Biodiversity And Conservation Chapter 7: Cnidaria and Ctenophora

13,000

Number of species in phylum Cnidaria

40

Number of freshwater species in phylum Cnidaria

Cnidocytes

Specialized cells found in Cnidarians that contain stinging organelles

Nematocysts

Stinging organelles in cnidocytes

Radial

Type of symmetry found in Cnidarians

Polyp

Tubular body with the mouth directed upward and surrounded by tentacles

Gastrovascular Cavity

The “stomach” in Cnidarians

Petal disk

Part of the polyp that attaches to the substrate

budding, fission, and pedal laceration

Asexual reproduction in polyps

Hydranth

Specialized feeding polyp in colonies

Dactylozooids

Specialized defense polyps in colonies

Gonangia

Specialized reproduction polyps in colonies; doesn’t have tentacles

Medusae

Bell shaped, with the mouth and tentacles usually facing downwards

Epetheliomuscular cells

Cells that perform muscular contraction, bending, and pulsing in Cnidarians

Nerve net

Diffuse nervous system in Cniardians; one at the base of the epidermis and one at the base of the gastrodermis, are interconnected

Neurotransmitters

Located in nerve nets on both sides of the synapses; allows for transmission in either direction

Ctenophores, molluscs, and flatworms

Animals that eat hydroids/cnidarians and use the nematocysts for their own defense

Hydras

Species of freshwater, solitary polyps in the Class Hydrozoa.

Class Hydrozoa

Class of cnidarians that are mostly marine and colonial, with both polyp and medusa forms

Obelia

Species of cnidarian that is a colony, with both a polyp and medusa stage, and is in the Class Hydrozoa. Medusae in the species are formed by gonangium, and reproduce sexually

Gonopore

Pore on the gonangium that releases the meduase buds

Class Scyphozoa

Class of cnidarians that makes up the majority of the larger jellies, and is medusae dominant

Mesoglea

Makes up the majority of the mass of jellyfish bells, and contains ameboid cells and fibers

Rhopalium

Sensory organ usually at the margin of the bell in jellyfish

Sexual reproduction of Scyphozoa

Sexes are separate and fertilization is internal, as sperm is carried into the gastric pouch of the females

Zygotes of Scyphozoa

This species’ young develop into ciliated planula larvae, and eventually develop into a scyphistema

Scyphistema

Polyps in the class Scyphozoa that undergo strobilation; the sections formed via strobilation eventually develop into ephyrae

Ephyrae

Sections of Scyphistema that break loose to form jellyfish medusae

Class Cubozoa

Class of cnidarians that is medusa form dominant, has a square shape when viewed from above, has four evenly spaced tentacles/branches of tentacles, and has developed eyes

Rhophalia of cubozoa

Makes 6 eyes and other sensory organs for this class of cnidarians

Velarium

Inverted dome edge of cubozoans that allows them to swim more efficiently

Class Myxozoa

Class of cnidarians that are microscopic obligate parasites, with reduced genomes and body plans, no mouth or GVC, and may require two hosts, a fish and an annelid, for the whole life cycle

Class Anthozoa

Class of cnidarians that are corals, anemones, sea pans, and sea fans; marine and polyp only

Broadcast spawning

Sexual reproduction of class anthozoa, in which there is a mass release of gametes by multiple organisms and species at once

Cues for broadcast spawning

Temperature, moonlight, the setting sun, and currents

Reef threats

Rising ocean temperatures and ocean acidification

Coral bleaching

When corals are stressed they expel the zooxanthellae that live in their tissues

Zooxanthellae

Algae that live in coral tissues that give them their nutrients and color

Ocean acidification

higher atmospheric concentrations of carbon dioxide acidifies the water, which makes precipitation of calcium carbonate by corals more difficult metabolically

Phylum Ctenophora

Phylum of 150 species of comb jellies; marine and medusae only; most are free-swimming; have a complete gut

Feeding habits of Ctenophora

Two tentacles capture planktonic organisms, and short tentacles collect food on their ciliated body surface

Colloblasts

Epidermal cell on Ctenophora that let them capture food

Photocytes

Cells that cause luminesce in Ctenophora

Monoecious

An individual has both types of sex organs

Reproduction of Ctenophora

Fertilized eggs are discharged through the epidermis into the water, and larvae are free swimming