AD Sponges and Cnidaria Flashcards
Describe sponges
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
What is the body symmetry of a sponge?
Radial (sphere,cone,cylinder) or asymmetrical
What is the growth form of a sponge?
Thick,erect,branching,encrusting
What is the sponge architecture?
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
Why is there a constant flow of water through incurrent pores into atrium and out the osculum of the sponge?
It carries food particles and oxygen and excretion products containing carbon dioxide
What is the outer surface of the sponge covered by?
Pinacocytes which make up the pinacoderm
In a sponge, beneath the pinacoderm is the mesohyl. What is this?
A gelatinous protein matrix
Contains skeletal material and amoeboid cells.
The skeletal components are spicules of calcium, carbonate or silica, spongin fibers.
What are archeocytes?
Amoeboid cells
They are phagocytic and function in digestion. They are totipotent.
What is a choanocyte?
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
The body plan of the sponge is based on 1 of 3 designs. What are these designs?
Asconoid - a hollow cylinder
Syconoid - interdigitating inpockets and outpockets
Leuconoid - Complex network of water vessels
What sized particles can and cannot enter the ostia and why?
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
What is suspension feeding?
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
Describe the skeleton of a sponge?
Usually an endoskeleton
Fibrous - made of spongin
Spicules - calcium carbonate or silica
Describe sexual reproduction in sponges
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
Describe asexual reproduction in sponges
Produce buds or gemmules (packets of several cells inside a protective covering)
What is the ecological and economic importance of sponges?
Water filters Organiser of communities Food for animals (turtles) Bio-erosion by some spp. Used as tools by humans and bottlenose dolphins
What animals are part of the sample Cnidaria?
Jellyfish, sea anemones, corals
Describe the phylum Cnidaria?
Muscle and nerve cells
Stinging cells - cnidocyte
Mostly marine, some freshwater
Polar regions to tropics
What is the basic ‘sac’ body plan of the Cnidaria
Gastrovascular cavity is surrounded by the gastrodermis and then the epidermis.
The gastrovascular cavity can act as a hydrostatic skeleton
What are the 2 variants of a single body plan of a Cnidaria?
Medusa - mouth and tentacles face downwards
Polyp - mouth and tentacles face upwards
What is the mesoglea?
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
How do the Cnidaria reproduce?
Asexual (budding) and sexual
No typical life cycle
What are hydrozoans?
They are polyps most of the time
Often colonial with specialised polyps (feeding, reproduction)
Is a Scyphozoa (jellyfish) a polyp or medusa most of the time?
Medusa
What is a cubozoa?
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
How do the Cnidaria move?
eg scyphozoa and cubozoa and zooplankton
Syphozoa and Cubozoa - contractions of the ‘bell’
Also passive movements - carried by current (zooplankton) or wind.
Describe Cnidaria’s nutrition
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
Describe the relationship between alga and polyp
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
What are the ecological and medical importance of Cnidarians
coral reefs - provide environment with high diversity of life, barrier against wave action
jellyfish stings - can be lethal, especially against cubozoans
Describe the major features of the Cnidaria
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
What is the rhizostome (root-mouth) jellyfish
No single downwards pointing mouth
Instead, there are several mouth on each of the 8 branching ‘arms’
Are Anthozoans (sea anemones and corals) polyps or medusas all of the time? Describe them
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)
