A comparison of oogenesis under constant and fluctuating temperatures in Doctor fish, Garra rufa Heckel, 1843 (Teleostei: Cyprinidae)

Abstract

The process of oogenesis in "Doctor Fish", Garra rufa living in the pools of a hot-spring, of which water has a constant high temperature (about 35 °C) and in Topardiç Stream where water temperature shows seasonal fluctuation, has been compared. Five oocyte developmental stage, namely chromatin-nucleolus stage, peri-nucleolar stage, cortical alveolar stage, vitellogenic stage and maturation stage were identified for both populations. Although the pattern of oocyte development stages is the same in both populations, vitellogenesis is depressed in the hot-spring population, presumably due to high temperature and starvation. In addition, the occurrence of atretic oocytes in the ovary of the hot-spring females was higher than those of the population of Topardiç stream. Atretic oocytes were even present at the pre-spawning stage in the ovary of the hot-spring females. Gonosomatic index (GSI)(%) values of the hot-spring females were found lower than those in the Topardiç stream. Nevertheless, GSI% values of females from both localities found to be the highest in July.