Central cardiovascular shunts in the perinatal marsupial.

BACKGROUND

Marsupials are born at an early stage of development after a short period of gestation. In this study the nature and timing of closure of the central cardiovascular shunts was investigated.

METHODS

Light and scanning electron microscopy were used to determine changes in central cardiovascular shunts in eight marsupial species with gestation periods of between 12.5 and 36.5 days and birth weights ranging from 12.5 mg to 740 mg. Laboratory mice with a birth weight of about 1,000 mg and a gestation period of 21 days were included for comparison.

RESULTS

Marsupials have a ductus arteriosus and an interatrial communication. The former closes rapidly after birth in the marsupial; however the interatrial communication is in the form of a fenestrated septum, which closes as a result of tissue proliferation over a period of days after birth. An additional central shunt, an interventricular foramen, was found to persist in three species for a short time after birth. In one species, the eastern native cat, Dasyurus viverrinus, which has a gestation period of about 19 days and low birth weight of about 12.5 mg, in addition to the two common shunts there was a large interventricular communication and septation of the outflow tract was incomplete.

CONCLUSION

In adapting from intra-uterine life, it seems that marsupials have adopted different, but equally effective strategies, with regard to the circulatory system.