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Phylum Hemichordata
This phylum is made up of marine deuterostome creatures. They are sometimes referred to as the Echinodermata's sister group. Phylum Hemichordata is a small phylum with only 100 recognized species and animals that resemble worms. Some species live alone, while others live in colonies. Hemichordata was previously classified as a sub-phylum of the Chordata phylum. However, because these species lack a post-anal tail or even the notochord, which is a distinguishing trait of chordates, they are now classified as a different phylum under non-Chordata.
Hemichordates, on the other hand, have a primitive structure comparable to the notochord in the collar region. This phylum is made up of a tiny group of worm-like marine organisms that are organized at the organ-system level.This phylum is made up of marine deuterostome creatures. They are sometimes referred to as the Echinodermata's sister group. Hemichordatesare bilaterally symmetrical and triploblastic animals.The body is divisible into proboscis, collar, and trunk.Simple, open, and well-developed circulatory system is present. The alimentary canal is a straight, complete, or U-shaped tube.Excretion by a single glomerulus situated in the proboscis.Reproduction is mainly sexual. Sexes are usually separate.External fertilization takes place in seawater.Development can be direct or indirect.An important example of a hemichordate is Balanoglossus or acorn worm. Other species are Saccoglossus, Rhabdopleura, Atubaria, and Dendrograptus.
