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Poriferans (sponges)
• ‘pore bearing’• Spongocoel• Choanocytes or Collar cells• Archeocytes• Epidermal cells• Has Mesophyl sandwiched between two thin layers
of cells.
Defining Characteristics
• Microvillar collars surround flagella, with units arising from either single cells or syncytia.
• Lack nerves and no true musculature.
Skeleton• Sponges are either radially symmetrical or
asymmetrical.
• Mesohyl=Endoskeleton • Spicules=Sclerocytes• Spongin=Spongocytes
Food Capture and Digestion
• detritus particles, plankton, bacteria
• Choanocytes
• Food items are taken into individual cells by phagocytosis, and digestion occurs within individual cells.
Excretion and Water Balance
• A sponge has carbon dioxide and other wastes removed as the water moves in and out through the pores.
Respiration and internal Transport
• Diffusion of gases through the help of water
• Archeocytes remove mineral particles that threaten to block the ostia.
Nervous System
• A sponge has a very low level reaction to the world around it and does not have a brain per se.
Reproductive system
• Asexual+fragmentation+buds
*external buds*internal buds or gemmules
• Sexual (mesohyl)+eggs and sperms+hermaphroditic
*External and internal fertilization
Development
• Hollow blastula or Coeloblastula
• Amphiblastula-the hollow sponge larvae
• Some species, from coeloblastula to stereoblastula
• Larvae are incapable to feeding and swim for less than 24 hours before metamorphosing.
Ecology and Evolution
• 98% in marine
• 2% in water and mostly with spongin fiber
• Many in tropics
• Sponges have strong structures that are able to handle the high volume of water that flows through them each day
• release toxic substances into the environment
PLACOZOANS (Flat plate)
• They were discovered in the late 1880's living on the glass walls of an aquarium in a European laboratory.
• Single species
Defining Characteristic
• Multicellular• Amorphous• Mobile• flagellated animals lacking a body cavity, digestive
system and nervous system • composed of 2 layers of epithelial cells.
• 2 distinct layers of epithelial cells +ventral- columnar cells w/ flagellum
- Glandular cells with enzymes - Endodermal
+Dorsal- Flat, thinner and No gland cells. -Ectodermal
+In between- fluid-Contractile fibrous cells.
Movement
2 Ways;
• gliding on their cilia
• changing their shape like an amoeba.
Digestion
• Atops the food using the Ventral surface • No sign of phagocytosis• Extracellular digestion
Reproduction
• Sexual
+ generally, produces one oocyte.
+developed embryos
• Asexual
+Budding
+Fragmentation
+Binary fission