 Multifactorial sex determination occurs in numerous Neotropical species and involves both XY and ZW systems . Multifactorial systems involve rearrangements of sex chromosomes and autosomes . For example , the darter characine has a ZW multifactorial system where the female is determined by ZW1W2 and the male by ZZ . The wolf fish has a XY multifactorial system where females are determined by X1X1X2X2 and the male by X1X2Y . Some teleosts , such as zebrafish , have a polyfactorial system , where there are several genes which play a role in determining sex . Environment @-@ dependent sex determination has been documented in at least 70 species of teleost . Temperature is the main factor , but PH levels , growth rate , density and social environment may also play a role . For the Atlantic silverside , spawning in colder waters creates more females , while warmer waters create more males . 
