Seasonality of reproduction

The determinants of F. have been subject to experimentation mostly in field and captive studies of ungulates. These support the expected association between the frequency and occurrence of Flehmen and the seasonality of reproduction. The elicitation of F. can also depend upon the social context presentation of urine or other stimuli alone may not produce consistent displays. When conspecific urine was tested out of context (i.e. no female present) in male Black-tailed deer, there was no discrimination between urine from individual adult males or between urine from estrous/non-estrous females (Altieri, 1980). Correlation of male endocrine status in reindeer (Rangifer tarandus) showed that the elevation of testosterone during rut and the duration of F. elicited by female urine was coincident F. bouts during rat were twice as long following exposure to adult female urine as to that of immature females (Mossing and Damber, 1981). 

Rhesus monkeys (Macaca mulatta) are another species used for DART evaluation [4], However, this species displays pronounced seasonality of reproductive activity for both sexes [13,14], In this primate, reproductive functions are entirely shut off or severely diminished for approximately half of the year. In environments with distinct seasons sexual activity and gonadal activity are present roughly throughout October until March, but this may vary substantially for individual animals. It is crucial to consider that the annual rhythmicity of reproductive cycles can persist over years in captivity and under indoor artificial light pattern conditions [15], Hence in indoor circumstances seasonality of reproduction may be uncoupled from the outdoor season, and eventually an animal may display periodic reproductive activation in unexpected months. 

Potential impacts of contaminants on habitat are reductions in cover and quality. The loss of preferred habitat may leave animals more susceptible to predation and disease. Loss of reproductive habitat may result in fewer animals reproducing in a given season or exposing the young to increased predation. For some animal populations, then, habitat changes may lead to decreased reproduction, increased mortality, and increased emigration. 

Season of collection (Fowler and Oregioni 1976 Sanders etal. 1991) and latitude (Anderlini 1974) also influenced silver accumulations. Seasonal variations in silver concentrations of Baltic clams (Macoma balthica) were associated with seasonal variations in soft tissue weight and frequently reflected the silver content in the sediments (Cain and Luoma 1990). Oysters from the Gulf of Mexico vary considerably in whole-body concentrations of silver and other trace metals. Variables that modify silver concentrations in oyster tissues include the age, size, sex, reproductive stage, general health, and metabolism of the animal water temperature, salinity, dissolved oxygen,... 

Fed diet with 15 mg Se/kg ration as selenomethionine for 21 weeks during winter, ending with onset of reproductive season Ducklings fed diets for 4 weeks containing 15 or 60 mg Se/kg ration as selenomethionine, with and without 1000 mg boron/kg ration Females that had just initiated egg laying were fed diet containing 20 mg Se/kg ration as selenomethionine for 20 days, then an untreated diet for 20 days... 

Pollen allelopathy can find utilization in field cultivations that could contain pollen of allelopathic crops or weeds. Pollen allelopathy could be an effective method for annual weed control that reproduce, at least in part, via wind pollination and flower concurrently with the allelopathic species. The effects of allelopathy should result in the loss of genetic variation and so in reduction of reproductive ability, but some plants are probably able to detoxify the pollen allelochemicals (Murphy and Aarssen 1995a, b). Murphy and Aarssen (1989) suggested possible delaying of weed flowering at later, less favorable times of the season or diurnal period, so decrease in weed pressure. However, infestation by perennial weeds can worsen due to compensation of pollen allelopathy through increase in the formation of rhizomes. 

Bronson, F. H., and Heideman, P. D. 1994. Seasonal regulation of reproduction in mammals. In The Physiology of Reproduction. Second Edition. Ed. E. Knobil and J. D. Neill. New York Raven Press, pp. 541-583. 

Strong chemical defenses of reproductive units such as seeds, bulbs, or tubers, as opposed to the vegetative parts, are commonplace. For instance, potatoes, which have to survive in the ground from one growing season to the next. 

At the beginning of the 2000s, a new species that came from the Black Sea -Acartia tonsa - was encountered. At present, it is present in all the zooplankton samples collected in the warm season of the year both in the Sea of Azov proper and in Taganrog Bay thus, it has formed its own reproductive population. 

The Jerusalem artichoke can reproduce by two primary means. It can reproduce and colonize an area by the allocation of photosynthate and nutrients into both asexual (tubers and, to a lesser extent, rhizomes) and sexual (seed) reproductive organs. Flexibility in the amount of resources allocated between sexual and asexual means of reproduction confers a selective advantage in that conditions that inhibit or block sexual production (lack of pollen, herbivory of floral structures, undesirable weather) allow increased allocation to asexual reproduction. Artificially reduced allocation of resources to sexual reproduction, for example, results in a substantial increase in those allocated to asexual means. With flower bud removal, more (82 vs. 69) and larger (4.4 vs. 3.8 g) tubers were formed per plant than those with unlimited sexual reproduction (Wesdey, 1993). Total biomass was not altered, potentially indicating a relatively complete diversion of resources to asexual reproduction when sexual reproduction is blocked. From a reproductive standpoint, the risk of making it to the next season is high with sexual reproduction and relatively low with asexual reproduction. Increased investment in tubers increases the opportunity for sexual reproduction in the future. 

The diameter of the head of the inflorescence ranges from 1.3 to 1.8 cm (six clones) and the mean number of seed per plant from 0.45 to 163 (Swanton, 1986). In wild clones, 9% of the biomass by the end of the season had been allocated to the flowers and fruit (Westley, 1993). If sexual reproduction was blocked, there was a substantial increase in biomass allocated to asexual means of reproduction in the form of more and larger tubers. Flowers in the late fall (November 1, Ontario, Canada) contained 2.46% N, 0.51% P, 2.02% K, 1.21% Ca2+, and 0.68% Mg2+ (Swanton and Cavers, 1989). 

During the out-of-season periods, reproductive hormone secretion and gonadal activity are at a complete halt. Although the basic reproductive and developmental physiology appear similar to human in the rhesus monkey and many endpoint parameters are established, the distinct reproductive seasonality requires special timing and has practical implications for widespread use of this model for DART studies. With regard to immune system evaluation it can be assumed that most of the available tests for cynomolgus monkey will also be applicable to rhesus monkeys. 

Seasonal variations in phase I and II enzymes are often seen in conjunction with breeding cycles. This is particularly true in amphibians, fish, and birds and probably reflect underlying endocrine changes associated with the establishment of reproductive competence. For example, in the razorbill, elevated metabolism of organochlo-rine insecticides such as aldrin has been reported in females collected in April-May. This correlated with increased ovarian size and may be related to increases in cir-... 

Dinkel CA, Minyard JA, Ray DE. 1963. Effects of season of breeding on reproductive and weaning performance of beef cattle grazing on seleniferous range. J Anim Sci 22 1043-1045. 

Factors known to influence metal concentrations and accumulation in aquatic organisms include metal bioavailability, season of sampling, hydrodynamics of the environmental, size, sex, changes in tissue composition and reproductive cycle (Boyden 1981). 

The two aforementioned modes of reproduction lead to three primary reprodudiue strategies. These are the primary use of asexual reproduction, the primary use of sexual reproduction and the sequential or seasonal use of both methods of reproduction. 

Sensitivity to chemical stimuli varies with the internal physiological status of an animal. In crustaceans, this includes molt stage, reproductive status, dominance status, and hunger, all of which are affected by hormonal mechanisms. Physiological differences are often linked to the seasonality of events and controlled via environmental factors such as temperature, light intensity, photoperiod, and circadian cycles, which therefore also influence both the sender and receiver of the chemical signals (Tierney and Atema 1988 Derby 2000 Koehl 2006). 

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