'Junk' science? For some crabs at least, size does matter
Private parts for public property
The so-called "private parts for public property" theory posited by the research tackles the question of how penis size relates to home size, for crabs anyway.
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Throes of passion
That risk is even more pronounced for certain types of hermit crabs, who "remodel" their shells by removing some internal structures.
The renovations make the shells more spacious and desirable, but also more difficult to cling onto, particularly in the throes of passion.
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To facilitate safe sex
"In theory, longer penises could enable individuals to reach out to sexual partners while simultaneously maintaining a safe grip on their property with the rest of their body, thus safeguarding property against thieves while having sex," Laidre wrote in the study in Royal Society Open Science.
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Size depends
If his theory was correct, he expected to find that crabs with the remodelled and most covetable shells would have the longest penises, while those with unmodified shells would have slightly shorter ones, and hermit crabs with no shells would be the least generously endowed of all.
He also wanted to rule out other possibilities, including that penis length was based on whether crabs were land or sea-based, or correlated with their overall body size.
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Trade-offs on the way
Crabs with unremodelled homes presented the next longest penises, while those who shed their shells as adults were found to have the shortest of all three types.
Further research could "explore such trade-offs by examining relative weapon and penis size in relation to private property value," Laidre wrote.
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