AD Sponges and Cnidaria

Question 1

Describe sponges

Answer 1

Mostly marine, some freshwater
Shallow to abyssal waters
Sessile as adults
4 classes - none monophyletic
No muscle or nerve cells
Connective materials well developed - form a complex skeletal lattice
Size: a few millimetres to more than 1m in diameter and height
Many brightly coloured

Question 2

What is the body symmetry of a sponge?

Answer 2

Radial (sphere,cone,cylinder) or asymmetrical

Question 3

What is the growth form of a sponge?

Answer 3

Thick,erect,branching,encrusting

Question 4

What is the sponge architecture?

Answer 4

No true tissues or organs
System of water canals
Surface perforated with openings
These are incurrent pores or ostia
Water enters here
Pores open into the atrium
Water leaves the atrium through the osculum

Question 5

Why is there a constant flow of water through incurrent pores into atrium and out the osculum of the sponge?

Answer 5

It carries food particles and oxygen and excretion products containing carbon dioxide

Question 6

What is the outer surface of the sponge covered by?

Answer 6

Pinacocytes which make up the pinacoderm

Question 7

In a sponge, beneath the pinacoderm is the mesohyl. What is this?

Answer 7

A gelatinous protein matrix
Contains skeletal material and amoeboid cells.
The skeletal components are spicules of calcium, carbonate or silica, spongin fibers.

Question 8

What are archeocytes?

Answer 8

Amoeboid cells

They are phagocytic and function in digestion. They are totipotent.

Question 9

What is a choanocyte?

Answer 9

Line the interior of sponges- make up the choanoderm
Have a flagellum, collar of microvilli and a cell body
Flagella beat to create the active pumping of water through the sponge
The collar is where nutrients are are absorbed

Question 10

The body plan of the sponge is based on 1 of 3 designs. What are these designs?

Answer 10

Asconoid - a hollow cylinder
Syconoid - interdigitating inpockets and outpockets
Leuconoid - Complex network of water vessels

Question 11

What sized particles can and cannot enter the ostia and why?

Answer 11

Large particles (more than 50um) cannot enter the ostia - pinacocytes consume them by phagocytosis
Medium sized particles (1um to 50um) are trapped in the ostia and are consumbed by archaeocytes - these cells partially excrude themselves through the walls of the ostia
Small particles (0.1-1.5um) pass through the ostia and are captured and consumed choanocytes.
Choanocytes typically capture 80% of a sponge’s available food supply

Question 12

What is suspension feeding?

Answer 12

Capturing suspended food particles
from water
by passing a current of water through the body
Some sponges harbour photosynthesising mutualists (green algae, dinoflagellates,
cynobacteria)
Sponges of the family Cladorhizidae are unusual in being carnivores - typically feed
by capturing & digesting whole animals (small crustaceans) with their spicules

Question 13

Describe the skeleton of a sponge?

Answer 13

Usually an endoskeleton
Fibrous - made of spongin
Spicules - calcium carbonate or silica

Question 14

Describe sexual reproduction in sponges

Answer 14

Sexual = hermaphrodites
Produce eggs and sperm at different times
However the barrel sponge is dioecious
Sperm is released into the surrounding area via the osculum
Can look as if the sponge is smoking
Sperm is captured by female-phase sponges via the ostia
Zygote develops into a ciliated larva
Some sponges release larva, some keep them for a while
Once the larva are in the water column, they settle and develop into juvenile sponges

Question 15

Describe asexual reproduction in sponges

Answer 15

Produce buds or gemmules (packets of several cells inside a protective covering)

Question 16

What is the ecological and economic importance of sponges?

Answer 16

Water filters
Organiser of communities
Food for animals (turtles)
Bio-erosion by some spp.
Used as tools by humans and bottlenose dolphins

Question 17

What animals are part of the sample Cnidaria?

Answer 17

Jellyfish, sea anemones, corals

Question 18

Describe the phylum Cnidaria?

Answer 18

Muscle and nerve cells
Stinging cells - cnidocyte
Mostly marine, some freshwater
Polar regions to tropics

Question 19

What is the basic ‘sac’ body plan of the Cnidaria

Answer 19

Gastrovascular cavity is surrounded by the gastrodermis and then the epidermis.
The gastrovascular cavity can act as a hydrostatic skeleton

Question 20

What are the 2 variants of a single body plan of a Cnidaria?

Answer 20

Medusa - mouth and tentacles face downwards

Polyp - mouth and tentacles face upwards

Question 21

What is the mesoglea?

Answer 21

Translucent jelly-like substance
Mostly water and fibrous proteins (collagen)
In hydroids, it is thinner than other layers (gastrodermis eg) but in large jellyfish it can make up the bulk of the body
Serves as an endoskeleton
Elastic properties help animals to restore shape after deformation by muscular contraction

Question 22

How do the Cnidaria reproduce?

Answer 22

Asexual (budding) and sexual

No typical life cycle

Question 23

What are hydrozoans?

Answer 23

They are polyps most of the time

Often colonial with specialised polyps (feeding, reproduction)

Question 24

Is a Scyphozoa (jellyfish) a polyp or medusa most of the time?

Answer 24

Medusa

Question 25

What is a cubozoa?

Answer 25

Box jellyfish Have 24 eyes 6 of those eyes have a lens + iris + retina, & may form an image of a distant object Venom of some spp. may have a delayed major effect on human physiology & psychology

Question 26

How do the Cnidaria move? | eg scyphozoa and cubozoa and zooplankton

Answer 26

Syphozoa and Cubozoa - contractions of the 'bell' | Also passive movements - carried by current (zooplankton) or wind.

Question 27

Describe Cnidaria's nutrition

Answer 27

Cnidocytes on tentacles & other structures discharge cnidae (harpoons) Prey is paralysed by venom injected by each cnida Cnidae may also inject a proteolytic enzyme Amino acids and other chemicals (reduced glutathione) released by stung prey stimulate mouth-opening, & the tentacles convey prey to mouth Many cnidarians also harbour mutualistic dinoflagellate algae (zooxanthellae) in gastroderm • e.g. corals

Question 28

Describe the relationship between alga and polyp

Answer 28

polyp supplies the alga with nutrients alga provide the polyp with oxygen and helps with the conversion of carbon dioxide to carbonate to form the skeleton of coral

Question 29

What are the ecological and medical importance of Cnidarians

Answer 29

coral reefs - provide environment with high diversity of life, barrier against wave action jellyfish stings - can be lethal, especially against cubozoans

Question 30

Describe the major features of the Cnidaria

Answer 30

Sac body plan • Tentacles surrounding mouth • Radial symmetry around mouth-foot axis • Muscles present • Nervous system: net or lattice • Skeleton in some: mesogloea/chitin/collagen/ calcium carbonate • Epidermis contains cnidocytes (harpoon-like stinging cells), these are also called nematocytes • Extracellular digestion (allows large food items to be digested) • Some have colonial growth form • Three stem cell lineages

Question 31

What is the rhizostome (root-mouth) jellyfish

Answer 31

No single downwards pointing mouth | Instead, there are several mouth on each of the 8 branching 'arms'

Question 32

``` Are Anthozoans (sea anemones and corals) polyps or medusas all of the time? Describe them ```

Answer 32

``` Polyps all of the time Sea anemones can detach and creep And they can detach and swim Coral colonies expand in size-area by budding-off zooids (forming a massive clone) ```