Monthly abundance, size and maturity in a population of the ‘Australian flatworm’, Australoplana sanguinea alba

Collections of the 'Australian flatworm', Australoplana sanguinea alba have been made in one garden in Southport, UK three times a week. All specimens were collected into 70% alcohol, one jar per month (February 1995-December 1997). Previously, counts of flatworms had been made over several periods from March 1992. Fixed weight is 91.40 plus or minus 2.7% of live weight, and fixed length is 64.2 plus or minus 5.83% of extended live length. Highest numbers of flatworms were found between November and April with low numbers in July, August and September. These fluctuations may be related to soil moisture content. Relatively low rainfall in the winter of 1995-96 may have caused low numbers of flatworms the following winter. An analysis of monthly size-frequencies suggests that individuals increase in size mainly between October and April. Hatchlings are most abundant October to December. Eighty percent of the specimens were mature, but in October immature flatworms form the majority. Specimens as small as 9.5 mm long may be mature. Only three egg capsules have been seen over six years, but flatworms have been seen fissioning and fission may be the main method of reproduction in this population.