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 Males have a lower investment in offspring Therefore, should be promiscuous in mate choice and mate with as many females as possible 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

Among hermaphrodites Male strategyFemale strategy choosinesspromiscuity Combine in one animal +

Types of Hermaphroditism 1.Simultaneous - animal is male and female at the same time Examples - Bryozoans/ Barnacles

Types of Hermaphroditism 1.Simultaneous - animal is male and female at the same time Examples - Molluscs

Types of Hermaphroditism 2. Sequential - animal changes from one sex to another a. Protandrous MaleFemale a. Protogynous FemaleMale

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

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

Models of Hermaphroditism Ghiselin 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

Models of Hermaphroditism Ghiselin Low Density Model Gonochoristic 10 animals – 5 potential mates10 animals – 9 potential mates Hermaphroditic

Low Density?

Models of Hermaphroditism Ghiselin 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

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

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

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

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

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

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

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

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

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 T > R >S R > P

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

Leonard - Hermaphrodite’s dilemma Offer to mate in both roles Insist on preferred role Offer to mate in both roles Insist on preferred role Player A Player B P = 0 S = -Y R = X - Y T = X T > R >P >S Assume X = eggs fertilized, Y = eggs given up fertilizes eggs reciprocatesno spawningeggs given up

Hermaphrodite’s dilemma Do hermaphrodites behave this way?

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

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.

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

Dendronotus frondosus

Ovotestis Female tissue Male tissue