Influence des factuers externes sur l'activité reproductrice de l'hirudinée rhynchobdelle Piscicola geometra L.

The annual cycle of P. geometra breeding activity depends on light, temperature and nutrition. A photoperiod of about 12-12 delays the genital maturation and prevents the incidence of breeding behaviour. A high temperature speeds up the genital maturation and above a threshold ranging from 15 to 17.5 °C it prevents light from acting. Fasting inhibits egg laying because of its immediate action on the clitellar gland activity. It only acts on oogenesis later.