Chapter 12 Porifera/sponges

Porifera characteristics

radial or no body symmetry
all aquatic, mostly marine but some freshwater, a few brackish
Cell level organization, but the cells have specialties that let them function like tissues
Body made of pores(ostia) and canals, with spicules and spongin for structural support
no organs, but can respond to stimuli
free- swimming embryo, adults are sessile/attached to something
no gastrulation = no gut
Skeletal structure of fibrillar/spongin collagen and calcareous/siliceous crystalline spicules
digestion intracellular
excretion and respiration by diffusion
asexual reproduction by buds or gemmules
sexual reproduction by eggs and sperm
Outer surface of flat pinacocytes
interior lined with choanocytes
mesohyl contains amebocytes of various types and skeletal elements

Homoscleromorpha

massive/encrusting in form
no skeleton, but if present is made of siliceous spicules
yes to spongin fibers
pinacoderm (possible true tissue) with a distinct basement membrane
sycon/leucon

Hexactinellids

‘glass sponge’
skeleton is made up of six-rayed siliceous spicules
syncytial body structure (a single cell containing multiple nuclei, formed by the fusion of several individual cell)
SYCON/LEUCON

Calcarea

skeleton is composed of calcareous spicules made of calcium carbonate
NO spongin
spicules are 3-4 ray
asconoid, syconoid, or leuconoid

Demospongiae

leuconid
skeleton : spicules of spongin fibres, the mineral silica, or both, which are monoaxon and triaxon
All but 1 are marine

spicules

point structures that are rigid skeletons and defense for sponges
made of silica or calcium carbonate

spongin

protein that makes up the flexible body wall of a sponge, provide sstructure

ostia/ostium

pore that allows for the entry of water in a sponge

oscula/osculum

the main ‘out’ hole in a sponge

ecological importance?

-protection to other animals
- food for some animals like turtles, angel fish, marine mollusks
-water filtration (remove organic substances (debris, oil, bacteria)

pharmacological use?

make many drugs used for humans (if they can filter shit for centuries and survive, they’re doing something right)
-ara-A (antiviral drug) is in clinical use against the herpes simplex encephalitis virus
-manzamine A has activity against malaria, tuberculosis, HIV and others
-lasonolides have antifungal activity
-psammaplin A has antimicrobial activity

asconoid

Ostulum→Spongocoel→Osculum
super simple
limitations because choanocytes line the spongocoel and can collect food only from water directly adjacent to the spongocoel wall
small, tube shaped

syconoid

dermal ostium→incurrent canal→prosopyle→radial canal→apocyte→spongocoel→osculum
tube body, ‘arger asconoid’ except the body wall (actually spongocoel lining) is now outward to increase surface area

leuconoid

Ostia→Incurrent Canal→Prosopyles→Flagellated Chambers (lined with choanocytes)→Apopyles→Excurrent Canals→Oscula
Most complex
lots of surface area=lots more to filter=biggest

how do sponges eat?

use endocytosis (plasma membrane pinches inward and surrounds the food) after choanocytes trap their food, and digested inside the cell. archaeocytes move left over food from cells that already ate to other cells

asexual reproduction

Somatic embryogenesis (complete regeneration of the structure from wounded or cut parts) – “involuntary”
Fragmentation followed by regeneration
External bud formation: Budding
Internal buds: Gemmulation

Sexual reproduction

Spawning
most are monoecious, gametes come from choanocytes OR archaeocytes
Some release both sperm and eggs into the water column
Some keep the egg and then the zygote (viviparous)
All have a free floating larva

pinacoderm

outer layer, ‘epithelial’ tissue
pinacocytes and myocytes

pinacocytes

protection & contraction (for surface area regulation)
can phagocyte food

myocytes

‘modified pinacocytes’
regulate water flow around the ostia and oscula (in and out)

mesohyl

middle layer
Gelatinous extra cellular matrix - forms the “connective tissue” of sponges
spicules, fibrils, and a few cells
Archaeocytes, sclerocytes, Spongocytes, Collenocytes

choanoderm

inner layer with choanocytes

archaeocytes

feeding through phagocytosis

sclerocytes

make spicules

spongocytes

make spongin fibers

collenocytes

make collagen fibers

choanocyte

used for water flow and food capture
have a central flagellum surrounded by a collar of microvilli connected by a thin membrane
also forms spermatocytes

basal tufts

anchor sponge in soft sediments

basal disc

cement sponge to hard surfaces