 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 <unk> has a ZW multifactorial system where the female is determined by <unk> and the male by ZZ . The wolf fish has a XY multifactorial system where females are determined by <unk> and the male by <unk> . Some teleosts , such as zebrafish , have a <unk> 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 <unk> , spawning in colder waters creates more females , while warmer waters create more males . 
