Reminder:
Protist = unicellular eukaryotes, no undergo gastrulation or tissue development
Metazoans = multicellular eukaryotes undergo gastrulation and tissue development
Basal Metazoan - early development
Porifera
sponges
benthic organisms ( bottom sea floor)
Not protist but also not metazoans
multicellular organism that has specialized cells for life functions
posses some metazoan characteristics
Characteristics
multicellular from embryonic layering
cell-cell communication
animal-like reproduction, with larval stage
Aquiferous system: water current channel powered by flagellated cells called choanocytes
nutrition: brings water containing food through the sponge where cells can phagocytize food particles
respiration: water contains oxygen where individual cells can carry out gas exchange
waste management: metabolic and digestive waste carried out through water currents
on cellular level: specialized cells carry out life function
Cellular Organization:
Cell types
organized into specific areas but are not true tissues
All cells = totipotent ( important for making up cell with aquifer)
pinacocyte: forms outer layer of sponge
amoebocyte: digestive and transports nutrients through body
porocyte: single cell, creates pores for water flow
choanocyte: all-purpose cells; water flow in, feeding, gas exchange, and waster
Body Type
Asconoid sponge
simplest
water flow through ostia
large cavity = spongocoel
water flows out through osculum
choanocytes line spongocoel
Syconoid sponge
bit more complex
water flow through ostia
channels line choanocytes
large cavity = spongocoel
water flows out through osculum
Leuconoid sponge
most complex
water flows through dermal pore ( ostia)
multiple canals and chambers
water flows out through osculum
choanocytes line chambers
Hexactinellid sponge
greater degree of radial symmetry
no pinacoderm
cellular distribution is sparse and forms trabecular network
Spicules
help give sponge form, shape, and support
type of spicules = taxonomy of sponge
Spicules Type:
silicious
calcareous
spongin
Feeding & Nutrient
filter feeders ( use choanocytes to create currents)
digestion carried out by individual cells
phagocytosis
pinocytosis
Sensory Capabilities
no evidence of use of neurons or discrete sense organs
still rely on individual cell responses
Reproduction and Development
sexual ( mostly)
cells release gametes ( sperm or eggs) into environment
Zygote = free-swimming larvae (they land somewhere and take root)
some budding ( asexual, clone off themselves and spread off, must contain archaeocytes)
Archaeocytes: totipotent cells capable of becoming anything
Gemmules: packets of archaeocytes protected by skeleton
Taxonomy
Class Calcarea
spicules of calcium carbonate
the 3 body types
all marine
Class Demospongia
spicules of silicon or sponging
Leuconoid
marine, brackish, and freshwater
Hexactinellida
spicules of silicon, 3 or 6-ray
trabecular network
glass sponge
all marine