asymmetrical
superficially radially symmetrical
No true tissue or organs
loosely organized interdependent cells
3 types of cells (division of labor)
pinacocytes,
mesenchyme,
choanocytes
Pinacocytes
thin, flat cells that line the outer surface of a sponge
-mildy contractile which changes shape
-some are specialized into tubelike, contractile porocytes
Porocytes
regulate water circulation
-make pathways for water moving the body wall
Mesenchyme (amoeboid)
move about in mesohyl, jelly-like layer below pinacocytes
-specialized for reproduction, secreting skeletal elements, transporting and storing food, and forming contractile rings around openings in sponge wall
Choanocytes (collar cells)
below mesohyl, and line inner chamber
- flagellated cells that create water currents
-cell collar filters food particles from water
Skeleton
made of 1 of 2 main types of cells
-spicules, spongin
Spicules
needle like spikes, take a variety of shapes, made of calcium carbonate or silica
Spongin
fibrous protein made of collagen
Adults are "sessile
doesn't move as an adult only in immature stages
Sponges are dependent on water currents created by
choanocytes
Porifera body forms
Ascon
Sycon
Leucon
Spongocoels
inner chambers
Ostia (ascon)
outer openings of porocytes (water INflow)
Dermal pores (sycon/leucon)
outer openings of porocytes (water INflow)
Osculum
single opening to spongocoel
- water OUTflow
(except in leucon which has multiple oscula)
Canals
incurrent, radial, and excurrent
-in complex, branched sponges
Ascon
vase-like
simplest but least common
-ostia lead directly to spongocoel
-choanocytes draw water in with flagella movement
-in ostia and out single terminal osculum
Sycon
folded walls
-water enters dermal pores of incurrent canals (inside the folds, but not inside the sponge)
-pores in radial canals (inside the fold and sponge lead to spongocoel)
-choanocytes like the radial canals (not incurrent)
-water exits through 1 os
Leucon
branched canals
-water enters by DERMAL PORES and flows thru branched incurrent canals, leading to choanocyte-lined chambers
-excurrent canals lead away from chambers
-no true spongocoel
-multiple oscula
internal surface area __ in __ sponges, and they have more choanocytes
greater
complex
Porifera Maintenance Functions
Filter feed on bacteria, algae, protozoa, and suspend organic matter
-choanocytes trap food and mesenchyme (in mesohyl) cells transport
-nitrogenous wastes diffuse from cells directly into water
-NO NERVOUS sys
Porifera - Sexual Reprouction
most are monoecious (produce both sperm and egg) but do not self fertilize
-some choanocytes lose collars/flagella and undergo meiosis to form sperm and others form eggs
-eggs and sperm are released from oscula and fertilization is in open water (external
Porifera - Asexual Reproduction
freshwater and some marine species form GEMMULES (capsules of amoeboid cells that resist freezing and drying)
-some sponges can regenerate from broken off pieces