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BiologyInhabits shallow, mud-bottomed ditches, bays, salt marshes and other brackish-water environments; also crab burrows (Ref. 5723). Can withstand heavy pollution of fresh or salty waters and shares its biotope with Poecilia vivipara which is much more abundant (Ref. 35237). Usually found in water with low oxygen content (Ref. 7251). Either male or hermaphroditic, females don't seem to exist. Only about 5% of a population are born as males; after 3-4 years about 60% of the (self-fertilizing) hermaphrodites transform into secondary males by losing female structure and function. The proportion of males depends on the environmental temperature. Below 20°C, majority are males, above 25°C all are hermaphrodites (Ref. 35237). It is the only known naturally occurring, self-fertilizing vertebrate (Ref. 13056, 35237). Not a seasonal killifish. Is very difficult to maintain in aquarium (Ref. 27139).