Brood parasitism is associated with increased bacterial contamination of host eggs: bacterial loads of host and parasitic eggs

Factors related to bacterial environment of nests are of primary interest for understanding the causes of embryo infection and the evolution of antimicrobial defensive traits in birds. Nest visitors such as parasites could act as vectors for bacteria and/or affect the hygienic conditions of nests and hence influence the nest bacterial environment. In the present study, we explored some predictions of this hypothetical scenario in the great spotted cuckoo (Clamator glandarius)–magpie (Pica pica) system of brood parasitism. Great spotted cuckoos visit the nests of their magpie hosts and frequently damage some of the host eggs when laying eggs or on subsequent visits. Therefore, it represents a good system for testing the effect of nest visitors on the bacterial environment of nests. In accordance with this hypothesis, we found that the bacterial load of magpie eggshells was greater in parasitized nests, which may suggest that brood parasitism increases the probability of bacterial infection of magpie eggs. Moreover, comparisons of bacterial loads of cuckoo and magpie eggs revealed that: (1) cuckoo eggshells harboured lower bacterial densities than those of their magpie hosts in the same nests and (2) the prevalence of bacteria inside unhatched eggs was higher for magpies than for great spotted cuckoos. These interspecific differences were predicted because brood parasitic eggs (but not host eggs) always experience the bacterial environments of parasitized nests. Therefore, the results obtained in the present study suggest that parasitic eggs are better adapted to environments with a high risk of bacterial contamination than those of their magpie hosts. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 836–848.     

Ecological Genetics of Tetrahymena thermophila: Mating Types, i-Antigens, Multiple Alleles and Epistasis

Until recently, Tetrahymena thermophila has rarely been isolated from nature. With improved sampling procedures, T. thermophila has been found in ponds in many northeastern states. The availability of resident populations makes possible both population and ecological genetic studies. All seven known mating types have been recovered; no eighth mating type has been found. Crosses among whole-genome homozygotes derived from Pennsylvania isolates reveal a spectrum genotypes with mating type alleles resembling traditional A (IV- and VII-) and B(I-) categories. The genotypes differ significantly with respect to mating type frequency, both among themselves and from previously described genotypes. One A-category genotype appears to lack mating type II, while one A-category and all B-category genotypes have low frequencies of mating type III, thus accounting for the low frequency of III in the pond. The low frequency of III in all five B-category genotypes examined suggests that the founding allele in this region was low for III. These and other differences are discussed both in terms of mating type frequencies in the pond and in terms of the possible molecular structure of mat alleles. By contrast, numerous variants of the cell surface immobilization antigen are found in addition to the previously described i-antigens. Variants of the known SerH alleles include those with restriction fragment length polymorphisms and temperature sensitivity as well as alleles with new antigenic specificity. Multiple alleles are present in single ponds. Genes exhibiting serially dominant epistasis over SerH genes also are found. In two instances (K and C), families of antigenically similar polypeptides are expressed in place of H i-antigen. Molecular weight differences suggest that these paralogous i-antigen genes evolve by gene duplication and unequal crossing over within central repeats. The existence of complex patterns of epistasis together with seasonal changes in i-ag frequencies suggest that i-ag play an important, but as yet unknown, ecological role related to the occurrence of frequent conjugation.     

Cell Surface Saccharides in Three Phytomonas Species Differing in Host Specificity

ABSTRACT. Cell surface carbohydrates of three phytoflagellates, Phytomonas francai. Phytomonas serpens and Phytomonas sp. from different hosts including cassava, coreid insect Phthia picta and the milkweed plant Euphorbia hyssopifolia, respectively, were analysed by agglutination assays employing a battery of highly purified lectins with affinity for receptor molecules containing N-acetylglucosamine (d-GlcNAc), N-acetylgalactosamine (D-GalNAc), galactose, mannose-like (D-Man-like) residues and fucose, and by binding assay using radiolabeled [¹²⁵I]-wheat germ agglutinin (WGA) and fluorescent WGA lectin, as well as glycosidases of known sugar specificity, Escherichia coli K with mannose-affinity fimbrial lectin was also used as an agglutination probe. In general, the presence of D-GlcNAc. D-GalNAc and D-Man-like residues was detected in the phytomonads' plasma membrane. These sugar moieties were confirmed in whole cell hydrolysates as assessed by gas-liquid chromatography (GLC) which in addition, also showed the presence of galactose and xylose. However, marked differences in cell surface carbohydrate structures were observed. Wheat germ agglutinin, which binds to sialic acid and/or d-GlcNAc-containing residues, shows selective agglutinin activities for P. francai and Phytomonas sp., while Bandeiraea simplicifolia II agglutinin (which recognizes d-GlcNAc units) specifically bound to Phytomonas sp. Helix pomatia agglutinin which binds to D-GalNAc-containing residues reacted preferentially with Phytomonas sp. and P. serpens. Con A, which recognizes D-Man-like receptors, agglutinates all the phytomonads; however, the higher interaction was observed with Phytomonas sp. P. francai was selectively agglutinated in the presence of E. coli fimbrial lectin. Fluorescence WGA binding was significantly decreased by N-acetylglucosaminidase activities and the cell agglutination was not altered by neuraminidase treatment, suggesting the presence of an exposed D-GlcNAc moiety on the P. francai and Phytomonas sp. surfaces. Binding studies with [¹²⁵I]-WGA essentially confirmed the fluorescence WGA binding and agglutination assays.     

CHANGES IN SEROTONIN LEVEL AND TURNOVER IN DISCRETE HYPOTHALAMIC NUCLEI AFTER PINEALECTOMY AND MELATONIN ADMINISTRATION TO RATS

The influence of the pineal gland on the hypothalamic serotonergic function was examined by studying the effects of long-term pinealectomy (1 month) and melatonin replacement (500 μg/kg; 10 days) on serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) content as well as on the in vivo 5-HT synthesis rate in discrete hypothalamic nuclei. Pinealectomy was followed by a significant decrease of 5-HT content in the anterior hypothalamic nuclei (AHN) and the ventromedial hypothalamic nuclei (VMHN), and also in 5-HIAA content in lateral (LPON) and medial preoptic nuclei (MPON). The 5-HT synthesis rate, estimated from the accumulation of 5-hydroxytryptophan after blockade of the 1-amino acid decarboxylase activity, were also decreased in the AHN and the paraventricular hypothalamic nuclei (PVHN) of pinealectomized rats. In contrast, an enhanced 5-HT synthesis rate and basal 5-HIAA content were found in the suprachiasmatic nuclei (SCN) after pinealectomy. Daily treatment with melatonin for 10 days reversed most of the effects induced by pinealectomy. Thus, melatonin increased the levels of 5-HT in the AHN and VMHN, and slightly increased the 5-HIAA content in preoptic nuclei. In addition, melatonin increased the 5-HT synthesis rate in the AHN and VMHN, but also in the MPON, VMHN and dorsomedial hypothalamic nuclei (DMHN) where pinealectomy had no effect. By contrast, melatonin treatment did not affect SCN 5-HT synthesis rate, although it decreased 5-HIAA levels. The results demonstrate that melatonin is able to stimulate 5-HT metabolism in most of the hypothalamic areas, but inhibits SCN 5-HT function. Some of the effects of melatonin seems to be exerted by modulating the synthesis of the amine, although melatonin likely also interacts with other regulatory processes of 5-HT function (i.e. release/uptake). The well defined presence of melatonin receptors in the rat SCN, and its absence in other hypothalamic structures, suggest that this may be the mechanism mediating the differential response to endogenous melatonin. Moreover, the larger effect of exogenous melatonin in relation to pinealectomy suggests the presence of melatonin unespecific effects possibly owing to supraphysiological doses. The present findings may be relevant for the mode of action of melatonin and its implication in several endocrine and behavioral functions mediated by serotonergic neurons. Copyright © 1996 Elsevier Science Ltd     

Coral successions in Upper Tortonian reefs in SE Spain

Martin, Jose M., Braga, Juan C. & Rivas, Pascual 1989 07 15: Coral successions in Upper Tortonian reefs in SE Spain. Lethaia , Vol. 22, pp. 271–286. oslo. ISSN 0024–1164,
During the Upper Tortonian (Upper Miocene), the Almanzora river corridor, a small Neogene basin in SE Spain, harboured coral reefs growing in three different environments: in fan deltas, beyond the influence of coarse terrigenous sedimentation; in the abandoned lobes of a delta complex; and on coastal margins. All of these reefs are composed of several successive beds, each of which may be made up mainly of Porites embedded in silt or of an initial Porites level followed by a silt-free Tarbellastraea level on top. Porites may be associated with corallines. This structure is interpreted as being the result of an ecological succession repeated over and over again. A pioneer association consisting mainly of Porites . by colonizing the substrate and continuing to grow through relatively adverse silt-deposition conditions, prepares the ground for Tarbellastraea to take over. A return to the previous conditions halts the growth of the Tarbellastraea colonies and the Porites association once more establishes itself in the silt, or else the renewed rate of deposition is sufficiently heavy to suffocate the whole bioconstruction.* Ecological succession. coral reefs, Tortonian, southeast Spain .     

Nitrogen fixation, stomatal response and transpiration in Medicago sativa, Trifolium repens and T. subterraneum under water stress and recovery

Stomatal behaviour, transpiration and nitrogen fixation were investigated in Medicago sativa L. (cvs. Tierra de Campos and Aragon, Hidalgo-Maynar 1966), Trifolium repens L. (cv. Aberystwyth S-184) and Trifolium subterraneum L. (cv. Clare) subjected to drought by withholding water and then to three days’ recovery after rewatering. Dawn leaf water potential was measured with pressure chamber, stomatal response with a diffusion porometer and nitrogen fixation by using acetylene reduction technique. At low water potentials, the leaf resistance was higher in Medicago than in Trifolium. As water stress developed all species decreased their transpiration, T. subterraneum being the one most affected by moderate deficits. During water stress ‘Tierra de Campos’ always maintained higher acetylene reduction levels than ‘Aragon’ and the Trifolium species, except for the lowest water potentials. During recovery from water stress only ‘Tierra de Campos’ reached predeficit transpiration rates. In ‘Tierra de Campos’ acetylene reduction recovery after rewatering was more rapid and intense than in ‘Aragon’. It is concluded that, of the plants investigated, ‘Tierra de Campos’ was best adapted to water deficits.     

Specificity of Cellular Immune Reactivity to Virus-induced Tumours

SPECIFICITY is one of the chief hallmarks of immune reactions. In many cases, specificity has been defined by reactivity against some antigens and not against others, but the results of direct tests may be misleading. In many cases, in transplantation and tumour immunology, direct reactivity may be absent in spite of the presence of the antigen. With HL-A antigens, the CYNAP phenomenon (cytotoxicity negative, absorption positive) has been described¹. Virus-induced tumours may have relatively small amounts of tumour specific cell surface antigens which are detectable only by absorption tests^2,3. In addition, immune reactions may occur against a particular antigen on one material and against different antigens on another material. With antibody reactions, specificity can be confirmed by the appropriate absorption experiments^4,5. With cellular immune reactions, comparable demonstration of specificity has been very difficult.     

A new species of Vella L. (Brassicaceae) from the south-eastern part of the Iberian Peninsula

CRESPO, MB., 1992. A new species of Vella L. (Brassicaceae) from the south-eastern part of the Iberian Peninsula . Vella lucenlina is described from the coastal, low, dry areas of Alicante Province (south-eastern Spain). This plant is a spineless shrub, woody at the base, with narrowly linear, entire leaves, and an acute tongue-shaped stylar part of the fruit. Affinities and differences with the other taxa in the genus are discussed, and ecological data and conservation proposals are reported.