Plesiochorus irwinorum n. sp. (Trematoda: Gorgoderidae) from the urinary bladder of the hawksbill turtle, Eretmochelys imbricata (Testudines: Cheloniidae), off the east coast of Australia.

Plesiochorus Looss, 1901 is a genus of Gorgoderidae infecting the urinary bladders of marine turtles globally. Currently, just two morphologically similar species are recognised, Plesiochorus cymbiformis (Rudolphi, 1819) Looss, 1901 and Plesiochorus elongatus Pigulevsky, 1953, which have been distinguished by molecular data and subtle morphological differences. Here we describe a new species, Plesiochorus irwinorum n. sp., infecting hawksbill turtles (Eretmochelys imbricata (L.)), which is primarily distinguished from the other two species of Plesiochorus on the basis of ITS2, cox1 and 28S sequence data. Morphometric data for specimens examined during this study overlap between P. cymbiformis and P. irwinorum n. sp. for every measured feature, rendering them functionally cryptic. However, principal components analysis clearly distinguishes the two species. Additionally, we report new specimens of P. cymbiformis, and provide new sequence data for specimens from Australian loggerhead (Caretta caretta (L.)) and hawksbill turtles. There is little understanding of the host-specificity or geographical distribution of the three species of Plesiochorus, and it remains possible that some of the previously reported sequences have been attributed to the wrong species.

Seasonal reproduction in wild and captive male koala (Phascolarctos cinereus) populations in south-east Queensland.

The effects of breeding season (late spring to early autumn) on south-east Queensland male koala fertility were examined to improve the efficacy of the AI procedure and to determine the practicality of using free-range animals as semen donors for a genome resource bank. Seasonal changes in male koala reproductive function were assessed in a wild free-range population (n = 14; obtained every 6 weeks from January to November 2005), a necropsied healthy wild population (n = 84; obtained monthly from September 2004 to August 2005) and a captive population (n = 7; obtained monthly from October 2005 to October 2006). Reproductive parameters investigated included bodyweight, coat score, sternal gland area and activity, testosterone secretion, reproductive anatomy volume and semen quality (before and after cryopreservation). Collectively, these findings show that reproduction in male koalas from south-east Queensland changes seasonally and that winter appears to be the optimal season in which to collect semen samples by electroejaculation. While it was possible to repeatedly collect semen from free-range koalas for future genetic management via potential storage in a genome resource bank, the survival of these spermatozoa after cryopreservation was poor and will require further improvement.

Control of the koala (Phascolarctos cinereus) anterior pituitary-gonadal axis with analogues of GnRH.

The aim of the present study was to determine whether analogues of gonadotrophin-releasing hormone (GnRH) could be used to both induce an acute testosterone response and suppress anterior pituitary function in male koalas, and induce a luteal phase in female koalas. Experiment 1 characterised the steroidogenic response of male koalas to administration of 30 microg (4.3 microg kg(-1)) natural-sequence GnRH. Intra-muscular injection of natural-sequence GnRH induced the release of LH and testosterone with peak concentrations at 30 min (3.7 +/- 1.9 ng mL(-1)) and 2 h (5.4 +/- 0.5 ng mL(-1)), respectively. In Experiment 2, a single injection of the GnRH antagonist acyline (100 microg (14.3 microg kg(-1)) or 500 microg (71.4 microg kg(-1))) did not influence the testosterone response to subsequent injections of natural-sequence GnRH. In Experiment 3, 4 microg (~0.67 microg kg(-1)) of the GnRH agonist buserelin induced a luteal phase in five female koalas based on a LH surge, secretion of progestogen, and a normal-length oestrous cycle. The findings have shown that (1) natural-sequence GnRH can be used to test gonadotroph cell function and determine the testosterone-secreting capacity of male koalas, (2) the GnRH antagonist, acyline, at the dose rates used, does not suppress the pituitary-testis axis in male koalas, and (3) the GnRH agonist, buserelin, induces a normal luteal phase in female koalas.