snails (Cornu aspersum)
The snail , along with many mollusks have an excretory organ called the nephidrium. This organ is necessary to maintain fluid balance within snails. The organ removes nitrogenous waste from the body of the snail. Urea is produced by the snail which contains very little small amounts of liquid. This is caused by the snails ability to resorb most of the water in their body. Even though they use the kidney to start the process of urea, the kidney is also used to process the blood and remove any unneeded toxins, minerals, and excess from the body.
clam (mercenaria)
The clam similar to snails also have a nephidrium. Inside the snail there are funnel-like tube filters which filters the blood of the clam, getting rid of unneeded toxins, and excess water. The clam also has two kidneys which move waste to the mantle cavity from the pericardial. The waste from the mantle cavity is washed away by water. This clam also produces ammonia, which is poisonous to humans.
squids (Loligo Duvaucelii)
The squid has two kidneys, this cleans the blood of any excess in it. This kidney is located around the heart. These kidneys are extended through to the liver, where it eventually is excreted in the funnel, which is a tube located behind the head of the squid. The squid also contains a sac, which allows the squid to squirt an ink like black substance at its prey. The use of excretion is to disorient the squids prey. The use of this is that when the squids prey is disoriented and confused it is much easier to kill and eat. On the reverse this also acts as a defense mechanism if the squid is the prey and wants to get away from the predator.