Crown-of-thorns Starfish

The wandering spiders is a term used to refer to the spider family Ctenidae. Previously, the term referred only to the genus Phoneutria but now usually refers to the entire family Ctenidae. The members of the genus Phoneutria are highly aggressive and venomous nocturnal hunters, and are the only wandering spiders known to pose a serious danger to humans. However, the venom of some other members of this family is very poorly known, meaning that all larger Ctenids should be treated with caution. Ctenids have a distinctive longitudinal groove on the top-rear of their oval carapace[1] (some other spiders have a similar groove; e.g., Amaurobiidae).

Physical description and physiology
The sharp spines on the sides of the starfish's limbs resemble thorns and create a crown-like shape, giving the creature its name. The thorns are very sharp and are capable of piercing through standard wetsuits and other clothing.[citation needed] They are also venomous. When the crown-of-thorns feed, they release a chemical which is known to attract more sea stars to the area.

Venom
The crown-of-thorns produces a neurotoxin which can be released through its spines. Not only are the wounds themselves serious, but the neurotoxin can cause a sharp stinging pain that can last for hours, as well as nausea and vomiting. Frequently, the area around the wound turns a dark blue and begins to swell (edema), which may persist for weeks.The spine(s) themselves may break off and become embedded inside the skin. This can lead to infection, and increased toxicity. Some divers kill these predators by injecting the sea star's own stomach acid into each of their many legs.

Behavior
The crown-of-thorns is a corallivore, a carnivorous predator that preys on reef coral polyps. They climb onto reef structures, and then extrude their stomach onto the coral. This releases digestive enzymes that allow the sea star to absorb nutrients from the liquefied coral tissue. The crown-of-thorns also preys on brittle stars in a similar fashion.[citation needed]

They are very voracious predators. An individual starfish can consume up to 6 square metres (65 sq ft) of living coral reef per year.[1]

During times of food shortage the crown-of-thorns can survive on energy reserves for over six months.

Natural predators
Venomous, sharp spines cover nearly the entire surface of the crown-of-thorns. These natural defenses make it a very unattractive target for most other reef predators. In spite of this, the Giant Triton (a mollusc) and the harlequin shrimp attack and feed on crown-of-thorns starfish. Some large reef fish, particularly humphead wrasse, may also prey on the starfish.[2]

Sea star larvae are planktonic, so the major population control of the species comes from planktonic predation of junior species members.

In an interesting reversal, a large solitary coral polyp of the genus Pseudocorynactis has been observed attacking, and then wholly ingesting a crown-of-thorns starfish of similar size.[3]

Decline in predator populations (through overharvesting, habitat destruction) has also been offered as an explanation for increasing outbreaks of crown-of-thorns starfish.