Laboratory culture and life-cycle experiments with the benthic amphipod Melita plumulosa (Zeidler).

In Australia, the collection of estuarine invertebrates from the field for whole-sediment toxicity tests is hindered because of temporal variability in their population densities and distributions. The present study aimed to develop culturing procedures for Melita plumulosa (Zeidler), an epibenthic and intertidal, deposit-feeding amphipod that is native to the southeastern coast of Australia. During a 28-d chronic exposure, the species was tested under a range of salinities (5-35 per thousand), temperatures (14-25 degrees C), and sediment particle sizes (sand to silt). Optimal culture conditions with respect to salinity, temperature, sediment particle size, feeding, and light regimes were determined. Compared to survival, amphipod growth and fertility were better predictors of optimal culture conditions. A life-history experiment was undertaken at the initial culture conditions of 22 degrees C and 35 per thousand salinity to establish the age at maturity, length of reproductive cycle, and life span for each sex. Under these test conditions, posthatch female M. plumulosa released their first offspring at seven weeks, after which each female produced an average of nine juveniles every 16 d. Male M. plumulosa had an average life span of eight months, whereas females had an average life span of 11 months. Optimal culturing conditions established in the present study have been incorporated into toxicity test procedures with this species and are being used to maximize reproductive output of this species in laboratory cultures to provide a supply of juveniles for routine use in whole-sediment toxicity tests