Poriferans and Placozoans
Published on: Mar 4, 2016
Transcripts - Poriferans and Placozoans
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 1880s 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.
Movement2 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