Thursday, September 8, 2011

Top 10 Unexpected Killers in Nature

Mother Nature is filled with formidable killing machines. Voracious flesh-eaters such as the thresher shark, the harpy eagle, the death stalker scorpion…and how about that rosy snail? Or the oyster mushroom? Some animals kill with teeth, claws and muscle…others kill with little more than mucus and patience.

10.  Planarian

terrestrial planarian
If you’ve taken college biology, you may be familiar with the humble planarian, a primitive animal consisting of little more than a thin sheet of tissue with a minimal nervous system. Most species inhabit water, but a few can be found slithering on dry land, and these nearly brainless creatures are sometimes carnivorous. Various land planaria live off a diet of earthworms, which they dissolve into mush with the secretion of a digestive enzyme.

9.  Katydids

Related to crickets and grasshoppers, katydids are usually tree-dwelling leaf eaters, best known for the male’s nocturnal mating calls. Australia’s Chlorobalius leucoviridis, however, modifies its mating call to sound like that of an entirely different insect, a male cicada, and devours any female cicada who falls for the ruse. Amazingly, the same katydid can recognize and imitate the call of any cicada it hears, including species not found in Australia.

8.  Fungi

While thousands of species of fungi feed parasitically on animals, only a couple hundred are truly predatory. The mycelia or “roots” of some fungi grow sticky, poisonous or even noose-like traps to ensnare microscopic prey, usually nematode worms. The most surprising example may be Pleurotus ostreatus, the commonly eaten “Oyster mushroom,” which kills nematodes to obtain more nitrogen.

7.  Sea Sponges

They may look like plants or fungi, but sea sponges are actually one of the simplest and most ancient forms of animal life. Most species feed on bacteria or other microscopic particles filtered from the surrounding water, but members of the genus Chondrocladia have adapted to a diet of tiny crustaceans, trapping them on their Velcro-like surface and draining them of nutrients. Appropriately, they inhabit such creepy locales as underwater caves and the deep-sea abyss.

6.  Corals

Corals appear rather similar to sponges on the outside, but are in fact colonies of polyps in the same phylum as anemones and jellyfish, armed with tiny stinging tentacles to trap planktonic food. Most coral prey is incredibly tiny, but even some of the world’s largest fish begin their lives as scarcely pinhead-sized larvae. Recently, certain mushroom corals have been found to catch the tentacles of larger passing jellyfish, and slowly slurp them in like a fork full of spaghetti.

5.  Snails

We like to think of slugs and snails or “Gastropods” as nature’s slowpokes, but many sea-dwelling species are full time hunters. Swimming species such as “sea angels” and “sea butterflies” can chase down prey at impressive speeds. Various nudibranchs feast on the tentacles of highly toxic jellyfish to “steal” the stinging cells for themselves, and the deadly cone snails can instantaneously paralyze fish (and sometimes humans) with their venomous barbs. Predatory gastropods are a bit rarer on land, but include such monsters as the “rosy wolf snail” – which preys exclusively on other snails – and the blind, subterranean “ghost slug,” which slurps up earthworms.

4.  Mussels

The “Bivalves” include the clams, oysters, scallops and other dual-shelled mollusks, which feed on plankton as they pump seawater in and out of tubular siphons. In just a few species, the siphon is modified into a large, roving “vacuum” to slurp in tiny animals, or even a muscular grabbing mechanism. Though they lack teeth, their gizzards may be lined with tough chitin to grind up their catch.

3.  Sea Squirts

sea squirt
Tunicates or “sea squirts” are yet another group of sea life which usually anchor in place and filter plankton, drawing water in through a lower “mouth” hole and out through an upper anus hole. In the deep sea abyss, however, plankton is almost nonexistent, so the abyssal species Megalodicopia hians has evolved a gaping “mouth” to fold over small passing animals. This was once believed to be the only carnivorous tunicate, but a second species was recently identified off the coast of Australia.

2.  Caterpillars

Of the roughly 120,000 known species of moth and butterfly, there are only a few dozen species whose caterpillars feed on anything other than plant matter. Most of the world’s few insect-eating caterpillars are inchworms native to Hawaii, which imitate twigs or leaves until their prey wanders too close. A few other species prey on the larvae of ants, using pheromones to disguise themselves as part of the colony. Another Hawaiian caterpillar feeds exclusively on snails, lodging its own cocoon under their shells to prevent their escape. Most morbid of all, however, is the bagworm Perisceptis carnivora of Panama. Like all other bagworms, this caterpillar hides itself in a protective casing built from the remains of its food, but unlike all other bagworms, this means it wears the severed, rotting limbs of various insects and spiders, the smell of which may serve to attract even more victims.

1.  Starfish

Believe it or not, a very large portion of “sea stars” are strictly predatory, though most only attack slower moving or unmoving prey such as snails, corals and sponges. More remarkable are those who manage to catch faster, more intelligent organisms such as shrimp and even fish; some stars simply hold out their serpentine arms like snares, waiting for something to swim too close. Others are covered in microscopic hooks and pincers to catch passing flesh like flypaper. Strangest of all are the “ambush stars,” which stand up on their arms to form a “tent” out of their broad, flat bodies. When an unsuspecting creature seeks shelter underneath, the star seals itself against the sea floor and extrudes its stomach, digesting the victim alive over the next few days.