Xiphinema Americanum - Life Cycle

Life Cycle

Identifying Xiphinema americanum as a separate species has been a difficult task because of overlapping morphological aspects; however, differences in the life cycles of X. americanum may differentiate it from other species. Findings may also suggest that two subgroups of X. americanum should be made due to the finding of either 3 or 4 juvenile stages. The eggs of X. americanum are laid directly into the soil in water films, and are not associated with an egg mass. No molt occurs within the egg, which means that the first stage juvenile is the stage that enters the soil. Before becoming sexually mature adults, the X. americanum nematodes undergo three to four juvenile stages with a molt occurring between each.

Measurements of the functional and replacement odontostyles allows for the determination of the current stage in development. Compounding the issue of determining the life cycle of X. americanum is their difficulty with being grown in culture or greenhouse conditions. It has been suggested that this is due to X. americanum's sensitivity to moisture tension, temperature fluctuation, physical handling, or oxygen deprivation.

Field evidence taken over a 2 year observation period indicates that X. americanum are most likely k-selected; they most likely have a long life span and a low reproduction rate. Unpublished results have shown greenhouse observations of X. americanum to develop from egg to adult in 7 months. Other results have suggested that X. americanum can live as long as 3-5 years.

Reproduction by fertilization from a male is rare if not nonexistent due to the lack of male X. americanum individuals, and therefore females reproduce parthogenetically. All of the stages of X. americanum occur in the soil, with no particular stage as an important survival stage. In places with low winter temperatures, however, the egg is the primary survival structure.