Monitored therapy of sporadic mycobacteriosis caused by Mycobacterium genavense in Atlantic canaries (Serinus canaria) and Bengalese finch (Lonchura striata)

Introduction Mycobacteriosis is a significant disease of companion and wild birds which causes emaciation and widely distributed lesions, as well as being a potential zoonosis. Its primary aetiological agents in birds are Mycobacterium avium subsp. avium and the fastidious Mycobacterium genavense. This study monitored the therapy of birds naturally infected with Mycobacterium genavense to gain understanding of its effectiveness and the interrelation of co-infections with the disease course and pharmacotherapy. Material and Methods Five Atlantic canaries (Serinus canaria) and one Bengalese finch (Lonchura striata) with tentative diagnoses of mycobacteriosis resulting from M. genavense infection were treated twice daily with clarithromycin at 40 mg/kg, ethambutol at 30 mg/kg, and moxifloxacin at 10 mg/kg for 6 months. Two canaries were also found to be carriers of Cryptosporidium galli. Mycobacteria in faecal samples of all birds were investigated by bacterioscopy and quantitative PCR. Results Molecular tests yielded positive results for up to four months after treatment initiation for M. genavense and Cryptosporidium, but microscopy failed to detect the latter after four weeks in specimens from one canary. Co-infections with polyomavirus (in all birds) and circovirus and bornavirus (in canaries) were diagnosed. Two birds died during treatment and one was euthanised because of other disease, 1 month after treatment completion. Three canaries were in relatively good health a year after treatment. Conclusion Canary circovirus and polyomavirus co-infection may suppress the immune system and this may facilitate the development of mycobacteriosis. The set of drugs used led to the complete cure of mycobacteriosis in three canaries. In one bird the disease returned. Clarithromycin was the active drug against C. galli. Molecular methods serve well to monitor mycobacteriosis therapy and identify M. genavense and C. galli carriage.

Domestication effects on aggressiveness: Comparison of biting motivation and bite force between wild and domesticated finches

ABSTRACTDomesticated animals evolve unique traits, known as domestication phenotypes or the domestication syndrome, due to their adaptation to a captive environment and changes in selection pressures. After being tamed, the Bengalese finch (Lonchura striata var. domestica) has undergone behavioural and physiological trait changes that differ from those of its wild ancestor, the white-rumped munia (Lonchura striata). The Bengalese finch has complex songs, lower fear response, and lower corticosterone levels than those in the white-rumped munia. We hypothesized that domesticated finches increase the effort to reproduce in lieu of maintaining fitness for survival as needed in the wild. Aggressiveness and bite performance affect survival rates and reproductive success, and are good indicators of adaptability in the natural environment. Therefore, we compared the aggressiveness and biting force of white-rumped munias with those of Bengalese finches to explore the evolutionary mechanisms of behavioural changes due to domestication. We found that the Bengalese finch had decreased aggressiveness (incidence of aggressive biting birds and the number of bite responses) and bite force than those in the white-rumped munia due to domestication. Therefore, we believe they could allocate more resources for breeding that would otherwise be needed for coping with predators through aggression.

Domestication effects on immune response: comparison of cell-mediated immune competence in wild and domesticated Bengalese finch

ABSTRACTDomesticated Bengalese finch (Lonchura striata var. domestica) lack natural selection pressures and consequently have more complex songs and altered behavioural and psychological traits when compared to their wild ancestor, the white-rumpud munia (Lonchura striata). Clarifying the sexual traits and life history trade-offs in Bengal finches will be help to improve our understanding of the evolution of complex songs and domesticated traits. Here, we have assessed the immune competence of the Bengalese finch and the white-rumped munia using phytohemagglutinin (PHA) tests to create an index of cell-mediated immune responses. We found that the Bengalese finch had a significantly larger immunocompetence than the white-rumped munia, indicating that they devote more resources to both immunity and reproduction. Thus, there is no trade-off but a positive relationship between immunocompetence and reproductive traits, which may be related to the release from natural selection pressures. These results will be useful in understanding the mechanisms by which domestication-induced changes due to a lack of natural selection pressure affect behavioural and physiological changes.

The Gut Microbial Composition Is Species-Specific and Individual-Specific in Two Species of Estrildid Finches, the Bengalese Finch and the Zebra Finch

Microbial communities residing in the gastrointestinal tracts of animals have profound impacts on the physiological processes of their hosts. In humans, host-specific and environmental factors likely interact together to shape gut microbial communities, resulting in remarkable inter-individual differences. However, we still lack a full understanding of to what extent microbes are individual-specific and controlled by host-specific factors across different animal taxa. Here, we document the gut microbial characteristics in two estrildid finch species, the Bengalese finch (Lonchura striata domestica) and the zebra finch (Taeniopygia guttata) to investigate between-species and within-species differences. We collected fecal samples from breeding pairs that were housed under strictly controlled environmental and dietary conditions. All individuals were sampled at five different time points over a range of 120 days covering different stages of the reproductive cycle. We found significant species-specific differences in gut microbial assemblages. Over a period of 3 months, individuals exhibited unique, individual-specific microbial profiles. Although we found a strong individual signature in both sexes, within-individual variation in microbial communities was larger in males of both species. Furthermore, breeding pairs had more similar microbial profiles, compared to randomly chosen males and females. Our study conclusively shows that host-specific factors contribute structuring of gut microbiota.

Manipulations of inhibition in cortical circuitry differentially affect spectral and temporal features of Bengalese finch song

The interplay between inhibition and excitation can regulate behavioral expression and control, including the expression of communicative behaviors like birdsong. Computational models postulate varying degrees to which inhibition within vocal motor circuitry influences birdsong, but few studies have tested these models by manipulating inhibition. Here we enhanced and attenuated inhibition in the cortical nucleus HVC (used as proper name) of Bengalese finches ( Lonchura striata var. domestica). Enhancement of inhibition (with muscimol) in HVC dose-dependently reduced the amount of song produced. Infusions of higher concentrations of muscimol caused some birds to produce spectrally degraded songs, whereas infusions of lower doses of muscimol led to the production of relatively normal (nondegraded) songs. However, the spectral and temporal structures of these nondegraded songs were significantly different from songs produced under control conditions. In particular, muscimol infusions decreased the frequency and amplitude of syllables, increased various measures of acoustic entropy, and increased the variability of syllable structure. Muscimol also increased sequence durations and the variability of syllable timing and syllable sequencing. Attenuation of inhibition (with bicuculline) in HVC led to changes to song distinct from and often opposite to enhancing inhibition. For example, in contrast to muscimol, bicuculline infusions increased syllable amplitude, frequency, and duration and decreased the variability of acoustic features. However, like muscimol, bicuculline increased the variability of syllable sequencing. These data highlight the importance of inhibition to the production of stereotyped vocalizations and demonstrate that changes to neural dynamics within cortical circuitry can differentially affect spectral and temporal features of song. NEW & NOTEWORTHY We reveal that manipulations of inhibition in the cortical nucleus HVC affect the structure, timing, and sequencing of syllables in Bengalese finch song. Enhancing and blocking inhibition led to opposite changes to the acoustic structure and timing of vocalizations, but both caused similar changes to vocal sequencing. These data provide support for computational models of song control but also motivate refinement of existing models to account for differential effects on syllable structure, timing, and sequencing.

Is neurogenesis in two songbird species related to their song sequence variability?

Neurogenesis takes part in the adult songbird brain and new neurons are integrated into the forebrain including defined areas involved in the control of song learning and production. It has been suggested that the new neurons in the song system might enable vocal variability. Here, we examined the basal levels of neurogenesis in two songbird species, zebra finch ( Taeniopygia guttata ) and Bengalese finch ( Lonchura striata var. domestica ), which do not learn new song elements as adults but differ in the level of song sequence variability. We found that Bengalese finches had less linear and stereotyped song sequence and a higher number of newborn cells in the neurogenic subventricular zone (SVZ) as well as the number of newly born neurons incorporated into the vocal nucleus HVC (used as a proper name) in comparison to zebra finches. Importantly, this vocal sequence variability in Bengalese finches correlated with the number of new neurons in the vocal nucleus HVC and more plastic song was associated with higher neuronal incorporation. In summary, our data support the hypothesis that newly generated neurons facilitate behavioural variability.