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Marine Biodiversity > Cnidaria > Flashcards

Cnidaria Flashcards

1
Q

What are the characteristics of the Cnidaria?

A

Mostly marine
Cells well differentiated to form tissues
Body wall two layered plus mesoglea
Single body cavity- the coelenteron
Mouth generally surrounded by tentacles
Two main structural types- the polyp and the medusa
Alternation of generations
Possess nematocysts
May be solitary or colonial

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2
Q

What classes of the cnidaria exist?

A

Class- Hydrozoa
Polyp stage ‘dominant’ in most species
Hydroids

Class- Scyphozoa
Medusoid stage ‘dominant’ in most species
Jellyfish

Class- Anthozoa
No medusoid stage
Sea anemones

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3
Q

What orders exist in the class hydrozoa?

A

Trachylina (no polypoid stage)

Hydroida (includes most hydrozoans, well developed polypoid stage)

Actinulida (tiny solitary polyps)

Siphonophora (colonial, includes polypoid and medusoid individuals)

Hydrocorallina (polypoid and colonial)

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4
Q

What is a defining characteristic of the order Trachylina?

A

No polypoid stage

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5
Q

What is the life cycle of Aglaura (a Trachylina)?

A

Alternates between asexual and sexual phases
Begins with planula larva that settles into a sessile polyp
Polyp reproduces asexually
Producing medusae
Medusae develop into a free swimming sexual phase and release gametes for external fertilization

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6
Q

How is the order Hydroida described?

A

Includes most hydrozoans, well developed polypoid stage
Vast majority colonial with an external skeleton- the perisarc

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7
Q

What is the life cycle of the Obelia (Hydroida)?

A

Alternates between sexual and asexual phases.
Sessile polyps asexually forming medusae
The medusae mature and release gametes for sexual reproduction
Fertilized eggs develop into larvae

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8
Q

What are some examples of the order Hydroida?

A

Athecate hydroids- skeletal covering does not surround hydranth (polyp does not sit in a cup) e.g. Clava

Thecate hydroids- Skeletal covering surrounds hydranth (polyp sits in a cup) e.g. obelia

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9
Q

What are most hydroids?

A

Most hydroids are thecate

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10
Q

What concept is commonly seen in the order hydroida?

A

Polymorphism
e.g. Hydractinia on hermit crab

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11
Q

What are the zooids seen in Hydractinia?

A

Gonozooid
Dactylozooid
Gastrozooid
Gonozooid
Dactylozooid
Gastrozooids

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12
Q

How is the order Actinulida described?

A

Tiny solitary polyps, interstitial inhabitants
e.g. Psammohydra, Halammohydra, Otohydra

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13
Q

How is the order Siphonophora described?

A

Colonial, pelagic, includes polypoid and medusoid individuals
e.g. Physalia physalis

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14
Q

Does polymorphism exist in the order Siphonophora?

A

Yes
Gasterozooid
Dacytlozooid
Gonozooid

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15
Q

How is the order Hydrocorallina described?

A

Polypoid and colonial with CaCo3 skeleton
Milleporina (fire coral)

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16
Q

What orders exist in the class Scyphozoa?

A

Order- Stauromedusae (sessile, attached by stalk)

Order- Cubomedusae (box jellyfish)

Order- Coronatae- (bell of medusa constricted by a groove, many deep sea jellyfish)

Order- Semaeostomae- (bowl or saucer shaped medusa with scalloped margins)

Order- Rhizostomae (bell of medusa lacks tentacles)

17
Q

How is the order Stauromedusae described?

A

Sessile, attached by stalk
e.g. Haliclystus

18
Q

What does the order Cubomedusae consist of?

A

Box jellyfish
e.g. Carybdea

19
Q

How is the order Corontae described?

A

Bell of medusa constricted by a groove, many deep sea jellyfish
Periphylla

20
Q

How is the order Semaeostomae described?

A

Bowl or saucer shaped medusa with scalloped margins
e.g. Chrysaora and Aurelia

21
Q

What is the reproductive cycle of Aurelia?

A

Alternates between medusa and polyp stages
The medusa reproduces sexually, releasing gametes that form larvae
The larvae settle to form a sessile polyp which asexually reproduces and forms an adult medusae

22
Q

How is the order Rhizostomae described?

A

Bell of medusa lacks tentacles, oral arms branched and folded
e.g. - Rhizostoma
- Casseopeia- shallow tropical lagoons, contains symbiotic algae and lies upside down on seabed absorbing sunlight

23
Q

What are the sub-classes of the class Anthozoa?

A

Subclass- Octocorallia - Polyp with 8 pinnate tentacles, mostly colonial

Subclass- Zoantharia- Polyps with more than 8 tentacles which are rarely pinnate. Solitary or colonial

24
Q

What orders exist in the subclass Octocorallia?

A

Order- Stolonifera
Order- Telestacea
Order- Alcyonacea
Order- Coenothecalia
Order- Gorgonacea
Order- Pennatulacea

25
Q

How is the order Alcyonacea described?

A

Soft corals, rubbery coenenchymal mass, skeleton calcareous spicules

26
Q

How is the order Gorgonacea described?

A

Gorgonian corals, upright plantlike growth, skeleton of horny organic material, include sea whips and sea fans
e.g. Swiftia

27
Q

How is the order Pennatulacea?

A

Sea pens, fleshy, flattened or elongate body, or rachis, skeleton of calcareous spicules
Sea pens are mostly feather-like in shape but there are other variations

28
Q

What orders exist in the subclass Zoantharia?

A

Order- Zoanthidea
Order- Actiniaria
Order- Scleractinia
Order- Corallimorpharia
Order- Ceriantharia
Order- Antipatharia

29
Q

How are the order Zoanthidea?

A

Small anemones with single siphonoglyph, no skeleton, solitary or colonial

30
Q

How are the order Actiniaria?

A

Sea anemones, solitary, no skeleton, mesenteries in hexamerous cycles, usually 2 siphonoglyphs
e.g Actinia- intraspecific aggression

31
Q

How are the order Scleractinia described?

A

Stony corals, mostly colonial, external calcareous skeleton, sclerosepta in hexamerous cycles
Mostly colonial but some solitary

32
Q

How are the order Corallimorpharia described?

A

Radially arranged tentacles, similar to true corals but lack skeleton
e.g. Corynactis

33
Q

How are the order Ceriantharia described?

A

Burrowing anemones with elongate bodies living in tubes in sediment, single siphonoglyph

34
Q

What are the phylum Ctenophora (comb jellies)?

A

Pelagic marine animals- Superficially similar to Schyphozoa jellyfish

35
Q

How are the phylum Ctenophora similar to Scyphozoa?

A

Similarities:
- Radial symmetry
- Jelly-like mesoglea
- Transparency
- Nematocysts present in one species

36
Q

What is the distinction between the phylum Ctenophora and the Scyphozoa?

A

8 rows of cilia running round body- used for swimming with oral end forward (Scyphozoans tend to swim aboral end forward)

Marine Biodiversity (6 decks)

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