Sexual reproduction brings with it its own set of behavioural implications, as individuals in a species must interact for the purpose of reproduction.
Parental investment refers to the input required by parents to ensure the survival of their offspring. This can be diverged even before the offspring are brought to life, in terms of the preparations required, whether biological or environmental. For example, the production and incubation of eggs requires more investment of energy for fewer offspring, while the production of sperm cells requires less energy for more cells.
In organisms that are immobile i.e. sessile, such as barnacles, sex poses a distinct problem.
Barnacles are attached to their rock, and cannot approach one another for sexual reproduction. A solution for this is the very long barnacle penis that extends quite some distance from its body in the hope of reaching a receptive barnacle nearby. Another solution is the casting of sperm into the sea for other barnacles to…