Jellies

Question 1

Tunicates

Answer 1

There are three classes of tunicates:
-Ascidiacea (2000 species)
-Thaliacea (70 species)
-Appendicularia (20 species)

-Kowalevsky (1866) discovered ascidian larvae have
tail bones
-Like all other chordates, tunicates have a notochord
during their early development, but it is lost by the
time they have completed their metamorphosis
-Genomics shows tunicates are the closest living
relatives to vertebrates
-Tunicates have been extensively studied to
understand the evolutionary origin of vertebrates

Question 2

Ctenophores (comb jellies)

Answer 2

Comb jellies > Greek ‘Cten’ = Comb, ’phero’ = bear
~100 species described, likely many more deep sea
species to be discovered
-Position in tree of life long debated and
controversial
-Wide range of body forms
-ROVs have expanded our ability to observe and
collect ctenophores in the deep-sea during the last
30 years

Question 3

Ctenophore characteristics

Answer 3

-Eight comb rows, called swimming-plates, which are
used for swimming
-Thick, jelly like mesoglea sandwiched between two
epithelia
-Colloblasts, special adhesive and sensory cells, are
present in tentacles and help capture food

Question 4

Cnidaria - anatomy

Answer 4

• Basic anatomy:
  -gastroventricular cavity with one opening
  -tentacles radiate outwards from rim of mouth
  -three body layers (epidermis, mesoglea,
  gastrodermis)

-Radial symmetry
-Life-cycle medusa stage
-Life-cycle polyp stage
-Cnidocytes – specialised stinging cells

Question 5

cubozoa - box jellies

Answer 5

• Smallest Cnidarian class, ~50 species
• Distinguished by cube like body shape
• At least four sets of tentacles, each attached to a
  side of the box body
• Possess true eyes (rophalia) arranged in clusters on
  each side of body
• Active, fish-like behaviour

Question 6

Hydrozoa

Answer 6

~3 700 species
-Polyp + medusa stage
-Distinguished from other groups by:
-complex life cycle
-growth of medusae from buds
-presence of velum inside the bell of the
medusa
-production of gametes from ectodermal, rather
than endodermal, tissue

Question 7

Siphonophores

Answer 7

-The Portuguese Man-O’-War is a conspicuous
member of the neuston
-All siphonophores are colonial hydrozoans
composed of functionally specialized bodies (termed
zooids)
-All zooids in a colony are genetically identical, but
fulfil specialized functions
-Together allow the colony to operate as a single
individual

Question 8

Scyphozoa - ‘true’ jellies

Answer 8

~200 species (incl. mood jelly and lions mane), three
orders
-Medusa is the prominent life stage
-Exclusively marine
-Medusae do not feature a velum
-Distinct pigmentation

Question 9

Staurozoa - stalked jellies

Answer 9

~50 species (incl. mood jelly and lions mane), three
orders
-Stalked jellyfishes have a benthic lifestyle, spending
most of their lives attached to substrate
-Frequently found on algae, rock and seagrasses