5. Toxoplasma Gondii
Toxoplasma gondii is a common parasite the definitive host of which is the cat, but the parasite can be carried by all known mammals including humans. T. gondii infections have the ability to change the behavior of rats and mice, making them drawn to rather than fearful of the scent of cats. This effect is advantageous to the parasite, which will be able to sexually reproduce if its host is eaten by a cat. The infection is almost surgical in its precision, as it does not affect a rat’s other fears such as the fear of open spaces or of unfamiliar smelling food.
4. Euhaplorchis Californiensis
This parasite lives in the gut of shorebirds and produces eggs that are released in the bird’s stool which are spread into the salt-water marshes and ponds of southern California. Some of these eggs get swallowed up by snails and hatch into larva. Once these larvae are mature enough they leave the snail and swim out into the marshes eventually finding a killifish, entering through the gills and making its way along a nerve and into the brain cavity. Once in the brain cavity the parasite will cause the fish to come to the surface, swim in circles, jerk around and display its silvery underside in an attempt to attract a bird’s attention. This behavior makes the infected fish 30 times more likely to be caught and consumed by a bird. Once the fish is consumed, the parasite lives in the bird’s gut and the process can begin anew.
3. Costa Rican Parasitoid Wasp
Hymenoepimecis Argyraphaga
Hymenoepimecis argyraphaga is a Costa Rican parasitoid wasp whose host is the spider Plesiometa argyra. The adult female wasp temporarily paralyzes the spider and lays an egg on its abdomen. The egg hatches into a larva which sucks the spider’s blood through small holes, while the spider goes on about its normal web building and insect catching behavior for the next one to two weeks. When the larva is ready to pupate, it injects a chemical into the spider, causing it to build a web whose design is completely different from any it has ever made, and then to sit motionless in the middle of this web. Even if the larva is removed prior to the web-building process, the spider still engages in aberrant web-spinning. The wasp larva then molts, kills the spider with a poison and sucks its body dry before discarding it and building a cocoon that hangs from the middle of the web the spider has just built. The larva pupates inside the cocoon, and then emerges to mate and begin the cycle over again.
2. Glyptapanteles
Glyptapanteles is a genus of parasitoid wasps found in Central and North America. A female Glyptapanteles will lay her eggs (about 80 at a time) inside a young caterpillar host. After hatching the larvae will feed on the caterpillar’s succulent juicy insides until they are fully developed. They then emerge from the body, attach themselves to a branch or leaf, and form a cocoon. However, one or two larvae remain behind and manipulate the caterpillar to take up position near the cocoons, arch its back, and cease to move or feed. However, when the cocoons are disturbed, the caterpillar will thrash around violently. The pupae effectively have themselves a zombie-caterpillar bodyguard. The caterpillar remains this way until the cocoons hatch at which point it dies.
1. Sacculina
Sacculina is a genus of barnacles that parasitize crabs. Upon finding a host crab, the female Sacculina larva walks on it until it finds a joint. It then molts, injecting its soft body into the crab while its shell falls off. The Sacculina grows in the crab, emerging as a sac on the underside of the crab’s rear thorax, where the crab’s eggs would be incubated. When a female Sacculina is implanted in a male crab it will interfere with the crab’s hormonal balance. This sterilizes it and changes the bodily layout of the crab to resemble that of a female crab by widening and flattening its abdomen, among other things. The female Sacculina has even been known to cause the male crabs to perform mating gestures typical of female crabs. The male Sacculina looks for a female Sacculina adult on the underside of a crab. He then enters and fertilizes her eggs. The crab (male or female) then cares for the eggs as if they were its own, having been rendered infertile by the parasite. The natural hatching process of a crab consists of the female finding a high rock and grooming its brood pouch on its abdomen and releasing the fertilized eggs in the water through a bobbing motion. The female crab stirs the water with her claw to aid the flow of the water. When the hatching parasite eggs of the Sacculina are ready to emerge from the brood pouch of Sacculina, the crab performs a similar process. The crab shoots them out through pulses creating a large cloud of parasites. The crab then uses the familiar technique of stirring the water to aid in flow.
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