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November 2, 2019

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

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

Key Points

  • Intact guinea that is female are “sows” and intact males are “boars”.
  • Mature boars have actually distinct scrotal pouches and big testes.
  • 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 around 2 months in females and between 2-3 months in men.
  • The symphysis that is pubic within the last few times of maternity.
  • Separation associated with symphysis that is pubic be insufficient in sows bred after 7-8 months of age and dystocia may result in these people. Other prospective reasons for dystocia consist of obesity and fetal size that is large.

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  • 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 problem is frequently noticed in primiparous, overweight sows in belated gestation. The prognosis is oftentimes guarded. Reduce the chance of being pregnant toxemia by motivating workout, preventing obesity, and minimizing stress when you look at the sow that is pregnant.
  • Unilateral or bilateral cysts that are ovarian quite typical, especially in older sows.
  • Ovariohysterectomy or ovariectomy is preferred to stop the growth of ovarian cysts as well as other problems that are reproductive non-breeding friend sows.

Introduction

Guinea pigs are helpful in reproductive studies simply because they share numerous reproductive faculties with humans (Fig 1). 26 Like people, guinea pigs have a very hemochorial placenta, for which maternal bloodstream is available in direct experience of the fetal chorion, in addition to comparable trophoblast intrusion habits and comparable uterine vasculature. 20 , 23 , 26 The guinea pig’s gestation duration can be divided in to trimesters, analogous to your human being condition. 26 needless to say, some options that come with guinea pig reproductive anatomy and physiology are distributed to other users of purchase Rodentia, as well as other features are unique for this unique species. This short article product reviews structure and physiology for the guinea pig tract that is reproductive summarizes some clinically significant medical dilemmas.

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

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

Boars are bigger than females, with both sexes having a pair that is single of mammae. 5 Mature boars have big, paired testes, that are situated on either region of the perineum in distinct, superficial scrotal sacs (Fig 2). 5 , 9 , 23 The testicles are frequently completely descended in 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 start using a shut method or a modified available method, in which the tunica is roofed into the suture which is used to tie from the spermatic cable and vessels. 32

Figure image that is 2.Gross of testicle (arrow) in an adult boar (Cavia porcellus). The epididymis lies over the surface that is dorsolateral of testis. The end of this 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 bottom associated with 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 which will be discovered inside the dorsal area of this whole period of the glans. 9 , 19 Like many hystricomorph rodents, your penis even offers moment, saw-toothed spurs that are white dorsolaterally in 2 synchronous lines from the urethral orifice to your glans. There’s also a sac that is intromittent the ventral area associated with glans penis. 9 During erection, the sac everts and two horny styles protrude. 5 , 9 , 23 the big event among these 3-5 mm projections that are long unknown. 9

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

Figure 3. Reproductive anatomy 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 (I) epididymis. Picture credit: Drs. Craig Franklin and Cindy Besch-Williford. Click image to enlarge.

  • The big, clear, smooth vesicles that are seminal the biggest reproductive glands of this boar, measuring 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 enter the urethra by a set of ducts instantly caudodorsal towards the ductus deferens. 9 , 19 , 23 , 27

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

Each locks follicle associated with guinea pig is related to an androgen-dependent sebaceous gland. These glands are abundant across the relative as well as will also be discovered across the rectum, where they’ve 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 utilized for fragrance marking (Fig 4). Boars usually rub or push their rump against an area, while the 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 female guinea pig or “sow”. 23 Peak reproduction is seen between 3-4 to 20 months and reproduction may carry on until 4-5 years old. 19 , 23 Guinea pigs are seasonally polyestrous and breed year-round in captivity. 9 , 23 Sows are spontaneous ovulators, by having an estrous period between 15-17 days (range 13-21 times). 19 Sows exhibit distinct signs and symptoms of estrus and proestrus. During proestrus, sows are more active, chasing cage mates around, swaying their hindquarters, and creating a definite guttural noise. Estrus lasts 6-11 hours, and in this time the sow shows lordosis, curvature for the back with elevated sides, in addition to vulvar dilation. 23

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

Figure 5.Both male and guinea that is female (Cavia porcellus) have an individual 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, consisting 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). Source: Drury Reavill, DVM, DABVP (Avian training), DACVP Click image to expand.

Figure 7.Gross view regarding 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.

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, 26 or 27 of gestation, and at parturition in many animals day. 19 , 22 , 23 , 29 The sow possesses depression that is y-shaped perineal cells. The opening that is vulvar at the intersection associated with branches together with anal area is found in the foot of the Y (Fig 8). 23

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

Copulation

Each time a female that is receptive introduced, the boar starts to purr and sway their posterior back and forth, while circling, and quite often cleaning contrary to the sow and sometimes even spraying urine in the sow. In the event that female is unreceptive, aggressive male behavior might be seen such as for instance barbering hair regarding the neck that is female’s. 19 A receptive feminine will permit the male to sniff and lick her anogenital region. 6 , 11 , 19 She assumes the lordosis place and enables a man to mount her. Whether ejaculation happens or perhaps not, a man will perform vaginal grooming by dragging their perineum over the cage flooring. Meanwhile the feminine doubles over and makes use of her lips to groom her genitals. 19 Mating frequently happens at night. 8

Copulation is verified by the existence of a strong, rubbery deposit inside the vagina called the copulatory or plug that is vaginal made up of an excellent mass of ejaculatory fluid. 23 There are lots of theories regarding the purpose of the copulatory plug in rodents, including semen storage space, avoidance of sperm 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 guinea that is average pregnancy persists 68 times, with a reported array of 59-72 times. 9 , 19 , 23 These times differ with stress, parity, and size that is litter. 23 average size that is litter 2-4 pups with a selection of 1-13 pups. 23 clear stomach distension isn’t seen until late gestation. 8