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ALTERNATE MATING PATTERNS - HERMAPHRODITISM-

ALTERNATE MATING PATTERNS - HERMAPHRODITISM-. Definition. An animal that can function and reproduce as both a male and female at some point in its life cycle. Hermaphrodite Mating Strategies. Females have a higher investment in offspring Therefore, should be choosy in mate choice

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ALTERNATE MATING PATTERNS - HERMAPHRODITISM-

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  1. ALTERNATE MATING PATTERNS - HERMAPHRODITISM-

  2. Definition An animal that can function and reproduce as both a male and female at some point in its life cycle

  3. Hermaphrodite Mating Strategies Females have a higher investment in offspring Therefore, should be choosy in mate choice and mate with only the ‘best’ male they can Male and female strategies conflict Males have a lower investment in offspring Therefore, should be promiscuous in mate choice and mate with as many females as possible

  4. Among hermaphrodites Female strategy Male strategy choosiness promiscuity + Combine in one animal

  5. Types of Hermaphroditism • Simultaneous - animal is male and female at the same time Examples - Bryozoans/ Barnacles

  6. Types of Hermaphroditism • Simultaneous - animal is male and female at the same time Examples - Molluscs

  7. Types of Hermaphroditism 2. Sequential - animal changes from one sex to another a. Protandrous Male Female a. Protogynous Female Male

  8. Types of Hermaphroditism 2. Sequential Examples - Stoplight parrotfish (Sparisoma) Terminal phase (mature male) Initial phase (immature male and mature female)

  9. Types of Hermaphroditism 2. Sequential Examples - Crepidula fornicata Males Intersex Female

  10. Models of Hermaphroditism Ghiselin - 1969 Low Density Model -adaptation to low densities or low mobility where the chance of meeting a conspecific is low -has the effect of doubling the effective population size

  11. Models of Hermaphroditism Ghiselin - 1969 Low Density Model Gonochoristic Hermaphroditic 10 animals – 5 potential mates 10 animals – 9 potential mates

  12. Low Density?

  13. Models of Hermaphroditism Ghiselin - 1969 2. Size advantage model -there are some reproductive functions best served by being one sex or the other -e.g. being a larger female allows the production of more eggs

  14. Models of Hermaphroditism Ghiselin - 1969 3. Gene dispersal model -in low density populations, having all the animals in one brood as the same sex prevents inbreeding

  15. Models of Hermaphroditism Comparison Sequential Simultaneous Low Density possible and likely possible (?) Size advantage doesn’t apply possible and likely prevents mating between siblings Gene dispersal possible (?)

  16. Charnov (1982) - Sex allocation 1.0 m + f = 1 Fitness as a female(f) 1.0 Fitness as a male (m) Hermaphroditism favoured Hermaphroditism not favoured

  17. When two hermaphrodites meet- What determines who will mate in which role? Or Is there a preferred role? ‘Preferred role’ depends on mode of mating and fertilization ‘Preferred role’ - the one that controls fertilization

  18. For simultaneous hermaphrodites: Both act as male and female -simultaneous & reciprocal sperm exchange -non-reciprocal sperm exchange = functional male ‘Female’ is preferred = functional female

  19. For simultaneous hermaphrodites: ‘Female’ is preferred -simultaneous & reciprocal sperm exchange -non-reciprocal sperm exchange

  20. For sequential hermaphrodites: functional male functional female Mating bouts 1,3,5, 7 … Mating bouts 2,4,6,8 … Male role is preferred

  21. For sequential hermaphrodites: Serranus baldwini Thalassoma bifasciatum Male role is preferred

  22. Leonard - Hermaphrodite’s dilemma Game theory approach modelled on Prisoner’s Dilemma Decisions available to two simultaneous hermaphrodites (assumes multiple bouts) 1. Offer to mate with a partner in both roles- cooperator role 2. Insist on mating in only the preferred sexual role - defector Payoffs: T- payoff to a defector whose partner cooperates R- payoff if both cooperate S- sucker’s payoff to a cooperator whose partner defects P - payoff for mutual defection R > P T > R >S

  23. Leonard - Hermaphrodite’s dilemma Player B Offer to mate in both roles Insist on preferred role Offer to mate in both roles S, T R, R Player A Insist on preferred role T, S P, P R > P T > R >S

  24. Leonard - Hermaphrodite’s dilemma Player B Offer to mate in both roles Insist on preferred role Offer to mate in both roles S = -Y R = X - Y Player A Insist on preferred role T = X P = 0 Assume X = eggs fertilized, Y = eggs given up T > R > P > S fertilizes eggs reciprocates no spawning eggs given up

  25. Hermaphrodite’s dilemma Do hermaphrodites behave this way?

  26. Hermaphrodite’s dilemma Do hermaphrodites behave this way? Ercolania felinus Time animal A animal B not copulating copulating

  27. Do hermaphrodites apportion their time and energy in different ways? (To take advantage of being male and female) Hypothesis: When mates are abundant, hermaphrodites should be more ‘male’ since sperm wastage is not a problem.

  28. Larger number of reproductively competent mates -waste of sperm not a problem Proportion of tissue to male Smaller number of reproductively competent mates -making eggs is more profitable Time in mating season OR number of available mates OR age/senesence

  29. Dendronotus frondosus

  30. Ovotestis Male tissue Female tissue

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