This animation by Hadley Witt, a student in my invertebrate zoology course in 2013, describes the life cycle of Dracunculus. This parasitic worm is endemic to Africa, and is also known as guinea worm and the fiery serpent. While in the human host, this worm can grow up to one meter long, leading to extreme suffering. However, because it is easily preventable by filtering contaminated drinking water, this worm may be the next human pathogen to be eradicated.
Music: “Sonata in C minor for Harp” by Jan Ladislav Dussek (1760-1812), played by Hadley Witt
Riley Thompson made this animation about the fascinating lifecycle of narco babies.
We usually don’t think of babies that grow inside their mothers as parasites, but sometimes the lines get very blurry. This is especially true in Narcomedusae, a group of poorly known jellyfish found throughout the world’s oceans. Some species of Narcomedusae (affectionately called narcos by the people that study them) can grow inside their own mother, who provides nourishment and a safe environment for her. The narco babies can then leave their mother, find another jellyfish of an entirely different species, attach to its flesh, and thrive on the nourishment and safe environment it provides. The physiological interaction of baby and host is similar in both cases – the host provides, the baby takes. But in one case the host is providing for its own offspring, in the other it is providing for somebody else’s offspring.
Thanks to Rebecca Helm and Fabien Lombard for their help translating the wonderful paper on narco life cycles: Bouillon, J. (1987) Considérations sur le developpement des Narcomeduses et sur leur position phylogénétique. Indo-Malayan Zoology 4 : 189-278.
Here is a little plant that starts it’s life high up in the tree tops, where it can find more light than the dark understory of the rainforest. As it grows though, soon getting enough water becomes limiting factor, and the plant will drop a shoot to the ground.
Matt Ogburn, a graduate student in Erika Edwards’ lab at Brown University, describes this little plant, the strangler fig, and explains how it eventually grows to take over the whole host tree and strangle it to death.
These little pinkish crustaceans have set up house inside the muscular pulsating swimming parts of the colonial jellyfish, Nanomia. Out in the deep sea, there are few solid structures to call home, so living things will often take shelter in or on other animals.
Fish or bugs often hang around the tentacles of jellyfish because the jellies catch food there and are likely to drop pieces that can be salvaged. But these crustaceans are taking a different approach. They are living inside of swimming bells that are nowhere near where food is caught and eaten. These powerful little pods contract to push the colony through the water. The amphipods are likely to be taking refuge in the sturdy tissue, and feeding off the jellies flesh from the inside of the swimming bell.
Stefan Siebert, a post-doc in the Dunn lab, took this photograph of a Nanomia that he caught on a collecting trip in California. The gas-filled gland that keeps the colony afloat is hanging off the left side of the page. Three swimming bells for jet propulsion (with one amphipod crustacean in each) are seen in the middle. The part of the colony that feeds, reproduces, protects, and more, starts in the bottom right corner of the photograph. These amphipod crustaceans happen to be very similar to the ones we just made an animation about, that live on the fried egg jelly.
Here is a video from Casey Dunn of some other colonial jellyfish, to get a sense of how this close up photograph fits into the context of the whole colony, and to see how the swimming bells pulsate.
In the vast ocean, without walls and far from the floor, jellyfish can become drifting islands of activity. Creatures from far and wide will congregate on them to act out the ups and downs of life and death. Jellyfish have symbiotic relationships with living things of all sizes, from fish and shrimp that feed off them or off the pieces of food left between their tentacles, to single-celled photosynthesizing organisms that take shelter inside the cytoplasm of the jellyfish’s cells.
In this video, Trisha Towanda talks about one particular jellyfish, the fried egg jelly, and some of the other creatures that hang around it. There are moon jellies that the fried egg jelly eats. These moon jellies have little parasitic crustaceans on them called amphipods, which jump to the fried egg jelly while the moon jelly is being eaten. There are also crabs that ride around on the fried egg jelly, that are parasitic in their youth, but then grow to be helpful symbionts by eating off the little amphipods. This sort of coming of age story, where a symbiont’s relationship changes over its lifespan is an unusual one. Trisha put the pieces together by staring at them for hours and days and weeks when she was in Erik Thuessen‘s lab at Evergreen State College.
Many thanks to Trisha Towanda, who is now stationed in the Seibel lab at the University of Rhode Island. This video was edited and animated by Sophia Tintori, with an original score by local pop hero Amil Byleckie. It is released under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 license. Here is the paper Trisha wrote about the story.
When collecting bugs out in the field, it can be easy to get more than one bargained for. Many flies, beetles, and other mobile beasties such as the harvestman shown above (Megalopsalis sp. from New Zealand) find themselves regular host to hitchhikers of arachnid origin: the five orangish globules nestled among the bases of this unfortunate individual’s limbs are parasitic mites hunkered down for the long haul.
Indeed, many tens of thousands of mite species spend their early lives attached to a host, slowly drawing nutrition from its internal fluids until they become large enough to drop off wherever their hosts have carried them, where they begin life as free-living adults. However, these parasitic freeloaders aren’t the only kind of tenants one will find on harvestmen; there are also diverse sorts of more benign bedfellows who climb aboard with no appreciable harm to their unwitting ride.
One group of these tag-alongs is the pseudoscorpions – distant relatives of true scorpions, living secretive lives in forest soil and tree bark – which many would doubtless find abjectly terrifying… if they ever got larger than a few millimeters. Below, you can see a pseudoscorpion hanging for dear life onto the leg of another Megalopsalis. There are reports of pseudoscorpions waiting eagerly around a flower for a bee pollinator to grab onto, or clustering around the pupal bores of flies just before the airborne adult emerges. The traditional interpretation of this behavior suggests that climbing aboard larger, more mobile animals is an adaptation meant to transport these tinier critters to a wider range of habitats. Others, however, have suggested that perhaps pseudoscorpions simply grab onto whatever passes by them in the hopes that they might be able to eat it.
Strangely enough, even pseudoscorpions can bear hitchhikers, as the parasitic mites on this neobisiid I collected during field work in Alabama attest (gray bugs next to the greenish dots). It’s hard not to be reminded of the poet Jonathan Swift’s famous verses:
“The vermin only teaze and pinch
Their foes superior by an inch.
So, naturalists observe, a flea
Has smaller fleas that on him prey,
And these have smaller still to bite ’em,
And so proceed ad infinitum.”
First three photographs by Gonzalo Giribet. Last photograph by Christopher Laumer.
The leaves are starting to turn and the garden is getting thin as most fruits and vegetables are harvested. There are some fun surprises among the plants that remain, including this tobacco hornworm (Manduca sexta) above that was chewing on our tomatoes. It stayed in one spot, and over the course of two days more and more parasitoid wasp larvae, probably Cotesia congregata, emerged to spin their cocoons. When the mother wasp injected her eggs into the young caterpillar, she also injected a virus that had been multiplying in her ovaries. This virus continued to reproduce in its new host, castrating the caterpillar and preventing it from metamorphosing. This trick provides the the perfect feeding ground for the wasp babies.
Other organisms are also at their peak, and the woods are full of beautiful and delicious fungi. The specimen below is Laetiporus, also known as chicken of the woods because it is so common and quite eatable.
Photos by Casey Dunn. Thanks to Doug Morse, Alan Bergland, and Erika Edwards.