Bird and Exotic Animal Hospital, Onderstepoort Veterinary Academic Hospital, South Africa
Reptiles have varied and complex reproductive strategies and in captivity they can develop a range of reproductive problems including different types of dystocia and prolapses of the cloaca, hemipenes and oviduct. The veterinary practitioner needs to understand the reproductive biology of the commonly seen reptile species in order to predict potential problems, to advise clients on measures to take to prevent breeding-related complications, and to effectively diagnose and treat dystocia and prolapses.
Sexual maturity in reptiles is governed by size, not age.1 Reptiles are either oviparous (egg laying), where the egg can be leathery (snakes, lizards) or rigid (crocodiles, tortoises, some geckos), viviparous (giving birth to live young [e.g., skinks]) or ovoviviparous (giving birth to live young, but when the majority of foetal sustenance is gained from the egg rather than through a placenta). In ovoviviparous species, the egg is retained in the female's body until birth.
The term "gravid" is used in place of "pregnant" when the animal is egg laying. Clutch size is extremely variable between species with a trade-off being made between foetal size and maturity and number of offspring.
Viviparity gives the young the best start but takes a greater toll on the mother and leads to very small litter sizes.
Parthenogenesis, where an unmated female produces viable young is known to occur in reptiles. Females can also store sperm from season to season and thus do not necessarily need to be mated before every clutch to produce young.
The majority of reptiles have a distinct breeding season, triggered by environmental stimuli such as hibernation, day length, humidity, barometric pressure, availability of suitable nesting sites etc. Lack of correct environmental stimuli is one reason for dystocia in female reptiles, where the development of young is begun but is inappropriately halted at some point during the cycle. Female reptiles also need to be in a good nutritional plane with sufficient reserves of energy and calcium to produce viable young. Blood calcium levels rise dramatically while the yolks are being formed.1
Most reptiles show no maternal care besides selecting an appropriate nesting site and concealing the eggs. Some pythons, however, will coil protectively around the eggs and can even thermoregulate the nest site to some degree by twitching their muscles during colder periods to warm the eggs up. Crocodilians and king cobras are known to guard nest sites and young.
Many species will eat infertile eggs to regain the energy lost in their production (a female reptile can lose up to 40% of her body mass during breeding).
The majority of male reptiles have paired copulatory organs known as hemipenes which are normally situated in the base of the tail just caudal to the cloaca. These organs engorge with sexual excitement and one is used to penetrate the cloaca of the female and deposit semen. A retractor muscle replaces the hemipene in its pouch.
The hemipenes have no function other than copulation and are not part of the urogenital system. Damage to or amputation of a single hemipene does not affect the breeding potential of the male reptile.
Certain families (Chelonians and Crocodilians) have a single copulatory organ known as a phallus which has a similar function to the hemipenes.
Hemipenal plugs may develop in the lumen of the invaginated hemipene in snakes and lizards. These plugs consist of inspissated smegma and can become fairly large. Unilateral or bilateral swelling of the hemipenal area, or the tip of a plug protruding from the cloaca may be seen. Removal of the plug is achieved via massage of the area and gentle traction on the tip of the plug. Eversion of the hemipene may occur with removal. Normally the hemipene will retract on its own but can be reduced with a lubricated cotton bud if needed.1
Occasionally, the hemipene will become abscessed and may need surgical drainage and antimicrobial therapy, preferably with culture and antibiogram.
Hemipenal prolapses may occur as a result of trauma, rough mating, metabolic bone disease, straining from constipation or parasites, infection, inflammation or neurological problems.1
Owners should be told to keep the prolapse moist and lubricated until arrival at the vet. Fresh, minimally oedematous prolapses can be reduced by using a lubricated cotton bud to invert the organ into its pouch just lateral to the midline, caudal to the cloaca. A single non-absorbable monofilament suture is placed across the entrance to the hemipenal pouch to prevent recurrences. The suture is removed in two weeks. Sedation may be beneficial to decrease muscular tone and straining during the procedure.1
Necrotic or unreducible prolapses can safely be amputated by placing a monofilament absorbable transfixing ligature at the base of the prolapsed hemipene. Amputation of a prolapsed phallus is more technically challenging due to the presence of the corpus cavernosum. The mucosa of the phallus should be closed with simple continuous sutures over the amputated stump.1
Dystocia in females can develop due to multiple underlying factors. Pre- and postovulatory forms occur. Dystocia is rare in wild reptiles.1
Obstructive dystocia is caused by malformed eggs, a narrow pelvis, oviductal torsion, tumors, or oviductal stricture.
Non-obstructive dystocia is caused by lack of a suitable nesting site, incorrect temperatures, dehydration, malnutrition, poor muscle tone (unfit), first-time breeder or by an infertile clutch (lack of proper hormonal stimulation?).1
In post-ovulatory egg stasis, mature eggs lying in the oviducts fail to be laid. In snakes typically some of the clutch is laid and the last several eggs retained.
Eggs are easily palpable in the snake. A dystocia should be suspected if more than 24 hours has passed since the last egg was laid.
Very caudally situated eggs may potentially be massaged out through the cloaca, but often the eggs are firmly adhered to the oviduct and massage simply results in the oviduct stretching and the egg not moving at all within the lumen. Oviductal trauma and rupture may thus occur.1
Percutaneous ovocentesis and collapse of overlarge eggs may allow the animal to pass them, but firmly adhered eggs more often than not need surgical removal.
Often multiple incisions in the oviducts and even in the skin are needed if a number of eggs are retained in the snake.
Dystocia is rare in ovoviviparous snakes but has been recorded. Surgery is similar to that in egg-laying species. As the period of gravidity is variable in reptiles, it can be difficult to identify dystocia in ovoviviparous snake species as often the entire clutch is retained. Ultrasound of the foetuses to evaluate viability may help with the diagnosis.
Some texts recommend the use of oxytocin in cases of postovulatory egg stasis, but this drug has a limited effect in reptiles, being more effective in chelonians and less so in lizards and snakes.1 Oxytocin is most effective if given within 48 h of initial oviposition.
In lizards, straining and discomfort may be seen with dystocia but more typically the animal has a markedly distended abdomen and becomes progressively anorexic. In chronic cases, severe weight loss and even collapse occur. The presence of a suitable nesting site is critical for oviposition in lizards as they will delay laying for prolonged periods should no nest be available.1
Medical management of dystocia is rarely rewarding and after a confirmation of the presence of eggs in a thin, anorexic female lizard, ovariosalpingectomy is the treatment of choice.
In preovulatory egg stasis, the development of eggs is halted before ovulation occurs. Ova develop in clusters on the ovaries and can become very large. Rupture of ova and subsequent yolk coelomitis is possible. These patients should be handled very gently to prevent iatrogenic rupture of the ova. Ovariectomy is the treatment of choice in these patients. Occasionally, offering a suitable nesting ground may stimulate the further development and ovulation of the ova, but waiting with the surgery is risky in compromised patients.
Ovariosalpingectomy is approached via a ventral paramedian incision to avoid the ventral abdominal vein. Ligaclips may be useful for ligation of ovarian ligaments. Both ovaries and both oviducts must be removed. Always carefully palpate caudally into the pelvis to ensure there is no egg lodged in the cloaca. The muscle layers are closed with a simple continuous line and the skin with horizontal mattress sutures. Monofilament absorbable suture material is recommended for all ligatures and sutures.
Postoperative care includes analgesia, assist feeding, and potentially antibiotic cover.
Straining to lay eggs can result in prolapses of the cloaca or oviduct. Simple cloacal prolapses can be reduced and a suture placed in the cloaca for a few days to prevent re-prolapse, but in cases of oviduct prolapse, ovariosalpingectomy is indicated.
Severe, chronic or necrotic cloacal prolapses may necessitate euthanasia if reduction is impossible. Hypocalcaemic animals seem particularly prone to prolapses and parenteral calcium treatment should be administered if indicated.
Reproductive problems in reptiles may seem daunting to the inexperienced clinician and while advanced or surgical cases may necessitate referral, simple problems can easily be treated at the first-opinion level. It is of paramount importance that clients understand the husbandry needs of their reptiles to minimise the occurrence of reproductive problems and the veterinarian can be of great help in this regard.
1. Mader DR. Reptile Medicine and Surgery. 2nd ed. St. Louis, MO: Elsevier Saunders; 2006: 376–390, 787–793, 862–865.