M12 Jellies

Question 1

Cnidaria

Answer 1

Radial symmetry, two thick layers; epidermis and gastrodermis (separated by mesoglea). No specialised respiratory, circulatory or excretory system. Network but n nerve cord. Two body forms (medusa or polyp, often biphasic). Cnidocytes (specialised stinging cells).

Question 2

Subphyla Medusozoa: Class Cubozoa 50 species (Hydrozoa, Staurozoa, Scyphozoa)

Answer 2

Box jellies:
-Smallest cnidarian class
-Marine mainly tropical
-At least 4 sets of tentacles, each attached to a side of the box body
-Has true eyes (rhopalia) arranged in clusters on each side of body (up to 24 eyes)

Question 3

Class Hydrozoa: 3700 species

Answer 3

-Polyp and medusa stage
-Distinguished by complex life cycle, growth of medusae from buds, velum inside the bell of the medusa for propulsion
-Production of gametes from ectodermal tissue (instead of endodermal)

Question 4

Siphonophores (Physalia physalis)

Answer 4

Portuguese Man O’War
-All signonophores are colonial hydrozoans composed of functionally specialised bodies (zooids), polymorphic
-zooids (genetically identical polys that do different functions)
-together zooids allow the colony to operate as a single individual

Question 5

Class Scyphozoa: 200 species

Answer 5

True jellies:
-marine, medusa in dominant phase
-no velum, relies on muscular contraction of bell for propulsion
-major planktonic predators, some filter feeders, some have photosynthetic symbionts
-asexual and sexual reproduction
-medusa and polyp stages
-egg is fertilised and develops to larval planula, can settle and metamorphose to polyp
-polyp grows and forms new polyps via budding
-release of ephyra (babies) from polyp via strobilation

Question 6

Class Staurozoa: 50 species

Answer 6

Stalked jellies:
-cold water, benthic
-medusa stage only
-no strobilation, do have a planula stage

Question 7

Subphyla Anthozoa: Class Hexocorallia (sea anemones, corals) (+ octocorallia)

Answer 7

Anemones, stony corals
-solitary, colonial and non-polymorphic
-tentacles in multiples of 6
-can have calcium carbonate skeleton (corals)
-association with photosynthetic zooxanthella (tropical, subtropical shallow waters)
-deep water forms

Question 8

Class Octocorallia

Answer 8

Soft corals, sea pens, gorgonians
-colonial, non-polymorphic
-8 pinnate tentacles, coelenteron divided into 8
-internal support by horny-chalk secreted by cells in mesoglea
-Cnidocytes in both cell layers
-predators but poor nematocysts

Question 9

Subphyla Ctenophora

Answer 9

(not jellyfish)
-comb jellies, 100 species, wide range of body forms
-have also been found and collected in deep sea
-8 rows of cilia for swimming. Thick jelly mesoglea between two epithelia.
-colloblasts = special adhesive and sensory cells, in tentacles to help catch prey