Chapter 4 - Cnidaria

Question 1

What are non-reef-building corals called?

Answer 1

Ahermatypes/ahermatypic coral

This is contrasted with reef-building coral which are hermatypes/hermatypic coral

Question 2

Name the most common types of cnidocytes.

Answer 2

• Penetrant
• Volvent
• Glutinant

Question 3

This type of cnidocyte captures prey with an elastric thread by entaglement

Answer 3

Volvent

Question 4

This type of cnidocyte secretes adhesive mucus for locomotion and attachment

Answer 4

Glutinant

Question 5

This type of cnidocyte penetrates prey and injects poison

Answer 5

Penetrant

Question 6

What are nematocysts?

Answer 6

A specialized stinging organelle which penetrates prey and injects a paralyzing toxin

Question 7

How many species are in phylum Cnidaria?

Answer 7

Over 9,000

Question 8

Name the classes of Cnidaria (including the most recent)

Answer 8

Hydrozoa, Scyphozoa, Cubozoa, Anthozoa, Staurozoa

Question 9

What do the Hydrozoans include?

Answer 9

Hydroids, fire corals, colonial siphonophores like Portuguese man o’ war

Question 10

What do the Scyphozoans include?

Answer 10

True jellyfish

Question 11

What do the Cubozoans include?

Answer 11

Cube or box jellyfishes

Question 12

What do the Anthozoans include?

Answer 12

Stony and soft corals, sea anemones

Question 13

What are the Staurozoans?

Answer 13

Cnidarians with no medusae in their life cycle, but have their polyp topped by a medusa-like region

Question 14

What are the shared features of both polyp and medusa forms?

Answer 14

They both retain sac-like body plans

Question 15

Polyp (hydroid) forms are…

Answer 15

adapted to sedentary or sessile lifestyle

Question 16

Medusa (jellyfish/sea jelly) forms are…

Answer 16

adapted to free-living and floating existence

Question 17

Describe the polyp form

Answer 17

• Tubular body with the mouth directed upward and surrounded by tentacles
• Mouth leads into a blind gastrovascular cavity
• Two ends, oral and aboral end
• Aboral end is attached to substratum, by pedal disc
• Reproduces asexually by budding, fission, pedal laceration

Question 18

Describe the medusa form

Answer 18

• Bell- or umbrella-shaped and exhibit tetramerous symmetry
  (arranged in fours)
• Usually free-swimming or free-floating
• Tentacles may extend down from the rim of the umbrella
• Medusae equipped with statocysts (orientation) and ocelli (light sensors)

Question 19

What type of symmetry do medusa forms exhibit?

Answer 19

Tetramerous symmetry

Question 20

How does the aboral end of polypoids stay attached to the substratum?

Answer 20

Pedal disc

Question 21

What helps medusae stay oriented?

Answer 21

Statocysts

Question 22

These are light sensors in medusae

Answer 22

Ocelli

Question 23

How do hydromedusae differ from scyphomedusae?

Answer 23

Hydromedusae have the presence of velum (shelf-like fold of tissue from the bottom of the bell that extends into the bell)

Question 24

What are the larvae of cnidarians called?

Answer 24

Planula larva

Question 25

What do the planula larvae develop from?

Answer 25

The zygote of the cnidarian

Question 26

Describe the life cycle of cnidarians

Answer 26

- Zygote develops into a motile planula larva - Planula settles on a substrate - Metamorphoses into a polyp which produces other polyps asexually - The polyps produce a free-swimming medusa by budding - Medusa then reproduce sexually and form a zygote

Question 27

What are the class of true jellyfish?

Answer 27

Class Scyphozoa

Question 28

True or False: Medusae are monoecious and can reproduce asexually

Answer 28

False, they are dioecious and reproduce sexually

Question 29

True or False: Scyphozoans have both attached and free-swimming stages that occupy pelagic and benthic environments

Answer 29

True

Question 30

Describe the scyphomedusae

Answer 30

Large and conspicuous; larger than hydromedusae; lack velum; have extended mouth edge called manubrium with four frilly oral arms or lobes that are used in capturing and ingesting prey

Question 31

What is the capsule of the nematocyst covered by?

Answer 31

Operculum

Question 32

Where are the cnidocytes located?

Answer 32

Invaginations of ectodermal cells (and some endodermal cells)

Question 33

What are the polyps of Scyphozoans generally?

Answer 33

Typically very small

Question 34

What are the polyps and medusae of colonial hydrozoans usually like?

Answer 34

Polyps form colonies and medusae are pelagic (except for Hydra which have freshwater polyps)

Question 35

True or False: Polyps are carnivorous but can also filter feed

Answer 35

False, they are purely carnivorous

Question 36

Describe the process of digestion in polyps

Answer 36

Gland cells discharge enzymes to begin extracellular digestion

Question 37

Describe Hydrozoans

Answer 37

Mostly marine and colonial, typical hydroid has a base, a stalk, and one or more terminal zooids

Question 38

What are zooids?

Answer 38

Individual polyp animals that make up the part of a colonial cnidarian

Question 39

Describe the epithelial layers of cnidarians

Answer 39

Epidermis - contains the cnidocytes, sensory cells, and nerve cells Mesoglea - extracellular matrix between epidermis and gastrodermis, acts as hydrostatic skeleton Gastrodermis - holds the gland cells which secrete enzymes

Question 40

What is the scientific name of Portuguese man o' war?

Answer 40

*Physalia* sp.

Question 41

Name the two orders of Hydrozoa that contain species that form polymorphic swimming or floating colonies

Answer 41

Siphonophora and Chondrophora