title: Prenatal development in fishers (Martes pennanti).
abstract: We evaluated and quantified prenatal growth of fishers (Martes pennanti) using ultrasonography. Seven females gave birth to 21 kits. The first identifiable embryonic structures were seen 42 d prepartum; these appeared to be unimplanted blastocysts or gestational sacs, which subsequently implanted in the uterine horns. Maternal and fetal heart rates were monitored from first detection to birth. Maternal heart rates did not differ among sampling periods, while fetal hearts rates increased from first detection to birth. Head and body differentiation, visible limbs and skeletal ossification were visible by 30, 23 and 21 d prepartum, respectively. Mean diameter of gestational sacs and crown-rump lengths were linearly related to gestational age (P < 0.001). Biparietal and body diameters were also linearly related to gestational age (P < 0.001) and correctly predicted parturition dates within 1-2 d.
authors.affiliation: Department of Wildlife Ecology, 5755 Nutting Hall, University of Maine, Orono, ME 04469-5755, USA. bert_frost@nps.gov
authors.forename: Herbert C
authors.initials: HC
authors.lastname: Frost
authors.forename: William B
authors.initials: WB
authors.lastname: Krohn
authors.forename: Edward A
authors.initials: EA
authors.lastname: Bezembluk
authors.forename: Ronald
authors.initials: R
authors.lastname: Lott
authors.forename: Charles R
authors.initials: CR
authors.lastname: Wallace
mesh_terms: D000818:Animals; D018568:Crown-Rump Length; D005260:Female; D047109:Fetal Development; D005865:Gestational Age; D006340:Heart Rate, Fetal; D045969:Mustelidae / Q000196:embryology*; D011247:Pregnancy; D016216:Ultrasonography, Prenatal / Q000662:veterinary