Post-implantation development of red-rumped agouti (Dasyprocta leporina Linnaeus, 1758)

- Embryos at 30 days were C-shape, heart prominence and CRL 10.75 ± 0.11 mm and at 35 days the liver bud was evident.
- At 45 days the conceptus assumes the form of a developing fetus and at 55 days, the cranial sutures noticeable.
- The sexual differentiation verified at 65th day; at 85 days, the body was covered with short hair.
- At 100 days, the phase was characterized as the phase of the mature fetus, and CRL was 164.3 ± 10.4 mm.
- The neonates had bristly hair, the eyes were open, and CRL was 179.1 ± 0.5 mm.

Fourteen pregnant agouti (Dasyprocta leporina Linnaeus, 1758) females at gestational ages of 30-100 days and two at gestational ages of 55-100 days, were studied, including 24 embryos/fetuses and two neonates (single offspring from two females). Females were euthanized and embryos/fetuses were examined, measured, and photographed. Embryos at 30 days post-copulation were “C-shaped,” with paddle-shaped limb buds and 10.75 ± 0.11 mm crown-rump length (CRL). In embryos at 35 days post-copulation, paddle-shaped forelimbs, fin-shaped pelvic limbs, and a liver bud were evident, with 15.6 ± 0.16 mm CRL; at 45 days, mouth and nostrils were evident, lower incisors were emerging, and tactile hairs could be seen near the nostrils, with 40.8 ± 0.4 mm CRL; at 55 days, cranial sutures had fused, digits were totally separated and claws formation was beginning, with 58.8 ± 0.1 mm CRL; at 65 days, the genital bud had differentiated, with 83 ± 0.08 mm CRL; at 85 days, the body was covered with short hair, with 127.7 ± 0.6 mm CRL; and at 100 days, the mature fetus had fully formed teeth and claws and an open external acoustic meatus, with 164.3 ± 10.4 mm CRL. Neonates had bristly hair and open eyes, with 179.1 ± 0.5 mm CRL. In conclusion, characteristics of the embryo/fetus during pregnancy can be used to estimate gestational age, and can be used as parameters during ultrasound examinations to help identify developmental pathologies and to test effects of nutrition, drugs, and pollution on pregnancy.

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