Prevalence of koala retrovirus in geographically diverse populations in Australia.

OBJECTIVE: To determine the prevalence of koala retrovirus (KoRV) in selected koala populations and to estimate proviral copy number in a subset of koalas. METHODS: Blood or tissue samples from 708 koalas in Queensland, New South Wales, Victoria and South Australia were tested for KoRV pol provirus gene using standard polymerase chain reaction (PCR), nested PCR and real-time PCR (qPCR). RESULTS: Prevalence of KoRV provirus-positive koalas was 100% in four regions of Queensland and New South Wales, 72.2% in mainland Victoria, 26.6% on four Victorian islands and 14.8% on Kangaroo Island, South Australia. Estimated proviral copy number per cell in four groups of koalas from Queensland and Victoria showed marked variation, ranging from a mean of 165 copies per cell in the Queensland group to 1.29 × 10(-4) copies per cell in one group of Victorian koalas. CONCLUSIONS: The higher prevalence of KoRV-positive koalas in the north of Australia and high proviral loads in Queensland koalas may indicate KoRV entered and became endogenous in the north and is spreading southwards. It is also possible there are genetic differences between koalas in northern and southern Australia that affect susceptibility to KoRV infection or endogenisation, or that environmental factors affecting transmission in northern states are absent or uncommon in southern regions. Although further studies are required, the finding of proviral copy numbers orders of magnitude lower than what would be expected for the presence of a single copy in every cell for many Victorian animals suggests that KoRV is not endogenous in these animals and likely reflects ongoing exogenous infection.

piggyBac-like elements in the pink bollworm, Pectinophora gossypiella.

A transgenic line of the pink bollworm, Pectinophora gossypiella, a key lepidopteran cotton pest, was generated previously using the piggyBac transposon IFP2 from Trichoplusia ni. Here we identified an endogenous piggyBac-like element (PLE), designated as PgPLE1, in the pink bollworm. A putatively intact copy of PgPLE1 (PgPLE1.1) presents the canonical features of PLE: inverted terminal repeats with three C/G residues at the extreme ends, inverted subterminal repeats, TTAA target site and an open reading frame encoding transposase with 68% similarity to IFP2. Vectorette PCR revealed large variation in the insertion sites of PgPLE1 amongst worldwide populations, indicating the potential mobility of PgPLE1. The PgPLE1 was undetectable in the genome of Pectinophora endema, implying the recent invasion of PgPLE1 after the divergence of these two closely related species.

Time relationships between oviposition, ovulation and egg formation in Khaki Campbell ducks.

1. Ten-month-old Khaki Campbell ducks were killed between 5 min and 15 h after oviposition. Time of oviposition and interval between eggs were recorded prior to killing. 2. Oviposition generally occurred between 04.00 and 06.00 h, 7 to 9 h after the onset of the dark period the previous day. Ninety-seven percent of eggs were laid by 07.00 h. 3. The mean +/- SD time interval between consecutive ovipositions was 24.0 +/- 0.3 h, with a range from 23.5 to 24.5 h. 4. It was estimated that ovulation occurred on average 10 min after oviposition, and the ovum spent 15 to 30 min in the infundibulum, 2.5 to 3 h in the magnum, 2 to 2.5 h in the isthmus and 18.6 h in the shell gland.