Which phylums are protostomes

Previously known as Zygoneura, the group was named Protostomia based on the fate of the blastopore, which should develop into the mouth rather than the anus, as in the Deuterostomia.

Almost every morphological and molecular study points to the protostomes as monophyletic. The Chaetognatha is placed in a trichotomy with Spiralia and Ecdysozoa, with the morphology and ontogeny of its nervous system supporting their protostomian affinities. The origin and evolution of the characteristic trochophora larva and nervous system, along with the complex of the tubular gut, are explained by the trochaea theory.

Keywords: bilateral animals , Protostomia , Spiralia , Ecdysozoa , blastopore , protostomes , Chaetognatha , nervous system , evolution , trochaea theory. Oxford Scholarship Online requires a subscription or purchase to access the full text of books within the service. Public users can however freely search the site and view the abstracts and keywords for each book and chapter. Please, subscribe or login to access full text content.

To troubleshoot, please check our FAQs , and if you can't find the answer there, please contact us. All Rights Reserved. OSO version 0. When they were alive, a tiny shrimplike animal occupied each white case. They belong to the order Ostracoda which is considered a class in some textbooks. Another order of minute crustaceans Conchostraca are called clam shrimp; however, the bivalve carapace of an ostracod is more strikingly similar to a clam shell.

Photo was taken along the shore of a desiccated vernal pool in the Santa Rosa Plateau of Riverside County, California. A thriving population of brine shrimp Artemia monica in Mono Lake, California. These minute crustaceans belong to the order Anostraca, along with the endangered fairy shrimp Branchinecta.

During the summer months, the shoreline of Mono Lake is colored pinkish-red by massive colonies of brine shrimp. The Phalarope right is swimming in circles as it feeds on the brine shrimp. A common southern California centipede Scolopendra polymorpha. The name centipede is derived from the Latin words "centi" and "pede" foot. Centipedes belong to the class Chilopoda in the phylum Arthropoda.

Adult centipedes in North America may have fewer or more than legs, one pair per body segment. Centipedes are the only animals with legs modified into fanglike "poison jaws" toxicognaths that inject poison for subduing and killing prey. Modified forelegs, called prehensors, are located under the head. Glands inside the prehensors release venom into ducts that lead into the fangs. The last pair of legs are longer than the others.

Some species use these to subdue prey or as defensive pincers. The posterior body segment with its unique pair of legs superficially resembles the head. This "pseudohead" found in some species may serve to confuse potential predators by misdirecting their attacks to a less vital part of their body, thus leaving the head free to bite the attacker. A common question that students ask is "can centipedes bite? Magnified view of the underside of a centipede Scolopendra polymorpha showing a pair of fanglike "poison jaws" or toxicognaths red arrow.

These are actually modified forelegs that inject venom. A large southern California millipede probably Hiltonius pulchrus , a member of the class Diplopoda in the phylum Arthropoda. Diplopoda means "double-footed," and refers to two pairs of legs on each body segment. The name millipede is derived from the Latin words "milli" and "pede" foot. Actually, adult centipedes in North America may have up to legs, typically two pairs per body segment.

Unlike centipedes, most millipedes are harmless detritis feeders detritivores and feed on rotting vegetation. The horseshoe crab Limulus polyphemus lives in shallow water along the Atlantic coast and the Gulf of Mexico. It belongs to the class Merostomata in the subphylum Chelicerata. The horseshoe crab is a living representative of the subclass Xiphosura, an line of aquatic chelicerates that dates back to ancient Cambrian seas million years ago. The subphylum chelicerata is characterized by arthropods with a cephalothorax, no antennae and jaws called chelicerae.

In addition to the horseshoe crab, this subphylum includes the large class Arachnida spiders, scorpions, ticks and mites. Another large subphylum, the Mandibulata, is characterized by a head, thorax and abdomen, paired antennae and jaws called mandibles. It includes the class Crustacea lobsters, crabs and barnacles , class Insecta insects , class Chilopoda centipedes and class Diplopoda millipedes. A sun spider or solpugid order Solpugida , an interesting member of the subphylum Chelicerata in the class Arachnida.

Unlike true spiders order Araneae , the solpugid has two pairs of formidable, scissorlike jaws called chelicerae red arrow. The jaws are arranged vertically rather than the single pair of horizontal jaws in most spiders. The elongate pair of anterior appendages are pedipalps, each tipped with a suckers that are used for capturing prey and climbing smooth surfaces.

Solpugids are extremely voracious carnivores, even attacking and killing other large, webless spiders, such as wolf spiders. With their twin pairs of huge, powerful jaws, solpugids literally crush and tear their prey to shreds. Close-up view of the anterior end of a tarantula Aphonopelma showing two sharp, fangs red arrow extending from the jaws or chelicerae.

This spider is a male because its pedipalps are tipped with a sharp-pointed, bulblike copulatory organ purple arrow. During mating the male inserts sperm into an opening on the underside of the female using the pointed copulatory organs on his pedipalps. Several closely-spaced, orange eyes can be seen on the front of the head cephalothorax. The tarantula kills its prey by crushing and injecting them with poison through its hollow fangs.

Although it is a large spider, the tarantula is hunted and killed by a large black wasp with bright red wings known as the tarantula hawk Peplis. Close-up view of several arrow worms phylum Chaetognatha. These planktonic marine animals are only about mm in length, about the size of duckweeds of the genus Wolffiella.

The have a torpedo-shaped body with lateral and caudal tail fins that superficially resemble the feathers of an arrow. The head is covered by a rounded hood that is retracted when the arrow worm feeds. During feeding, the arrow worm captures small plantonic organisms, including copepods and other chaetognaths, with minute spines or bristles around the mouth.

Two well-preserved, fossilized echinoderms. Both of these organisms belong to the class Echinoidea along with sea urchins. Garibaldi Hypsypops rubicundus , a bright orange fish of the shallow waters off the coast of California. Like California's state flower golden poppy and state freshwater fish golden trout , the garibaldi has been selected to be the state's official marine fish.

Phylum Sporozoa Parasitic Protozoans : e. Phylum Ciliophora Ciliated Protozoans : e. Phylum Rhizopoda Amoeboid Protozoans : e. Phylum Zoomastigophora Flagellate Protozoans : e. Barnes, R. Invertebrate Zoology. Saunders Company, Philadelphia. Borror, D. Jessop, N. Zoology Schaum's Outline Series.

One such group of animals are called the metazoans whose body cells are differentiated into tissues and organs. Based on the embryonic development of these metazoans, they are classified into two groups - protostomia and deuterostomia or protostomes and deuterostomes.

The reason for this naming is based on their mode of embryonic development. When the embryo develops, the protostomes first form the mouth from the blastopore, and the anus develops later after the mouth has been created.

A protostome is a group of animals that includes invertebrates like arthropods insects and crabs , molluscs clams and snails , and worms of phylum Annelida. Developments in the last few decades in molecular biology techniques such as DNA sequence analysis has suggested that protostomes can be divided into two major super phyla or groups called Spiralia and Ecdysozoa. While Spiralia includes Platyhelminthes, molluscs, and annelids, Ecdysozoa comprises nematodes and arthropods.

In deuterostomes, the opening at the bottom of the gastrula, known as the blastopore, forms the anus. In deuterostomes, the anus and the mouth are located at the opposite ends of the blastopore, and a digestive tract develops in the middle to connect the mouth and the anus.

Deuterostomes further have three significant classifications which are - Chordata, Echinochordata, and Hemichordata. Chordata includes all the vertebrates like birds and mammals. So, are humans deuterostomes? Well, yes, they are!