Effects of mother presence and photoperiod on egg production and hatching of two asexual lineages of Eucypris virens (Crustacea: Ostracoda)

Parental care is a source of maternal effects and the lack of genetic variation expected among clonal organisms makes them ideal material for investigating environmental mother effects. Using laboratory experiments at two photoperiods, 16:8 and 6:18 L:D, we evaluated the effect of mother’s age and mother presence/absence, on the production of resting eggs and on egg development time in two different clonal lineages of Eucypris virens from vernal pools from different latitudes (from Ventina, Italy and from Bramhope, UK). Mother presence/absence had a clear effect on egg hatching time, although, as expected, hatching was strongly influenced by photoperiod. Extended daylight, a reliable cue of incoming drought, induces dormancy. The effect was stronger in the Southern clone (only resting eggs were produced and the effect of mother presence on hatching could not be tested). The Northern clone laid both resting and non resting eggs and mother presence produced a small but significant delay in hatching. In short daylight, a reliable cue of incoming favourite environmental conditions, both clones produced both resting eggs and non-resting eggs. Mother presence/absence had a strong, opposite effect in the two clones: hatching was delayed by her presence in the Southern and by her absence in the Northern. We found no effect of mother age on proportion of resting eggs and on egg development time. We discuss our results in terms of environmental predictability and suggest the contrasting effect of mother presence in shorter daylight as a possible mechanism for the expression of a risk spreading strategy.