Lab 13: Flatworms and Roundworms

Platyhelminthes (Flatworms)

Planaria, Trematodes, Cestodes

Nematodes (Roundworms)

Vinegar Eel, Ascaris, Trichinella

What symmetry do these worms have?

Bilateral

Bilateral Symmetry Planes

Anterior v Posterior / Dorsal v Ventral

Ectoderm

Germ Layer covering the surface of the embryo. Gives rise to the skin and nervous system.

Endoderm

Innermost germ layer; it lines the developing digestive tube (archenteron), and forms the intestine and other digestive organs.

Mesoderm

Between the ectoderm and the endoderm. This embryonic germ layer gives rise to the skeleton and muscles as well as the circulatory, excretory and reproductive systems of animals.

Triploblastic

Having three types of embryonic tissue.

Coelomate

Lined by mesoderm on both gut and body wall.

Acoelomate (Flatworms and ribbon worms)

Having an ectoderm, mesoderm, endoderm, digestive cavity

Pseudocoelomate (The nematodes)

Having an ectoderm, mesoderm, psuedocoelom, endoderm, digestive cavity

Coelom

A fluid-filled or air-filled space separating the digestive tract from the outer body, absorbs shock, acts as hydrostatic skeleton, support

Hydrostatic Skeleton

Cavity that muscles exert a force against to produce movement; protects internal structures and gives support

Zygote

Single cell formed when a sperm and egg fuse during fertilization.

Blastula

The hollow ball of cells.

Blastocoel

Fluid or yolk filled cavity in the center of the blastula.

Blastopore

The groove that forms during the early stages of embryonic development.

Gastrulation

Process by which gastrula forms into blastula.

Archenteron

Rudimentary alimentary cavity of an embryo at the gastrula stage.

Vitelline Gland

Yoke production

Vas Deferens

How sperm travels between the testes and the genital pore

Genital Pore

Opening for male and female gametes.

Gravid

Egg carrying

Oviduct

A tube passing from the ovary to the uterus

Flame Cells

Removes excess water from tissue to maintain osmotic balance.

Pharynx

Muscular tube that connects the nasal and oral cavities.

Mesenchyme

Loosely organizes embryonic tissue.

Platyhelminthe Parasites

Trematodes (flukes), Cestodes

Nematoda Parasites

Ascaris, Trichinella

Tegument

Out covering in flukes and tapeworms, its a living protective layer; similar to intestinal lining of its host

Proglottids

Sections with male and female reproductive organs.

Intermediate hosts

Inhabited by immature stages of a parasite.

Definitive host

Parasitized by sexually mature, egg-laying stages of the parasite

Sheep liver fluke hosts

Snail-intermediate; vertebrates-definitive

Miracidia

Eggs develop and hatch in larvae called this

Cercariae

Free-swimming larvae develop

Metacercariae

Cysts formed called this on aquatic plants

Blood fluke hosts

Snails=intermediate, humans=definitive

Schistosomulae (for blood flukes)

Cercariae lose their tails and migrate into the blood and liver of humans

Scolex in tapeworm

Hooks and suckers in males

Cuticle

Tough non-living covering, protects, aids in water balance

Which roundworm is larger?

Females are larger