Life cycle studies of the earthworm Lumbricus friendi (Cognetti, 1904)

摘要

The objective of this work was to obtain data on aspects of the life cycle of Lumbricus friendi. Field-collected specimens from NW Spain were grown to maturity and maintained under controlled laboratory conditions. Thereafter experiments were undertaken to determine mode of reproduction, reproductive output, cocoon viability and development, and hatchling growth rate. Effects of density and temperature on growth were also examined. Plastic culture vessels containing a substrate of Kettering loam were incubated in temperature-controlled chambers, with dried horse manure as food. Paired, mature animals were sampled monthly over a period of 9 months for cocoon production. Cocoons were incubated on moist filter papers in Petri dishes. Results showed that at 15°C, individuals matured at a live mass of 3.5g. Zero cocoons were produced by virgin animals maintained in isolation, but recently matured, paired L. friendi produced 2.16 cocoons individual ~(-1)wk ~(-1). Cocoons were lemon-shaped with a smooth pale yellow-coloured outer surface and had a mean mass of 28mg. At 15°C, cocoons required 90 days to hatch and hatchability from the first 5 months of cocoon production was 85% successful. The majority of cocoons produced a single hatchling (twins recorded < 1%). Growth of hatchlings to maturity was achieved within a period of 5 months, with tubercula pubertatis developed after 3 months. Increased temperatures in the range of 5-15°C led to significantly increased growth rates, whereas increased earthworm density led to a significant decrease in rate of growth. These findings permit comparisons with more closely studied anecic species such as Lumbricus terrestris.