Question

9. You are studying cuttlefish and you observe that females mate primarily with larger males. You suspect that sexual selection may be influencing male size.

9a. Place a check (√) next to the pieces of information provided by your existing observations and place an X next to missing information you still need to be certain sexual selection is operating:

____Trait variation in males

____Trait variation in females

____Fitness differences in males

____Fitness differences in females

____Variation in the male trait confers a fitness benefit

____Variation in the female trait confers a fitness benefit

____Genetic basis for the male trait

____Genetic basis for the female trait

9b. Females may be choosing larger males because large size is a proxy for high __________________

Answer 1

9a. Trait variation in males  √ --> There are two sized males, and they show different traits of cuttlebone(provides buoyancy) , the small size males can show some female like characters so that large males cannot attack them.

Trait variation in females X --> not much variation is being reported

Fitness differences in males √ --> the larger males are more fit than smaller males. The smaller males can change their skin color to camouflage themselves from predators.

Fitness differences in females X --> All females have the same level of fitness to lay eggs.

Variation in the male trait confers a fitness benefit √ --> The larger male is superior and have special tentacle to inject sperm.

Variation in the female trait confers a fitness benefit X --> not much is reported

Genetic basis for the male trait X

Genetic basis for the female trait X

9b. Females may be choosing larger males because large size is a proxy for high chances of laying eggs. The larger males uses a special tentacles to put sperm into the sperm sac of females through mouth. The larger males do not leave the females until they lay eggs and to protect the eggs the female secretes ink on eggs to make them look like grapes. During this course the larger males fight against the threateners too.