The sea is filled with many mysterious creatures that serve a purpose for the environment, their own species or others. Today I will be examining two strange organisms, phoronids and nautilus, and comparing how they have adapted to the life in the sea.
Phoronids, or horseshoe worms, are part of the phylum Phoronida which is one of the smallest and least familiar phyla with only twelve or so living species. Phoronids are long and worm-shaped with a mouth surrounded with a ciliated feeding structure called lophophore.
They are nicknamed horseshoe worms because of the because the lophophore can sometimes be folded over into the shape of a horseshoe. They have a U-shaped digestive tract so the gut loops and ends close to the mouth instead of passing straight through the body like other annelids or wormlike organisms. They are found in all oceans and seas, except the polar seas, and are found from 70 meters or 400 meters of depth.
The adult horseshoe worms live in tubes which they make out of chitin which can be buried in the mud or can be resting on the surface.
Some could live in holes in rocks, sea shells, or cement piers that are lined with their secreted tubes. Phoronids are suspension eaters; they eat food particles in the water which are trapped in a stream of mucus, traveling through the tentacles until it reaches the oral ring. The food particles then draw into the mouth and into the digestive tract.
Next I will talk about the chambered nautilus.
They are part of the mollusk family, which are related to octopuses, squids, clams and snails but if we narrow it more down, it belongs to the cephalopods, meaning head foot because their tentacles are attached to the head. The nautilus is the only cephalopod that has a fully developed shell used for protection. It has more than 90 sucker-less tentacles that have grooves and ridges to catch prey and deliver it to a crushing parrot-like beak. They feed on crabs, shrimp and fish and scavenge on dead animals which is located by smell, since they do not have great eyesight like octopus. The spiraled shell of the nautilus is divided into chambers with it occupying the outermost chamber. A young nautilus begins life with only 4 chambers and then goes on to develop around 30. The inner chambers are filled with gas which helps the nautilus remain neutral buoyancy. The nautilus has undergone little change in more than 400 million years and appeared 250 million years before the dinosaurs. There used to be 10,000 different species but today only a few remain.
These two organisms have very different ways that they have adapted to life. For example, the phoronid makes a tube for themselves to live in, and usually only has their head out in order to eat. The nautilus, on the other hand, uses its shell to control the buoyancy which allows it to freely move up or down. Another difference is that there is no known body fossils of the horseshoe worm since their bodies are completely soft, but the nautilus is known as a “living fossil” since it has been around for millions of years. One similarity we might spot is the way they eat. They both use some kind of body part in order to move food into their mouth. For example the phoronid uses lophophores and the nautilus uses its tentacles. Another similarity is how they reproduce. Internal fertilization is present in both species and they both lay eggs, but another tiny difference is that some horseshoe worms can reproduce asexually.
I chose these two strange organisms because I was interested in learning more about them. The horseshoe worm looks very odd by just looking at it, which makes one wonder how it even functions. I was interested in learning more about what it eats, where its found and how it lives. Same thing goes for the nautilus. It’s part of the octopus family but it is way different looking and different functioning. I needed to know why it looks the way it does and what functions it has.