A HISTORIC AND LATITUDINAL COMPARISON OF TESTES AND GONOPODIUM IN MALE WESTERN MOSQUITO FISH (Gambusia affinis)
Frangello, Michael A. III
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Mosquito fish (Gambusia affinis) are widespread and abundant due to anthropogenic introduction. In North America, G. affinis’ range extends from Louisiana, Texas, Alabama, and Mississippi to Cook County, Illinois, and as far west as New Mexico. These fish are typically introduced as baitfish or for pest control (e.g. mosquito populations) and quickly become established in the introduced environment. They are territorial toward native fish. With this behavior and their ability to reproduce at a rapid rate, G. affinis could easily disrupt a balanced ecosystem when introduced in small numbers. Gonadosomatic indices (GSI) and gonopodium length were calculated for each fish to further examine their reproductive biology. Testes were extracted for GSI calculation and to undergo histological examination to confirm GSI numbers. The aforementioned examinations were performed on mosquito fish from Louisiana (30 degrees N latitude), Oklahoma (35 degrees N), and Nebraska (40 degrees N) to determine any differences in primary and secondary sexual characteristics across both temporal and latitudinal gradients. Gonopodium length across latitudes showed no variation and GSI across latitudes were variant. There was a significant increase in GSI across time from the same site.