Which animal is the biggest asshole?

Any of these three:

Emerald Cockroach Wasp

It delivers an initial sting to a thoracic ganglion and injects venom to mildly and reversibly paralyze the front legs of its victim. Temporary loss of mobility in the roach facilitates the second venomous sting at a precise spot in the victims's head ganglia (brain), in the section that controls the escape reflex. As a result of this sting, the roach will first groom extensively, and then become sluggish and fail to show normal escape responses. In 2007 it was reported that the venom of the wasp blocks receptors for the neurotransmitter octopamine.

The wasp proceeds to chew off half of each of the roach's antennae. Researchers believe that the wasp chews off the antenna to replenish fluids or possibly to regulate the amount of venom because too much could kill and too little would let the victim recover before the larva has grown. The wasp, which is too small to carry the roach, then leads the victim to the wasp's burrow, by pulling one of the roach's antennae in a manner similar to a leash. Once they reach the burrow, the wasp lays a white egg, about 2 mm long, on the roach's abdomen. It then exits and proceeds to fill in the burrow entrance with pebbles, more to keep other predators out than to keep the roach in.

With its escape reflex disabled, the stung roach will simply rest in the burrow as the wasp's egg hatches after about three days. The hatched larva lives and feeds for 4–5 days on the roach, then chews its way into its abdomen and proceeds to live as an endoparasitoid. Over a period of eight days, the wasp larva consumes the roach's internal organs in an order which maximizes the likelihood that the roach will stay alive, at least until the larva enters the pupal stage and forms a cocoon inside the roach's body. Eventually the fully grown wasp emerges from the roach's body to begin its adult life. Development is faster in the warm season.

Sacculina

The female Sacculina larva finds a crab and walks on it until it finds a joint. It then molts into a form called a kentrogon, which injects its soft body into the crab while its shell falls off. The Sacculina grows in the crab, emerging as a sac, known as an externa, on the underside of the crab's rear thorax, where the crab's eggs would be incubated.

After this invasion of the Sacculina, the crab is now unable to perform the normal function of molting. This results in a loss of nutrition for the crab, and impairs its overall growth. The natural ability of regrowing a severed claw that is commonly used for defense purposes is therefore lost after the infestation of Sacculina.

The male Sacculina looks for a female Sacculina adult on the underside of a crab. He then implants himself into her body and starts fertilizing 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.

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 then forces the crab's body to release hormones, causing it to act like a female crab, even to the point of performing female mating dances.

Although all energy otherwise expended on reproduction is directed to the Sacculina, the crab develops a nurturing behavior typical of a female crab. 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

Zombie Snail worm

bonus video

The worm in its larval, miracidia stage, travels into the digestive system of a snail to develop into the next stage, sporocyst. The sporocyst grows into long tubes to form swollen "broodsacs" filled with tens to hundreds of cercariae. These broodsacs invade the snail's tentacles (preferring the left, when available), causing a brilliant transformation of the tentacles into a swollen, pulsating, colorful display that mimics the appearance of a caterpillar or grub. The broodsacs seem to pulsate in response to light intensity, and in total darkness do not pulse at all. The infection of the tentacles of the eyes seems to inhibit the perception of light intensity. Whereas uninfected snails seek dark areas to prevent predation, infected snails have a deficit in light detection, and are more likely to become exposed to predators, such as birds. In a study done in Poland, 53% of infected snails stayed in more open places longer, sat on higher vegetation, and stayed in better lit places than uninfected snails. Only 28% of the uninfected snails remained fully exposed for the duration of the observation period. Birds are the definitive hosts where the cercariae develop into adult distomes in the digestive system of the bird. These adult forms sexually reproduce and lay eggs that are released from the host via the bird's excretory system. These droppings are then consumed by snails to complete the life cycle of this parasitic worm.

The resulting behavior of the flatworm is a case of aggressive mimicry, where the parasite vaguely resembles the food of the host. This gains the parasite entry into the host's body; this is unlike most other cases of aggressive mimicry, in which only a part of the host resembles the target's prey and the mimic itself then eats the duped animal.

This life cycle is similar to other species of genus Leucochloridium.

/r/AskReddit Thread