The guinea pig (Cavia porcellus) is a favorite friend animal and a typical research model.

The guinea pig (Cavia porcellus) is a favorite friend animal and a typical research model.

Key Points

  • Intact guinea that is female are “sows” and intact males are “boars”.
  • Mature boars have actually distinct scrotal pouches and testes that are large.
  • Male guinea pigs have actually a few accessory intercourse glands, including big, paired seminal vesicles or vesicular glands, that could be recognised incorrectly as uterine horns.
  • Puberty does occur at more or less 2 months in females and between 2-3 months in men.
  • The pubic symphysis separates within the last times of maternity.
  • Separation of this symphysis that is pubic be inadequate 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 big fetal size.
  • Sows frequently give delivery to 2-4 big, precocial pups. Other rodent types generally speaking have actually big litters.
  • Pregnancy toxemia is definitely a cause that is important of mortality in guinea pigs. This disorder is oftentimes seen in primiparous, obese sows in belated gestation. The prognosis can be guarded. Minmise the chance of pregnancy toxemia by motivating workout, preventing obesity, and minimizing stress in the sow that is pregnant.
  • Unilateral or bilateral ovarian cysts are common, especially in older sows.
  • Ovariohysterectomy or ovariectomy is advised to stop the growth of ovarian cysts as well as other problems that are reproductive non-breeding friend sows.

Introduction

Guinea pigs are of help in reproductive studies since they share numerous traits that are reproductive humans (Fig 1). 26 Like people, guinea pigs have a very hemochorial placenta, for which maternal bloodstream will come in direct experience of the fetal chorion, in addition to comparable trophoblast invasion habits and comparable uterine vasculature. 20 , 23 , 26 The guinea pig’s gestation duration can certainly be split into trimesters, analogous into the human being condition. 26 needless to say, some options that come with 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 product reviews physiology and physiology associated with guinea pig reproductive tract and summarizes some clinically significant medical issues.

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

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

Boars are generally bigger than females, with both sexes having a solitary set of inguinal 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 days. 2 In the event that testes have never descended by 4 months of age, the guinea pig should be thought about cryptorchid. 9 The canals that are inguinal available for a lifetime. 9 , 19 to avoid herniation post-castration, numerous clinicians use a shut strategy or a modified open strategy, in which the tunica is roofed into the suture which is used to connect from the spermatic cord and vessels. 32

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

Clinical Suggestion: Although big, paired testes are unmistakeable 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 regarding the prepuce to partially extrude your penis. 23

The S-shaped penis comprises of the human body and glans. Guinea pigs have a penis that is os that will be found in the dorsal area of this whole duration of the glans. 9 , 19 Like other hystricomorph rodents, your penis comes with moment, saw-toothed white spurs arranged dorsolaterally in 2 synchronous lines through the urethral orifice to your glans. Additionally there is a sac that is intromittent the ventral surface for the glans penis. 9 During erection, the sac everts and two horny styles protrude. 5 , 9 , 23 the event among these 3-5 mm long projections is unknown. 9

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

Figure 3. Reproductive structure for 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 vesicles that are seminal 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 Tip: The big, paired seminal vesicles can be seen erroneously as uterine horns.

Each hair follicle of this guinea pig is related to an androgen-dependent gland that is sebaceous. These glands are numerous over the straight back and are also discovered all over rectum, where these are generally called the caudal gland or “grease gland”. 9 , 23 The caudal gland is more developed in the boar and it is useful for fragrance marking (Fig 4). Boars frequently rub or hit their rump against an area, in addition to secretions deposited act as a sexual attractant and to mark territory. 9 , 23

Figure 4.Caudal gland (big 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 within the guinea that is female or “sow”. 23 Peak reproduction adult friend is observed between 3-4 to 20 months and reproduction might carry on until 4-5 years. 19 , 23 Guinea pigs are seasonally polyestrous and breed year-round in captivity. 9 , 23 Sows are spontaneous ovulators, with an estrous period between 15-17 times (range 13-21 days). 19 Sows display distinct signs of estrus and proestrus. During proestrus, sows are more active, chasing cage mates around, swaying their hindquarters, and creating a definite sound that is guttural. Estrus lasts 6-11 hours, and with this time the sow shows lordosis, curvature for the 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), nevertheless supernumerary nipples are typical. 9 , 19 , 22 in comparison to the boar, the sow’s nipples are much much longer and much more prominent. 9

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

Sows have paired ovaries and a bicornuate uterus, composed of paired uterine horns, an uterine that is short, 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 expand.

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 expand.

The vaginal opening in hystricomorph rodents is sealed with an epithelial membrane called the vaginal closure membrane during anestrus and pregnancy. The membrane layer starts at estrus, Day 26 or 27 of gestation, and also at parturition in several pets. 19 , 22 , 23 , 29 The sow includes a depression that is y-shaped perineal cells. The vulvar opening lies at the intersection regarding the branches and also the anal area is situated during the root of the Y (Fig 8). 23

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

Copulation

Whenever a receptive feminine is introduced, the boar starts to purr and sway their posterior back and forth, while circling, and quite often brushing resistant to the sow and sometimes even spraying urine during the sow. In the event that female is unreceptive, aggressive male behavior can be observed such as for instance barbering hair regarding the female’s throat. 19 a female that is receptive permit the male to sniff and lick her anogenital area. 6 , 11 , 19 She assumes the lordosis place and enables a man to mount her. Whether ejaculation does occur or perhaps not, a man shall perform vaginal grooming by dragging his perineum over the cage flooring. Meanwhile the feminine doubles over and makes use of her lips to groom her genitals. 19 Mating often does occur at night. 8

Copulation is verified by the existence of a company, rubbery deposit within the vagina called the copulatory or plug that is vaginal made up of a good mass of ejaculatory fluid. 23 there are many theories from the purpose of the copulatory plug in rodents, including semen storage space, prevention of semen leakage, advertising of semen transportation, and/or to stop later on fertilization by other males. 23 The copulatory plug falls out a long time after mating. 23

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