Cnidaria and Ctenophora

Question 1

What are the 2 forms of Cnidaria?

Answer 1

Polyp- Stationary and Medusa- free swimming/ floating

Question 2

Which Cnidarian form is sexual and which one is asexual?

Answer 2

The medusa form is generally the sexual form, and polyp is the asexual form

Question 3

Do all Cnidarian species have a polyp and medusa form?

Answer 3

No, most do but the life cycle does vary

Question 4

What are the traditional classes of Cnidaria?

Answer 4

Hydrozoa, Cuboza, Scyphozoa, and anthozoa

Question 5

What are the 2 newer classes of Cnidaria?

Answer 5

Staurozoa and myxozoa

Question 6

What are some features of hydrozoa?

Answer 6

Mostly marine and colonial, both polyp and medusa

Question 7

What are the 2 Zooidforms in hydroids?

Answer 7

Hydranths- feeding polyps that are various shapes and have a terminal mouth surrounded by tentacles
Gonangium - Reproductive polyps

Question 8

What are some hydroid life cycle features?

Answer 8

Some species with medusae remain attached to the colony and shed gametes

Question 9

What are the 3 functions Cnidocytes can have in hydras?

Answer 9

1) penetrates prey and injects toxin 2) recoils and entangles prey 3) secretes an adhesive substance used for attachment and locomotion

Question 10

How does asexual hydra reproduction work?

Answer 10

Budding

Question 11

How does sexual hydra reproduction work?

Answer 11

Mostly dioecious, gonads typically appear in autumn, eggs and sperm shed externally, zygotes undergo holoblastic cleavage which forms a hollow blastula
the embryos are contained in cysts over the winter and hatch in spring

Question 12

Summarize class scyphoza

Answer 12

Larger sea jellies, all marine, lack a velum

Question 13

Define Rhopalial lappet structure

Answer 13

Paired lappets have rhopalia in between, each rhopalium is club shaped and contains hollow statocysts and on eor two pits lined with sensory epithelia

Question 14

What is the scyphozoas nervous system?

Answer 14

They contain a subumbrellar nerve net

Question 15

How do Scyphozoans reproduce?

Answer 15

They are dioecious and gonads are located in gastric pouches

Question 16

How does fertilization occur in cnidarians?

Answer 16

Internally, sperm is carried by ciliary currents into female pouches, the zygotes are shed or brooded

Question 17

Define strobilation

Answer 17

the scyphistoma (~hydra) develops into a series of saucer like buds called ephyrae which eventually break free and mature

Question 18

Summarize class cubozoa

Answer 18

Medusa is the dominant form, tentacles at each corner of the umbrella margin, pedalium at base of tentacles, rhopalia is present

Question 19

What is unique about Cubozoan eyes?

Answer 19

6 eyes, 3 types of eyes, 2 ocelli types and one camera like eye with cornea and cellular lens

Question 20

What is special about the cubozoan umbrella margin?

Answer 20

Not scalloped, the subumbrella edge folds inwards to form a velarium

Question 21

Summarize the class staurozoa

Answer 21

No medusa stage, unusual stalked polyp, sexual reproduction and non- swimming planula directly develops into a new polyp

Question 22

Summarize the class myxozoa

Answer 22

highly reduced cnidarians, obligate parasites hosted by either fish or worms, economically important as it can cause diseases in some fish

Question 23

Summarize class anthozoa

Answer 23

All marine
No medusa stage
Polyps can be sexual/Asexual and mono or di oecious
Attahed to substrate via pedal disc
have cnidocytes but no cnidocils

Question 24

Summarize Asexual sea anemone reproduction

Answer 24

Primarily through pedal laceration - portions of the pedal disc detach and form new individuals
Longitudinal fission
Transverse fission and budding

Question 25

Summarize Sexual reproduction in sea anemones

Answer 25

Dioecious or hermaphroditic
Gonads on septa margins
Fertilization is internal or external
Zygotes develop into ciliated planula larva which settle and become a new polyp
Male gametes mature prior to female ones (protandry)

Question 26

Summarize corals

Answer 26

Similar to anemone but secrete calcium carbonate exoskeletons and are colonial

Question 26

Why do corals enter symbiosis with zooxanthellae

Answer 26

Their photosynthesis provides nutrients, and helps with calcium carbonate deposition

Question 27

Summarize phylum Ctenophora

Answer 27

Typically free-swimming
Transparent bodies with a gelatinous layer
Nerve net

Question 28

What are some identifying characteristics of Ctenophores

Answer 28

Tentacles with colloblasts to catch prey
2 solid retractable tentacles
Complete gut

Question 29

What is unique about Ctenophores tentacles?

Answer 29

Specialized for capturing plankton
Extend and trail through the water as colloblasts ensnare prey
Colloblasts release an adhesive substance when they make contact with prey