******So complex and utterly alien are the sex lives of seaweeds that my original blog post on the subject from April required some updating. With much thanks to Dr. Chopin for editing assistance, here’s a revisit to the scandalous sex life of a seaweed. ******
Lo-lee-ta: the tip of the tongue taking a trip of three steps down the palate to tap, at three, on the teeth. Lo. Lee. Ta.
One of the greatest opening lines of all time, this is the introduction to Vladimir Nabokov’s brilliant and disturbing Lolita. A long-held favorite of mine, I was utterly thrilled when seaweed guru Dr. Thierry Chopin referred to this modern classic as a model for understanding the complex and rather shocking sex life of a common edible seaweed.
I know what you may be thinking: seaweeds have sex lives?
Long recognized as a healthy and delicious food in Asia, seaweed farming is gaining traction in the west, including in Canada, Chile, Europe, and the USA. And it’s not just food that seaweed bestows; this video provides a great overview of the varied and everyday uses for seaweed.
Fast growing and photosynthetic, seaweeds don’t need to be fed like fish or shrimp; they just need sunlight and nutrient rich waters (which they help keep clean) to grow. They are being tested as natural ways to clean up effluent from fish farms (a key focus of Chopin’s work on Integrated Multi-Trophic Aquaculture), mitigate climate change, and produce healthy and abundant food. But in order for us to grow more seaweeds, we’ve got to know how they reproduce. We need to understand in intimate detail, the intimate acts of seaweed.
Talking with Chopin, it is clear that there is no one “sex life” of seaweeds. Instead, there is an endless fractal-like sexscape with every imaginable permutation: male-female couplings? They got that. Hermaphrodites? Sure. Asexual inter-generational phases? Check. Dwarf females? Yup. Self-perpetuating parthenogenetic gametes alternating with asexual spore germination…they’ve got that too. And, they can also claim, according to Chopin, “old male perverts” and temptress nymphets. Which brings us back to Lolita.
Deciphering the wild life cycles of these remarkable food factories has challenged many a phycologist (note: that’s not a typo for a shrink, but a scientist who studies algae). But, with the help of Chopin’s expertise and anything-but-prude French perspective (and a few kelp cocktails), I’m slowly wrapping my nori around it all. Here, for your summer reading pleasure, is the tantalizing tale of a seaweed named dulse (Palmaria palmata) though “Dolores” would be more appropriate. May your innocent strolls along the seaside never be quite the same again.
It all starts with the females, who, according to Chopin, are all young and extremely sexually precocious (seaweeds, like many plants, can have separate sexes, with individuals maturing as males or females). At just a few weeks old, female dulse have fully mature sexual organs called trichogynes which are slender tubes that reach out to receive the male gametes.
But, these blossoming beauties (what Chopin refers to as the “Lolitas”) are also microscopic in size, a tiny disc less than a millimeter in diameter. For decades scientists searched for the mature females in vain, only discovering them through some accidental lab experiments in the 1980s. The much larger mature males were more easily spotted in the field (but specialists in the lab still had to confirm identification), while the females remained a mystery, their small size but one contributing factor…
…the other reason was that they were rapidly buried alive by their own offspring. But, we’ll get to that.
First, it’s important to note that male dulse, like in some other species we know, don’t grow-up quite as quickly as their female counterparts. In fact, males the same age as mature females are but young, pre-pubescent boys, incapable of satisfying the females’ desires. Males of the previous generation, however, don’t have this problem. Having weathered a winter, so to speak, these older males are more than capable of giving the females what they want: a shower of seed. These older males readily release their tail-less, sperm-like spermatia into the water, relying on the currents to whisk them atop the thin crust of the female. If just one lucky spermatium makes contact with a female’s trichogyne, fertilization can progress.
But the product of this union is rather unusual. As Chopin explained it in Lolita terms: “So, say a female dulse, Dolores, receives a spermatium from an older male dulse, Humbert. When this happens, the fertilized egg develops into what looks like a mini Humbert, but is actually an asexual sporophyte that starts to sprout from Dolores’ thin surface.”
Chopin concludes: Precocious sexuality of little Palmaria females with their mother’s male siblings, who have finally reached maturity, condemns them to being buried by their offspring’s overgrowing holdfast on the same rocky spot they occupy, hence leading people to believe for a very long time that they never existed!
It’s a female-mates-with-mother’s-brother-bares-asexual-offspring-that-smothers-mother world out there for dulse. Figuring out this convoluted life cycle was an important step forward in our ability to cultivate this popular food—and learn how other seaweeds might be doing it.
Of course, there’s another bonus to understanding seaweed sex, besides the opportunities for food production, ecosystem restoration, and other advantages: whatever drives their sex could help our own sex drive, too. Something to consider next time you crunch through that sushi roll.