Promiscuous lamprey found to conduct 'sham matings'

February 06, 2017

Researchers at Hokkaido University have discovered that the nonparasitic lamprey Lethenteron kessleri mates repeatedly without releasing eggs, in a behavior termed "sham mating," suggesting the possibility that females choose their mates while engaged in promiscuous mating habits.

Many kinds of lampreys are promiscuous, with multiple numbers of males and females gathering at a spawning site. A single female will mate with multiple males dozens of times -- sometimes more than 100 times. Until now, however, it was unknown as to why female lampreys mated this way, which requires a lot of energy and increases the danger of predation.

Researchers Chitose Yamazaki of the Graduate School of Environmental Science and Itsuro Koizumi of the Faculty of Environmental Earth Science revealed that most mating events were not real; no eggs were released despite the apparent mating behavior, a behavior they termed "sham mating". They subsequently conducted their experiments based on the hypothesis that females choose a male to fertilize her eggs with.

Two experimental areas were set up with differing numbers of males. In Experiment Area A, one male and one female were placed together. In Experiment Area B, three males and one female were placed together. Following each spawning event, eggs were removed with an aspirator and counted. The researchers predicted the proportion of sham mating would be lower in A, as the female could not select her mate.

The experiment was repeated fifteen times using different females. Each female mated an average of 77 times (ranging from 20 to 196 times). On average, sham mating occurred 65 percent of the time (ranging from 35 to 90 percent). Their analysis showed sham mating increased with a larger number of males, while the number of eggs released on each occasion fell. It was also confirmed that males often release sperm in sham mating. These findings are consistent with the hypothesis that female lampreys choose their mates.

The researchers also investigated the influence of body size on sham mating. A male lamprey mates by wrapping its tail around the female's tail, and as previous research has shown, reproductive success varies depending on the male to female body-size ratio. Indeed, their experiments showed this ratio affected sham mating and the number of eggs released, suggesting that eggs cannot be released successfully when the body size ratio is not good.

"The study shows there is a possibility that, despite the presence of many males, females recognize individual males and actively control when they release their eggs; and that this depends on the body size, nest-building abilities, and other qualities of the male," says Dr. Koizumi, "The discovery of pre-breeding mate selection in highly promiscuous creatures is a new finding and of great interest."

Although futile mating behavior is common in birds and mammals, there have been almost no reports of it in organisms that fertilize eggs externally, as in the present study. "It is highly advantageous for females if they can choose their mate even when a large number of females and males gather at a single spawning site. Even though our results are only preliminary, further examination of the lampreys' breeding behavior should give us a deeper understanding of mate selection and the evolution of breeding systems," Dr. Koizumi adds.

Hokkaido University

Related Behavior Articles from Brightsurf:

Variety in the migratory behavior of blackcaps
The birds have variable migration strategies.

Fishing for a theory of emergent behavior
Researchers at the University of Tsukuba quantified the collective action of small schools of fish using information theory.

How synaptic changes translate to behavior changes
Learning changes behavior by altering many connections between brain cells in a variety of ways all at the same time, according to a study of sea slugs recently published in JNeurosci.

I won't have what he's having: The brain and socially motivated behavior
Monkeys devalue rewards when they anticipate that another monkey will get them instead.

Unlocking animal behavior through motion
Using physics to study different types of animal motion, such as burrowing worms or flying flocks, can reveal how animals behave in different settings.

AI to help monitor behavior
Algorithms based on artificial intelligence do better at supporting educational and clinical decision-making, according to a new study.

Increasing opportunities for sustainable behavior
To mitigate climate change and safeguard ecosystems, we need to make drastic changes in our consumption and transport behaviors.

Predicting a protein's behavior from its appearance
Researchers at EPFL have developed a new way to predict a protein's interactions with other proteins and biomolecules, and its biochemical activity, merely by observing its surface.

Spirituality affects the behavior of mortgagers
According to Olga Miroshnichenko, a Sc.D in Economics, and a Professor at the Department of Economics and Finance, Tyumen State University, morals affect the thinking of mortgage payers and help them avoid past due payments.

Asking if behavior can be changed on climate crisis
One of the more complex problems facing social psychologists today is whether any intervention can move people to change their behavior about climate change and protecting the environment for the sake of future generations.

Read More: Behavior News and Behavior Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to