Porifera and Cnidaria: Biology Notes

PORIFERA (Parazoans) ★​ Meaning “pore-bearing” ★​ Highly harvested for research ★​ Sponges are in marine environments Structure ​ Cellular level of body organization, simple body plan. ​ Asymmetrical (entire body) or radial symmetry (not perfect). ​ Get food through filtration. ​ M...

PORIFERA (Parazoans) ★​ Meaning “pore-bearing” ★​ Highly harvested for research ★​ Sponges are in marine environments Structure ​ Cellular level of body organization, simple body plan. ​ Asymmetrical (entire body) or radial symmetry (not perfect). ​ Get food through filtration. ​ Mesohyl - the middle layer, also known as the “no germ layer.” ○​ Composed of spongin and spicules. ​ Spongin - a collagen protein that forms a network of fibers within the mesohyl. ​ Spicules - a needle-like skeletal system made of calcium carbonate or silica that stiffens the mesohyl, used to ID sponges; crucial for identification, has three classes: 1.​ Calcarea (calcium) 2.​ Demospongiae (calcium and/or silica) 3.​ Hexactinellida (silica) ​ Spongocoel - water enters; the large, central cavity of sponges ​ Osculum - water exits; excurrent pore, the central opening which serves as both mouth and anus ​ Porocytes - tube-like cells that make up the pores of the sponges (ostia), control the amount of water that enters pores into the spongocoel ​ Prosopyles - facilitates water and food particles to the choanocytes ​ Ostium/Ostia - incurrent pore, allows water to enter the sponge Incurrent vs. Excurrent Pores ​ Incurrent pores - ostia, opening where water first enters the sponge and then is distributed to all pores, facilitates filter feeding and gas exchange ​ Excurrent pores - osculum, a large opening through which water is expelled after carrying in nutrients and oxygen through smaller pores called ostia. Difference Between Choanocytes vs. Amoebocytes ​ Choanocytes - flagellated collar cell among sponges​ ​ ​ - from choanoflagellates (ancestors), flagellum has whip-like ​ ​ ​ structure​ ​ ​ - lining the body plan for poriferans​ ​ ​ - facilitates filtering (food particles and movement of water in/out of ​ ​ ​ sponges  ​ Amoebocytes - from amoeba​ ​ ​ - food through absorption; gastrovascular cavity​ ​ ​ - facilitates digestion​ ​ ​ - have pseudopodia extend to engulf Classification of Sponges ​ Based on body type ​ Counterpart: Hydra (freshwater, no flagellated collar cell) ​ To distinguish the body plan and type of the sponge, it is crucial to dissect their parts and identify them through a dissecting microscope. 1.​ Asconoid - smallest part, simplistic body plan​ ​ - radially symmetrical (resembling tubes) with a central cavity ​ ​ (spongocoel) 2.​ Syconoid - middle-sized, one of the bases in classifying, has thick body wall​ ​ - thicker with more complex canal systems than asconoid sponges. 3.​ Leuconoid - largest size, most complex canal system, typically asymmetrical​ ​ - provides a large surface area for filtering water ​ Sponges are sedentary/sessile. They are stuck to the ground, which is why scientists only acquire a portion of the sponge when doing research; getting the whole sponge is equivalent to destroying biodiversity. Reproduction in Poriferans ​ Sponges are capable of sexual reproduction but mostly do asexual reproduction. ○​ Asexual Reproduction 1.​ Budding - in asconoid and syconoid 2.​ Fragmentation 3.​ Regeneration - repair of damaged tissues for animalia ○​ Sexual Reproduction ​ Monoecious - hermaphroditic, has both male and female reproductive organs ​ Identification of Gametes ​ Sperm (Male): Choanocytes ​ Egg (Female): Amoebocytes ​ Fertilization ↳​ Internal: more advantageous ↳​ External: at a disadvantage due to pH levels, temperature, currents, and predators ↳​ Cleavage is holoblastic; complete cleavage that divides the egg into distinct and separate blastomeres ​ Sponges’ respiration is through diffusion. CNIDARIA (Coelenterata) ★​ Has ~9,000 species Description and Composition of Cnidaria ​ Consists of jellies (jellyfish; cnidocytes), hydras (freshwater), sea anemone, and corals (hard or soft) ○​ They only have one opening that acts as both the mouth and anus ​ Soft-bodied invertebrates (except for hard corals), and are carnivorous ​ Have stinging capsules called nematocysts ​ Cnidocytes - contain nematocysts and are inverted cells ​ Majority have tentacles ​ Diploblastic, sessile, has a nerve net, gastrovascular cavity, simple muscles, and radial symmetry Body Forms 1.​ Medusa/Medusae - umbrella-shaped with mouth, surrounded with tentacles 2.​ Polyp - tube-like, surrounded with tentacles​ - for hydras, corals, and sea anemones, but some (corals and sea anemones) ​ ​ are medusa in their first stages of life. ​ Mesoglea - gelatinous between endo and ecto, hydrostatic skeleton ​ Zooxanthellae - tube dwellers, symbiotic protists, photosynthesis Coral Bleaching ​ Built upon global warming 1.​ Pollution 2.​ High/Warmer Temperature Sensory Organs ​ Statocysts - gravity sensing, found among cnidarians and determines the direction of gravity ​ Ocelli/Ocellus - light sensing, spots that can detect light ​ Respiration is facilitated through simple diffusion Reproduction in Cnidaria ​ Asexual reproduction: budding, fragmentation, regeneration ​ Sexual reproduction: gametes (external fertilization) ○​ Majority of cnidarians are hermaphrodites Three Classes Under Phylum Cnidaria 1.​ Anthozoa - anthozoans; sea anemones, corals, sea pens; sessile 2.​ Hydrozoa - hydrozoans; hydroids, siphonophores, and some medusae  3.​ Scyphozoa - scyphozoans; true jellyfish; medusa ​ Cubozoa - cubozoans, old classification; box jellyfish Ecology ​ Corals are distributed worldwide ​ Criteria for cnidarians: ○​ Temperature ○​ Water depth