Age effect on last male precedence and post copulatory selection on North African houbara bustards

Started in december 2020

Private funding (Reneco)

Supervisors: Gabriele Sorci (Biogéosciences), Janaina Torres Carreira (Reneco International Wildilfe consultants LLC) & Michel Saint Jalme (Muséum national d’histoire naturelle)

Abstract

Polyandry is a widespread mating system in nature, referring to the female propensity to mate with several males during the same reproductive bout. A direct consequence of polyandry is that sperm of different males are concomitantly present in the female reproductive tract. Polyandry, therefore, extends the opportunity for sexual selection to operate, since in addition to the competition between males to access the female (pre-copulatory sexual selection), sperm of different males also compete to access the egg (post-copulatory sexual selection). In many invertebrate and bird species, this typically results in most offspring being sired by the last male, a phenomenon called last male sperm precedence. Polyandry has been observed in females of various species, including the North African houbara bustard. In this system it is reasonable to assume that paternity confers different chances of survival and reproduction to the offspring, hence the choice of male and matting order of a female has an important evolutionary consequence. Male age can alter the overall quality of the ejaculate and several studies have reported decreased reproductive success of senescing males, especially when the sperm of old males must compete with sperm of young individuals. Previous work conducted in the houbara bustard has shown that young males have a higher share of paternity when females are inseminated with a mix of sperm from young and old males (with equal contribution of both age classes) and offspring sired by old males had impaired hatching success, growth and post-release survival (in females). However, this does not mimic the natural situations where females mate in order and males contribute with different number of sperm of different quality.

The houbara bustard represents an ideal model system to explore the mechanisms underlying male reproductive success and the ecological/evolutionary consequences of post-copulatory sexual selection both for captive birds and those released to restore natural populations. This thesis project is rooted in previous work conducted in the houbara bustard and aims to go further in our understanding of the effect of male age on the issue of sperm competition and male reproductive success.

To improve the knowledge on the species physiology of reproduction and to construct a solid base for sperm characteristics, production and later storage system in the female tract, the first chapter of this PhD thesis will explore anatomy and histology of the female and male reproductive systems. Since understanding the species spermatogenesis duration and variations brings important information on applied science and on ecology aspects, as to understand aspects of sperm competition, or seasonal variations on sperm quality, the sperm cycle will be followed across the season using histological testicular analysis across season. Sperm ultrastructure and organelle distribution will be described for houbara birds by transmission microscopy of ejaculated samples. Finally, females will be inseminated with different fluorescent innocuous semen samples and euthanized for sperm SST display evaluation. The second chapter aims are to investigate last sperm precedence and the interference of age and sperm quality on this feature. Females will be inseminated blindly (with no prior sperm evaluation) by old and young males following different inseminations orders. One aliquot of the ejaculate will be reserved for analysis. Sperm function will be accessed analysing sperm morphology, movement (CASA), sperm viability, concentration, ejaculate volume, mitochondrial potential status, DNA integrity and compaction, Guanine oxidation and free radicals and antioxidant content. Sperm parameters will be later confronted with father age and siring success, and results of chick production and development compared.

Keywords

African Houbara bustard, sperm competition, male age, reproductive success, senescence

extrait:

lien_externe:

titre:

Effet de l’âge sur la préséance du dernier mâle et sur la sélection sexuelle post-copulatoire chez l’outarde Houbara d’Afrique du Nord

date_de_debut_these:

décembre 2020

nom:

Meunier

date_de_debut_these_numerique:

202012

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kc_raw_content:

Age effect on last male precedence and post copulatory selection on North African houbara bustards

Started in december 2020

Private funding (Reneco)

Supervisors: Gabriele Sorci (Biogéosciences), Janaina Torres Carreira (Reneco International Wildilfe consultants LLC) & Michel Saint Jalme (Muséum national d’histoire naturelle)

 

Abstract

Polyandry is a widespread mating system in nature, referring to the female propensity to mate with several males during the same reproductive bout. A direct consequence of polyandry is that sperm of different males are concomitantly present in the female reproductive tract. Polyandry, therefore, extends the opportunity for sexual selection to operate, since in addition to the competition between males to access the female (pre-copulatory sexual selection), sperm of different males also compete to access the egg (post-copulatory sexual selection). In many invertebrate and bird species, this typically results in most offspring being sired by the last male, a phenomenon called last male sperm precedence. Polyandry has been observed in females of various species, including the North African houbara bustard. In this system it is reasonable to assume that paternity confers different chances of survival and reproduction to the offspring, hence the choice of male and matting order of a female has an important evolutionary consequence. Male age can alter the overall quality of the ejaculate and several studies have reported decreased reproductive success of senescing males, especially when the sperm of old males must compete with sperm of young individuals. Previous work conducted in the houbara bustard has shown that young males have a higher share of paternity when females are inseminated with a mix of sperm from young and old males (with equal contribution of both age classes) and offspring sired by old males had impaired hatching success, growth and post-release survival (in females). However, this does not mimic the natural situations where females mate in order and males contribute with different number of sperm of different quality.

The houbara bustard represents an ideal model system to explore the mechanisms underlying male reproductive success and the ecological/evolutionary consequences of post-copulatory sexual selection both for captive birds and those released to restore natural populations. This thesis project is rooted in previous work conducted in the houbara bustard and aims to go further in our understanding of the effect of male age on the issue of sperm competition and male reproductive success.

To improve the knowledge on the species physiology of reproduction and to construct a solid base for sperm characteristics, production and later storage system in the female tract, the first chapter of this PhD thesis will explore anatomy and histology of the female and male reproductive systems. Since understanding the species spermatogenesis duration and variations brings important information on applied science and on ecology aspects, as to understand aspects of sperm competition, or seasonal variations on sperm quality, the sperm cycle will be followed across the season using histological testicular analysis across season. Sperm ultrastructure and organelle distribution will be described for houbara birds by transmission microscopy of ejaculated samples. Finally, females will be inseminated with different fluorescent innocuous semen samples and euthanized for sperm SST display evaluation. The second chapter aims are to investigate last sperm precedence and the interference of age and sperm quality on this feature. Females will be inseminated blindly (with no prior sperm evaluation) by old and young males following different inseminations orders. One aliquot of the ejaculate will be reserved for analysis. Sperm function will be accessed analysing sperm morphology, movement (CASA), sperm viability, concentration, ejaculate volume, mitochondrial potential status, DNA integrity and compaction, Guanine oxidation and free radicals and antioxidant content. Sperm parameters will be later confronted with father age and siring success, and results of chick production and development compared.

 

Keywords

African Houbara bustard, sperm competition, male age, reproductive success, senescence