Search

The nomadic or dispersive movements of many Australian waterfowl in response to irregular environmental cues make satellite telemetry studies the only means by which these long-distance movements can be tracked in real time. Unlike some large-bodied soaring species, attaching satellite transmitters to small-bodied waterfowl (<1 kg) is not straightforward because ducks have high wing loadings and need to maintain active flapping to stay aloft. In the present paper, we detail one harness design and attachment method that enabled us to track grey teal (Anas gracilis) for up to 879 days. In addition, we detail rates of data loss, changes in data quality over time and variation in data quality from solar-powered satellite-tags deployed on ducks in Australia and Papua New Guinea. Up to 68% of all locational fixes have a nominal accuracy of less than 1 km, and satellite-tags deployed on wild birds can provide up to 22 location fixes per day and store enough energy during the day to run continuously throughout the night. [ABSTRACT FROM AUTHOR]

Pituitary adenylate cyclase-activating polypeptide (PACAP) releases LH and FSH from anterior pituitary cells. Although this effect is relatively weak, it has a strong sensitizing action on GnRH-induced gonadotropin secretion. Here we investigated the possibility that ovarian steroids, which are well-known modulators of LH secretion, interact with PACAP and GnRH in pituitary gonadotrophs. Rat pituitary cells were treated for 48 h with vehicle, 1 nmol/l estradiol, 1 nmol/l estradiol + 100 nmol/l progesterone or 48 h with 1 nmol/l estradiol and 4 h with 100 nmol/l progesterone. The cells were stimulated for 3 h with 1 nmol/l GnRH or 100 nmol/l PACAP. Estradiol treatment alone enhanced basal as well as GnRH- or PACAP-stimulated LH secretion. LH release was facilitated by additional short-term progesterone treatment. Long-term treatment with estradiol and progesterone led to reduced LH responses to GnRH and PACAP. Neither treatment paradigms affected cAMP production. However, estradiol treatment led to enhanced cAMP accumulation in quiescent or GnRH-stimulated cells. PACAP-induced increases of cAMP production were inhibited by estradiol treatment. After 7-h preincubation with 10 nmol/l PACAP, cells responded with enhanced LH secretion to GnRH stimulation. When steroid pretreatment was performed the responsiveness of gonadotrophs to low concentrations of GnRH was still increased. In contrast, at high concentrations of GnRH the sensitizing action of PACAP on agonist-induced LH secretion was lost in steroid-treated cells. There were no significant differences between the steroid treatment paradigms. It is concluded that estradiol but not progesterone acts as a modulator of adenylyl cyclase in gonadotrophs. The stimulatory effect of estradiol is thought to be involved in its sensitizing action on agonist-induced LH secretion. The inhibitory effect of estradiol on PACAP-stimulated adenylyl cyclase activities seems to be responsible for the loss of its action to sensitize LH secretory responses to GnRH.