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On this page, you will find an overview of puberty in the male along with important physiological processes for reproductive success and the endocrine control over these processes.
Puberty in the Tom
Puberty in the Tom
Puberty in the tom is typically characterized by the commencement of spermatogenesis, the cyclic process by which spermatogonia differentiate into mature spermatozoa and typically is attained at 8-10 months (1, 2). However, there is significant variation between breeds, with some breeds (Main Coon, Persian, Chartreux) unable to produce viable sperm until 2 years (3). The process of puberty begins early on in the male cat’s life. Testosterone levels begin increasing at 1 month and Leydig cells in the testes do not become active until the male cat has sufficient testosterone levels at around 3 months (5).
Also accompanying the increase in testosterone at puberty is the separation of the penis from the prepuce via the breakdown of the balanopreputial fold (4). This process is typically complete by 6 months (2). Additionally, androgen-dependent growth of penile spines on the glans penis typically starts at 3 ½ months and is complete at 6-7 months (4, 5). Because sperm does not appear in the seminiferous tubules (no spermatogenesis) until 8-10 months, the presence of penile spines and the lack of balanopreputial fold do not indicate that the tom is capable of producing sufficient mature spermatozoa to sire offspring successfully (4).
Increased testosterone levels also result in various behavioral changes associated with puberty such as increased roaming, intermale aggression, and scent marking with urine (5). Behavioral sexual maturity is characterized by complete copulations and occurs at 9-12 months; this occurs after spermatogenesis has begun and sufficient numbers of sperm can be found in the seminiferous tubules (5).
Spermatogenesis
Spermatogenesis
Spermatogenesis in cats is a cyclic and highly coordinated process in which spermatogonia differentiate into mature spermatozoa. Spermatogenesis aims to ensure a consistent supply of male gametes over extended periods through stem cell renewal, promote genetic diversity, and produce billions of sperm daily (6). The blood-testis barrier (BTB) offers a protected environment where developing germ cells are shielded from the male's immune system as the cells are haploid (7). For the tom, it takes 47 days for sperm to mature from its inception in the testicle to its release into the epididymis. An added 10–12 days are needed for the sperm to transit and mature within the epididymis, bringing the total spermatogenic cycle to around 60 days (4).
Figure 1. Typical Sequence of Spermatogenesis; Image Source: Senger, 2012 pg 207 (6)
According to Senger (2012), the process of spermatogenesis in cats involves three stages:
Proliferation Phase: This initial phase is characterized by the mitotic divisions of spermatogonial germ cells into A-spermatogonia. Within this phase, several generations of A-spermatogonia undergo divisions to produce a substantial number of B-spermatogonia. A crucial aspect of this phase is the concept of stem cell renewal. Some spermatogonia, due to the loss of intercellular bridges, revert back to their stem cell state, known as spermatogonial stem cells. This renewal ensures a consistent source of new spermatogonia for future development.
Meiotic Phase: This phase commences with primary spermatocytes. The genetic diversity of the sperm is ensured during this phase through crossing over, which takes place during the prophase of the first meiotic division. As a result, each sperm’s genetics is unique. The culmination of the meiotic phase, marked by the second meiotic division, results in the formation of haploid spermatids.
Differentiation Phase: Also commonly referred to as "spermiogenesis", this phase does not involve any further cell divisions. Instead, the previously spherical and undifferentiated spermatids undergo a significant transformation into a fully differentiated spermatozoon, equipped with a head containing nuclear material and a flagellum that includes a midpiece with a mitochondrial helix and a principal piece. This phase consists of four sub-phases described below.
Golgi phase: During this phase, differentiation leads to the formation of acrosomic vesicle that contains an acrosomic granule, which is the first part of acrosome development. This occurs due to the small vesicles of the Golgi apparatus in the spermatid, fusing together. At the same time, centrioles are moving to the nucleus of the spermatid, which will give rise to the place where the future flagellum will be anchored and the developing axoneme (sperm tail).
Cap phase: during this phase, the acrosomic vesicle spreads out to be a distinct “cap” over the nucleus. The developing tail begins to protrude into the seminiferous tubule lumen.
Acrosomal phase: During this phase, the spermatids deeply embed in the Sertoli cells while the acrosome spreads over the nucleus and the nucleus elongates. The manchette, a group of microtubules, develops, and parts of it attach to the posterior nucleus, and other microtubules of the manchette develop into the post-nuclear cap.
The cytoplasmic droplet formed as the sperm goes from round to elongated, and the excess cytoplasm forms this droplet on the outside of the cell just below the head. It migrates to the junction of the mid-piece and tail of the spermatozoa in the 4th region of the epididymis, and then this droplet is removed during ejaculation (4).
Maturation phase: The post-nuclear cap fully develops; mitochondria move towards the flagellum and create a spiral pattern that forms the midpiece of the sperm. A fibrous sheath is produced to cover the flagellum. At this stage, a plasma membrane covers the entire spermatozoon, and it is fully developed, motile, and able to fertilize an oocyte.
Endocrinology of the Tom
Endocrinology of the Tom
Endocrine regulation is critical to successful spermatogenesis in the tom. Specific endocrine prerequisites include:
sufficient GnRH secretion from the hypothalamus,
FSH and LH release from the anterior pituitary, and
high gonadal steroid secretion, notably testosterone and estradiol (6).
Optimal testicular function necessitates pulsatile GnRH secretion, high intratesticular testosterone concentrations, systemic testosterone dilution, and sufficient LH receptors in Leydig cells (6). The tom’s hypothalamus lacks a surge center and, thus, releases GnRH in intermittent episodes throughout the day, triggering subsequent LH discharges. LH acts on Leydig cells in the testes, which, upon binding, synthesize progesterone and convert it to testosterone (8). Pulsatile LH release prevents Leydig cell refractoriness due to the down-regulation of LH receptors (6). Intratesticular testosterone concentrations are significantly higher than systemic levels due to the tight junctions of the BTB, essential for spermatogenesis, preventing GnRH/LH feedback system down-regulation, and alleviating FSH negative feedback. (6, 7). Besides testosterone, Leydig cells secrete estradiol, which, when elevated, suppresses GnRH and LH releases (6). Additionally, Sertoli cells produce inhibin, suppressing FSH secretion; however, the role of this hormone is not well understood (6).
References for Puberty, Spermatogenesis, and Endocrinology:
Tiptanavattana, N., Radtanakatikanon, A., Hyttel, P., Holm, H., Buranapraditkun, S., Setthawong, P., Techakumphu, M., & Tharasanit, T. (2015). Determination phase at transition of gonocytes to spermatogonial stem cells improves establishment efficiency of spermatogonial stem cells in domestic cats. The Journal of reproduction and development, 61(6), 581–588. https://doi.org/10.1262/jrd.2015-094
Kutzler, M. A. (2022). Reproductive Anatomy and Puberty in the Tom. Feline Reproduction. 153-166. https://doi.org/10.1079/9781789247107.0017
Malandain, E., Little, S., Casseleux, G., Shelton, L., Pibot, P., et al. (2006) Reproduction from oestrus to kittening. Practical Guide to Cat Breeding . Aniwa SAS, Lyon, France, pp. 63–79.
Johnson, A. (2022) Normal Feline Reproduction: The Tom. Journal of Feline Medicine and Surgery. Volume 24, Issue 3, p.212-220. https://doi.org/10.1177/1098612X221079707
Beaver, B. V. (2003). Male Feline Sexual Behavior. Feline Behavior, 164–181. doi:10.1016/b0-72-169498-5/50006-x
Senger, P.L. (2012) Pathways to Pregnancy and Parturition. 3rd ed. Current Conceptions, Inc.
Gobello, C. (2022). Key aspects of domestic cat spermatogenesis. Reproduction in Domestic Animals, 57, 459–464. https://doi.org/10.1111/rda.14089
Talcott, P. A., Peterson, M. E. (2012). Small Animal Toxicology. Elsevier Health Sciences. 176-178.
Maturation and Transport of Spermatozoa in the Epididymus
Maturation and Transport of Spermatozoa in the Epididymus
Spermatozoa are released from the lumen into the rete testis by the process if spermiation (1). From the rete testis, the spermatozoa then enter the epididymus (1). In the cat, it takes 10-12 days for maturation and transport in the epididymus (3). The epididymus can be generally divided into the caput, corpus and cauda and then further divided into 6 regions within the cat (2). Within the epididymus, the spermatozoa obtain motility and the ability to potentially fertilize an oocyte (1). Along the epididymus, principal cells can be found which have steriocillia (which increase fluid absorption), lysosomes and each cell has a large golgi apparatus (2). Epididymosomes are released throughout the epididymus and function to help protein transport, secrete special proteins to help to enhance the motility of spermatozoa and ensure the sperm can penetrate the zona pellucida (2). The storage of spermatozoa occurs within the 5th and 6th region in the cauda portion of the epididymis and the sperm within these reservoirs can be released during ejaculation. (3)
Changes that occur during maturation and transport include:
A change in the plasma membrane fluidity due to cholesterol, which changes its permeability (2)
The chromatin within the head of the spermatozoa condenses (3)
Motility is obtained through sections 4-5 of the epididymus in correlation with an increase in cyclic adenosine monophosphate (cAMP) levels. The cAMP activates protein kinase A which acts in cellular processes that lead to changes in the sperm tail, increasing sperm motility (3)
The cytoplasmic droplet migrates to the to the junction of the mid-piece and tail of the spermatozoa, in the 4th region of the feline epididymus, and then this droplet is removed during ejaculation (4).
Figure 2. Diagram of the anatomy of the epididymus, along with key maturation factors that occur within each of the anatomical sections.
Image Source: Diagram modified from original source
Figure 3. Diagram showing the basic pathway of ejaculation from stimulation to biological response
Image Source: Senger, 2012 pg 245 (1)
Erection, Emission and Ejaculation
Erection, Emission and Ejaculation
The male cat has a musculocavernous penis. In order for successful copulation the following processes must occur:
Erection: Erection is a necessary process for successful copulation that consists of neural and vasomotor reactions that lead to increased rigidity of the penis. The specific process of erection is as follows:
The tom must be stimulated through olfaction, visual or auditory stimuli. The erotogenic stimuli causes afferent sensory nerve firing to the behavior center of the hypothalamus
In the hypothalamus, the afferent sensory nerve endings synapse with efferent neurons that innervate penile arterioles (both parasympathetic and sympathetic neurons)
The parasympathetic neuron firing leads to the release of nitric oxide at the nerve terminals. Nitric oxide is a neurotransmitter that causes the conversion of GTp to cGMP. cGMP causes the relaxation and vasodilation of corporal sinusoid smooth muscle.
The vasodilation of the smooth muscle leads to increased blood flow and pressure to the penis causing rigidity. The increased blood flow and pressure causes tightening at the base of the penile spines and they begin to protrude out (4).
The increased pressure due to the blood flow coupled with motor neuron signals for the contraction of ischiocavernosous, urethalis and bulbospongiosus muscles compresses the penile veins and prevents back-flow of blood out of the penis, allowing for maintenance of the erection.
Mounting and Intromission: The male will mount the female and insert the erect penis into the female (more detail on reproductive behavior can be found here)
Ejaculation: After intromission is achieved, ejaculation can occur which is a neural reflex that expels the spermatozoa and seminal fluids from the reproductive tract(1). The specific process is as follows:
The reflex for ejaculation is initiated by stimulation of the glans penis. The glans penis has sensory receptors that detect changes in temperature and pressure, which sends a signal to the brain through afferent sensory neurons.
Next, efferent motor neurons signal for the penile muscles to contract and push the sperm and seminal fluids into the urethra and then out of the urethral opening, with the help of the hormone oxytocin.
Emission: Emission is the release of seminal fluids from accessory sex glands (prostate and bulbourethral glands) into the pelvic urethra. This process is important to ensure the seminal plasma mixes with the sperm and it occurs during ejaculation. The seminal plasma adds important proteins that help protect the sperm until capacitation occurs in the female tract (more detail on capacitation can be found here).
All information in this section is from source 1 unless otherwise noted
References for Maturation of Spermatozoa and Erection, Emission, and Ejaculation
Senger, P.L. (2012) Pathways to Pregnancy and Parturition. 3rd ed. Current Conceptions, Inc.
Hassan, H., Domain, G., Luvoni, G., Chaaya R., Soom A., Wydooghe E. (2021) Canine and Feline Epididymal Semen- A plentiful Source of Gametes Animals https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8532807/
Axner E. (2006) Sperm Maturation in the domestic cat Theriogenology 66(1) https://www.sciencedirect.com/science/article/pii/S0093691X0600183X?via%3Dihub
Johnson A. (2022) Normal feline reproduction: the tom Journal of Feline Medicine and Surgery https://journals.sagepub.com/doi/full/10.1177/1098612X221079707
Artificial Insemination
Artificial Insemination
Artificial insemination (AI) is not commonly used in breeding domestic cats. AI is more common in wild cat species, conservation, and research. AI is difficult to do, both in terms of collection and timing of inseminating the queen. Due to queens being induced ovulators, causing ovulation can be difficult (3). Toms also ejaculate small volumes of semen which makes it difficult to insure pregnancy in the queens . Overall, there has been a higher demand of AI use in domestic cats but the technology is not advanced is enough for practical use (1). This demand is mostly within the purebred community. These cat breeders want more variety in their genetic pool for their animals to prevent inbreeding. AI is difficult and not useful for most domestic cat breeders because of the lack of research done to improve the results. In wildlife, AI is used to exchange genetics between zoos, enable reproduction in animals with disabilities, provide rapid population growth, maintaining a balance in males and females of a species, etc (2).
References for Artificial Insemination
E, A., & C, L. F. (2002, July 5). Semen collection and assessment, and artificial insemination in the cat. International Veterinary Information Service. https://www.ivis.org/library/recent-advances-small-animal-reproduction/semen-collection-and-assessment-and-artificial#:~:text=While%20the%20more%20advanced%20biotechnology,the%20cat%20as%20it%20has
Rodrigues da Paz, R. C. (2012). Wildlife Cats Reproductive Biotechnology. (I. I. Katkov, Ed.).Current Frontiers in Cryobiology. https://doi.org/10.5772/32464
Zambelli, D., & Cunto, M. (2022). Artificial insemination in Queens in the clinical practice setting: Protocols and challenges. Journal of Feline Medicine and Surgery, 24(9), 871–880. https://doi.org/10.1177/1098612x221118756
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