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.     

Nolleria pulicis N. Gen., N. Sp. (Microsporida: Chytridiopsidae), a Microsporidian Parasite of the Cat Flea, Ctenocephalides felis (Siphonaptera: Pulicidae)

A new species of microsporidium, Nolleria pulicis, is described and named here from the cat flea, Ctenocephalides felis. The genus Nolleria is created and placed within the family Chytridiopsidae. The family is slightly modified to accommodate certain features of intracellular development seen in N. pulicis, which is otherwise very similar to other species in the family Chytridiopsidae. Sporulation is described from ultrastructural analysis of infected midgut epithelial cells of adult C. felis. The term “multiple division by vacuolation” is proposed for describing sporogony as it occurs in this species and certain related species of microsporidia. The probable mode of transmission and apparent absence of merogony are discussed.     

Herbivory and patch dynamics on rocky reefs in temperate Australasia: The roles of fish and sea urchins

Sea urchins are widely considered to be the major grazers in temperate subtidal systems, with herbivorous fish being browsers of minor importance. This paper reviews spatial and temporal patterns in these herbivores on rocky reels in temperate Australasia, with the aim of assessing their relative impacts on patch structure and dynamics. Herbivorous fishes are widespread and make up a significant numerical component the reel fish fauna. Sea urchins are also abundant, but not all geographic locations support actively grazing species. Both fish and sea urchins exhibit distinct patterns of distribution among depth strata. Within depth strata, all herbivores are restricted to (sea urchins) or forage preferentially in (fish) particular habitat patches, causing a mosaic of different feeding activities. These patches are either related to specific features of the habitat (e.g. Kelp patches, topography) or behavioural interactions. Foraging by sea urchins and demersal-nesting damselfishes is intense and persistent, whereas in the kelp-feeding fish Odax cyanomelas, foraging reaches greatest intensity at predictable locations during a few months of every year. Many fish and sea urchins consume some algae in preference to others. However, feeding preferences may determine the nature of the impact only in fishes. For sea urchins, preference may occasionally determine the order in which algae are consumed, but at high densities they consume all available macroalgae. Impacts of both types of herbivore on the abundance of algae have been recorded. Some sea urchins (e.g. Evechinus chloroticus, Centrostephanus rodgersii) appear to severely modify biogenic habitat structure by maintaining ‘barrens’ (areas devoid of macroalgae) over long periods. In contrast to this, the effects of fishes may be more transitory (e.g. seasonal impact of Odax cyanomelas on brown algae) or occur at smaller spatial scales (e.g. nest sites maintained by male Parma victoriae) Herbivorous and other fishes appear to respond to spatial patterns in algal distributions, rallier than having it major impact upon them. The relative effects of fish and sea urchins on the long-term dynamics of kelp forests are unknown, hut temporal patterns in herbivore abundance and behaviour, and algal demography arc urgent targets for research.     

Ants remove virtually all western myall (Acacia papyrocarpa Benth.) seeds at Middleback,South Australia

Abstract Ants can have a profound effect on the numbers of seeds present in the seed-bank. We investigated the removal of seeds of an important arid zone tree species, the western myall (Acacia papyrocarpa Benth.). The species has seed characteristics typical of other Acacia species: a hard seed-coat and a small, white aril or elaiosome; the latter is reported to be attractive to ants. An experiment was conducted to see how rapidly and completely the seeds would be removed under various caging treatments. Observations were also made to discover the major seed removers and the fate of the seeds. Seed removal was rapid (< 12h) and was almost entirely by ants, and while our observations were not conclusive, we speculate that much of the seed supply is effectively destroyed by seed harvester ants which thus act as true granivores, not seed dispersers. Whether this matters for western myall in the long term is problematic because the species is so long-lived; rare but successful recruitment events may well be sufficient for its long-term survival.     

A METHOD FOR ISOLATION OF CAMPYLOBACTER SPP. (JEJUNI, COLI AND LARI) FROM SHELLFISH AND THE MARINE ENVIRONMENT

A method has been developed to detect thermophilic species of Campylobacter in shellfish, marine and tributary waters, sediment and farm runoff by-products such as manure and silage. The method consists of a 48 h enrichment incubation and subcultured to selective agars. Presumptive colonies confirmed with a latex agglutination (antibodies) to common flagellar antigens of C. jejuni, C. coli and C. lardi. Over an 8 year period, West Coast estuaries (Washington, Oregon, and California) were sampled, resulting in analysis of a total of 512 samples. Results suggest that Campylobacter spp. are well distributed in the marine environment. Two enrichment broths were compared for the recovery of campylobacters from environmental samples. The method described in the Food and Drug Administration Bacteriological Analytical Manual (FDA/BAM) (1984), was compared to a modified method. Use of the modified method described here resulted in higher recovery rates of Campylobacter spp. Recoveries of campylobacters from sediment, shellfish, and water were 10,13, and 28% higher for the modified method, respectively.     

Oviposition substrate affects adult mortality, independent of reproduction, in the seed beetle Callosobruchus maculatus

Abstract.

• 1 Seed beetles (Coleoptera: Bruchidae) are commonly used to study the influence of reproduction on life-span and senescence. To study the physiological trade-off between reproduction and mortality, many experiments rely on manipulating access to oviposition substrates to manipulate the reproductive rate of females.
• 2 The presence of host seeds, independent of reproduction, results in increased mortality of female Cullosobruchus muculutus. This influence on mortality varies between two host seed species, suggesting a role of either allelochemicals or energetic costs associated with behaviour on hosts.
• 3 The influence of host seeds on survivorship, independent of reproduction, confounds the interpretation of cost-of-reproduction studies with seed beetles. This complication must thus be considered in the design and interpretation of life-history studies of seed beetles and other insects.

     

Population Interactions and the Determinants of Population Size

Abstract The flux of individuals within populations is dependent upon six controlling processes: the intrinsic rate of increase of the plant, intraspecific competition for resources, interspecific competition, natural enemies, mutualisms and refuge effects such as the immigration of seeds from other populations. Although population interactions are generally believed to play a major role in determining the flux of individuals within populations, little attempt has been made to quantify the strength of these interactions and their role in the dynamics of populations. In this paper we examine the role of competition, herbivory and mutualistic interactions in determining the dynamics of a range of annual plant species. Firstly, it is shown that the dynamics of three weed species ( Bromus sterilis, Galium aparine, Papaver rhoeas ) in an experimental community in an arable cropping system of winter wheat are determined primarily by the rapid population growth of B. sterilis . Interactions between the species play a minor part in the dynamics of the system. Secondly, it is shown that current levels of grazing by overwintering populations of brent geese have a minor impact on the abundance of Salicornia europaea , but that increased grazing has the potential to reduce abundance and increase the instability of S. europaea populations. This is a consequence of the aggregative response of the geese, which results in an increasing proportion of the seeds of S. europaea being eaten as plant density increases. Thirdly, it is shown that there is a complex interaction between root pathogenic and arbuscular mycorrhizal fungi in natural field populations of Vulpia ciliata and that the benefit of mycorrhizal fungi to the plant is in providing protection against pathogens.