Question

flatworms are hermaphroditic ,having both sexes.In mating interactions ,they are known to have fights over which individual will be male.Why would being male be preferable to being female?

Answer 1

Flatworms are under Phylum platyhelminthes with

• classes Turbellaria ( free living flatworms)
• Trematoda (parasitic fluke) and  
• Cestoda (parasitic tapeworms).

Flatworms are ubiquitous in all continents and aquatic environments. They are dorsoventrally flattened , bilaterally symmetrical organisms, free living or parasitic with few marine being hermaphrodite.

PREFERENCE TO BE MALE THAN FEMALE:

• Flatworms are hermaphroditic with both male and female reproductive organs in same organism and can take up the parental role, based on who does the inseminating or being inseminated.
• While mating the two organisms glide over each other raising the front portion of their bodies and the everted male organ protrude out of their bodies.
• The flatworms while mating in form of a fight lasting for 30 minutes sometimes try to stab the other with their male organ and the first who inseminate the other wins. This is known as Fencing.
• During fencing the flatworms will be stabbed multiple times.
• The one that deposits sperm into the other will be emerged victorious completing the paternal obligation.
• The flatworm that got inseminated starts searching for food to making up the resources getting itself prepared for motherhood and taking the pain of raising the young and caring for eggs while the one which inseminate will be free of any responsibility.
• After bearing and producing the offspring, the mother flatworm then takes on another round of brutal fencing, so that it do not become a mother again by taking all the pain.

Hence flatworms prefer to be male rather than female.