Porifera Flashcards
Sponges consist of ____ cell layers and are filled with ______
Two, mesohyl
Sponges have _____ cells that can _____ between cell layers
unspecialized, migrate
Sponges were ______ to branch off of evolutionary tree.
First
How are sponges similar to other animals? How are they different?
Similar: multicellular heterotrophs that lack cell walls and produce sperm cells
Different: lack true tissues, organs and have no body symmetry
What is the hole that water leaves through called?
The osculum
What is the internal skeleton of a sponge like?
Spongin (collagen bound fibers) and/or spicules of calcium carbonate or silicon dioxide.
Describe their life cycle
Most species use sexual reproduction, releasing sperm cells into the water to fertilize ova that in some species are released and in others are retained by the “mother”. The fertilized eggs form larvae which swim off in search of places to settle.[9] Sponges are known for regenerating from fragments that are broken off, although this only works if the fragments include the right types of cells.
What is the function and composition of the mesohyl?
The mesohyl functions as an endoskeleton in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks. More commonly, the mesohyl is stiffened by mineral spicules, by spongin fibers or both.
Calcareous sponges, which have calcium carbonate spicules and, in some species, calcium carbonate exoskeletons, are restricted to ______ marine waters where production of calcium carbonate is easiest
shallow
Difference between Porifera and Cnidaria?
Porifera:
: no nervous system
: no inter cell connections or basement membrane
: lots of cells in middle jelly layer compared to few in Cnidaria
: cells can migrate between layers and change functions.
What is a choanocyte?
Cells with cylindrical or conical collars surrounding one flagellum per choanocyte. The wave-like motion of the whip-like flagella drives water through the sponge’s body
What is an ostia?
Channels leading to the interior through the mesohyl, and in most sponges these are controlled by tube-like porocytes that form closable inlet valves
Describe the process of water flow in a sponge.
Sponges can control the water flow by various combinations of wholly or partially closing the osculum and ostia (the intake pores) and varying the beat of the flagella, and may shut it down if there is a lot of sand or silt in the water.
Describe the skeleton of Porifera
The mesohyl functions as an endoskeleton in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks. More commonly the mesohyl is stiffened by mineral spicules, by spongin fibers or both. Spicules may be made of silica or calcium carbonate, and vary in shape from simple rods to three-dimensional “stars” with up to six rays. Spicules are produced by sclerocyte cells,[21] and may be separate, connected by joints, or fused.[20]
Some sponges also secrete exoskeletons that lie completely outside their organic components. For example, sclerosponges (“hard sponges”) have massive calcium carbonate exoskeletons over which the organic matter forms a thin layer with choanocyte chambers in pits in the mineral. These exoskeletons are secreted by the pinacocytes that form the animals’ skins.[21]
How do sponges feed?
They filter food particles out of the water flowing through them. Particles larger than 50 micrometers cannot enter the ostia and pinacocytes consume them by phagocytosis (engulfing and internal digestion). Particles from 0.5 μm to 50 μm are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by archaeocytes which partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5 micrometers, pass through the ostia and are caught and consumed by choanocytes.[21] Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge’s food supply
Describe respiration and excretion in Porifera
Sponges’ cells absorb oxygen by diffusion from water into cells as water flows through body, into which carbon dioxide and other soluble waste products such as ammonia also diffuse. Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons
Describe sponge life span
Sponges in temperate regions live for at most a few years, but some tropical species and perhaps some deep-ocean ones may live for 200 years or more. Some calcified demosponges grow by only 0.2 mm (0.0079 in) per year and, if that rate is constant, specimens 1 m (3.3 ft) wide must be about 5,000 years old. Some sponges start sexual reproduction when only a few weeks old, while others wait until they are several years old
What is sponge’s role as primary producer?
Sponges with photosynthesizing endosymbionts produce up to three times more oxygen than they consume, as well as more organic matter than they consume. Such contributions to their habitats’ resources are significant along Australia’s Great Barrier Reef but relatively minor in the Caribbean
Describe sponge defenses
Many sponges shed Sponge spicules, forming a dense carpet several meters deep that keeps away echinoderms which would otherwise prey on the sponges.[31] They also produce toxins that prevent other sessile organisms such as bryozoans or sea squirts from growing on or near them, making sponges very effective competitors for living space
Describe the role of sponges in bioerosion of reefs
The Caribbean chicken-liver sponge Chondrilla nucula secretes toxins that kill coral polyps, allowing the sponges to grow over the coral skeletons.[21] Others, especially in the family Clionaidae, use corrosive substances secreted by their archeocytes to tunnel into rocks, corals and the shells of dead mollusks.[21] Sponges may remove up to 1 m (3.3 ft) per year from reefs, creating visible notches just below low-tide level.[
