At my former blog, The Oyster’s Garter, I occasionally wrote an advice column inspired by Dr. Tatiana’s Sex Advice to All Creation and Dan Savage. I think it is time to get back to this glorious tradition.
Dear Deep Sea News,
I never thought I’d be writing to you – not least because it’s really hard to type with my radula – but I don’t know what else to do. I’m a predatory marine snail and I’ve always been FEMALE. I know that many of my molluscan cousins are hermaphrodites, but whelks like us (I’m from the illustrious Thais orbita species) don’t hold with such shenanigans. We believe that gluing a clump of egg sacs to a rock and abandoning it to its fate is a sacred act between a male and a female!
But because my family is so conservative, I don’t know who else to turn to with my very embarrassing problem. I seem to have sprouted a penis from the right side of my head. Of course, having a penis coming out of one’s head is perfectly normal – if you’re a male snail (or a hermaphrodite, if I must include them). I’ve spent the last few days hiding under a rock, afraid to show up in public with this hideous protrusion. We are dignified snails, not sex-changing perverts like those nasty slipper shells! How can I go back to normal?
Penis Problem in Perth
I can understand your distress. Female whelks aren’t supposed to grow penises – but unfortunately, you’ve run afoul of an antifoulant. The culprit is tributyltin (TBT), a highly toxic compound used to prevent growth on the bottoms of boats. TBT is certainly effective, but it has the known side effect of causing staid and dignified snails such as yourself to undergo a involuntary sex change. Your ovaries and such are still there – it’s just that a penis and perhaps a sperm duct has grown over them. This is called imposex.
I don’t want to embarrass you, so I’ll show photos of a different species of snail from Brazil. Below are photos of a normal male and two imposex females. Look on the bright side, PPP – at least you haven’t grown two penises, like the unfortunate snail (e) below.
Despite the recent news coverage from Perth, sex-changing snails is nothing new. Imposex in whelks was first reported in the UK in 1970 (PDF), and linked to TBT in 1981. TBT causes gastropod females to produce way too much testosterone, leading to your current predicament. (Oddly enough, TBT only affects gastropods, not other molluscs such as bivalves.)
In some gastropod species, imposex doesn’t seem to affect reproduction much. But in others, it causes total reproductive failure – the sperm duct can block the oviduct, making it impossible for the female to release her egg sacs and leading to internal rupture and a very unpleasant death. I can only hope that your species is relatively resistant, PPP.
Today, TBT is restricted, but not banned. In Australia, where you live, TBT is banned on vessels less than 25 meters (75 feet) in length. Vessels greater than 25 meters can apply for a permit to use TBT, but are limited to a maximum leaching rate of 5 μg cm−2 day. A 2003 study on the east coast of Australia found that imposex had decreased since the restrictions went into effect in 1989, but that hotspots remained, particularly within harbors and bays. It seems that Perth is one of those hotspots. Sorry.
Imposex is irreversible, so I’m afraid you’re stuck as you are. I hope that with time (and if you don’t die from a ruptured oviduct), you’ll come to appreciate and even enjoy your new body parts. But rest assured – if Perth has a TBT problem, there are other female snails in the same antifouling-coated boat. Have you considered forming a support group?
Cardoso, R., Caetano, C., & Cabrini, T. (2009). Biphallia in imposexed females of marine gastropods: new record for Nassarius vibex from Brazil Brazilian Journal of Biology, 69 (1) DOI: 10.1590/S1519-69842009000100030
Matthiessen, P., & Gibbs, P. (1998). Critical appraisal of the evidence for tributyltin-mediated endocrine disruption in mollusks Environmental Toxicology and Chemistry, 17 (1), 37-43 DOI: 10.1002/etc.5620170106