Phylum Chaetognatha
Chaetognatha is the first phylum stated so far that almost all scientists agree is in Bilateria, having bilateral symmetry. Also, unlike the majority of Bilaterians, Chaetognatha and 3 other phyla are classified as Deuterostomes, rather than Protostomes. Deuterostomes are distinguished from Protostomes in many ways, but the major difference is that during their development, their anus develops before their mouth. Chaetognatha is a phylum of about 120 species, which are commonly known as arrow worms. Arrow worms are worms that can range from just a few millimeters to almost a half of a foot. Some arrow worms are clear and sea-through, while others are colored. Arrow worms are basically an inner body with a cover of cells covering the body. Similarly to insects, they are divided into 3 different body parts. Arrow worms, like many worms, are strictly marine. Most dwell on the seafloor. Arrow worms are carnivores and eat plankton. They have spines on their body, which is what they use for hunting. Unlike humans, when they swallow their food, it goes straight to an intestine that leads down to the anus. Arrow worms do not have a circulatory or respiratory system, which means no blood flow or gills. Instead, they have special ways they survive. Arrow worms are hermaphrodites and reproduce sexually. This happens when sperm and egg get released and travel through pores on one of the mate’s body. The pores lead to inside the body, which is where the fertilization takes place. Although most scientists place Chaetognaths in Deuterostomia, some classify them as Protostomes.
Symmetry: Bilateral
Species Number: 120
Classification:
Kingdom Animalia
Eumetazoa
Bilateria
Deuterostomia
Phylum Chaetognatha (arrow worms)
Class Sagittoidea (arrow worms)
Symmetry: Bilateral
Species Number: 120
Classification:
Kingdom Animalia
Eumetazoa
Bilateria
Deuterostomia
Phylum Chaetognatha (arrow worms)
Class Sagittoidea (arrow worms)