Natures wonders: surfing oceanic crabs mating habits (Introduction)

by David Turell , Wednesday, September 21, 2016, 20:13 (2983 days ago) @ David Turell

Some couples live by a loggerhead sea turtle's tail, and are monogamous; other live on debris and play the field:- https://www.newscientist.com/article/2106508-surfing-on-a-turtles-tail-makes-swinging-c... Oceanic crab, Planes minutus
Habitat: Turtles and floating debris in the north Atlantic
Surfing the world's oceans on the back of a turtle may sound like a life of luxury, but for a small crab it also means restricting itself to a single mate.
A species of small oceanic crab, Planes minutus often makes its home on the shells of loggerhead turtles. They tuck themselves into a tiny space above the turtle's tail and below the shell, just the right size for a pair of crabs - a male and a female living in a simple monogamous relationship.
But these crabs will also make their homes on floating debris, where they nestle among stalked barnacles, and often enjoy a more swinging, polyamorous lifestyle.-"Joseph Pfaller, at the University of Florida in Gainsville, wondered what influenced the crabs' choice of mating system. He found that the overall size of the turtle or the floating debris didn't matter - just the size of the refuge that the crabs occupied.-"If its home was small enough to easily defend against rivals, like on a turtle's tail or a small patch of barnacles, they would choose monogamy.
But once it got too large to effectively protect and there were more crabs around, the crabs would opt to play the field instead.-"Switching hosts to seek out new mating options is not an option - turtles and floating debris are few and far between and for an ocean-going crab P. minutus are pretty poor swimmers, says Pfaller.-"Miranda Dyson, from the UK's Open University, says this shows how the crabs adapt their mating strategy to whatever conditions they happen to grow up in.
“If you find yourself on a large refuge you stay because you can mate with lots of other crabs and the benefits associated with promiscuity outweigh the costs of confrontations with other crabs over mating opportunities,” she says. “Conversely, if you find yourself on a small refuge, there is no scope for promiscuity so the best thing to do is to stay put and defend your refuge.”
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Pfaller says the research shows how the ecological conditions in which an animal lives can dictate how it interacts with its own species, such as how it chooses to mate. And it shows that monogamy is a more common mating strategy than we thought.
“We tend to think of monogamy as something that birds and mammals do, but if the conditions are right, anything can be monogamous,” he says."-Comment: Life's organisms are opportunistic.