|This bobtail squid is very surprised at the absence of squid gynaecologists! Image credit: NOAA OKEANOS Explorer Program|
I first saw squid pimples in 2006, on a research cruise in the Sea of Cortez. The little bumps around the female’s mouth looked exactly like whiteheads, as if squid could get clogged pores. They even oozed white stuff when you squeezed, but it wasn’t pus.
It was sperm.
I was just beginning as a graduate student, learning to extract eggs and sperm from Humboldt squid in order to study fertilization and development—or, as I glibly described my thesis, “squid sex and babies.” Though technically I wasn’t studying sex, since in squid copulation is separate from fertilization. Females mate and store sperm for weeks or even months before laying eggs.
|We don't know how the female market squid who laid these egg cases selected which sperm was used to fertilize them. Image credit: "SquidEggCases-MontereryAquarium-April2-07" by User:Captmondo. Licensed under CC BY-SA 3.0 via Wikimedia Commons.|
In the ship’s laboratory, we were able to fertilize eggs with sperm from spermatophores, spermatangia, and spermathecae. But I’m pretty sure squid don’t lay their eggs in Petri dishes, so this doesn’t tell us a whole lot about natural reproduction. Which of the three sperm sources do females use to fertilize their eggs? Why bother with all the processing steps? Does it have to do with female selection or sperm competition?
No one knows, which is a bit surprising because spermatophores themselves have been studied quite intensively. Videos of spermatophore ejaculation and attachment can be found online, and I’ve written about more than one exciting new study. But this is the first time I’m writing about spermathecae, and it’s not because of recent research—it’s to popularize the lack of it.