Invertebrates radiata

Question 1

How many phyla are animals grouped into?

Answer 1

35 phyla (but we only focus on about 15 phyla)

Question 2

What do invertebrates lack?

Answer 2

Backbones

Question 3

How many known species do invertebrates account for?

Answer 3

They account for 95% of known animal species
- Vertebrates comprise only ~5% of animals

Question 4

What kinds of habitats do invertebrates inhabit?

Answer 4

They inhabit nearly all environments, though most are aquatic, mot marine
- Terrestrial habitats pose special problems for animals - primarily because of desiccation
- Only vertebrates and arthropods have great diversity on land

Question 5

What are sponges?

Answer 5

• Basal animals that lack true tissues
• Porifera (“pore bearer”)
• Sponges are sedentary animals from the phyla Calcarea and Silicea (once thought to be plants)
• Have no nerves or muscles (an exception)
• Lack true tissues and organs, loose federations of unspecialized cells
• Possess choanocytes

Question 6

What are the three main classes of sponges?

Answer 6

Glass sponges
- Siliceous spicules
Demosponges
- Most diverse (~90% of living sponges)
- Have a collagen-based skeleton
Calcareous sponges
- Calcium carbonate spicules

Question 7

Where do most sponges live?

Answer 7

Most are marine; oly ~100 species live in fresh water

Question 8

How does the body of sponges work?

Answer 8

• The body of a simple sponge resembles a sac perforated with holes
• Water drawn into the spongocoel, expelled through the osculum
• Complex sponges have branched canals and several oscula

Question 9

How do sponges feed?

Answer 9

They suspension-feed
- Flagellated choanocytes (collar cells) lining the spongocoel create water flow through the sponge & trap food with their collars

Question 10

What is the structure of a sponges body?

Answer 10

• Pinacocyte forms the outer covering of the sponge; may phagocytize large food particles
• Oocyte egg cell
• Lophocyte or collenocyte secretes collagen
• Porocyte controls water flow through ostia
• Amoebocyte delivers nutrients to cells, and differentiates into other cell types
• Sclerocyte secretes silica spicules
• Choanocyte generates water current and filters food particles from water

Question 11

How do sponges reproduce?

Answer 11

• Most sponges are hermaphrodites, individuals produce both sperm and eggs (generally sequential hermaphrodites)
• Gametes arise from choanocytes or amoebocytes
• The eggs are typically retained, but sperm are carried out the osculum by the water current
• Sperm are drawn into neighboring individuals and fertilize eggs in the mesohyl
• The zygotes develop into flagellated, swimming larvae that disperse from the parent
• When a larva finds a suitable substratum, it develops into a sessile adult

Question 12

Are sponges capable of regeneration?

Answer 12

yes, sponges are capable of extensive regeneration, the replacement of lost parts

Question 13

What health benefits do sponges have for humans?

Answer 13

• Sponges produce a variety of bioactive metabolites such as antibiotics and other defensive compounds
• Cribrostatin 6 isolated from marine sponges can kill penicillin-resistant strains of the bacterium Streptococcus
• Cribrostatin 4 is a potent anti-cancer agent

Question 14

Who won the nobel prize in chemistry in 2010 and why?

Answer 14

Richard Heck, Ei-ichi Negishi and Akira Suzuki for palladium-catalyzed cross couplings in organic synthesis”
- Palladium-catalyzed cross coupling reactions key for synthesizing complex organic molecules in lab
- Scientists now are able to make anti-cancer drug discodermolide in labs

Question 15

The origins of what is traced to sponges?

Answer 15

The origin of nerves
- Search of the genomic sequence of the sponge Amphimedon queenslandica reveal existence of core neurological genes
- Neurological genes expressed in the globular cells found in epithelia of larvae
- Globular cells have protrusions out into environments and may represent rudimentary sensory organs

Question 16

What was found about the internal composition of Trichoplax adhaerens and what did it suggest?

Answer 16

• They have just 4 cell-types and lack a stomach, muscles, nerves, and gonads - no organs
• Its genome contains ~11,514 protein-coding genes many which are counterparts (orthologs) to genes essential for organogenesis in more complex organisms
• Suggests that many genes have a deep evolutionary history

Question 17

What phyla do all animals except sponges belong to?

Answer 17

Eumetazoa, animals with true tissues

Question 18

Phylum Cnidaria

Answer 18

• The cnidarians (hydras, jellies, sea anemones, and coral) have a relatively simple radial body plan that arose 570 mya in the Ediacaran biota
• Most are marine
• The basic cnidarian body plan is a sac with a central digestive compartment, the gastrovascular cavity
• A single opening to this cavity functions as both mouth and anus

Question 19

Polyp & Medusa

Answer 19

Two variations on a basic body plan, one sessile (polyp), the other floating (medusa)
- Cylindrical polyps adhere to substratum by the aboral end, extend tentacles, and wait for prey
- Medusas (also called jellies) are flattened, inverted versions of polyps that drift passively and by contacting their bell-shaped bodies

Question 20

Cnidarians are carnivores

Answer 20

• Cnidarians use tentacles around the mouth to capture prey and push food into the gastrovascular chamber for digestion
• Batteries of cnidocytes on the tentacles for defense or prey-capture
  - Organelles called cnidae evert a thread that can inject poison into, stick to, or entangle prey
• Cnidae called nematocysts are stinging capsules

Question 21

How does the stinging of the nematocysts work?

Answer 21

• Discharge is very fast, microseconds
• Nematocysts are triggered when adjacent chemo and mechanoreceptors are triggered
• Nematocysts must be replaced once fired

Question 22

What is special about anemone fish?

Answer 22

• They exist in a mutual symbiosis with anemone
  
  • Fish defends host and uneaten food and feces
    feed the anemone
  • Slow moving fish get protection from host
• Avoids being stung by having a sugar-based mucous coating

Question 23

Muscles & Nerves

Answer 23

• Muscles and nerves exist in their simplest forms Epidermal & gastrodermal cells have contractile fibers of bundled microfilaments
  
  • True muscles appear first in triploblastic animals
  • With mouth closed, the gastrovascular cavity acts
    as hydrostatic skeleton for contractile cells to
    work
• Movements are controlled by a non-centralized nerve net associated with simple, radially distributed sensory receptors
• Can respond to stimuli from all directions

Question 24

What are the four main classes of Cnidarians?

Answer 24

• Hydrozoa (Portuguese man-of-war, hydras, Obelia, some corals)
• Scyphozoa (jellies, sea nettles)
• Cubozoa (box jellies, sea wasps)
• Anthozoa (sea anemones, most corals, sea fans)

Question 25

What are the three possible life histories of cnidarians?

Answer 25

- Some cnidarians exist only as polyps - Some exist only as medusas - Others pass sequentially through both a medusa stage and a polyp stage in their life cycle

Question 26

Hydrozoan Life Cycle

Answer 26

Most hydrozoans, e.g. Obelia, alternate between asexual polyps and medusa sexual stages

Question 27

Hydras

Answer 27

One of just a few freshwater cnidarians - In favorable environments, reproduces asexually by budding, forming outgrowths that pinch off from the parent - In poor conditions, they reproduce sexually to produce resistant zygotes - They have profound regeneration capacities

Question 28

Medusa-dominated life cycles

Answer 28

- The medusa generally prevails in the life cycle of the Cubozoa & Scyphozoa - The medusas of most species live among the plankton as jellies - Costal scyphozoans have small polyp stages during their life cycles - Jellies that live in the open ocean generally lack the sessile polyp

Question 29

What's so dangerous about cubozoa box jellyfish?

Answer 29

Toxins attack the heart, nervous system, and skin 1000's deaths by drowning attributed to stings

Question 30

What is the Anthozoa phylum mainly comprised of?

Answer 30

Anemones and corals - All occur only as polyps

Question 31

Corals

Answer 31

Solitary or colonial forms and secrete a hard skeleton of calcium carbonate - Each generation builds on the skeletal remains of earlier generations to form what eventually becomes a coral reef

Question 32

Sexual reproduction

Answer 32

- 75% of hard corals are hermaphrodites - Most hard corals "broadcast spawn" releasing eggs and sperm into the water - Event is synchronized by lunar cycle - Mass spawning events may explain the high rate of hybrid formation amongst corals

Question 33

What was discovered after the completion of the Nematostella genome sequence in 2007?

Answer 33

The genome shared remarkable 'synteny' with human genome, ie. many segments of genome with conserved gene order - Compelling evidence for shared ancestry of eumetazoans

Question 34

Who won the nobel prize in chemistry in 2008 and why?

Answer 34

Osamu Shimomura, Martin Chalfie and Roger Tsien for the initial discovery of GFP and a series of important developments which have led to its use as a tagging tool in bioscience - By using DNA technology, researchers can now connect GFP to other interesting, but otherwise invisible, proteins - This glowing marker allows them to watch the movements, positions and interactions of the tagged proteins

Question 35

Where is GFP found?

Answer 35

It is isolated from the jellyfish Aequorea victoria - used as a reporter of gene expression in molecular biology

Question 36

What is the difference between fluorescence and bioluminescence?

Answer 36

- In fluorescence, energy from a light source is absorbed and re-emitted as another photon - In bioluminescence is light produced by a chemical reaction, also used by many cnidaria

Question 37

Ctenophora

Answer 37

Named for their eight rows of comb-like plates composed of fused cilia which are used for movement - Most comb jellies have a pair of long retractable tentacles - These tentacles are armed with adhesive structures (colloblasts) that secrete a sticky threat to capture food

Question 38

What are some distinctive characteristics of ctenophores?

Answer 38

- Diploblastic with ectoderm and endoderm but have a middle layer called a mesoglea made of collagen - Tentacles covered in filaments called tentilla which contain colloblasts which lasso prey (do not possess nematocysts) - Some species are spherical or ovoid, others are elongate and ribbonlike