Chapter 13 - Cnidarians and Ctenophores

What does diploblastic mean?

Two embryonic layers (ectoderm and endoderm)

What do the epidermis and gastrodermis develop from?

Epidermis develops from the ectoderm and the gastrodermis develops from the endoderm.

What is the common name for cnidarians?

stinging cell animals

What is the common name for ctenophora?

comb jellies

What is mesoglea?

Secreted non-living jelly layer that lies between gastroderm and epidermis

What are polyps?

Hydroid form of cnidarians with tubular bodies that are sessile or sedentary; monoecious.

How do polyps reproduce?

Asexually by either budding or fission by pedal laceration (individual divides in half).

What are medusa?

Free-floating jellyfish form of cnidarians with a concave mouth, as well as a nerve ring at the base of the bell; dioecious.

What kind of digestion system do cnidarians have?

An incomplete digestive system where extracellular(enzymes in gut) and intracellular(gastrodermis cells) digestion occurs, with waste leaving through the mouth.

What are cnidocytes?

stinging cells that are located along cnidarians tentacles and sometimes the body and gut

What are nematocysts?

specialized organelles within cnidocytes that eject a stinging thread covered in barbs and poison, triggered by chemical and mechanical stimuli

What does radial symmetry mean for cnidarians?

They have an oral(mouth) and aboral(not mouth) ends for multi-directional movement and reactions.

What is primary radial symmetry?

Radial symmetry throughout the entirety of an animals life.

What does alternation of generations in form mean?

Medusa reproduce sexually, creating planula larva that is ciliated and eventually settles down, becoming a polyp. The polyp reproduces asexually, with the buds becoming medusa.

What is a nerve net in cnidarians?

Diffuse nervous "system" (tissue) that is spread throughout the body like a net, allowing bidirectional transmission of impulses.

What other kind of cell can be found the cnidarian epidermis and gastrodermis, allowing movement?

Muscle cells

Describe the class Hydrozoa and two unique properties.

Hydroids; Exists in both forms in marine and freshwater environments as either solitary or colonial. Unique in that it has a velum for medusa(internal upturned bell) and has only freshwater animals of the phylum.

Describe the genus hydra and what class it resides in.

Solitary freshwater polyps(NO medusa) that eats microcrustaceans and can reproduce sexually or asexually. Class Hydrozoa!

Describe the genus obelia and what class it resides in.

Marine colonial polyps & medusa with two types of polyp: hydranths(feeding/tentacle) and gonangium(reproductive/buds). Class Hydrozoa!

Describe the genus physalia and what class it resides in.

Portugese-man-o-war; Marine floating polyp colony of tentacles(polyps) and a float(pneumatophore). Class Hydrozoa!

What is a pneumatophore?

gas filled polyp float for physalia/portugese-man-o-war

Describe the class Scyphozoa and two unique properties.

True jellyfish; Using Aurelia(genus) as the guidline, they are larger medusa(short polyp phase) with short tentacles and lots of mesoglea. Unique in that they have oral arms(like lips to help catch & digest prey) and have four gastric pouches(gut pouches that contain gonads).

Describe the life cycle of a Scyphozoa.

In their short polyp phase, they start as scyphistoma after the planula larva settles. The scyphistoma then becomes a strobila(looks like stacked buds tower) that produces medusa disc buds. The medusa buds then become ephyra with a notched body that develops into a medusa with short tentacles.

Describe the class Cubozoa.

Box jellyfish or sea wasps; Box shaped jellyfish with tentacles at four corners, all marine and very small.

Describe the genus chironex and what class it resides in.

Larger box jellyfish that are extremely toxic to humans. Class Cubozoa!

Describe the class Anthozoa and two unique properties.

Flower animals (sea anemone, coral); Largest class(2/3 of phylum) with all being marine and polyps, and can reproduce sexually or asexually. Unique in that it has zooxanthellae(symbiotic prey that lives in the polyps) and septa(walls separating gastrovascular cavity into sections).

Describe the genus metridian and what class it resides in.

Anemone and coral that have a pedal disc at aboral end, allowing gliding movement and aids in asexual reproduction with pedal laceration.

What is the hard outer covering on coral?

Calcium carbonate secretion that protects the anemone like colonies of coral.

What is the sclerosepta?

The skeletal secretion of coral that provides structural support.

What kind of digesive system do ctenophora have?

An incomplete digestive system with anal canals and anal pores that remove a small fraction of the waste.

What are comb rows?

In ctenophora, eight evenly spaces bands with comb plates of fused cilia(like a comb) that allow movement. Largets animal that uses cilia for movement!

What are tentacle sheaths?

In ctenophora, two very long tentacles that can be retracted into sheath cavities in the body.

What are collophores or colloblasts?

In ctenophora, epidermal glue cells that discharge glue to catch prey and pull into their mouth.

What is a unique property of ctenophora thats purpose is still being theorized?

Bioluminescence, possibly used for mate attraction or defense mechanisms.

How do ctenophora reproduce?

Sexually, even though they are monescious.