Sperm or egg?

Hermaphroditic species face a fundamental question: How much energy should they expend on males and females? Over the course of evolution, planarians have found various answers to this question that are directly related to their mating behavior

Many plants and animals have both male and female reproductive organs

While the issue of sex assignment has long been the subject of plant research, relatively few studies have been done on hermaphrodites

In doing so, the researchers didn't just discover a solution

strange exercise

With water and damp places all over the world, planarian worms are known as simultaneous hermaphrodites - they are male and female at the same time

The many species of this genus usually mate with each other in a consensual game of give and take

two strategies

As the researchers report in the journal BMC Biology, mating behavior has a major impact on how a species evolves to devote more resources to male or female reproduction

"At first glance, this is a surprising finding," said Jeremias Brand, who is currently conducting research at the Max Planck Institute for Multidisciplinary Science.

In species that mate with each other, there are a number of mechanisms that reduce competition between sperm—for example, if sperm are replaced by competitors, or if sperm receptors influence which sperm are used for fertilization after mating with several partners

ability to self

So why do species that mate primarily subcutaneously invest more in females? Here, the researchers hypothesize based on another important observation: Population genetic analysis suggests that species that mate subcutaneously appear to be more self-promoting Fertilization

They do this by injecting sperm into the front of their body, from where it enters the egg

Interestingly, a similar relationship exists in plants—plants that self-pollinate frequently or exclusively spend more on their female reproductive organs

article title

Mating behavior and reproductive morphology predict macroevolution of sex allocation in hermaphroditic flatworms