Hermaphroditism and Sex Allocation

• Environmental sex determination is an adaptive mechanism wherein sex is determined post-conception in response to environmental cues
• In alligators, sex is determined by temperature - below 35 degrees gives males, above gives females
• In red deer, offspring sex is affected by maternal dominance and can produce above average sons and daughters
• It can be advantageous for sex to be under control of offspring rather than mother in circumstances of no maternal or parental care, and in fast-changing environments
• The sex of offspring can be predicted by the patch environment which effects reproductive fitness, whether mating happens outside the patch, and if there is control over the patch entered
• In Atlantic Silverside fish, offspring produced early in the breeding season are mostly female, whereas later are mostly male, and because there is no competition for reproduction it is more beneficial for females to be bigger to improve fertility
• Romanomermis culicivorax (parasite) sex is cued by degree of crowding in the host as it is an index of food availability, males born in crowded and females born in solitary
• To avoid the costs of being a small male, males can be sneaky or endure a sex change - such as anadromous and parr salmon
• 2 types of sequential hermaphroditism: protandry (male into female), protogyny (female into male)
• A sex change can be adaptive when size is important for males, to be territorial and defend females
• Sex changes happen when size/age affects fitness, when the population's sex ratio calls for it, and depending on the relative fitness as a male/female
• Changing sex isn't common due to genital morphology, its longevity and care required
• Simultaneous hermaphroditism is an organism possessing both sexes genitals and produces both types of gametes