Monitoring of the Reproductive Cycle in Captive-Bred Female Boa constrictor: Preliminary Ultrasound Observations

Abstract

The Boa constrictor is one of the most common reptiles bred in captivity. To achieve a successful breeding season, thorough knowledge of the females’ reproductive activity is necessary. In this regard, information on the Boa constrictor is still rather scarce. The aim of the present study was to monitor the ovarian activity and the embryonic development of boas by ultrasound. We performed brief scans on thirty non-anaesthetized snakes using a portable ultrasound system and a 7.5–10 MHz linear array transducer (Esaote MyLab™ Classic). Ultrasound features, dimensions, and echogenicity of the preovulatory and postovulatory follicles were determined. As gestation progresses, the postovulatory follicle size increases, and the embryonic silhouette becomes increasingly recognizable. During the second month after ovulation, by using color Doppler, early embryos’ heart activity could be evaluated. It is possible to highlight vascular connections between the mother and the membrane covering the embryonic structures. Ultrasound also allows one to identify follicular regression or slugs (nonfertilized eggs) early. The present study suggests that ultrasound could be an excellent noninvasive technique to evaluate the reproductive activity of Boa constrictor, allowing us to precisely identify the correct time for mating, monitor embryo development and viability, and allow the early diagnosis of follicular regression.

Ultrasound Description of Follicular Development in the Louisiana Pinesnake (Pituophis ruthveni, Stull 1929)

“…Although the use of ultrasound has become more common to monitor reproductive status by commercial and private snake breeders there are still limited scientific references using ultrasound to detail follicular cycle of oviparous snakes [ 16 , 20 , 21 ] and no descriptions of follicular cycles of any endangered snake in a wildlife recovery program. This is the first detailed report of the entire reproductive cycle and follicular morphology throughout maturation of any endangered snake and for the Louisiana pinesnake specifically.…”

“…One of the major challenges in developing captive successful breeding programs and assisted reproductive technologies, such as artificial insemination, is the lack of detailed knowledge of species-specific reproductive biology; which is particularly lacking for endangered reptiles. In this paper we describe in detail the follicular morphology, ovarian cycle, and reproductive anatomy of the female Louisiana pinesnake ( Pituophis ruthveni ) which produces significantly larger eggs than other North American colubrids (Reichling 1990) and previously described oviparous snakes [ 16 , 20 , 21 ] Follicle descriptions of reptiles have been traditionally divided into two categories: preovulatory (previtollogenic and vitellogenic) and post ovulatory, using season, mating, or fetal development to distinguish between pre and post ovulation development [ 13 , 14 , 16 , 21 ]. Here, using ultrasonography, we present a detailed classification of 7 follicular development stages within these categories from previtellogenic to shelled eggs for the Louisiana pinesnake with the aim of improving our captive breeding program by developing markers of fertility.…”

“…Follicles were imaged ventrally in both longitudinal and transverse plane. Width (ventral to dorsal) and length (cranial to caudal) measurements for longitudinal and width (ventral to dorsal) and length (right to left) measurements on transverse plane of follicles were recorded for each female, and follicles were assigned to development categories based on soft tissue echogenicity and previous reptile and snake ultrasound findings [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ].…”

“…However, fine-scale assessment of follicular morphology and egg development throughout the reproductive cycle requires frequent serial assessments that can be more accurately and safely performed using ultrasonography. Here, we propose to characterize the reproductive cycle of captive Louisiana pinesnakes using ultrasonography [ 13 , 14 ] to describe size and appearance shifts of maturing follicles and developing post ovulated eggs throughout the captive breeding season and use previously described soft tissue echogenicity descriptions of follicle stages for other snakes [ 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ] to develop markers of maturation, ovulation, fertility, and atresia for the Louisiana pinesnake. Louisiana pinesnake oviposits eggs that are 2 times larger than other species previously evaluated throughout the reproductive cycle, therefore, we expected the relatively large size of eggs to drive differences in markers of ovulation and fertility for this oviparous species [ 14 , 15 ].…”

>b<Determinação do ciclo reprodutivo da jararaca do norte (>i<Bothrops Atrox>/i< - Linnaeus 1758) através de dosagens hormonais e análise ultrassonográfica das gônadas>/b<

“…Ocorre uma concentração maior em espécies não peçonhentas gigantes, que estão entre as mais comumente presentes na criação em cativeiro. O acompanhamento do ciclo reprodutivo da jiboia (Boa constrictor) e outros boídeos neotropicais como a sucuri (Eunectes murinus), cobra-veadeira (Corallus hortulanus) e jiboia arco-íris (Epicrates cenchria) foi realizado utilizando unicamente acompanhamento de imagens ultrassonográficas(BERTOCCHI et al, 2021;GARCIA;ALMEIDA-SANTOS, 2021).O uso de equipamento ultrassonográfico portátil possibilita estudos de ecologia do desenvolvimento e reprodutiva in situ, tais como o realizado em uma população de cascavel do deserto de Sonora (Crotalus atrox), a qual foi acompanhada com a associação do uso de radiotelemetria (TAYLOR;DENARDO, 2005); e com duas populações simpátricas de Tamnophis sirtalis e É importante considerar técnicas minimamente invasivas para obtenção de amostras para dosagens hormonais, com o intuito de causar mínimo stress ao animal, quando se trata de acompanhamento contínuo. Para isso são utilizadas técnicas de obtenção de amostras a partir de análise fecal, onde são obtidos metabolitos de hormônios sexuais.…”