Metabolic rate in diapause and nondiapause brown locust eggs correlated with embryonic development

Insects use dormancy to survive adverse conditions. Brown locust Locustana pardalina (Walk.) eggs offer a convenient model to study dormancy (diapause and quiescence), which contributes to their survival under arid conditions. The metabolic rates of developing nondiapause, diapause and quiescent eggs are compared in the present study using closed‐system respirometry. The embryo becomes committed to continue development and hatch or to enter diapause 6 days after the eggs are placed on moist soil. The metabolic rate of nondiapause eggs increases exponentially until hatching, whereas that of diapause eggs is low and stable. The metabolic rate of diapause laboratory eggs (1.9 ± 0.6 µL CO₂ mg^?1 h^?1) is significantly higher than that of field eggs (0.5 ± 0.3 µL CO₂ mg^?1 h^?1), although the ranges of metabolic rate overlap and the embryos are all in late anatrepsis. The metabolic rate of quiescent eggs is similar to that of diapause eggs but decreases with time. Low metabolic rates during arrested development allow eggs to persist over long periods before hatching.     

Cell-Cell Interactions and Distal Outgrowth in Amphibian Limbs

SYNOPSIS. A current model concerning the process of limb regenerationin vertebrates is examined. According to this model (Bryantet al, 1981), new positional values in the proximal-distal limbaxis are laid down as a result of local interactions betweencells in the limb circumference. Cells with disparate circumferentialpositional values come together at the site of future outgrowthand intercalation between them generates more distal levelsof the pattern. The results of a number of experiments on surgicallycreated symmetrical limb stumps are discussed in relation tothis model. In addition, an extension of this model to accountfor digit formation is presented, and the implications of thisformulation for limb evolution are discussed.     

Post-juvenile dispersal of Hazel Grouse Bonasa bonasia in an expanding population of the southeastern French Alps

We studied the post-juvenile dispersal of 18 radiotagged juvenile Hazel Grouse Bonasa bonasia (14 males, four females) in an expanding population in the southeastern French Alps between 1998 and 2001. The mean dispersal distances between the capture sites of juveniles in September–October and the centre of the home range in the following spring was 4 km for males (range 0.1–24.9 km) and 2 km for females (range 0.2–5.6 km). The distances recorded for two long-dispersing males (15 and 24.9 km) are greater than those reported to date for Hazel Grouse. Using our radiotracking data, we interpret the pattern of range expansion that has been occurring since the 1950s around our study area. Barriers to dispersal included rocky ground and other alpine habitats above 2000 m and over 1 km wide, but Hazel Grouse did cross open agricultural land at lower elevation. Two patterns of dispersal movements were recognized in juveniles: erratic movements that led to settlement on or near the natal site, and direct movements to a new range relatively far from the natal area. We discuss the adaptive consequences of these different behaviour patterns.     

Low dissolved oxygen levels reduce anti-predation behaviours of the freshwater clam Corbicula fluminea

1. When dissolved oxygen levels decline in aquatic systems, prey may be unable to maintain behaviours protecting them from predators. We examined how oxygen availability affected anti‐predator responses in the freshwater clam, Corbicula fluminea. 2. When attacked, bivalves protect their soft tissues by closing their protective valves. This reduces vulnerability to small predators, but ventilation and oxygen uptake are suspended. We found that after a simulated attack, clams under low oxygen conditions reopened their valves sooner than clams under high oxygen conditions, suggesting that hypoxia increases vulnerability to predation. 3. Bivalves may also evade predators through burial into the substratum. Deeper burial confers greater refuge from predators, but increases the costs of ventilation. In a second experiment, we studied how burial depth of C. fluminea is affected by oxygen availability. Additionally, we examined whether clams changed burial depth following a simulated attack by a small predator, and whether this response was affected by oxygen availability. Our results offered partial support for the hypothesis that burial depth is reduced under hypoxic conditions, but the simulated attack did not affect burial depth in any oxygen treatments.     

Changing attitudes in nature conservation: the Nature Conservancy and Nature Conservancy Council

An official organization responsible for ecological research and nature conservation was formed in 1949. This paper traces its development and vicissitudes, first as an independent Nature Conservancy, then as a part of the Natural Environment Research Council, and finally as the Nature Conservancy Council. Much has been achieved: ecology is now a household word; there is a strong voluntary tide for nature conservation in the country; and there have been notable achievements in practical conservation. But the dangers to nature in Britain have proved to be much greater than anticipated.     

The inhibition of potato sprout growth by light.

The effect of light intensity on sprout growth in seed potato tubers (Solanum tuberosum) was examined using diffuse daylight in Peru and diffuse artificial light at Glasgow. Mean temperatures below 20 °C produced strong sprout growth that was inhibited by both daylight and artificial light, at visible irradiances above 0.01 Wm^-2. The percentage inhibition of sprout growth increased linearly with the logarithm of the irradiance, 50% inhibition being at 0.04 - 0.1 Wm^-2 provided that the temperature was suitable for substantial sprout growth in the absence of light. Cultivar and temperature had very little effect on the 50% inhibition point. At high irradiances growth inhibition was up to 95%, but the sprout length was never reduced to zero; short, robust green sprouts remained. Sprout numbers were increased by daylight, but not by artificial light. Diffuse daylight also reduced the total weight loss from seed tubers during a storage season of 180 days. At mean temperatures above 20 °C., sprout growth in the absence of light was much reduced and the effect of light on sprout elongation was less obvious.     

The effect of ammonia treatment on the solubilization of straw and the growth of cellulolytic rumen bacteria

Pre-treatment of straw with anhydrous ammonia increased its susceptibility to solubilization by the predominant cellulolytic bacteria from the rumen, Bacteroides succinogenes, Ruminococcus albus and R. flavefaciens. Ammonia treatment also increased the production of microbial protein and fermentation products by all three species. Scanning electron microscope observations of straw during digestion suggested that the attack of straw by these bacteria was accompanied by the formation of substantial numbers of adherent microcolonies.