Protostomes

Flashcards based on the lecture notes covering Protostome classification, characteristics, and examples of Lophotrochozoans, Ecdysozoans, and Arrow worms.

Protostomes

Animals in which the blastopore develops into the mouth.

Deuterostomes

Animals in which the blastopore develops into the anus.

Protostome General Traits

Possess an anterior brain that surrounds the entrance to the digestive tract and a ventral nervous system with paired or fused longitudinal nerve cords.

Acoelomate

A fluid-filled cavity is absent; the internal cavity is full of cells forming the mesenchyme.

Pseudocoelomate

Internal cavity full of fluid in which organs are suspended (pseudocoel); muscles on the outside.

Coelomate

Internal cavity full of fluid (coelom) and lined with a layer of tissue called peritoneum, which also covers the organs.

Hemocoel

The body cavity in arthropods that became a hemocoel or blood chamber, part of the open circulatory system facilitating free circulation within the body.

Lophotrochozoa and Ecdysozoa

Two main clades within the protostomes, classified based on genetic data.

Chaetognathes (Arrow Worms)

Predatory, usually planktonic, marine worms; their position within protostomes is currently unclear.

Trocophore

A type of free-living larva found in many Lophotrochozoans.

Lophophore

A feeding structure called lophophore is present in some Lophotrochozoans.

Ecdysozoa

Animals that molt, and molting is called “ecdysis”.

Molting (Ecdysis)

The external cuticle secreted by the epidermis in ecdysozoans must be shed, or molted, and replaced with a larger one to grow.

Lophophore

A horseshoe-shaped crown of ciliated tentacles around the mouth which are used in filter-feeding.

Brachiopods and Bryozoans

Sessile groups which possess the lophophore.

Trochophore (trocophora)

A type of free-living larva, characterised by bands of cilia.

Annelids and Molluscs

The trochophore is found in various Lophotrochozoans.

Platyhelminthes (Flatworms)

Approximately 30,000 species, acoelomates, dorsoventrally flattened and possess no gas transport system.

Rotifera (Rotifers)

1,800 species, mostly freshwater, tiny (50–500 µm), but have specialized internal organs and a complete gut, can survive desiccation and very resistant to ionizing radiation.

Bryozoans

“Moss animals” with 6,500 living species; all aquatic, mostly marine and sessile. Colonies made of many zooids (small!) that construct an organic or calcerous colonial exoskeleton.

Cycliophora

Microscopic marine invertebrates discovered in 1995 with 3 species known that are found on the mouthparts of lobsters!

Nemertea

Ribbon worms that possess a muscular proboscis for feeding.

Brachiopods

Solitary marine animals with two-part shells connected by a ligamentthat resemble bivalve mollusks, but the shell evolved independently and they possess the lophophore.

Annelida

19,000 species that are clearly segmented; the coelom in each segment is isolated from the coelom in other segments and are restricted to aquatic or moist habitats and possess a Trocophore.

Mollusca

Includes the largest known invertebrates and their body plan has been modified in different groups, many have a calcerous shell and have trochophore larvae.