Priapulids have a shape that gives them names ranging from penis worm to cactus worm.
Have you seen this Penis Worm? The Priapulid
Priapulid worms are marine invertebrates grouped under the phylum Priapulida. These marine worms are also known as cactus worms. They are found in the benthic (bottom layer) of the ocean and live in burrows.
This worm does not have a circulatory system and the blood corpuscles are found in the coelomic fluid (body fluid). They measure about 0.5 mm to 200 mm. The common name “penis worms” was originally coined because the proboscis of this worm resembled the human penis and its extensible nature. It actually resembles a cactus and thus it is now known as the cactus worm, though it is a aquatic/marine organism.
The excretory and reproductive systems of priapulids are integrated and they are the simplest animals to have such an integrated system.