Animal Bio: Sponges

Phylum

Porifera

choanoflagellates

solitary aquatic eukaryotes with each cell carrying a flagellum surrounded by collar of microvilli

choanocytes

water current brings food down to the cell for feeding (feeding cells)

they look like choanoflagellates and bear flagellum surrounded by a collar

choanocytes

body plan of sponges

all aquatic (mostly marine) many types of sponges

adults are sessile (not moving)

asymmetrical

internal skeleton (endoskeleton) with no muscles, sense organs, or nervous system

Ostia

draws water through the sponge mediated by the beating of choanocytes (they line the Ostia and water current is created in the chamber to draw it up and through the top)

Osculum

water passes out through diffusion (sponges obtain oxygen and filter food from water)

asconoid body plan

choanocytes line spongocoel (cavity where water flows up and out the osculum)

synconoid body plan

larger unfolds lined by choanocytes that pull water up and through the osculum

leuconoid body plan

osculum is smaller and has incurrent canals from chamber of choanocytes that pull water up and through the osculum

Endoskeleton of sponges

fibrous matrix (spongin and calcium-based) or siliceous or crystalline spicules (rigid components)

some animals like shrimp can get inside endoskeleton and produce offspring

mesohyl cell type

gelatinous extracellular matrix contains cells, fibrils, spicules

pinacocytes cell type

outer surface of thin, flat, epithelial-like cells (body sits down in the mesohyl)

archaeocytes cell type

amoeboid cells involved in digestion of food particles

sclerocytes cell type

secrete spicules

collenocytes cell type

secrete spongin (fibrous component of endoskeleton and mesohyl)

microvilli forms…

collar comprises fine filtering device for straining small food particles and organic carbon

beating of flagellum

pulls water through collar and forces water out

food particles too large…

get trapped In secreted music and slide down collar to base where they are taken into cell by phagocytosis

food engulfed in choanocytes…

is passed to archeocytes for digestion (then nutrients get distributed to rest of the cells)

asexual reproduction (somatic embryogenesis)

a single somatic cell that divides to create a new sponge (a form of budding)

external bud formation

portion of sponge breaks free and floats away to form new sponge

internal bud formation

gemmules are formed when sponge cells becomes covered in spongin and spicules

when a gemmule forms…

the parent animal dies

micropyle

cells in gemmule escape through here and develop into new sponges (at the top)

Sexual reproduction in sponges

monoecious (male and female organs), sperm from one sponge released into water and drift into canals of other sponge (external)

sperm are carried by…

choanocytes and archaeocytes to oocytes

parenchymula larva

embryo grows into this after fertilization (specialized for movement)

released into the water and settled onto substrate (undergoes development to then form a new sponge)

Class Calcispongiae

spicules composed of calcium carbonate

small, tubular or vase-shaped

asconoid, synconoid, or leuconoid body forms

Class Hexactinellida (glass sponges)

spicules composed of silicon dioxide (what makes up glass)

spicules have 6 rays (hence “hexa”)

found in deep ocean (Arctic and Northern Pacific waters)

long, vase-shaped

lattice-like network of spicules

Class Demospongiae

95% of all species of sponges (most common and diverse)

variety of shapes, sizes, colours,

siliceous spicules bound by spongin

leuconoid body form (tube form)

look similar to coral reefs sometimes