Hormonal correlations at transition from reproduction to molting in an annual life cycle of Humboldt penguins (Spheniscus humboldti)
To understand the hormonal mechanism behind a unique strategy of breeding and molting in Humboldt penguins, six pairs of captive Humboldt penguins kept in an outdoor open display pen were observed and blood collected weekly for a year. They all molted between the middle of June and the middle of August within 10 days except […]
Reproductive and thyroid hormone profiles in captive Western fence lizards (Sceloporus occidentalis) after a period of brumation
Abstract 10.1002/zoo.20159.abs Seasonal fluctuation in serum concentrations of sex steroid (testosterone [T] and 17β-estradiol [E2]) and thyroid (triiodothyronine [T3] and thyroxine [T4]) hormones was determined in captive Western fence lizards (Sceloporus occidentalis). Samples were collected from male and female breeding pairs weekly for a 4-month period after their emergence from artificial brumation. Circulating levels of […]
Seasonal cycles in testicular activity, gonadotropin, and thyroxine in the painted turtle, Chrysemys picta, under natural conditions
Plasma levels of testosterone (T), thyroxine (T4) and follicle-stimulating hormone (FSH) were measured in a field population of the painted turtle, Chrysemys picta, in Michigan. All three hormones showed pronounced seasonality; plasma luteinizing hormone (LH) remained nondetectable. Plasma T and FSH concentrations were highly correlated and exhibited biphasic cycles with peaks in spring and fall, […]
Endocrine Changes in Harbor Seal (Phoca vitulina) Pups Undergoing Rehabilitation
Rehabilitating pinniped pups are often admitted to care centers as neonates and generally lack maternal investment and are in poor body condition. Upon admittance to a rehabilitation facility, pups are typically fed a milk replacement formula via gavage, which is switched to frozen fish upon weaning. While rehabilitation has been successful in terms of recovery […]