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 no 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