The guinea pig (Cavia porcellus) is a well known friend animal and a research model that is common.

02 Nov The guinea pig (Cavia porcellus) is a well known friend animal and a research model that is common.

Key Points

• Intact female guinea pigs are “sows” and intact males are “boars”.
• Mature boars have actually distinct scrotal pouches and testes that are large.
• Male guinea pigs have actually several sex that is accessory, including big, paired seminal vesicles or vesicular glands, and this can be seen erroneously as uterine horns.
• Puberty does occur at more or less 2 months in females and between 2-3 months in men.
• The symphysis that is pubic within the last times of maternity.
• Separation of this pubic symphysis may be insufficient in sows bred after 7-8 months of age and dystocia may result in him or her. Other prospective reasons for dystocia consist of obesity and fetal size that is large.
• Sows usually give delivery to 2-4 big, precocial pups. Other rodent types generally have actually big litters.
• Pregnancy toxemia is a essential reason behind perinatal mortality in guinea pigs. This problem is frequently noticed in primiparous, overweight sows in belated gestation. The prognosis is oftentimes guarded. Minmise the chance of being pregnant toxemia by motivating workout, preventing obesity, and minimizing stress in the expecting sow.

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• Unilateral or bilateral ovarian cysts are common, especially in older sows.
• Ovariohysterectomy or ovariectomy is advised to avoid the introduction of ovarian cysts as well as other reproductive dilemmas in non-breeding companion sows.

Introduction

Guinea pigs are helpful in reproductive studies simply because they share numerous reproductive faculties with people (Fig 1). 26 Like humans, guinea pigs have a very hemochorial placenta, by which maternal bloodstream comes in direct experience of the fetal chorion, in addition to comparable trophoblast intrusion habits and uterine vasculature that is comparable. 20 , 23 , 26 The guinea pig’s gestation duration could be split into trimesters, analogous into the individual condition. 26 needless to say, some attributes of guinea pig reproductive anatomy and physiology are distributed to other people in purchase Rodentia, along with other features are unique for this species that is special. This short article ratings physiology and physiology of this guinea pig tract that is reproductive summarizes some clinically significant medical dilemmas.

Figure 1.Guinea pigs (Cavia porcellus) are helpful in a lot of studies that are reproductive.

Intact male guinea pigs, or “boars”, enter puberty between 70-90 times, nevertheless men start to show intimate behavior, such as mounting, at 30 days of age. 9 , 17 , 23 At 2 months, boars start to ejaculate while mounting. 23 Expression of intimate behavior and physical development is notably suppressed in the event that boar is housed along with its mom and/or siblings. 11

Boars are generally bigger than females, with both sexes having a pair that is single of mammae. 5 Mature boars have big, paired testes, that are found on either region of the perineum in distinct, superficial scrotal sacs (Fig 2). 5 , 9 , 23 The testicles are frequently completely descended to the scrotum by 81 times. 2 In the event that testes never have descended by 4 months of age, the guinea pig is highly recommended cryptorchid. 9 The inguinal canals remain available for a lifetime. 9 , 19 to avoid herniation post-castration, numerous clinicians use a shut strategy or perhaps a modified available method, where in fact the tunica is roofed within the suture which is used to connect from the spermatic cord and vessels. 32

Figure image that is 2.Gross of testicle (arrow) in an adult boar (Cavia porcellus). The epididymis lies across the dorsolateral area of this testis. The end regarding the epididymis provides increase towards the ductus deferens. Credit: Drury Reavill, DVM, DABVP (Avian Training), DACVP. Click image to expand.

Clinical Suggestion: Although big, paired testes are clear in mature boars, sex identification could be challenging in young pups. In the event that testicles aren’t apparent, sexing are facilitated by putting mild stress at the beds base associated with the prepuce to partially extrude your penis. 23

The S-shaped penis comprises of a human anatomy and glans. Guinea pigs possess a penis that is os which will be discovered in the dorsal area associated with the whole duration of the glans. 9 , 19 Like other hystricomorph rodents, your penis comes with moment, saw-toothed spurs that are white dorsolaterally in 2 parallel lines through the urethral orifice to your glans. Addititionally there is a sac that is intromittent the ventral surface associated with the glans penis. 9 During erection, the sac everts and two horny styles protrude. 5 , 9 , 23 the big event of the 3-5 mm projections that are long unknown. 9

Male glands that are reproductive the seminal vesicles (vesicular glands), coagulating glands, bulbourethral glands, as well as the prostate (Fig 3). 5 , 27 A rudimentary gland that is preputial additionally be contained in the boar. 9

Figure 3. Reproductive structure regarding the guinea pig (Cavia porcellus) boar. (A) seminal vesicle (B) testis C) vas deferens (D) anterior prostate gland or coagulating gland (E) urinary bladder (F) Cowper’s or bulbourethral gland (G) urethra (H) penis (we) epididymis. Picture credit: Drs. Craig Franklin and Cindy Besch-Williford. Click image to expand.

• The big, clear, smooth seminal vesicles are the biggest reproductive glands of this boar, calculating as much as 100 mm in total and 6-9 mm in diameter. These long, coiled, paired blind sacs lie ventral to the ureters and go into the urethra by a set of ducts instantly caudodorsal into the ductus deferens. 9 , 19 , 23 , 27

Clinical Suggestion: The big, paired seminal vesicles can be recognised incorrectly as uterine horns.

Each locks follicle of this guinea pig is associated with an androgen-dependent gland that is sebaceous. These glands are numerous over the relative as well as may also be discovered across the anal area, where they have been called the caudal gland or “grease gland”. 9 , 23 The caudal gland is much more developed when you look at the boar and it is useful for fragrance marking (Fig 4). Boars usually rub or hit their rump against a area, together with secretions deposited act as a sexual attractant and to mark territory. 9 , 23

Figure gland that is 4.Caudalbig arrow) and perineum (little arrow) in a male guinea pig (Cavia porcellus). Supply: Uwe Gille via Wikimedia Commons. Click image to expand.

Puberty happens around 2 months of age into the guinea that is female or “sow”. 23 Peak reproduction is seen between 3-4 to 20 months and reproduction may carry on until 4-5 years. 19 , 23 Guinea pigs are seasonally breed and polyestrous year-round in captivity. 9 , 23 Sows are spontaneous ovulators, by having a cycle that is estrous 15-17 times (range 13-21 times). 19 Sows display distinct signs and symptoms of estrus and proestrus. During proestrus, sows are more active, chasing cage mates around, swaying their hindquarters, and creating a distinct guttural noise. Estrus lasts 6-11 hours, and with this right time the sow shows lordosis, curvature of this back with elevated sides, along with vulvar dilation. 23

The sow possesses a solitary set of inguinal mammary glands with an individual set of inguinal mammary nipples (Fig 5), but supernumerary nipples are typical. 9 , 19 , 22 when comparing to the boar, the sow’s nipples are much much much longer and much more prominent. 9

Figure 5.Both male and guinea that is female (Cavia porcellus) possess just one couple of inguinal mammary glands. Supply: Drury Reavill, DVM, DABVP (Avian Training), DACVP. Click image to expand.

Sows have paired ovaries and a bicornuate womb, composed of paired uterine horns, a quick uterine human anatomy, and just one os cervix (Fig 6, Fig 7). 5 , 9 , 23

Figure 6.View of just one uterine horn (arrow) in mature guinea pig (Cavia porcellus). Supply: Drury Reavill, DVM, DABVP (Avian training), DACVP Click image to enlarge.

Figure 7.Gross view for the uterine horns (little arrows) and the body (big arrow) in a guinea pig (Cavia porcellus). Supply: Drury Reavill, DVM, DABVP (Avian Training), DACVP. Click image to enlarge.

During anestrus and pregnancy, the genital opening in hystricomorph rodents is sealed having an epithelial membrane called the genital closing membrane layer. The membrane layer starts at estrus, Day 26 or 27 of gestation, and also at parturition in a lot of animals. 19 , 22 , 23 , 29 The sow includes a depression that is y-shaped perineal cells. The opening that is vulvar at the intersection regarding the branches in addition to anal area is based during the foot of the Y (Fig 8). 23

Figure 8.Y-shaped despair within the perineum of the guinea pig sow (Cavia porcellus), illustrating the vulva (white arrow) additionally the rectum (yellow arrow). Supply: Dorcas O’Rourke, DVM, MS, DACLAM. Click image to expand.

Copulation

whenever a female that is receptive introduced, the boar starts to purr and sway their posterior back and forth, while circling, and quite often cleaning up against the sow as well as spraying urine during the sow. In the event that female is unreceptive, aggressive male behavior can be seen such as for instance barbering hair in the female’s throat. 19 a female that is receptive let the male to sniff and lick her anogenital region. 6 , 11 , 19 She assumes the lordosis position and enables the male to mount her. Whether ejaculation happens or otherwise not, the male will perform vaginal grooming by dragging their perineum over the cage flooring. Meanwhile the doubles that are female and makes use of her lips to groom her genitals. 19 Mating often happens at nighttime. 8

Copulation is verified by the existence of a strong, rubbery deposit inside the vagina called the copulatory or genital plug, made up of a good mass of ejaculatory fluid. 23 there are numerous theories in the purpose of the copulatory plug in rodents, including semen storage, avoidance of semen leakage, advertising of semen transportation, and/or to stop later on fertilization by other men. 23 The copulatory plug falls out a long time after mating. 23

The typical guinea pig maternity persists 68 times, with a reported array of 59-72 times. 9 , 19 , 23 These times differ with stress, parity, and litter size. 23 Normal litter size is 2-4 pups with a variety of 1-13 pups. 23 clear stomach distension just isn’t seen until late gestation. 8