Phases Of Annual Reproductive Cycle Research Articles

Gonadotropin receptors of Labeo rohita: Cloning and characterization of full-length cDNAs and their expression analysis during annual reproductive cycle

Follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh), secreted from pituitary, stimulate gonadal function by binding to their cognate receptors FSH receptor (FSHR), and LH/choriogonadotropin receptor (LHCGR). Rohu (Labeo rohita) is a commercially important seasonal breeder freshwater fish species, but till date, the regulation of expression of gonadotropins and their receptors gene during different phases of annual reproductive cycle has not been investigated. We envisaged the critical role of these molecules during seasonal gonadal development in this carp species. We cloned full- length cDNAs of fshra and lhcgrba from rohu testis using RACE (Rapid amplification of cDNA ends) and analyzed their expression along with fsh and lh by quantitative real time PCR (qRT-PCR) assay at various gonadal developmental stages of the annual reproductive cycle. Full-length rohu fshra and lhcgrba cDNA encodes 670 and 716 amino acids respectively, and in adult fish, they were widely expressed in brain, pituitary, gonad, liver, kidney, head kidney, heart, muscle, gill, fin, eye and intestine. In male, both fsh and fshra transcripts showed high level of expression during spermatogenesis, however, in female, expression level was found to be higher in the fully grown oocyte stages. The expression of rohu lh and lhcgrba mRNA increased with increment of gonadosomatic index and showed highest level during spermiation stage in male and fully matured oocyte stage in female. These results together may suggest the involvement of fshra and lhcgrba in regulating function of seasonal gonadal development in rohu.

Molecular characterization of two kiss genes and their expression in rohu (Labeo rohita) during annual reproductive cycle.

Kisspeptin is an important regulator of reproduction in mammals and presumably non-mammalian species. In the Indian subcontinent, rohu (Labeo rohita) is a commercially important seasonal breeder freshwater fish species, but till date, the expression of kisspeptin gene during different phases of annual reproductive cycle has not been investigated. To address this, we cloned and characterized kiss1 and kiss2 full-length cDNA by RACE (rapid amplification of cDNA ends), and analyzed their expressions in brain-pituitary-gonad (BPG) axis by quantitative real time PCR (qRT-PCR) assay at various gonadal developmental stages of the annual reproductive cycle. Full-length rohu kiss1 and kiss2 cDNA encodes 116 and 125 amino acids respectively, and in the adult fish, they were widely expressed in brain, pituitary, gonad, liver, muscle, kidney, intestine and eye. In male, kiss1 mRNA in brain and testis showed the highest level of expression during meiosis division of the gonad. The kiss2 mRNA revealed the highest expression during recrudescence stages in the brain, spermiation stages in pituitary and post-spawning stages in testes. In females, significantly (p<0.05) a higher level of kiss1 transcript was expressed in brain and ovary, in the full grown oocyte stages, whereas during pre-vitellogenic and vitellogenic stages in pituitary. The kiss2 gene expression was almost similar at various gonadal developmental stages in the brain and ovary, but, highest expression was detected in full grown oocyte stages in the pituitary. These results together may suggest the involvement of two kiss genes in the control of seasonal gonadal development in rohu.

Daily and seasonal rhythms in immune responses of splenocytes in the freshwater snake, Natrix piscator.

Present study was designed to examine daily and seasonal variability in the innate immune responses of splenocytes in the fresh water snake, Natrix piscator. Animals were mildly anesthetized and spleen was aseptically isolated and processed for macrophage phagocytosis, NBT reduction, nitrite production, splenocyte proliferation and serum lysozyme activity. Samples were collected at seven time points, viz., 0000, 0400, 0800, 1200, 1600, 2000 and 0000 h during three different seasons, namely summer, winter and spring. Cosinor analysis revealed that percent phagocytosis had a significant 24-h rhythm during summer and spring seasons. The peaks of rhythms in NBT reduction and nitrite release occurred in the morning hours at 10.88 h and 8.31 h, respectively, in winter. A significant 24-h rhythm was also observed in lysozyme concentration and splenocyte proliferation (both Basal and Concanavalin A stimulated) in all three seasons. A significant phase shift in splenocyte proliferation was obtained with a trend of delayed phase shift from winter to spring and from spring to summer. Of the nine variables, significant annual (seasonal) rhythms were detected in almost all variables, excluding phagocytic and splenosomatic indices. All rhythmic variables, except spleen cellularity, exhibited tightly synchronized peaks coinciding with the progressive and recrudescence phases of annual reproductive cycle. It is concluded that the snake synchronizes its daily and seasonal immune activity with the corresponding external time cues. The enhancement of immune function coinciding with one of its crucial reproductive phases might be helping it to cope with the seasonal stressors, including abundance of pathogens, which would otherwise jeopardize the successful reproduction and eventual survival of the species.

Surfacing activity rhythm in Clarias batrachus: effect of different phases of annual reproductive cycle

The surfacing activity rhythm in Clarias batrachus during different phases (preparatory, spawning, post-spawning and resting) of its annual reproductive cycle was examined. Live Clarias batrachus of mixed sex were procured from the local market during the respective phases and kept in stock aquaria under laboratory conditions for proper acclimation. Following acclimation, the individuals were randomly selected from the stock aquaria and kept in the specially designed glass aquaria inside the chronocubicles for recording of the surfacing activity. The animals were exposed under a LD 12:12 regime (lights on at 06:00) during each phase of the annual reproductive cycle. The surfacing activity was recorded with the help of infrared photoswitches and a microprocessor based event recorder. During all the studied phases of the annual reproductive cycle under standard LD 12:12, most of the individuals exhibited a statistically significant circadian rhythm with a prominent 24 h period in their surfacing activity. In addition, statistically significant rhythms with τ = 12 h and 6 h have also been noticed in most of the individuals during all the studied phases. It appears from actograms that the activity rhythm is entrained with the timings of light on/off, irrespective of phases of the annual reproductive cycle. The activity elevation started synchronously with the onset of dark and declined as the lights came on. Acrophases of the activity also occurred during the dark phase of the light–dark cycle. The daily mean of the surfacing activity was found to be elevated during the spawning phase compared to the other phases of the annual reproductive cycle and the lowest level of daily mean activity was noticed during the resting phase.

Effect of safe application rate (SAR) concentrations of some biocides on the gonads of the fresh water murrel, Channa punctatus (Bl.)—A biochemical study

The effect of safe application rate (SAR) concentrations of fenitrothion 50% EC—an organophosphate and carbofuran 3% G—a carbamate on the gonads (ovaries/testes) of Channa punctatus was studied for 120 days (mid-April through mid-August) extending over the preparatory, prespawning, and spawning phases of annual reproductive cycle. The studies have revealed that the levels of total proteins, RNA, total lipids, and ascorbic acid decreased, while those of the cholesterol and the phospholipids increased following exposure to the two biocides. Furthermore, it was observed that in both treatments the decline in the levels of total proteins, RNA, total lipids, and ascorbic acid was relatively more marked in the testes than in the ovaries. On the contrary, increase in the levels of cholesterol was relatively more in the ovaries, while increase in the levels of phospholipids was more in the testes in both treatments. The results suggest that the decrease/increase in the levels of the above-mentioned biochemical parameters was more in the fenitrothion treatment than in the carbofuran treatment and, therefore, may be considered relatively more toxic to this species.

In vivo modification of fatty acids and glycerides metabolism in response to 1,2,3,4,5,6-hexachlorocyclohexane and cythion exposure in the catfish, Clarias batrachus

Specimens of either sex of the freshwater catfish, Clarias batrachus, were exposed to safe and sublethal concentrations of γ-BHC (2 and 8 ppm) and cythion (1 and 4 ppm) for 4 weeks during different phases of annual reproductive cycle. Their effects on free fatty acids (FFA) and acyl glycerides, viz., monoglycerides (MG), diglycerides (DG), and triglycerides (TG), were studied in liver, plasma, gonads, and muscle. During the preparatory phase, both pesticides suppressed the levels of FFA and acylglycerides (MG, DG, and TG) in liver of either sex but had no effect on their levels in plasma, ovary, and muscle; however, FFA and TG were reduced in testis. Unlike the preparatory phase, in the prespawning phase different lipids responded variedly to the concentrations of both Cythion and γ-BHC. In the female, FFA in liver and plasma was raised but in ovary and muscle it was decreased. Acylglycerides in studied tissues were also reduced except ovarian TG which was increased by both pesticides at safe concentrations. Contrary to this, in the male these lipids were raised in liver and testis. Moreover, during the spawning phase, these pesticides enhanced the hepatic FFA together with acylglycerides in the female but failed to elicit any change in their levels in the male. Plasma levels of FFA and TG were reduced in the female; however, in the male FFA was raised and TG remained unchanged. Ovarian FFA and TG were decreased and increased, respectively. During the postspawning phase, none of the lipid fractions could be affected in the male except hepatic FFA which was reduced; however, in the female TG along with FFA was decreased.

Effect of two pesticides on ovarian 32P uptake and gonadotrophin concentration during different phases of annual reproductive cycle in the freshwater catfish, Heteropneustes fossilis (Bloch)

Ovarian 32P uptake and gonadotrophic contents of the pituitary gland and blood serum after 4 weeks of treatment with Cythion and Hexadrin at safe or sublethal concentrations were measured in Heteropneustes fossilis during five different phases of the annual reproductive cycle. Gradual reduction in the ovarian 32P uptake as well as in gonadotrophin level started from the preparatory phase and was more pronounced and significant during prespawning and spawning phases. In early postspawning period the changes in ovarian 32P uptake and gonadotrophin content were less than those observed in the previous two phases after Cythion treatment but similar to those observed after Hexadrin administration. Values in the late postspawning period were similar to those observed in preparatory phase. These pesticides seem to interfere with gonadotrophin secretion and their action on ovary with resultant decrease in ovarian activity during all phases of the annual reproductive cycle in H. fossilis.