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BIOL 2030 Lecture Notes - Mesohyl, Choanocyte, Mesoglea

Course Code
BIOL 2030
Scott Kelly

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Porifera - Sponges
[Sponges] Phylum of simple multicellular animals, with a simple body enclosing a
single central cavity (in simple sponges) or penetrated by numerous interconnected
cavities. The body wall consists of an outer layer of epithelium seprated from an inner
layer of ciliated choanocytes (feeding cells) by a mesogleal layer. There are no nerve
or muscle cells. Water is drawn into the internal cavities through pores (ostia), food
particles are taken up by the choanocytes and the water flows out through a large
pore (the osculum). There are three classes: the Calcarea, the calcareous sponges,
which have spicules of calcium carbonate embedded in the mesoglea and projecting
to the outside; the Hexactinellida, the glass sponges, with silica spicules; and the
Demospongia, which includes some species with silica spicules and some species
without, and which often have the body wall strengthened by a tangled mass of
fibres (ex. The bath sponge)
Exhalent pore of sponges (leading from radial canal to spongocoel)
Amoeboid cells found in the mesohyl of sponge
Flagellated cell, with protoplasmic collar around base of the flagellum, lining body
cavity of sponges. Involved in uptake of food particles from water drawn into cavity
by the beating of the flagella
Dermal ostium
Skin ostium, present in leuconoid sponges
Incurrent canal
Ectoderm-lined canas which admit water into sponges (no choanocytes)
[mesoglea] gelatinous, non-cellular layer between the inner and outer body wall in
sponges and coelenterates.
Large pore in body wall of sponge through which water flows out the body cavity
Opening from exterior into body cavity of sponges through lateral wall, through
which water is drawn in
Flattened plate-like cells of outer epithelium of sponges
Inhalent pore of sponges
Radial Canal
[Coanocyte Chamber]
Small needle-like structure or part, of silicate or calcium carbonate, providing
structural integrity in sponges
Fibrous protein component of the horny sponges, such as bath the sponge
The cavity, or system of cavities in sponges
Ability of forming any cell type
Overview of filter-feeders
Cellular level of organization (no tissues/organs)
Share few chars with metazoans (“Parazoans”)
Sessile, aquatic filter feeders
09% marine (few freshwater ~10K species); free-living @ larval stage
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