Acute effects of light and darkness on sleep in the pigeon (Columba livia)

In addition to entraining circadian rhythms, light has acute effects on sleep and wakefulness in mammals. To determine whether light and darkness have similar effects in birds, the only non-mammalian group that displays sleep patterns comparable to mammals, we examined the effects of lighting changes on sleep and wakefulness in the pigeon. We quantified sleep behavior (i.e., bilateral or unilateral eye closure) in pigeons maintained under a 12:12 LD cycle, and immediately following a change from a 12:12 to a 3:3 LD cycle. During both LD cycles, sleep was most prevalent during dark periods. During the 3:3 LD cycle, darkness had the greatest sleep promoting effect during the hours corresponding to the subjective night of the preceding 12:12 LD cycle, whereas light suppressed sleep across circadian phases. As previously suggested, the light-induced decrease in sleep in the subjective night might be partly mediated by the suppression of melatonin by light. Although the sleep promoting effect of darkness was modulated by the circadian rhythm, sleep in darkness occurred during all circadian phases, suggesting that darkness per se may play a direct role in inducing sleep. In addition to the effects of lighting on behavioral state, we observed an overall bias toward more right eye closure under all lighting conditions, possibly reflecting a response to the novel testing environment.     

Hair cell loss and regeneration after severe acoustic overstimulation in the adult pigeon

The extent of hair cell regeneration following acoustic overstimulation severe enough to destroy tall hair cells, was determined in adult pigeons. BrdU (5-bromo-2′-deoxyuridine) was used as a proliferation marker. Recovery of hearing thresholds in each individual animal was measured over a period of up to 16 weeks after trauma. In ears with loss of both short and tall hair cells, little or no functional recovery occurred. In ears with less damage, where significant functional recovery did occur, there were always a few rows of surviving hair cells left at the neural edge of the basilar papilla. In the region of hair cell loss, numerous BrdU labeled cells were found. However, only a small minority of these cells were regenerated hair cells, the majority being monolayer cells. Irrespective of the extent of the region of hair cell loss, regenerated hair cells were observed predominantly in a narrow strip at the transition from the abneural area of total hair cell loss and the neural area of hair cell survival. With increasing damage this strip moved progressively towards the neural edge of the papilla. No regeneration of hair cells was observed in the abneural region of total hair cell loss, even up to 16 weeks after trauma. The results indicate that there is a gradient in the destructive effect of loud sound across the width of the basilar papilla, from most detrimental at the abneural edge to least detrimental at the neural edge. Both tall and short hair cells can regenerate after sound trauma. Whether they do regenerate or not depends on the degree of damage to the area of the papilla where they normally reside. Regeneration of new hair cells occurs only in a narrow longitudinal band, which moves from abneural into the neural direction with increasing damage. In the area neural to this band, hair cells survive the overstimulation. In the area abneural to this band, sound damage is so severe, that no regeneration of hair cells occurs. As a consequence morphological and functional deficits persist.     

Keratinophilic fungi from the feathers of Emu (Dromaius novaehollandiae) in Maharastra India

A total of 70 feathers samples of Emu (Dromaius novaehollandiae) were collected from 7 Emu farms situated at two districts (Raigad and Thane) of Maharashtra (India) and screened for resident keratinophilic fungi. Among them, 44 isolates were recovered and identified by evaluating characteristic macro- and micro-morphological features. Further gene products corresponding to the ITS1-5.8S-ITS2 rDNA region from all isolates were amplified and sequenced. Homology search was performed using BLAST program against non-redundant nucleotide database, and significantly matched DNA sequences deposited to the NCBI Gene Bank for reference purposes. Eight identified fungal species belongs to 7 different genera named as Aphanoascus terreus Ac_MW577456 (21.43%), Microsporum gypseum Ac_MW580920 (14.29%), Ctenomyces serratus Ac_MW577459 (10.0%), Uncinocarpus orissi Ac_MW577461 (5.17%), Aphanoascus verrucosus Ac_MW577458 (4.29%), Gymnascella dankaliensis Ac_MW577460 (2.86%), Gymnoascoideus petalosporus Ac_MW577462 (2.86%) and Arthroderma tuberculatum Ac_MW577457 (1.43%).     

Occurrence of a mosquito vector in bird houses: Developmental consequences and potential epidemiological implications

Even with continuous vector control, dengue is still a growing threat to public health in Southeast Asia. Main causes comprise difficulties in identifying productive breeding sites and inappropriate targeted chemical interventions. In this region, rural families keep live birds in backyards and dengue mosquitoes have been reported in containers in the cages. To focus on this particular breeding site, we examined the capacity of bird fecal matter (BFM) from the spotted dove, to support Aedes albopictus larval growth. The impact of BFM larval uptake on some adult fitness traits influencing vectorial capacity was also investigated. In serial bioassays involving a high and low larval density (HD and LD), BFM and larval standard food (LSF) affected differently larval development. At HD, development was longer in the BFM environment. There were no appreciable mortality differences between the two treatments, which resulted in similar pupation and adult emergence successes. BFM treatment produced a better gender balance. There were comparable levels of blood uptake and egg production in BFM and LSF females at LD; that was not the case for the HD one, which resulted in bigger adults. BFM and LSF females displayed equivalent lifespans; in males, this parameter was shorter in those derived from the BFM/LD treatment. Taken together these results suggest that bird defecations successfully support the development of Ae. albopictus. Due to their cryptic aspects, containers used to supply water to encaged birds may not have been targeted by chemical interventions.     

Expression of vesicular glutamate transporter 3 mRNA in the brain and retina of the pigeon

Vesicular glutamate transporters (vGluTs), which accumulate glutamate into synaptic vesicles, are classified into three subtypes in mammalian brains: vGluT1, vGluT2, and vGluT3. VGluT3 is localized in non-glutamatergic neurons of the brain and retinal amacrine cells. In birds, the vGluT3 genome is found, but its distribution in the brain or retina is unknown. The present study was conducted to analyze vGluT3 cDNA sequence and elucidate its distribution in the pigeon brain and retina. The vGluT3 cDNA comprises 1761 bp and showed 95% and 88% identity to the chicken and zebra finch vGluT3 cDNAs, respectively, and 74% identity to human vGluT3 cDNA. In situ hybridization revealed that the vGluT3 mRNA was expressed in neurons of the caudal linear nucleus (LC) of the brain and in amacrine cells of the inner nuclear layer of the retina. A combination of in situ hybridization and serotonin immunohistochemistry revealed three types of stained cells in LC and retina: vGluT3⁺/serotonin⁺, vGluT3⁺/serotonin⁻, and vGluT3⁻/serotonin⁺. The vGluT3⁺/serotonin⁺ cells were approximately 22% in LC and 16% in the retina. The present results suggest that the pigeon vGluT3 mRNA is comparable with the mammalian type.     

Endocrine correlates of the breeding asynchrony between two Corsican populations of blue tits (Parus caeruleus)

Analyses of the development of the reproductive system in seasonally breeding birds in the framework of long-term ecological studies are rare. Here, we present the first results of such a study in two Corsican populations of a European passerine bird, the blue tit (Parus caeruleus). The two study populations occupy different oak habitats and are separated by only 25 km. Despite their close proximity, they show a one-month difference in onset of egg laying, even after controlling for altitude. This micro-geographic difference in breeding date appears adaptive because both study populations raise chicks when food is most plentiful. In our study, males reached their maximum song activity during the egg-laying stage while maximal testosterone levels and testes sizes were reached 2-3 weeks before egg laying. The rate of development of the reproductive system in males was much faster in the earlier population, in spite of a similar onset of gonad development and song activity for the two study populations. No change in the volume of the song-control nuclei (HVC and RA) could be detected during the study period. Development of brain nuclei was completed 2-3 months before the beginning of intense sexual activity.     

Glutamatergic thalamopallial projections in the pigeon identified by retrograde labeling and expression of vGluT2 mRNA

A neocortical hypothesis as to homology of certain nuclear components of the avian brain proposes that the entopallium and field L2 are homologous to layer 4 of mammalian extrastriate and auditory neocortex, respectively. However, the hypothesis lacks support from the neurochemistry of thalamopallial projections. We investigated whether these projections are glutamatergic by injecting cholera toxin B into either the entopallium or field L2 in combination with in situ hybridization. Retrogradely labeled neurons in nucleus rotundus and nucleus ovoidalis were found to express vesicular glutamate transporter 2 mRNA, showing that the thalamopallial projections are glutamatergic. The results are consistent with the neocortical hypothesis.     

Bird orientation and the geomagnetic field: A review

The possibility that birds use the geomagnetic field to guide their orientation has been repeatedly suggested over the last century. Early attempts to experimentally verify this hypothesis were largely unsuccessful. Recently, however, this issue has been more thoroughly examined, from a variety of approaches, with positive results. Magnetic fields have been shown to have a biological effect on a variety of animals ranging from unicellular organisms to mammals. Many of these organisms, including birds, show changes in orientation behavior as a result of changes in the ambient magnetic field. Specific data supporting the existence of a “magnetic-compass” in birds include demonstrations that (a) changes in the intensity of the ambient magnetic field disrupt various kinds of orientation behavior and (b) that systematic changes in the direction of the ambient magnetic field are accompanied by systematic changes in the direction of orientation. The biggest obstacle in further study of the “magnetic-compass” is the almost complete ignorance of the biophysical mechanism(s) involved in the biological detection of the geomagnetic field. Some theoretical speculations about possible biomagnetic mechanisms are discussed and suggestions for the direction of future research on the “magnetic-compass” and its relation to other orientation behaviors are provided.