Reversing the Food Chain
BY ALPER ÖZKAN (MSN/PhD I)
d_ozkan@ug.bilkent.edu.tr
You might be expecting a Christmas-related column for this week, but if truth be told, a game I had been looking forward to for the better half of this year recently came out, and I've been playing it exclusively for the last three days or so. Since finishing this game is clearly more important than paying attention to silly distractions like eating or sleeping, my health has deteriorated a slight bit, and I'm not exactly in a condition to carry out the research required to write on a topic I'm not very knowledgeable about. So, while I had in fact initially intended to write a column about Saint Nicholas, I haven't yet had the time to delve into “Acta Sanctorum” and the like (which would have taken some time, since it's 68 volumes long and took about 300 years to compile, not to mention the fact that the text is all in Latin and Greek), and you'll have to contend with carnivorous plants instead of old Saint Nick's adventures.
Thriving in bogs, swamps and other wetlands where the soil is severely lacking in nitrogen, carnivorous plants are required to capture live prey mainly to obtain this essential element -- and since their main prey items, insects and other small arthropods, just so happen to have chitinous exoskeletons and a high protein content, they couldn't ask for a better source of nitrogen. But despite their shared need for insect carcasses, these plants' capture methods run the full gamut: butterworts and sundews use sticky leaves designed to attract and trap small insects alighting on them while bladderworts draw small aquatic animals into vacuum chambers; the Venus fly-trap snaps at unwary flying insects while pitcher plants and some bromeliads drown their prey in rainwater-filled pits; corkscrew plants force subterranean protozoa to advance into a labyrinth terminating in a digestive chamber while the cobra lily lures flies into a maze filled with numerous false exits designed to wear them out until they start dropping. Plants are not the only producers of such elaborate traps, however: fungi and sponges, united with plants only in their sessile lifestyle, have developed equally bizarre methods, such as hanging small nematodes with organic nooses (in the case of nematophagous fungi) or trapping crustaceans in an array of small hooks (in the case of carnivorous sponges).
Such complex mechanisms do not evolve overnight. Thus, it is not surprising that there are many plants that can trap and kill insects but cannot directly digest them on their own, having not yet taken the final step that will conclusively define them as carnivorous plants. These often form symbiotic relationships with various bacteria, protozoa or insects that can digest what the plant has captured and transform it into a form that can be absorbed, essentially providing fertilizer in return for food. Many carnivorous plants also have similar associations with an astounding diversity of animals, including even mosquito larvae and a species of crab, which may either actively contribute to the digestive process or just enjoy the benefits that living in this environment can bring (such as a stable source of free food, provided that the organism in question can avoid being digested itself!). Pitcher plants, in particular, host their own local fauna within their traps, as you might remember from last year's column on the pitcher-dwelling frog Microhyla nepenthicola, or from the news of the recently discovered giant pitcher plant Nepenthes attenboroughii (the name honors the famed naturalist Sir David Attenborough, whose work you absolutely must see if you haven't yet). The latter (the plant, not Sir David) has pitchers that can reach about 30 cm in length, and there's a particular image where you can see those very pitchers crawling with mosquito larvae. I'm not including it here, in case you're reading this while eating.
But while the prey capture methods of carnivorous plants may seem cruel or unusual, there exist far more bizarre, and even sinister, mechanisms for processes as simple as pollination. Male flowers of the orchid genus Catasetum are capable of launching their pollen onto passing insects unfortunate enough to touch certain bristles, a property first noted by Charles Darwin (a renowned biologist, famous for his work on barnacles, plant movement and... I forget the third one. Some theory about evolution by natural something-or-other. Couldn't have been important). Worse yet, fly and bee orchids trick insects into thinking that the flowers are females of their species, leading to many a male fly, bee or wasp courting a flower for hours and covering himself in pollen, which he will later deposit on another flower in another failed courtship attempt. (It's rather like being in a stable relationship with your girlfriend for five years and proposing marriage to her, only to notice that your "girlfriend" is in fact a giant, vaguely human-shaped plant. Fortunately, orchids are not carnivorous, so at least there won't be a Little Shop of Horrors sort of scenario where your girlfriend Audrey II demands that you bring more humans for her to eat. Actually, never mind: a giant man-eating orchid trying to pass as a human girl and convincing her "boyfriend" to bring her victims would be awesome.) Combine this with the fact that virtually all orchids steal carbon from their symbiotic fungi, and what the entire group is named after, and the flowers don't seem so attractive anymore.
Anyhow, back to the game! (Er, I mean research! You know, in case my advisor is reading this.) Let's hope I don't follow the fate of Lee Seung Seop.