Senescence in Acartia Tonsa (copepoda, Calanoida): Male’s Reproductive Performance Preliminary Results from a Southern Population

The effect of age on fertilization capacity and reproductive potential were examined in males from a laboratory population ofAcartia tonsaover their life time providing new empirical data for a foundational estuarine species. The reproductive functions spermatophore production (SPR), number of fertilized females (NFF), percentage of males that effectively fertilized females (M), egg production rate (EPR), and hatching success (EHS) were evaluated during the adult life of maleA. tonsa, from maturation until advanced age (38 d) under controlled laboratory conditions. The ageing process of the male was manifested occurred as a general decrease in most of the reproductive functions, but these followed specific patterns: SPR did not decay significantly with advanced male age, as it did happen with NFF, M and EPR; EHS increased at an intermediate age. Those changes were out of phase: while EPR declined already at intermediate age, NFF and M evidenced a decline at more advanced ages. Results suggest that reproductive senescence in copepod males involves the interaction of several mechanisms whose study will require comprehensive approaches.