Influence of squid extracts on the triggering of secondary vitellogenesis in Penaeus vannamei

A series of five experiments were carried out to find an alternative to eyestalk ablation for inducing and controlling vitellogenesis in penaeid shrimps. Several extracts from squid were tested as supplements to a basal diet. Polar components of hydro-alcohol (ethanol/dicloromethane/water, 2:2:1:8) soluble and lipid squid fractions (Bligh & Dyer), when incorporated in formulated feed at low doses, trigger secondary vitellogenesis in 15-35 g female Penaeus vannamei, showing maturations of the same order of magnitude as the eyestalk-ablated controls. Achievement of vitellogenesis was estimated by a homologous ELISA-vitellogenin test. Even though the nature of the active molecules was not completely elucidated, the results obtained indicate that they may probably be steroid-like molecules of cephalopods, acting in a heterologous way.