The Funnel-web spider

This revolting creature lives only in Australia, and grows to be about 4 centimetres long. The males live for about a year—a tenth of the life span of the female—and basically spend their entire adult lives trying to feed or mate. The funnel-web spider has large fangs—so large the male has evolved a set of spurs on its second pair of legs to hold the female down during mating, thus preventing her from cracking open his skull with her fangs.

The male spider wanders around and likes to hide in dark places—like boots, beds or gardening pots. It has been known to survive underwater for upwards of a half-hour. It also attacks anything that moves, rearing up on its hind legs to get better leverage before stabbing its victim. Its poison is strong enough to kill a child in less than two hours without treatment.

The Candiru Fish

The Candiru fish is a tiny species of catfish that lives in the Amazon river and is the only vertebrate known to parasitize humans. The Candiru burrows inside the gills of larger fish, and unfurls sharp fins around its head, drawing blood and securing itself to the larger fish at the same time. It then drinks the blood, unhooks its fins and sinks to the bottom of the river to digest its meal.

Ah, but humans don’t have gills, I hear you say.

The Candiru can also taste urine in water and can follow the stream to the source. There the fish swims into the animal’s urethra, and spreads out its fins to cause bleeding. Unfortunately, once in, the fish can’t get back out and eventually suffocates, leaving the luckless individual in considerable pain and danger if it isn’t removed. The most straightforward (if extreme) solution is amputation, but apparently there is also this thing they can do by inserting this weird fruit/plant cocktail…you probably don’t want to know about.

Incidently, there is currently a movement to ban the import of these wonderful creatures as pets to the U.S., where some individual will inevitably dump them into lakes and rivers.