BOOKS REVIEWS

Book reviewed in this article:
Archeology: Computer Analysis of Chronological Seriation . FRANK HOLE and MARY SHAW
Archeology: Archéologie et calculateurs: problèmes sémi-ologiques et mathématiques . CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE     

The Control of Color in Birds

SYNOPSIS. The colors of birds result from deposition of pigments—mainlymelanins and carotenoids—in integumentary structures,chiefly the feathers. The plumages of birds indicate their age,sex, and mode of living, and play important roles in camouflage,mating, and establishment of territories. Since feathers aredead structures, change of color of feathers is effected throughdivestment (molt) and replacement. The color and pattern ofa feather are determined by the interplay of genetic and hormonalinfluences prevailing in its base during regeneration. Mostbirds replace their feathers at least once annually. Some wearthe same kind of basic plumage all the time butothers alternatea basic and breeding plumage, either in one (the male) or bothsexes. Still others may have more than two molts, adding supplementalplumage at certain times in the plumage cycle. The varietiesof patterns of molt, the kinds of plumage, and the colors andpatterns of feathers among birds apparently are the result ofseveral kinds of selection pressures working through evolution.     

Development of Amblyospora campbelli (Microsporida: Amblyosporidae) in the Mosquito Culiseta incidens (Thomson)

The complete life cycle of Amblyospora campbelli (Kellen and Wills, 1962) (Microsporida: Amblyosporidae) requires a two-host system involving the mosquito host, Culiseta incidens (Thomson), and an obligatory intermediate copepod host. The parasite has dimorphic spore development producing meiospores (haploid condition) and binucleated spores (diploid condition), either as an exclusive infection or simultaneously (within females only). This is the 1st known report of concurrent spore development within an adult mosquito host, and, therefore, shows the Amblyospora campbelli system to be uniquely different from other Amblyospora spp. cycles previously described. The significance of dimorphic spore development is discussed. In females, diplokaryotic meronts may invade oenocytes, causing a benign-type of infection. A blood-meal is required to initiate sporulation of the binucleate spore. The binucleate spore contains the sporoplasm involved in transovarial transmission. A 2nd sporulation sequence, primarily in adipose tissue, may involve both males and females. In this sequence, repeated merogonic division greatly increased the density of diplokaryotic meronts and generally involved most of the body of the host. Production of meiospores, unlike that for the binucleate spore, appeared to be spontaneous (i.e. no obligatory blood meal). Survivorship of male and female larval mosquitoes was nearly equal. Adult females spread the parasite in three ways: transovarial, transovum, and by meiospore deposition.     

A protocol for classifying regional dynamics,exemplified by using woodland birds in southeastern Australia

Abstract Communities of forest and woodland birds are usually studied intensively at only one or a few locations. This provides a perspective that perhaps emphasizes local phenomena at the expense of placing local dynamics in the context of processes operating at the landscape or regional scale. The present paper seeks to redress partially this imbalance by studying the dynamics of individual bird species among several habitat types (all Eucalyptus-dominated forests or woodlands) over the annual cycle. This regional-scale (250km), continental study reveals that species exhibit idiosyncratic dynamics of various kinds: restricted or more ubiquitous occupation of habitats and three forms of seasonal dynamics at the regional scale (resident, migrant and itinerant). By using this classificatory scheme, it becomes evident that the bird communities found in different habitats consist of diverse collections of strategists and that the level of diversity differs among habitat types. The difficulties that many field workers have had in reconciling their observations with community theory most likely reflect the underlying dynamism of bird communities, especially in the temperate regions on continents where seasonal fluxes are pronounced.     

Nitrate fluxes in soybean seedling roots and their response to amino acids: an approach using 15N

This study was undertaken to determine which of the two NO₃^? fluxes (influx or efflux) across plasma membranes of root cells is the target of those amino acids which have been shown to inhibit net NO₃^? uptake (Muller & Touraine 1992, Journal of Experimental Botany 43 , 617–623). Parallel experiments were performed to mea-sure either the time course of ¹⁵NO₃^? release from roots of soybean seedlings previously labelled with this isotope into non-labelled solution, or the time course of ¹⁵N accumulation from labelled ¹⁵NO₃^? solution in non-labelled seedlings. Focusing on the fate of ¹⁵NO₃^? in the cytoplasmic compartment, a model is developed to describe the time courses of the accumulation and release of tracer across the plasma membranes of root cells. Both time courses can be described by the sum of an exponential plus a linear term. In our material, the linear part of the accumulation time course is obscured by the NO₃^? fluxes exiting the cytoplasm, and the curve thus appears to be quasilinear over several minutes. However, we show that the use of the net tracer accumulation rate during this time period as an estimate of NO₃^? influx does not provide accurate estimates of influx and efflux. By contrast, ¹⁵NO₃^? efflux analysis permits calculation of the unidirectional fluxes across plasma membranes of root cells and the kinetic parameters of the cytoplasmic NO₃^? pool. Under our experimental conditions, efflux accounted for 30 to 50% of influx, and the cytoplasmic NO₃^? content was found to be in the 70–400nmol g^?1 fw range. Using this methodology, the effect of amino acid accumulation on unidirectional fluxes of nitrate was then examined. Pretreatments of the seedlings with an amino acid which has been shown to inhibit net NO₃^? uptake led to concomitant decreases in net accumulation rates of ¹⁵NO₃^? and of reduced ¹⁵N in roots and total ¹⁵N in cotyledons. NO₃^? influx was markedly inhibited by these treatments, while NO₃^? efflux remained essentially unaffected, or even decreased. It is concluded that the target of the regulation of NO₃^? uptake by phloemtranslocated amino acids is the influx system.