Tritiated water measurements of water flux in nestling and adult zebra finches (Poephila guttata)

• 1.1. Total body water volume (TBWV) and daily water turnover rates (WTR) were measured in nestling and adult zebra finches using tritiated water (TOH).
• 2.2. TBWV and daily WTR increased with age up to 13 days post hatching.
• 3.3. TBWV and WTR approached adult levels after 13 days of age. WTR varied among ages and nest mates. All nestlings turned over at least 50% of their body water pool per day.
• 4.4. The WTR data for adult birds are consistent with natural history data suggesting zebra finches are dependent on water for breeding and survival.

     

The source of the nutrients required for egg production in zebra finches Poephila guttata

The source of nutrients used for egg formation are poorly known for most bird species. This study of the zebra finch Poephila guttata showed that food intake did not increase during egg production, but the decline in female body reserves of protein and fat were sufficient to account for most of the nutrients in a clutch of four eggs. Female birds significantly reduced their activity levels during ova enlargement, which may play a role in diverting resources to egg production. Birds increased their intake of calcium-rich food items when eggs were being laid, and this intake accounted for all the calcium needed for eggshell formation. The zebra finch depends heavily on stored body reserves for egg formation, which is probably unusual in small passerines.     

Experimental (tamoxifen-induced) manipulation of female reproduction in zebra finches (Taeniopygia guttata)

Experimental manipulation of reproductive phenotype is a potentially powerful approach for understanding the fitness relationships of traits such as egg size, egg composition, and egg number. In this study, I investigated the effect of the antiestrogen tamoxifen on multiple, estrogen-dependent reproductive traits in female zebra finches (Taeniopygia guttata). Short-term tamoxifen treatment of egg-laying females (two daily injections before laying) had no effect on the timing or the pattern of egg laying compared to sham controls. However, tamoxifen treatment caused (1) a marked, but transient, decrease in egg size; (2) increased within-clutch egg-size variation; (3) a reduction in plasma vitellogenin (VTG) levels; and (4) lower dry yolk and yolk protein content of tamoxifen-treated females. Plasma levels of the second yolk precursor, very low density lipoprotein (VLDL), were not affected by tamoxifen, and tamoxifen appeared to have no effect on oviduct function in egg-laying females. These results are consistent with tamoxifen blocking estrogen receptors in the liver, suppressing VTG production, and decreasing the plasma pool of yolk precursors below a level required to maintain yolk formation at the normal rate. Tamoxifen treatment can therefore be used successfully to manipulate several components of the female reproductive phenotype (egg composition, intraclutch egg-size variation) to further explore the fitness consequences of these traits.     

Intrauterine Neospora caninum inoculation of heifers and cows using contaminated semen with different numbers of tachyzoites

OBJECTIVE: To investigate the potential of different Neospora caninum tachyzoite doses to infect heifers (experiment 1) and cows (experiment 2) when administered in utero by artificial insemination via contaminated semen. METHODS: In experiment 1, five groups of 5, 7, 8, 9, and 5 cyclic heifers were hormonally synchronized and artificially inseminated with semen containing 0 (A, controls), 10(2) (B), 5 x 10(3) (C), 5 x 10(4) (D), and 5 x 10(5) (E) live N. caninum NC-1 isolate-tachyzoites, respectively. Experimental infection was followed for 100 days. Parasitaemia and specific serum IgG, and interferon-gamma (IFN-gamma) responses were studied. In experiment 2, four groups of 9, 10, 9, and 9 adult multiparous cows with confirmed infertility problems of diverse aethiology were hormonally synchronized and artificially inseminated with semen containing 0 (a, controls), 10(2) (b), 5 x 10(3) (c), and 5 x 10(5) (d) live N. caninum NC-1 isolate-tachyzoites, respectively. Experimental infection was followed for 63 days. Parasitaemia and specific serum IgG responses were studied. RESULTS: In experiment 1, parasitaemia was detected in 1, 2, and 3 heifers from groups B, C, and D, respectively, between 9 and 23 days after insemination. Persistent specific serum antibody responses were detected in 2 and 3 heifers from groups D and E, respectively. Transient specific serum antibody responses were detected in 2, 1 and 1 heifers from groups C, D, and E, respectively. In addition, 1 heifer from group B showed a serum-specific antibody level higher than cut off value at 21 days post-insemination. Heifers seroconverted between 23 and 47 days after insemination. Specific IFN-gamma levels were detected in 1, 4, 6, and 3 heifers from groups B, C, D, and E, respectively, between 9 and 55 days after insemination. Pregnancy rate in the control group (60%) was higher than those observed in inoculated heifers (0-42.9%). Pregnancy rates in inoculated heifers were lower when the tachyzoite dose was increased (B 42.9%, C 12.5%, D 11.1%, and E 0%). In experiment 2, no Neospora DNA in blood nor specific serum IgG to N. caninum were detected in any of the cows studied, except in one cow inoculated with 5 x 10(5) tachyzoites (group d) which showed a relative index x100 (RIPC) values of 9.4, 18.9, and 18.1 at 42, 56, and 63 days after insemination, respectively. CONCLUSIONS: This study provides evidence that the intrauterine infection via contaminated semen using 5 x 10(4) and 5 x 10(5) tachyzoites caused persistent serum-specific antibody responses in some heifers. On the basis of serological data, a dose-response effect was also observed. In addition, N. caninum would be a probable cause of early foetal death in inoculated heifers. In contrast, results obtained in a similar experiment with cows showing confirmed infertility indicate that higher doses, such as of 5 x 10(5) tachyzoites, were necessary to induce seroconversion in at least one animal.     

Sperm-storage glands in a passerine: the zebra finch Poephila guttata (Estrildidae)

Sperm-storage glands in the zebra finch are described; the first passerine for which such information is available. Sperm-storage glands occurred only in paired females, and were located in folds throughout the vagina and on the vaginal side of the utcro-vaginal region. Mean dimensions of the glands were: internal diameter 17·5 μm and length 254 μm; these values are similar to those found for two other (much larger) bird species. The need for passerines to possess sperm-storage glands is discussed.     

Infections in mice with tachyzoites and bradyzoites of Neospora caninum (Protozoa: Apicomplexa)

Tachyzoites of 2 isolates of Neospora caninum (NC-1 and NC-2) were inoculated subcutaneously (s.c.), intraperitoneally (i.p.), or orally into mice to compare the effects of route of inoculation on pathogenicity. Mice developed more severe disease, and disease occurred sooner when inoculated with the NC-1 isolate compared to the NC-2 isolate. Deaths occurred earlier in mice inoculated i.p. with either isolate. Mice inoculated orally or s.c. with tachyzoites responded similarly to infection. Tissue cysts of the NC-2 isolate produced infections in mice following oral or s.c. inoculation. Lesions seen in mice inoculated with tachyzoites or bradyzoites were primarily acute pneumonia, myositis, encephalitis, ganglioradiculoneuritis, and pancreatitis. In vitro studies demonstrated that tachyzoites of both isolates were killed by incubation in pepsin-HCl solution but not 1% trypsin solution. Bradyzoites of the NC-2 isolate were able to withstand treatment with pepsin-HCl solution.     

Neural correlates of singing behavior in male zebra finches (Taeniopygia guttata)

This study examined the relationship between the volumes of four song control nuclei: the high vocal center (HVC), the lateral part of the magnocellular nucleus of the anterior neostriatum (lMAN), Area X, and the robust nucleus of the archistriatum (RA), as well as syrinx mass, with several measures of song output and song complexity in male zebra finches (Taeniopygia guttata). Male zebra finches' songs were recorded in standardized recording sessions. The syrinx and brain were subsequently collected from each bird. Volumes of the song control nuclei were reconstructed by measuring the cross-sectional area of serial sections. Syrinx mass was positively correlated with RA volume. The volume of lMAN was negatively related to element repertoire size and the number of elements per phrase. We found no other correlations between brain and behavioral measures. This study, combined with others, indicates that the evidence for a general relationship among songbirds between HVC volume and song complexity is equivocal. There are clear species differences in this brain-behavior correlation. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 421–430, 1998     

Genetic variation and differentiation in captive and wild zebra finches (Taeniopygia guttata)

The zebra finch (Taeniopygia guttata) is a small Australian grassland songbird that has been domesticated over the past two centuries. Because it is easy to breed in captivity, it has become a widely used study organism, especially in behavioural research. Most work has been conducted on domesticated populations maintained at numerous laboratories in Europe and North America. However, little is known about the extent to which, during the process of domestication, captive populations have gone through bottlenecks in population size, leading to inbred and potentially genetically differentiated study populations. This is an important issue, because (i) behavioural studies on captive populations might suffer from artefacts arising from high levels of inbreeding or lack of genetic variation in such populations, and (ii) it may hamper the comparability of research findings. To address this issue, we genotyped 1000 zebra finches from 18 captive and two wild populations at 10 highly variable microsatellite loci. We found that all captive populations have lost some of the genetic variability present in the wild, but there is no evidence that they have gone through a severe bottleneck, as the average captive population still showed a mean of 11.7 alleles per locus, compared to a mean of 19.3 alleles/locus for wild zebra finches. We found significant differentiation between the captive populations (F(ST) = 0.062). Patterns of genetic similarity closely match geographical relationships, so the most pronounced differences occur between the three continents: Australia, North America, and Europe. By providing a tree of the genetic similarity of the different captive populations, we hope to contribute to a better understanding of variation in research findings obtained by different laboratories.     

Sex-dependent effects of nutrition on telomere dynamics in zebra finches (Taeniopygia guttata)

At a cellular level, oxidative stress is known to increase telomere attrition, and hence cellular senescence and risk of disease. It has been proposed that dietary micronutrients play an important role in telomere protection due to their antioxidant properties. We experimentally manipulated dietary micronutrients during early life in zebra finches (Taeniopygia guttata). We found no effects of micronutrient intake on telomere loss during chick growth. However, females given a diet high in micronutrients during sexual maturation showed reduced telomere loss; there was no such effect in males. These results suggest that micronutrients may influence rates of cellular senescence, but differences in micronutrient requirement and allocation strategies, probably linked to the development of sexual coloration, may underlie sex differences in response.     

Foraging zebra finches (Taeniopygia guttata) are public information users rather than conformists

Social learning enables adaptive information acquisition provided that it is not random but selective. To understand species typical decision-making and to trace the evolutionary origins of social learning, the heuristics social learners use need to be identified. Here, we experimentally tested the nature of majority influence in the zebra finch. Subjects simultaneously observed two demonstrator groups differing in relative and absolute numbers (ratios 1 : 2/2 : 4/3 : 3/1 : 5) foraging from two novel food sources (black and white feeders). We find that demonstrator groups influenced observers'' feeder choices (social learning), but that zebra finches did not copy the majority of individuals. Instead, observers were influenced by the foraging activity (pecks) of the demonstrators and in an anti-conformist fashion. These results indicate that zebra finches are not conformist, but are public information users.     

Ultrastructure of tachyzoites, bradyzoites and tissue cysts of Neospora caninum

Dividing tachyzoites of Neospora caninum were 4 x 3 microns and had ultrastructural characteristics typical for the cyst-forming coccidia. Unusual ultrastructural characteristics of fully-formed tachyzoites included no micropores, 8-12 anterior and 4-6 posterior rhoptries, and a few posterior micronemes. Most tachyzoites were located free in the host cell cytoplasm; only a few occurred within a parasitophorous vacuole. Parasite multiplication appeared to be rapid because most organisms were in various stages of endodyogeny. Neural tissue cysts of N. caninum were 24.3 x 19.2 microns and contained 50-200 bradyzoites (7.3 x 1.5 microns), which lacked micropores. The cyst wall was 0.74-1.12 microns thick and consisted of the primary cyst wall (the parasitophorous vacuole membrane) and a thick granular layer with electron-dense vesicles.     

Susceptibility of Psammomys obesus and Meriones tristrami to tachyzoites of Neospora caninum

The susceptibility of Psammomys obesus (sand rat) and Meriones tristrami (Tristram's jird) to Neospora caninum was investigated by subcutaneous (s.c.) and intraperitoneal (i.p.) inoculation of 10-fold doses of culture-derived tachyzoites. Groups of 5 animals were inoculated with doses of 10-10(7) parasites via each route of inoculation. All but 2 of the sand rats inoculated with doses of 10-10(4) parasites succumbed to the infection by 7-18 days postinfection. All jirds inoculated with 10(7) tachyzoites succumbed by 5-16 days postinfection and those inoculated with 10(6) tachyzoites by 9-25 days. A considerable proportion of the jirds inoculated with 10-10(5) tachyzoites survived. Fibrinous peritonitis with ascites containing numerous tachyzoites was observed in the i.p.-inoculated sand rats and jirds that succumbed to the infection. In the jirds, tachyzoites were also found in pleural exudate. A considerable number (42.8%) of the jirds inoculated s.c. or i.p. exhibited neuromuscular symptoms, expressed in ataxia, head tilt, circling movement, and posterior paralysis. Seven successive passage of tachyzoites were achieved in sand rats with doses of 10(5) parasites and in jirds with doses of 10(7) parasites. All surviving jirds became seroconverted and were immune to lethal challenge.     

Detection of surface-associated and intracellular glycoconjugates and glycoproteins in Neospora caninum tachyzoites

The surface-associated molecules of the invasive stages of apicomplexan parasites such as Neospora caninum and Toxoplasma gondii are most likely crucially involved in mediating the interaction between the parasite and its host cell. In N. caninum, several antigens have recently been identified which could participate in host cell adhesion and/or invasion. These are antigens which are either constitutively expressed on the outer plasma membrane, or antigens which are only transiently localised on the surface as they are expulsed from the secretory vesicles either prior, or after host cell invasion. Some of these proteins have been characterised at the molecular level, and it has been shown that they are, with respect to protein sequences, closely related to homologous counterparts in T. gondii. Nevertheless, there is only a low degree of cross-antigenicity between the two species. In microbial interactions it has been shown that carbohydrates could also play a crucial role in host cell recognition and immunological host parasite interactions. In this study we present data which strongly suggest that the surface of N. caninum tachyzoites is glycosylated. In SDS-PAGE, glycoproteins comigrated largely with glycosylphosphatidylinositol-anchored proteins which were identified using in vivo [3H]ethanolamine labelling followed by autoradiography. The lectin Con A reacted strongly with the surface of these parasites, binding of which is indicative for the presence of N-glycans. Additional surface binding was observed, although only in a subpopulation of all tachyzoites, for wheat germ agglutinin and Jacalin. Intracellular binding sites for Con A were mainly associated with the parasite dense granules. By lectin labelling of Western blots of N. caninum protein extracts, glycoproteins were identified which reacted specifically with the lectins Con A, wheat germ agglutinin, Jacalin and soy bean agglutinin.     

Colour bands,dominance, and body mass regulation in male zebra finches (Taeniopygia guttata)

The arbitrary assignment of different coloured leg bands to zebra finches (Taeniopygia guttata) has profound effects on mate preference, reproductive success, mortality rates, parental investment and sex ratio. Choice chamber experiments indicate that the effect is mediated by altered attractiveness to members of the opposite sex. Effects on intrasexual dominance are more equivocal. We present two experiments which demonstrate significant effects of band colour on behavioural dominance (red bands are more dominant than light green bands) and the resulting diurnal pattern of gain in mass, fat, and seeds stored in the crop. Consistent with the literature on dominance and strategic regulation of body mass in other species, subordinate (green-banded) birds maintain higher fat reserves at dawn, but dominant (red-banded) birds show the highest overall daily mass gains. The lack of obvious effects of band colour on dominance in previous studies may lie in the degree to which food can be monopolized by particular individuals.     

Dogs shed Neospora caninum oocysts after ingestion of naturally infected bovine placenta but not after ingestion of colostrum spiked with Neospora caninum tachyzoites

An experiment was carried out to determine whether bovine colostrum or placenta could be a source of infection of Neospora caninum for dogs. For this purpose, two dogs were fed bovine colostrum to which culture-derived N. caninum tachyzoites were added and two other dogs were fed placental cotyledonary tissue from N. caninum seropositive cows. One dog served as a negative control during the start of the experiment but this control dog was fed cotyledonary tissue later on. None of the dogs did produce serum antibodies to N. caninum. All three dogs that were fed cotyledonary tissue did shed N. caninum oocysts, but no oocyst shedding was seen in the two dogs that were fed colostrum with N. caninum tachyzoites. Oocyst excretion did not resume in two dogs after repeated feeding of N. caninum infected placenta. The identity of the oocysts was confirmed by a bioassay in gerbils. It is concluded that ingestion of bovine placenta by dogs is an effective mode of transmission of N. caninum from cattle to dogs.     

The interplay of within-species perceptual predispositions and experience during song ontogeny in zebra finches (Taeniopygia guttata)

Vocal acquisition in songbirds and humans shows many similarities, one of which is that both involve a combination of experience and perceptual predispositions. Among languages some speech sounds are shared, while others are not. This could reflect a predisposition in young infants for learning some speech sounds over others, which combines with exposure-based learning. Similarly, in songbirds, some sounds are common across populations, while others are more specific to populations or individuals. We examine whether this is also due to perceptual preferences for certain within-species element types in naive juvenile male birds, and how such preferences interact with exposure to guide subsequent song learning. We show that young zebra finches lacking previous song exposure perceptually prefer songs with more common zebra finch song element types over songs with less common elements. Next, we demonstrate that after subsequent tutoring, birds prefer tutor songs regardless of whether these contain more common or less common elements. In adulthood, birds tutored with more common elements showed a higher song similarity to their tutor song, indicating that the early bias influenced song learning. Our findings help to understand the maintenance of similarities and the presence of differences among birds'' songs, their dialects and human languages.