Asymmetry

1
Asymmetry

• Not similar in any plane

2
Spherical Symmetry

• The same in any plane drawn through the center

3
Radial Symmetry

• virtually the same in any plane through the same
  axis
• no obvious halves

4
Biradial Symmetry

• Specialization in parts so that complete radial
  symmetry is not possible
• obvious halves

5
Bilateral Symmetry

• Similarity in only one plane

6
Bilateral Symmetry
7
Presence of three primary tissues

• Ectoderm Skin, Nervous system
• Mesoderm Muscle, Skeletal, Organs, Circulatory
  system
• Endoderm linings of organs and digestive system

8
ZOO 115

• Cnidaria

9
Where do they live?

• Mostly marine

10
Phylogeny
Purves et al.
11
When did they show up?
600-700 MYA
12
Assorted facts

• Cnidaria means stinging thread
• Only Phylum that has Cnidae
• 11,000 species
• Cnidarians appeared early in evolutionary history
  and radiated in the late Precambrian.
• The cnidarian body plan combines a low metabolic
  rate with the ability to capture large prey,
  allowing cnidarians to survive in environments
  where prey is scarce.

13
Tissues

• Diploblastic derived from two primordial tissues

14
Symmetry - Radial
15
Cnidarian body plan
16
Circulatory system
Radial Canals - for digestion and circulation
Muscle fibers
17
Nervous system

• Nerve rings
• beginning of a central nervous system for
  swimming
• Nerve net
• ectoderm of subumbrella to operate mouth and
  tentacles
• Statocysts

From Ruppert, Fox and Barnes (2004), Invertebrate
Zoology
18
Rhopalium
webs.lander.edu/rsfox/rsfoximages1/scyphozoa5L_x55
0_x_412x.gif
19
Some have image-forming eyes
Box jellyfish
pharyngula.org/images/cubozoan_rhopalium_diagram.g
if
20
Musculature

• Myoepithelial cells most primitive muscle cells
• On epidermis called epitheliomuscular cells
• On gastrodermis called nutritive muscular cells
• some have meschenchymal muscles

21
Musculature

• Feeding tentacles

• Both have longitudinal muscle fibers

_at_ 2001 Sinauer Associates, Inc.
22
Musculature

• Bell

• have circular muscle fibers

_at_ 2001 Sinauer Associates, Inc.
23
How do they move?

• Nerve ring - swimming
• Nerve net tentacles and mouth

Top of jellyfish
Jellyfish from the side
24
How do they move?
25
How do they move?
Mesoglea acts as an antogonist
Muscle fibers relax
26
Cnidae- Unique to Cnidarians

• Cnidocyte or Cnidoblast is the cell that creates
  cnidae

27
Cnidae - Nematocyst
From Ruppert, Fox and Barnes (2004), Invertebrate
Zoology
28
How do they feed ?

• Cnidocyte on tentacle capture food

• Tentacles move food to mouth

• Particles are digested

• Circulate to other tissues via gastrovascular
  system

29
How do they excrete ?

• Solid waste is excreted out the mouth

30
Polyp General Anatomy

• Similar to Medusa but
• Manubrium short
• Large gastric region but not radial canals
• Stalk instead of bell
• No nerve ring

31
Polyp General Anatomy

• Different muscle FIBERS arrangement
• Both

Longitudinal
Circular
32
How do they move?

• Somersault
• creeping

33
Reproduction

• Varies with the different Classes of Cnidarians

34
Taxonomy Classes
35
Taxonomy - Classes

• Class Hydrozoa (polyp or medusa or both)

36
Taxonomy Classes

• Class Scyphozoa (medusa dominant)

37
Class Anthozoa - characteristics

• 6000 species
• Medusa stage is absent
• Polyp is responsible for both sexual and asexual
  reproduction
• Size range from 0.5cm to 1m.
• Only cnidarian class that has all three types of
  cnidae (nematocysts, spirocysts and ptychocysts).

38
Anthozoa General Anatomy

• 1. Tentacles
• 2. Pharynx
• 3. Siphonoglyph
• 4. Gastrovascular cavity

5.-7. Septae 8. Gonads 9. Pedal disk
39
Anthozoa Retractor muscles
40
Anthozoa nervous system

• Nerve net for epidermis (tentacles)
• Nerve net for gastrodermis (body)

41
Anthozoa Feeding and Digestion
42
Anthozoa Gas Exchange and Excretion

• Diffusion from tentacles and body cells
• Siphonoglyph directs currents to remove waste.

43
Anthozoa - Reproduction

• Asexual
• Fission
• Fragmentation
• Budding
• Some asexual larval formation (Planula larvae) in
  corals