreek Headwaters, Ohio, U.S.A.

Ohio is typical among the Midwestern and Eastern United States with high levels of water pollutants, the main sources being from agriculture. In this study, we used a digital elevation model in conjunction with hydrological indices to determine the role of landscape complexity affecting the spatial and temporal variation in pollutant levels, in one of the most impaired headwater streams in Ohio. More than eighty five percent of the study area is dominated by agriculture. Spatial distribution of slope (S), altitude and wetness index along with other watershed parameters such as flow direction, flow accumulation, stream networks, flow stream orders and erosion index were used within a Geographic Information Systems framework to quantify variation in nitrate and phosphate loads to headwater streams. Stream monitoring data for nutrient loads were used to correlate the observed spatial and temporal patterns with hydrological parameters using multiple linear regressions. Results from the wetness index calculated from a digital elevation model suggested a range of 0.10–16.39, with more than 35% having values less than 4.0. A Revised Universal Soil Loss Equation (RUSLE) predicted soil loss in the range of 0.01–4.0 t/ha/yr. Nitrate nitrogen levels in the study area paralleled precipitation patterns over time, with higher nitrate levels corresponding to high precipitation. Atmospheric deposition through precipitation could explain approximately 35% of total nitrate levels observed in streams. Among the different topographic variables and hydrological indices, results from the step-wise multiple regression suggested the following best predictors, (1) elevation range and upstream flow length for nitrate, (2) flow direction and upstream flow length for ammonia-nitrogen and slope, and (3) elevation range for phosphate levels. Differences in the landscape models observed for nitrate, phosphate and ammonia-nitrogen in the surface waters were attributed partly to differences in the chemical activity and source strengths of the different forms of these nutrients through agricultural management practices. The results identify geomorphologic and landscape characteristics that influence pollutant levels in the study area.