IUCN / SSC Cat Specialist Group - Digital Cat Library |
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| Painer, J. | |
| Reproduction management in female lynx (_Lynx lynx_) | |
| 2016 Full Book | |
Lynxes undergo a non-cat like ovarian cycle. Before conducting the studies contained in this thesis, hardly anything of the cycle was fully understood. Concerning conservation aspects, it was important to understand how luteogenesis functions and if it could be manipulated artificially to increase the reproductive output. Therefore, results from examinations of Lynx from different latitudes, from captivity and the wild, and of two different species (Iberian and Eurasian Lynx) were gathered, using high resolution ultrasonography and serum hormone analysis. During our investigations we found out, that the persistent CL, unique to Lynx, are physiological and remain active over an extended period of more than two years. We established a new term for this period: the "prolonged di-oestrus". These CL seem to undergo one of the longest known lifespan of luteal tissue in mammals. After ovulation, which can be spontaneous or induced in Lynx, the follicular tissue undergoes a typical felid transformation into luteal tissue. Contrarily, the CL do not undergo regression after parturition or pseudopregnancy, as they do in other felids and most mammals. They continue the secretion of P4 and E2, which we could proof to be of luteal origin. Interestingly, each time E2 starts to increase (which indicates the onset of a new follicular phase), P4 increases simultaneously. This might be a negative feedback mechanism to inhibit a second oestrus within the same season and maintain the monoestrus status of the Lynx. All Lynx within a geographical region give birth approximately within the same week. This phenomenon seems to be of low plasticity, which might hinder the Lynx in adapting fast enough to anthropogenic or climatic changes. Hence, it was important to discuss a variety of hormone protocols and if those were able to influence the Lynx' cycle. Artificial luteolysis resulted in similar reactions to a natural functional regression before oestrus onset and parturition. Naturally, PGFM elevations were detected before oestrus onset and parturition, followed by decreased luteal vascularisation and a drop in serum P4. The influence of artificial prostaglandins resulted in a significant reduction of the luteal vascularisation, as well as a drop in P4. Similarly to the natural cycle, a structural regression of the luteal tissue did not occur. Unfortunately, the hypothesised natural onset of oestrus was not achieved. The detailed molecular mechanism behind the female Lynx reproductive cycle remains unclear yet. The reason why an atypical monoestrous cycle evolved in Lynx was hypothesised to be due to nutritional or climate advantages for the birthing period, a phylogenetic constraint or an anti-infanticide strategy. The last seems to be the a more reasonable hypothesis, since an infanticide would not lead to a second oestrus onset in Lynx; however, it needs further studies to elucidate that point. |
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