title: Foetal age determination and development in elephants.
abstract: Elephants have the longest pregnancy of all mammals, with an average gestation of around 660 days, so their embryonic and foetal development have always been of special interest. Hitherto, it has only been possible to estimate foetal ages from theoretical calculations based on foetal mass. The recent development of sophisticated ultrasound procedures for elephants has now made it possible to monitor the growth and development of foetuses of known gestational age conceived in captivity from natural matings or artificial insemination. We have studied the early stages of pregnancy in 10 captive Asian and 9 African elephants by transrectal ultrasound. Measurements of foetal crown-rump lengths have provided the first accurate growth curves, which differ significantly from the previous theoretical estimates based on the cube root of foetal mass. We have used these to age 22 African elephant foetuses collected during culling operations. Pregnancy can be first recognized ultrasonographically by day 50, the presumptive yolk sac by about day 75 and the zonary placenta by about day 85. The trunk is first recognizable by days 85-90 and is distinct by day 104, while the first heartbeats are evident from around day 80. By combining ultrasonography and morphology, we have been able to produce the first reliable criteria for estimating gestational age and ontological development of Asian and African elephant foetuses during the first third of gestation.
authors.affiliation: Institute for Zoo and Wildlife Research, Alfred-Kowalke-Strasse 17 10315 Berlin, Germany. hildebrandt@izw-berlin.de
authors.forename: Thomas
authors.initials: T
authors.lastname: Hildebrandt
authors.forename: Barbara
authors.initials: B
authors.lastname: Drews
authors.forename: Ann P
authors.initials: AP
authors.lastname: Gaeth
authors.forename: Frank
authors.initials: F
authors.lastname: Goeritz
authors.forename: Robert
authors.initials: R
authors.lastname: Hermes
authors.forename: Dennis
authors.initials: D
authors.lastname: Schmitt
authors.forename: Charlie
authors.initials: C
authors.lastname: Gray
authors.forename: Peter
authors.initials: P
authors.lastname: Rich
authors.forename: Wolf Juergen
authors.initials: WJ
authors.lastname: Streich
authors.forename: Roger V
authors.initials: RV
authors.lastname: Short
authors.forename: Marilyn B
authors.initials: MB
authors.lastname: Renfree
mesh_terms: D000818:Animals; D001837:Body Weights and Measures; D004606:Elephants / Q000033:anatomy & histology / Q000196:embryology*; D005260:Female; D005865:Gestational Age; D008954:Models, Biological; D011247:Pregnancy; D011270:Pregnancy, Animal; D012044:Regression Analysis; D036761:Ultrasound, High-Intensity Focused, Transrectal