Search

Photoperiodic responses of a photosensitive species depend on the species-specific critical day length (CD), determined by the entrainment of the endogenous circadian rhythm of photoinducibility. We examined the entrainment pathway of the circadian photoperiodic system of photosensitive weaver birds. Birds were subjected to T = 22,24 and 26 h photocycles, with 11- and 12-h photophase to study the photoperiodic induction and synchronization of bird's circadian system with reference of different light wavelengths. Two experiments were performed on adult male weaver birds. In experiment 1, birds were exposed to T = 22 and 26 h LD-cycles, having 11-h photophase with red and blue light wavelength, while in experiment 2, birds were exposed to T = 22, 24 and 26 h LD-cycles, having 12-h photophase with red and blue light wavelength. Observations on change in body mass and testis size were recorded at monthly intervals. There was a significant effect of red light wavelength on photoperiodic induction of testicular growth in the birds exposed to T = 22 h (11L:11D and 12L:10D) and T = 26 h (11L:15D and 12L:14D; both wavelength), but not when exposed to T = 24 h (12L:12D) photophase. Further, body mass regression was faster in birds of T = 26 h photophase (12L:14D) under blue wavelength. Thus, the above results are indicative of the influence of light wavelength on the endogenous programming that times seasonal responses in body fattening and testicular growth-regression of Indian weaver bird. [ABSTRACT FROM AUTHOR]

Population studies on avian lice are confined solely to the examination of body population of selected birds. The population characteristics of Colpocephalum turbinatum belonging to different parts deserve investigation. Present report furnishes information on the population level of amblyceran louse on the pigeons in district Meerut, during the year 2017. As many as 56.1% pigeons were found infested with this louse (mean intensity- 40.9 lice per bird; n=360). The frequency distribution pattern of Colpocephalum turbinatum was skewed / aggregated but it could not correspond to negative binomial model. Females, dominated the population of lice (M : F = 1 : 1.3) but adult, nymph ratio remained nearly similar (A : N = 1 : 1.1). The mean monthly prevalences and mean intensities of louse were found significantly correlated to the environment temperature and photoperiod, but not to be relative humidities. [ABSTRACT FROM AUTHOR]

Migratory birds need continued food supply and efficient metabolic machinery to meet high energy demands of the magnanimous feat of flight. Two questions are important i.e. as to 1) how a bird adapts to a temporary food constrain on a daily basis, and 2) how peripheral leptin, an anorectic hormone, impacted feeding and migratory behaviour in buntings? The aim of this study was to induce a non-photoperiodic tweak in the physiology of redheaded buntings through exogenous leptin administration and study its effect on their food intake and migratory behaviour. Groups of male redheaded buntings, Emberiza bruniceps (n=17) were transferred from short (8L: 16D) to long (16L: 8D) days and presented with food only either for first (morning food presence, MFP) or second (evening food presence, EFP) half of the 16h lighted phase, while control group received food ad libitum. Total daily food intake (FI) did not differ significantly between the MFP, EFP and controls, but hourly FI in MFP and EFP indicated increased activity differences based on time of food availability and bird's tendency to cache food/recompense for food scarcity during migration. In another experiment, a chemical tweak in bird's FI was induced by peripheral administration of leptin, to add to current understanding of transition in buntings' metabolic efficiency during high energy demanding migratory journey. Exogenous leptin appeared to safeguard cadaveric effect of exogenous injection in migrating buntings through promoting blood cholesterol and reduced liver fibrosis. Food restriction in the morning was better responded by buntings than that in evening. Therefore, migratory buntings exhibited diurnal variation in response to food scarcity. [ABSTRACT FROM AUTHOR]

Out of 360 pigeons examined in district Meerut, during the year 2017, only 22.8% were found infested with haematophagous amblyceran louse, Hohorstiella lata and the infestation rate was 10.3 lice, per bird. The frequency distribution pattern of H. lata on the pigeons was skewed but it could not conform to the negative binomial model. Females dominated the population, as the M : F ratio was 1:1.6, while adult, nymph ratio remained 1:1.2. Mean monthly prevalence were significantly correlated to temperature and photoperiod while mean monthly intensities of H. lata were not found correlated to the mean monthly values of three eco-factors i.e. temperature, photoperiod and relative humidities. [ABSTRACT FROM AUTHOR]

The brighter nights have posed new challenges to the wild species by affecting their temporal physiology. The present study on Indian weaver bird (Ploceus philippinus) investigated if exposure to bright light at different phases of night affects their clock-mediated daily functions. Birds were placed individually in specially designed activity cages under short days and long nights (8L:16D; L = 100 lux, D < 0.1 lux) for ~3 weeks (19 days). Thereafter, they were divided into four groups (n = 6-9), and given ~2 lux light either for the entire night (ZT 08-24; zeitgeber time 0 = time of light on; pattern A) or for 4 hr (pattern B), placed in 16 hr night such that its onset coincides with the onset of night (early night group, ZT 08-12), its end with the end of night (late night group, ZT 20-24), or the night was interrupted in the middle (midnight group, ZT 14-18). The results showed that bright light in entire night induced early onset of day activity and fragmented rest at night, however, if given at different phases of night, it made the days longer by delaying end (early night group) or advancing onset of daily activity (late night group). It also suppressed the melatonin levels and increased body temperature. These results suggest that bright light at night alters the perception of daylength and affects the underlying physiology. The findings may be useful in adopting a strategy for use of night light without disturbing species fitness in their environment. [ABSTRACT FROM AUTHOR]

An analysis of the crop contents of four pigeon lice indicated that two philopterid Ischnocera (Columbicola columbae and Companulotes bidentatus compar) are feather feeder species. Menoponid (Amblycera) louse, Colpocephalum turbinatum also appeared to be non-haematophagous in nature. However, the presence of red content compatible with host blood has been detected in crop contents of other menoponid louse, Hohorstiella lata. Adults of this louse appeared to be more haematophagous than nymphal instars. Presence of pieces of egg chorion were noted in crop contents of C. turbinatum. But, the presence of any triturating agent was not noted in any of the four pigeon lice. [ABSTRACT FROM AUTHOR]

An ischnoceran pigeon louse, Companulotes bidentatus compar was reared in vitro condition (35±oC, 75% RH, at feather diet) to determine the bionomics. The data obtained through in vitro experimentation was used to construct the life table of the louse and for the computation of the vital statistics. The intrinsic rate of natural increase of the louse appeared to be 0.042. At this, rate the doubling time of the population of louse was determined as 15.8 days. Thus, in contrast to other ischnocerans, C. bidentatus compar appears to be a moderate breeder. [ABSTRACT FROM AUTHOR]

Reproductive biology of an Indian Silurid catfish, Ompok pabda were determined in a moderately impacted tropical River Gomti in India. Samples offish were collected monthly between May 2008 to April 2009 in two zones; upstream site at Mishrikh, Sitapur and midstream site at Lucknow. Length at first maturity calculated through maturity curve was 12.9 cm (males) and 13.9 cm (females) in total length. The gonado-somatic index indicated that spawning generally occurred between June - September and sex ratio showed a predominance of females, representing 54.3% of the total sample. The fecundity was found to vary from 2460 to 5986 nos, with mean of 4330 +/- 799 for the fish with total length of 11.5-20.0 cm. The relationship of fecundity with total length and total body weight of the fish was Log F = 0.374 Log L+ 0.37, r2 = 0.999 and Log F = 0.337 Log W-0.40, r2 = 0.966. The well defined traits of O. pabda from the Ganges basin provide basic information which can be further used for species conservation planning.

A study was performed to investigate the effects of complete and skeleton photoperiods on gonadal stimulation in baya weaver, Ploceus philippinus. In August 2003, five groups of acclimatized birds (n = 7 each) were exposed to 6L: 13D: 1L: 4D, 6L: 6D: 1L: 11D, 11L: 13D and 13L: 11D. Birds were refractory and their exposure to 6L:13D:1L:4D, 6L:6D:1L:11D, 11L:13D and 13L:11D did not evoke any response. This clearly indicates that the birds were insensitive to the stimulatory effects of these photoperiods and perceived them as short days. An attempt was made to test the responsivity by subjecting all these groups to long day exposure after 16 weeks of experiment. Under 16L: 8D, birds did not show a response during the first 4 weeks of exposure (week 16 to week 20), but thereafter there was a significant photoinduction except 11L:13D (week 24), but the rate and magnitude was different. Until the end of the experiment (32 weeks), all groups of birds had maximum testicular volume except 11L:13D. Birds pre-exposed to 6L:13D:1L:4D, 6L:6D:1L:11D, 11L:13D and 13L:11D responded to 16L:8D, which suggests that these photoperiods helped the birds in recovering their photosensitivity. The results from this experiment indicate that baya weaver interprets a light period depending when the light falls relative to its endogenous circadian system.

Two experiments studied the relative effects on body mass and testicular growth of stimulatory photoperiods applied simultaneously to two photosensitive species, the house sparrow (Passer domesticus) and brahminy myna (Sturnus pagodarum). Experiment 1 on the house sparrow consisted of two parts. In experiment 1A, beginning on 24 March 2002, short day pretreated sparrows were exposed for 12 weeks to 13L: 11D (13 h light: 11 h darkness), 20L: 4D and NDL (control). Experiment 1B was similar to 1A except that it used sparrows that were not treated with short days. This experiment was repeated at three different times in the year. Beginning on 29 December 2002 (for 24 weeks), 26 March 2003 (for 12 weeks) and 16 August 2003 (for 8 weeks), sparrows captured from the wild and acclimated to captive condition for 1 week were exposed to 13L: 11D and 20L: 4D. Each time, a group was maintained in NDL and served as the control. Experiment 2 was performed on myna and used an identical protocol. Beginning on 24 March 2002, myna that were captured from the wild and acclimated to captivity conditions were exposed for 16 weeks to 13L: 11D and 20L: 4D; a group was maintained in NDL and served as the control. There was photostimulation and subsequent regression of the testes on all day lengths except in the August group of experiment 1B. The effect on body mass was variable. Interestingly, however, the response to 20L:4D was relatively smaller as compared to 13L:11D. Taken together, these results confirm that the two species use photoperiods in control of their reproductive cycle, and tend to indicate that exposure to unnatural long photoperiods may in fact be unfavorable and could compromise gonadal growth and development.

We investigated the effects of food availability on the seasonal testicular growth in the photoperiodic house sparrow (Passer domesticus). Two experiments were performed, each lasting 4 weeks. In experiment 1, sparrows were exposed to natural (NDL; group 1), short (8L:16D; group 2) and long (16L:8D; groups 3-5) day lengths with access to food ad libitum (groups 1-3) or for 10 h (zeitgeber time (zt) 0-10, group 4; zt 0 is the time of light onset) or for 8 h (zt 8-16, group 5). Testes recrudesced under long, but not short and natural, day lengths, and the recrudescence under long days was influenced by the duration of food availability. In experiment 2, the sparrows were exposed to short (8L:16D, group 1) and long (16L:8D, groups 2-5) day lengths with access to food ad libitum (for groups 1 and 2) or for 6 h (for groups 3-5) at different times during the 16 h light period (group 3- zt 0-6, group 4- zt 5-11, group 5- zt 10-16). As the expected, the testes recrudesced only under long lengths, but the photoinduction was variable among the 4 groups. The testes grew to full size in groups 2 and 3 that received food either ad libitum or for 6 h at zt 0-6, but to sub-maximal size in the groups that received 6 h food either at zt 5-11 (group 4) or at zt 10-16 (group 5). Altogether, these results support the idea that the photoperiodic regulation of reproduction in a seasonally breeding species is influenced both by the duration and the time of food availability.