Role of testosterone and photoperiod on seasonal changes in horn growth and sperm variables in the Iberian ibex: a model for polygynous wild bovids

Abstract

This work examines the effect of testosterone secretion and photoperiod on seasonal changes in horn growth and sperm variables in the Iberian ibex (Capra pyrenaica), here used as a model for polygynous wild bovids. The hypothesis that high levels of testosterone provide an endocrine signal that inhibits horn growth in autumn was tested by assessing the effect of cyproterone acetate (CA), an anti-androgen, administered in October -coinciding with the period of natural increases in plasma testosterone concentrations -under different photoperiodic conditions (natural photoperiod and artificial long days). The persistence of horn growth during autumn in all ibexes held under the long-day photoperiodic conditions clearly shows that horn growth regulation in the mating season is primarily modulated by day length and not by a fall in testosterone concentration. A retrospectively designed second experiment involving testosterone propionate (TP) administration in April (when horns are growing) was then undertaken to confirm that high levels of testosterone do not inhibit horn growth. Overall, the results strongly suggest that the rise in testosterone secretion during the autumn mating season does not act as an endocrine signal for the arrest of horn growth, although the rate of horn growth before the mating season may be related to springtime testosterone levels. A direct relationship was seen between the rate of horn growth and the incidence of sperm abnormalities. Neither CA treatment in October nor TP administration in April affected the studied sperm variables. By contrast, CA treatment plus artificial long days in autumn had a negative effect on sperm motility and sperm morphology.

Seasonal dimorphism in the horny bills of sparrows

“…Although the effect of nutrition and photoperiodicity spe-cifically on rhamphothecal growth is generally not known, support for these mechanisms can be found for other keratin-based structures. The effect of ambient temperature on nutritional status has been demonstrated in affecting the growth rate of horns in sheep (Hoefs and Nowlan 1997;Giacometti et al 2002) and photoperiod has been implicated in breeding season increases in horn growth as well (Santiago-Moreno et al 2012). Seasonal variation in growth rate has been documented in bovine hoofs, another keratinized structure (Hahn et al 1986).…”

“…) and photoperiod has been implicated in breeding season increases in horn growth as well (Santiago‐Moreno et al. ). Seasonal variation in growth rate has been documented in bovine hoofs, another keratinized structure (Hahn et al.…”

Influence of circulating testosterone concentration on sperm cryoresistance: The ibex as an experimental model

“…The two treatments modified the plasma testosterone concentration as expected 33 -modifications that were associated with changes in sperm cryoresistance. The rapid reduction in blood plasma testosterone levels after CA treatment was similar to that observed in white-tailed deer, 42 fallow deer, 23 and domestic goat.…”

“…However, the results are controversial. For example, some researchers have reported that SARS-CoV-2 was not detected in the male reproductive tract, [25][26][27][28][29][30][31][32][33][34] while others reported that SARS-CoV-2 RNA was found in the semen or testes of COVID-19 patients. 35,36 There are also unknown factors regarding COVID-19 and male reproduction.…”

Descriptive analysis of sperm head morphometry in Iberian ibex (Capra pyrenaica): Optimum sampling procedure and staining methods using Sperm-Class Analyzer®

“…The Iberian ibex has been used as a model for reproductive studies in wild caprine species (Santiago-Moreno et al, 2012). Hence, this methodology for sperm morphometric assays is recommended for other related wild species such as the Alpine ibex (Capra ibex), Nubian ibex (Capra nubiana), chamois (Rupicapra pyrenaica), etc.…”