Asconoid
Encyclopedia
Asconoid is one of three possible body plans for sponges, which form the phylum
Porifera in kingdom Animalia and subkingdom Parazoa
which means that they do not have a definite body shape. The asconoid body plan is characterized by a stalk-like spongocoel surrounded by a single layer of choanocyte
s. These choanocytes are cells that have flagella, and the flagella beat to push water through the spongocoel, creating a current
. At somewhat regular intervals along the lining of the spongocoel are openings called ostia (singular, ostium). These protrude through the outer layer of the sponge (somewhat like an epidermis
, but not entirely like it, since this terminology implies germ layer
s, which sponges do not have). Finally, at the top of the sponge is the osculum
, which is the final exit for water circulating through the sponge.
This single layer of choanocytes limits the size of asconoids, with the largest having a diameter of only 1 mm. This is due to the surface area : mass ratio which would not allow an asconoid sponge of larger size sufficient nutrition.
Phylum
In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....
Porifera in kingdom Animalia and subkingdom Parazoa
Parazoa
The Parazoa are an ancestral subkingdom of animals, literally translated as "beside the animals".-Description:Parazoans differ from their choanoflagellate ancestors in that they are not microscopic and have differentiated cells. However, they are an outgroup of the animal phylogenetic tree being...
which means that they do not have a definite body shape. The asconoid body plan is characterized by a stalk-like spongocoel surrounded by a single layer of choanocyte
Choanocyte
Choanocytes are cells that line the interior of Asconoid, syconoid and leuconoid body type sponges that contain a central flagellum surrounded by a collar of microvilli which are connected by a thin membrane. It is the closest family member to the free-living ancestor called choanoflagellate...
s. These choanocytes are cells that have flagella, and the flagella beat to push water through the spongocoel, creating a current
Ocean current
An ocean current is a continuous, directed movement of ocean water generated by the forces acting upon this mean flow, such as breaking waves, wind, Coriolis effect, cabbeling, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
. At somewhat regular intervals along the lining of the spongocoel are openings called ostia (singular, ostium). These protrude through the outer layer of the sponge (somewhat like an epidermis
Squamous epithelium
In anatomy, squamous epithelium is an epithelium characterised by its most superficial layer consisting of flat, scale-like cells called squamous epithelial cells...
, but not entirely like it, since this terminology implies germ layer
Germ layer
A germ layer, occasionally referred to as a germinal epithelium, is a group of cells, formed during animal embryogenesis. Germ layers are particularly pronounced in the vertebrates; however, all animals more complex than sponges produce two or three primary tissue layers...
s, which sponges do not have). Finally, at the top of the sponge is the osculum
Osculum
The osculum is an excretory structure in the living sponge, a large opening to the outside through which the current of water exits after passing through the spongocoel. Wastes diffuse into the water and the water exits through the osculum at a velocity of nearly 8.4 cm/second, carrying away with...
, which is the final exit for water circulating through the sponge.
This single layer of choanocytes limits the size of asconoids, with the largest having a diameter of only 1 mm. This is due to the surface area : mass ratio which would not allow an asconoid sponge of larger size sufficient nutrition.