Athene Brama Research Articles

Effects of Photoperiod Alterations on Adrenocortical, Pineal and Gonadal Activity in Nocturnal bird, Athene brama and Diurnal bird, Perdicula asiatica

Abstract Present study showed the influence of photoperiod alterations on adrenal gland weight, adrenal lipids and plasma corticosterone profiles (adrenocortical function), and pineal and gonadal weights of two Indian tropical male and female birds belonging to nocturnal (Spotted owlet, Athene brama) and diurnal (Jungle bush quail, Perdicula asiatica) habitats. Exposure of both sexes of nocturnal birds to long photoperiod (LP, 16L:8D, light between 6:00 to 22:00hr) and continuous illumination (CL) during reproductive recrudescence and active phases, respectively, increased adrenal weight, adrenal lipids, such as phospholipids, free and esterified cholesterol, as well as plasma corticosterone levels. Concomitantly, the LP treatment elevated the gonado-somatic index while decreased the pineal gland weight, however, the CL treatment was ineffective to alter gondal and pineal activity. Exposure of both sexes of nocturnal birds to short photoperiod (SP, 8L:16D, light between 9:00 to 17:00hr) and continuous dar...

Pineal gland of a nocturnal bird, Indian spotted owlet, Athene brama: morphological and endocrine observations.

It has been reported that owls (Strigiformes) do not have a pineal gland. However, our light microscopy study revealed an intermediate form of tubulofollicular and solid-type large pineal gland in a tropical owlet, Athene brama. The epithelial cells forming follicles (6-8) in the distal region and the solid cluster of parenchymal cells of different diameters in the proximal region anteriorly tapered with a long cylindrical stalk and continued into commissural organs and choroid plexus. The intrapineal localization of perivascular nerve fibers and blood vessels clearly explained the sympathetic innervation as well as vascularization of this neuroendocrine gland. Further, electron microscopy revealed a developed intracellular structure of the pinealocytes with a large number of mitochondria, Golgi bodies, and granular as well as clear vesicles in the process terminals. The evidence of intrapinealocyte lipid droplets and dense bodies and a moderate amount of melatonin in plasma (ranging from 100-365 pg/mL) during different reproductive phases finally proved a defined secretory activity of the gland in this tropical, nocturnal bird.

Circadian Rhythms of Melatonin and Sex Steroids in a Nocturnal Bird, Indian Spotted Owlet Athene brama During Reproductively Active and Inactive Phases

The epiphyseal neurohormone melatonin (MEL) exhibits circadian cyclicity, as noted extensively in diurnal vertebrates although very little information is available regarding nocturnal species. We have studied the MEL rhythmicity with 24-hour periodicity in a tropical nocturnal bird, Indian spotted owlet Athene brama, which possesses a well-developed pineal organ. We performed our study during two crucial reproductive phases (active and inactive), when the pineal gland activity in owlet exists in inverse states, i.e., inactive and active respectively. Independent of sex, the circadian rhythm of plasma MEL in owlets showed a two-peak cyclicity with a smaller peak at around 1400 h and the higher one at about 0200 h, while the lowest value was found at 1000 h. The night (0200 h) peak activity of plasma MEL in owlet has a resemblance with the earlier findings in diurnal birds and strongly suggests that independent of species habit the peak activity of MEL is invariably dark dependent. However, the daytime peak of MEL may be due to the daytime hiding nature of this nocturnal bird. Interestingly, it was also noted that the hours of peak activity of MEL (1400 and 0200 h) were the same during both of the reproductive phases, though the environmental day length was longer and ambient temperature was higher during the reproductively inactive phase. During daytime these birds hide in a dark burrow where, in general, the intensities of light and temperature are less, and the amplitude of variations of these factors is not prominent. Hence, the seasonal variations in these oscillatory components may not have affected the entrainment of the owlet pineal oscillator, which regulates the daily MEL rhythm in a similar pattern during both the studied phases. On the other hand, a single circadian peak (around 1000 h) circadian cyclicity of gonadal steroids (i.e., testosterone in the male and estradiol and progesterone in the female) showed an inverse relationship with plasma MEL. Possibly, MEL regulates the daily steroidogenic status in owlets by an inhibitory influence.

OWL PERCHES FOR RODENT MANAGEMENT IN RICE ECOSYSTEM

Owl perches of various designs are used in different parts of Tamil Nadu for rodent management. Efficacy of one such owl perch was tested in the rice fields by counting the number of live rat burrows, 30 days after erection of perches and at weekly intervals thereafter in fields with and without owl perches. The owl perch was made of wooden rod (2-3m long) with a ball of straw in the top. These were pegged at random, mostly near the bunds at the rate of 45 per ha from the booting to harvesting stages of rice crop. Ther perches helped the owls, mostly the Barn Owl. Tyto alba (Scopoli) and the Spotted Owlet, Athene brama (Temuninck) to hunt rats effectively. In fields with owl perches, there was no increase in the number of live burrows and in fields without perches, there was rapid increase in the number of live burrows. Rice yield from fields with owl perches was two times more than that from fields without perches. When owl perches were removed after a time, dramatic increase in the number of rat burrows was observed. The perches were used by the King Crow, Dicrurus adsimilis (Bechstein) during day time for perching and they hunted the flying insects.

Ecological adaptation of angiotensin-induced thirst mechanism in tetrapods

Dipsogenic action of angiotensin II (AII) was tested by intraperitoneal injection in 2 species of amphibians, 9 species of reptiles, 18 species of birds, and 8 species of mammals. The amphibians did not respond to AII by drinking. Most of the tetrapods other than the amphibians responded to AII (5–30 μg/100 g) by drinking. Among reptiles, birds, and mammals, however, the following species were relatively insensitive to AII: (1) the hibernating reptiles, Calotes versicolor and Natrix piscator, (2) the animals originated in arid areas, such as Testudo graeca, Melopsittacus undulatus, Lonchura malabarica, Meriones unguiculatus and Mus musculus, and (3) the carnivorous birds, Accipiter badius, Athene brama and Falco tinnunculus. Thus, it is likely that animals, which drink little water in nature, are relatively insensitive to AII in drinking. These observations suggest that AII has become adaptively involved in the physiological mechanisms inducing thirst during the evolutionary process. Evolution of receptive sites for AII in the brain is discussed in vertebrates.

Stereometric observations on the hypothalamic neurosecretory system of the spotted owlet, Athene brama Temminck, in total preparations.

The configuration of the HNS of the spotted owlet, Athene brama Temminck, was studied by employing the bulk-staining technique. This enabled a three-dimensional view of the HNS. The neurons of the SON are distributed into three divisions, namely, the preoptic, median and lateral. The PVN is U-shaped; the distal portion of the arms of the U extends laterally to form the lateral division of the PVN, which remains in continuity with the lateral division of the SON. The periventricular division of the PVN joins ventrally the median division of the SON. Unlike in the passerine birds, in the spotted owlet the PVN is more prominently developed than the SON. Since the axonal pathways are not stained, the proximal portion of the hypothalamo-hypophysial tract could not be demonstrated in bulk-stained preparations. Hence it was not possible to trace with certainty the origin of the axonal terminations in the ME and in the NL. Anterior of the ME, the tract branches into two; one branch enters the zona externa to the ME and the other is continued into the NL. The ME is divisible into an AF-positive anterior region and an AF-negative posterior region. The NL is saccular and heavily loaded with the NSM. Studies on the HNS of the spotted owlet by the bulk-staining technique reveal that the general configuration of the system is comparable to that of the HNS of birds studied previously.

Changes induced by formalin in the hypothalamic neurosecretory system of the spotted owlet, Athene brama temminck.

Histological changes induced in the HNS of the spotted owlet, Athene brama Temminck, by injection of 1 ml 5 or 10% formalin are described. No difference could be detected in the response of the HNS to 5 or 10% formalin administration. In the HNS of birds killed within 5 min of formalin administration, there was only partial depletion of NSM from the neurons, the tract and the NL; the quantity of NSM in the AME remained more or less unchanged. In animals killed 10-90 min after formalin injection, the depletion of NSM from the neurons, the tract and the NL was more complete. The neurons of the preoptic division of the SON exhibited the maximum response; these neurons were also moderately hypertrophied. The NL also was hypertrophied in some animals; the NSM in the AME registered only a partial loss. The interval between formalin administration and killing did not influence the degree of changes in the HNS. The depletion of NSM was no greater at 90 min following formalin injection than at 10 min. Since it is well established that formalin stress causes augmented secretion of ADH and that there is a close functional relationship existing between ADH and NSM, the depletion of NSM noticed in the HNS of the spotted owlet following formalin administration is interpreted as indicating augmented secretion of ADH. Hence it seems that the response of the HNS of birds to formalin stress are comparable to those of the HNS of mammals. The results thus provide histological evidence in favour of the concept that stressful stimuli cause increased secretion of ADH.

Effect of ethanol on the hypertonic saline-induced histological changes in the hypothalamic neurosecretory system of the spotted owlet, Athene brama Temminck.

It is well established that in mammals ethanol is a potent chemical inhibitor of the release of the antidiuretic hormone (ADH), including the antidiuresis that follows the administration of hypertonic saline (see Kleeman & Cutler, 1963; Heller & Ginsburg, 1966). Ethanol also inhibits histological changes in the mammalian hypothalamic neurosecretory system (HNS) that normally follow treatment with hypertonic saline (Raiha, 1960; Kulshreshtha & Dominic, 1972). However, very few studies are available on the effect of ethanol on the neurohypophysis of birds and other non-mammalian vertebrates. The present report deals with the effect of ethanol on the HNS of the spotted owlet after treatment with hypertonic saline. Birds weighing 120–140 g were divided into four groups with 25 individuals of either sex in each group, and were given the following treatments, Group 1: 3% NaCl solution (1 ml/animal/day) for 3–5 days; Group 2:3% NaCl solution (1 ml/animal/day), and 15% ethanol

Acid phosphatase activity in the cerebellar cortex of the small brown dove, Streptopelia senegalensis; spotted owlet, Athene brama, and house-sparrow, Passer domesticus.

Acid phosphatase activity in the cerebellar cortex of the small brown dove, Streptopelia senegalensis; spotted owlet, Athene brama, and house-sparrow, Passer domesticus.