Evolution of avian eggshell structure

Data are presented suggesting that birds have evolved eggs with shells containing different structures (numbers of mammillae per unit of inner eggshell surface area, i.e., mammillary densities) to cope up with different calcium requirements imposed by different growth rates and modes of development. Precocial bird species grow slowly, but have high mammillary density, while altricial bird species grow rapidly, but have low mammillary density. These results suggest an adaptation associated with growth rate and mode of development and show, moreover, that the mammillary layer is indicative of the breeding biology of the bird. J. Morphol. 2012. © 2011 Wiley Periodicals, Inc.     

Contribution of thermal and nonthermal factors to the regulation of body temperature in humans.

The set point has been used to define the regulated level of body temperature, suggesting that displacements of core temperature from the set point initiate heat production (HP) and heat loss (HL) responses. Human and animal experiments have demonstrated that the responses of sweating and shivering do not coincide at a set point but rather establish a thermoeffector threshold zone. Neurophysiological studies have demonstrated that the sensor-to-effector pathways for HP and HL overlap and, in fact, mutually inhibit each other. This reciprocal inhibition theory, presumably reflecting the manner in which thermal factors contribute to homeothermy in humans, does not incorporate the effect of nonthermal factors on temperature regulation. The present review examines the actions of these nonthermal factors within the context of neuronal models of temperature regulation, suggesting that examination of these factors may provide further insights into the nature of temperature regulation. It is concluded that, although there is no evidence to doubt the existence of the HP and HL pathways reciprocally inhibiting one another, it appears that such a mechanism is of little consequence when comparing the effects of nonthermal factors on the thermoregulatory system, since most of these factors seem to exert their influence in the region after the reciprocal cross-inhibition. At any given moment, both thermal and several nonthermal factors will be acting on the thermoregulatory system. It may, therefore, not be appropriate to dismiss the contribution of either when discussing the regulation of body temperature in humans.     

Nutrient responses to the liming of lake Gårdsjön

The acidified lakes Lake Gårdsjön and Lake Stora Hästevatten the reference lake have been monitored since 1979 and 1980 respectively. The lakes are situated in SW Sweden; in an area severly affected by acid deposition. Lake Gårdsjön was limed in spring 1982. This paper analyses changes in nutrient concentrations upon liming of Lake Gårdsjön. The liming of Lake Gårdsjön was followed by a slight increase in ammonium, nitrate, and dissolved organic nitrogen concentrations. A drastic decrease occurred in particulate nitrogen and particulate carbon, whereas dissolved organic carbon increased. Total phosphorus and particulate phosphorus concentrations were similar to pre-limed conditions. The long-term decrease in phosphorus concentration, exhibited by the reference lake, was not identified in Lake Gårdsjön after liming, but total phosphorus concentration was still less than half compared to Lake Gårdsjön in the early 1970's. Additional measures such as phosphorus fertilization, should in certain cases be considered in addition to liming if the goal is to restore lakes to their pre-acidic conditions.     

Early post-fire tree regeneration in a Picea-Vaccinium forest in northern Sweden

Abstract. Age and size structure of saplings of Picea abies, Pinus sylvestris and Betula pubescens were examined in a 26-yr old forest fire area in a Picea abies-Vaccinium myrtillus forest in northern Sweden. Picea, which is a shade-tolerant species, had its maximum regeneration prior to the shade-intolerant Pinus. The shift from Picea to Pinus regeneration in the late 1970s, did not seem to be related to variations in summer temperature. Instead, it is suggested that Picea established in the shade created by dead trees, and, that increased reindeer browsing of Betula in combination with a simultaneous thinning of the tree layer, favoured Pinus recruitment. These regeneration patterns do not confirm conventional views of post-fire succession in Sweden.