INSTITUTO TECNOLOGICO DE CHASCOMUS
Unidad Ejecutora - UE
congresos y reuniones científicas
Description of pejerrey odontesthes bonariensis gonadal stages during spawning season in Cochicó shallow lake (Pampas region, Argentina). Relation with sex steroids plasma levels and temperature
DEL FRESNO P; MIRANDA LA; COLAUTTI DC; BERASAIN GE
Simposio; 11th International Symposium on Reproductive Physiology of Fish; 2018
INTRODUCTION In this study it was analyzedthe reproductive status of pejerrey (Odontesthesbonariensis) population during the spawning season in relation with plasmasex steroids levels and air temperature in Cochicó lake. This lake belongs to aSystem of Pampas lakes that extends between the parallels 36° 30 "and 37° 30" S and meridians 61 ° 00 "and 63 ° 30" W, not studied yet and surroundedby an intense agricultural activity. METHODS Pejerrey of both sexes werecaught using gill nets in Cochicó lake in the beginning of spawning season(August), peak of the spawning (October) and at the end of the spawning (December)of 2015. Fish were measured, and a piece of a gonad of each fish was dissectedand processed by histology techniques to assess gonadal stage. Also, bloodsamples were taken to measure plasma levels of testosterone (T) in males andestradiol (E2) in females by ELISA. Air temperature data was recordedby The Argentinean Meteorological Service (Coronel Suarez Weather Station,close to the lake). RESULTSAND DISCUSSION Pejerrey gonadaldevelopment, the gonadosomatic index (GSI) and the plasma levels of T and E2fluctuated in the same pattern and in relation with temperature variation.In August, practically all the females were found at cortical alveoli stage witha few, beginning the vitellogenesis. For males, 20% were at spermatogenesisstage and the rest were releasing sperm showing that males mature before the females.The air temperature (° C) in the day of sampling was: Max: 13.3, Mean:7.8, Min: 2.4; being permissive to pejerrey maturation. In October, thehighest values of IGS and sex steroids levels for both sexes were recorded. Ahigh proportion of ovulated females were found, and all males were spermiating.The temperature was: Max: 19,Mean: 12.9, Min: 6.8; showing that they were optimal for pejerrey spawning. In December,75% of the females were at vitellogenic stages (new reproductive cycle), 15%were ovulated and 10 % were arrested. For males, 80 % were spermiating and 20% werearrested. That day the temperature was: Max: 26.1, Mean: 18.3, Min: 10.6demonstrating the ending of reproduction. It is important to mentionthat in August sampling, 2 males with testis-ova were found. CONCLUSION These findings, confirmedthat temperature changes modulate pejerrey maturation and spawning. Theidentification of pejerrey with testis-ova it is a warning signal due to theuse of agrochemicals in this region.