2005 BES Annual Meeting Presentation and Poster Abstracts
Differential growth of the invasive Amynthas hilgendorfi in the laboratory and field
Miriam Vishniac, Andrew Yang, Katalin Szlavecz
Abstract: Earthworm invasion has recently become a pertinent topic. In the Mid-Atlantic region Asian pheretimoids are of special importance, as they can dominate urban and suburban habitats during the growing season. Sparse data exist on the life history of these earthworms in their new environment. We have been monitoring a suburban population of Amynthas hilgendorfi, a common Asian invader, since early April, when the first juveniles emerged. The objective of the study was to obtain information on its size distribution over time, as well as to compare field and laboratory growth rates. About 100 animals were collected biweekly, weighed, and returned to the field. For the laboratory experiments, we collected 50 Amynthas from the same backyard and kept them individually in plastic containers. Contrary to our expectations, the laboratory population did not grow better than the field population. Mortality rates were also high in the laboratory. It is not clear why Amynthas is difficult to keep in the lab. While average live weight increased over time in the field population, so did variance. We postulate two possible explanations: 1) small juveniles were continuously emerging or 2) individuals were growing differentially.