Cnidaria and Ctenophora Flashcards
What are the 2 forms of Cnidaria?
Polyp- Stationary and Medusa- free swimming/ floating
Which Cnidarian form is sexual and which one is asexual?
The medusa form is generally the sexual form, and polyp is the asexual form
Do all Cnidarian species have a polyp and medusa form?
No, most do but the life cycle does vary
What are the traditional classes of Cnidaria?
Hydrozoa, Cuboza, Scyphozoa, and anthozoa
What are the 2 newer classes of Cnidaria?
Staurozoa and myxozoa
What are some features of hydrozoa?
Mostly marine and colonial, both polyp and medusa
What are the 2 Zooidforms in hydroids?
Hydranths- feeding polyps that are various shapes and have a terminal mouth surrounded by tentacles
Gonangium - Reproductive polyps
What are some hydroid life cycle features?
Some species with medusae remain attached to the colony and shed gametes
What are the 3 functions Cnidocytes can have in hydras?
1) penetrates prey and injects toxin 2) recoils and entangles prey 3) secretes an adhesive substance used for attachment and locomotion
How does asexual hydra reproduction work?
Budding
How does sexual hydra reproduction work?
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
Summarize class scyphoza
Larger sea jellies, all marine, lack a velum
Define Rhopalial lappet structure
Paired lappets have rhopalia in between, each rhopalium is club shaped and contains hollow statocysts and on eor two pits lined with sensory epithelia
What is the scyphozoas nervous system?
They contain a subumbrellar nerve net
How do Scyphozoans reproduce?
They are dioecious and gonads are located in gastric pouches
How does fertilization occur in cnidarians?
Internally, sperm is carried by ciliary currents into female pouches, the zygotes are shed or brooded
Define strobilation
the scyphistoma (~hydra) develops into a series of saucer like buds called ephyrae which eventually break free and mature
Summarize class cubozoa
Medusa is the dominant form, tentacles at each corner of the umbrella margin, pedalium at base of tentacles, rhopalia is present
What is unique about Cubozoan eyes?
6 eyes, 3 types of eyes, 2 ocelli types and one camera like eye with cornea and cellular lens
What is special about the cubozoan umbrella margin?
Not scalloped, the subumbrella edge folds inwards to form a velarium
Summarize the class staurozoa
No medusa stage, unusual stalked polyp, sexual reproduction and non- swimming planula directly develops into a new polyp
Summarize the class myxozoa
highly reduced cnidarians, obligate parasites hosted by either fish or worms, economically important as it can cause diseases in some fish
Summarize class anthozoa
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
Summarize Asexual sea anemone reproduction
Primarily through pedal laceration - portions of the pedal disc detach and form new individuals
Longitudinal fission
Transverse fission and budding
Summarize Sexual reproduction in sea anemones
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)
Summarize corals
Similar to anemone but secrete calcium carbonate exoskeletons and are colonial
Why do corals enter symbiosis with zooxanthellae
Their photosynthesis provides nutrients, and helps with calcium carbonate deposition
Summarize phylum Ctenophora
Typically free-swimming
Transparent bodies with a gelatinous layer
Nerve net
What are some identifying characteristics of Ctenophores
Tentacles with colloblasts to catch prey
2 solid retractable tentacles
Complete gut
What is unique about Ctenophores tentacles?
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
