Biology 1407 - Chapter 34 - Protostomes

All protostomes belong to either the

Ecdysozoa or the Spiralia

Ecdysozoa

Contains animals that molt. Exoskeleton (Hard external skeleton). Two large groups: Arthropods and Nematodes.

Spiralia

Embryos develop using spiral cleavage. Most live in water. Move using cilia or contractions of body musculature. Two clades: Lophotrochozoa and Platyzoans (Flatworms).

Flatworms

Are ciliated, soft-bodied animals. Bodies are solid aside from an incomplete digestive cavity. Many species are parasitic and others are free living

Flatworms have

Only one opening to digestive cavity. They lack circulatory system. Excretory and osmoregulatory systems. Simple nervous system.

Flame cells

Located on the side branches. Primarily regulate water balance.

Two major groups of flatworms

Turbellaria (Free-Living, Probably not Monophyletic, Dugesia - common planarian in bio labs). Parasitic Neodermata (Trematoda - flukes. Attached to host by suckers, anchors, or hooks. And Cercomeromorpha - Tapeworms)

Corona

Wheel animals. Ring of cilia at anterior end. Used for locomotion and sweeping food into mouth.

Lophotrochozoans

All have a coelom surrounding the heart.

Mantle of Mollusk

Thick epidermal sheet that bounds mantle cavity.

Foot of Mollusk

Used for locomotion, attachment, food capture, and digging. Divided into arms or tentacles.

Internal organs of Mollusk

Coelom is highly reduced but limited to small spaces. Ctenidia - gills in aquatic mollusks. Gill of bivalves filter out food.

Nitrogenous waste removal

By nephridia (kidney like structure). Nephridia also maintains osmotic balance. Tube runs to excretory pore to mantle cavity.

Circulatory system of Mollusk

Open circulatory system.

Trochophore

Free-swimming larval stage.

Veliger

Second free-swimming larval stage. Only in bivalves and most marine snails.

Bivalves

Water enters through inhalant siphon (oxygen and food) and exits through exhaling siphon (wastes and gametes).

Lophotrochozoans - Nemertea

Closed circulatory system and has a complete gut.

Clitellata

Clitellum (saddle) found in all members. Earthworms.

Leeches

Occur mostly in fresh water. Suckers at both ends of body.

The Lophophorates

Include two phyla of mostly marine animals: Bryozoa and Brachiopoda. Both characterized by Iophophore.

Brachiopoda

Or lamp shells. Has two calcified shells one dorsal and one central. The lophophore lies in the body in between the shells.

Phoronids

Lives inside a chitinous tube that the animal secretes. The lophophore consists of two horseshoe-shaped ridges of tentacles.

Eutely

Adults consist of a fixed number of cells. Important in genetic and developmental studies.

Hookworms

Produce anemia and common in southern US

Trichinella causes trichinosis

Forms cysts in muscles. Infection from eating undercooked meat.

Pinworms

Infects 30% of children in the US. Causes itching of the anus.

Intestinal roundworm

Infects one in six worldwide. Adult females can be 30 cm long. Rare in areas with modern plumbing.