Ctenophores and Cnidarians: Jelly Fish

Rhopalia house what 3 sensory structures:

CHEMORECEPTORS STATOCYSTS OCELLI (EYE SPOTS)

How does the term Polymorphism distinguish Phylum Cnidaria?

Two body types: POLYP MEDUSA

Stinging cells are called ___________ and contain organelles called _______________.

Cnidocytes Nematocysts

Name three classes of Phylum Cnidaria and give a representative of each class:

CLASS HYDROZOA- Hydra, Obelia, Portuguese man-of-war CLASS SCYPHOZOA- Jellyfish (Aurelia) CLASS ANTHOZOA- Sea anemones, coral

NAME THE CELL TYPES OF PHYLUM CHNIDARIA

CNIDOCYTE GLAND CELL SENSORY CELL EPITHELIOMUSCULAR CELL NUTRITIVE-MUSCULAR CELL INTERSTITIAL CELL

Briefly explain the mechanism of nematocyst discharge.

A nematocyst is a stinging capsule within a cnidocyte. When the small trigger on the cell is stimulated, a rapid increase in osmotic pressure within the cnidocyte causes the nematocyst to discharge violently, exploding out of the cell and releasing a long, hollow, thread like filament, driving its barbs and poison into the flesh of its victim.

Describe the body wall of Phylum Cnidaria and name the two tissue layers:

DIPLOBLASTIC- (EPIDERMIS, GASTRODERMIS)

Does Hydra reproduce sexually? Asexually? Give evidence to support your answers.

Members of the genus Hydra are unusual in that they do not produce medusae. Rather, Hydra exist as single, mobile polyps that reproduce either sexually through production of sperm and eggs or asexually through budding. If environmental conditions become unfavorable ( for example food and dissolved oxygen becomes scarce), they rely on sexual reproduction rather than asexual reproduction.

Nematocysts are discharged by what process?

Osmotic pressure (Hydrostatic Pressure)

Name the phylum whose name is derived from unique stinging cells

PHYLUM CNIDARIA

What increases the GVC surface area of class ANTHOZOA?

PRIMARY SEPTA SECONDARY SEPTA TERTIARY SEPTA

What are RHOPALIA?

Scyphozoan medusa sense organs

In which tissue layer are the cnidocytes located? Why?

The body wall of Cnidarians is arranged in two discrete tissue layers. One is known as the diploblastic arrangement consisting of an outer epidermis and inner gastrodermis. The Cnidocytes are located in the outer epidermis layer.

What do you propose is the function or purpose of the folds of the gastrovascular cavity wall (the septa)?

The folds of gastrovascular cavity wall is for digestion and allows for the circulation of water (phagocytosis of small food particles and intracellular digestion).

What type of digestion is Hydra capable of: intracellular, extracellular, or both?

The gastrovascular cavity has a single opening that is used to ingest food and expel undigested waste. Hydra have the ability to digest food extracellularly through the gastrovascular cavity. Digestive enzymes are released from gastrodermal cells and partially break down the food, followed by phagocytosis and intracellular digestion concluding that Hydra are capable of both digestions.

Compare and contrast the scyphozoan medusa with the medusa bud of Obelia.

The scyphozoa is the most prominent and free-floating of the medusa. It lacks velum (membranous structure) and has a thicker gelatinous mesoglea. It is much larger in size. On the other hand, medusa bud of Obelia is reproduced asexually and once mature will become independent of its parent.

Count the number of primary septa on your specimen and record that value below. Compare your finding with other lab groups. Do all of the sea anemone specimens in your lab have the same number of primary septa?

There are six primary septa on the specimen. No, all sea anemone specimens do not have the same number of septa.

List several ways in which Obelia differs from Hydra.

Though Hydra and Obelia are both Cnidarians found in the Class Hydrozoa, there are several ways Obelia differ from Hydra. Obelia is a colonial hydrozoan species connected by branches of a common gastrovascular cavity (coenosarc) and live as polyps in an interconnected branch network while Hydra are a solitary species attached to substrates. Obelia is exclusively in marine habitats whereas Hydra lives in freshwater habitats. Hydra does not have medusa form in their life cycle but Obelia has both polyp and medusa form. Unlike Obelia, Hydra has remarkable regenerative powers.