Lecture 7 MARB 435Outline Last Lecture1. Phylum Porifera (Sponges) Introduction2. Sponge Cells & Body Wall Structures and Functions3. Sponge Tissues4. Levels of Complexity of Sponges5. Sponge Taxonomy6. Class Calcarea7. Class Demospongiaea. Demosponge Diversity8. Class Hexactinellida9. Feeding and Nutrition10. Cladorhizidae- Carnivorous demosponges11. Bioactive Metabolites12. Sponge Natural Products13. Bioerosion14. Sponge Symbionts15. Gemmules16. Sexual Reproduction17. Development18. Sponge Reefs19. Reef-Building Sponges20. ConservationOutline of Current Lecture1. Introduction of Cnidariaa. Cnidaria Diversity Examples2. General Morphology3. Cnidaria skin & cell layer (Structure and Function table)4. Cnidocytes5. Prey Capturing and Feeding of Cnidaria6. Photosynthetic symbionts in Cnidaria7. Cnidaria Reproduction8. Development and life cycle9. Cnidaria Taxonomy10. Medusozoa11. Class Scyphozoa12. Rhopalia13. Scyphoza14. Class Cubozoa (box jellies) & Box Jelly DiversityCurrent LectureIntroduction of CnidariaCnidarians are a very diverse group of marine species that inhabit marine and freshwater environments. They range in size, development patterns, and morphological structures which are later discussed in the notes.Cnidarian DiversitySix types of cnidarians are sea anemones, corals, sea pens, sea fans, hydroids and jellyfish.General MorphologyCnidarians are diploblastic organisms which mean they only have two germ layers which are endoderm and ectoderm. They have radial symmetrical around the oral-aboral axis. Radial symmetry means the organism can be separated in any direction and the two pieces will show mirror like images of the organism. When stating the oral-aboral axis this represents the oral cavity (mouth) and the aboral end. The aboral region is located parallel to the oral region and is either in the bottom or top of the organism depending on the morphological structure.There are two types of cnidarians and those are polyp and medusa. The main difference is that medusa are pelagic and are free swimming or free floating organisms. Polyp structured cnidarians are benthic and are commonly anchored to rocks or sea floors. Medusa styled cnidarians have the oral cavity on the bottom and the aboral end on the top. For polyp styled cnidarians the oral cavity is on top and the aboral end is on the bottom and is anchored to the ground.Cnidarian skin and cell layersStructure FunctionEpidermis The outermost layer of skin and acts as a protective barrier to the outside environment.Mesoglea Middle layer between epidermis and gastrodermis. Assists cnidarians with buoyancyand transparency.Gastrodermis Lines the gastrovascular cavity and has glandarcells which produce digestive enzymes and assist in digestion.Cnodocil The trigger located on a cnidoblast which activates the discharge of nematocyst when touched.Nematocyte A cell which are located on the outer surface of a cnidarians and is used to capture prey or defend themselves.Ciliary receptor A primary ciliaEpitheleomuscular cells A cell that has fibrils which assist inlocomotion and muscle contractions.Interstitial cell The cells that represents the space between cnidarians structures. They also give rise to sperm and eggReceptor Cell (sensory neuron) The cells that allow cnidarians to gather information rather it be reproduction or defense and react.Motorneuron Assists in locomotion and movement.Longitudinal muscle filaments Assists in locomotion and movement.Basal Lamina Anchors the epidermis and mesoglea to the gastrodermis.Circular muscle filaments Assists in locomotion and movement.Nucleus Regulate all cell activity.Secretion vesicles Used to move cell inside of the body and from the inside to the outside of the cell.Enzymatic gland cells Assist in initial digestion. Helps with breaking down of food prior to digestion.Forming vacuole Assists in digestion.Cilium Assist in locomotion.CnidocytesCnidocytes are unique organelles to cnidarians. They are combined sensory and effector cells. They’re distributed over the epidermis but are concentrated along the tentacles. Nematocysts are the most common type of cnidarians.Prey Capture and FeedingNematocyst are discharged when prey get in contact with the tentacles. Cnidae sometimes paralyze their prey prior to digestion which makes it easier to eat because they spend less energy going after their prey. Once the prey is paralyzed or captured by the tentacles the cnidarians ‘lick’ there tentacles and retrieve the prey. The glandular cell in the gastrodermis produces digestive cells to assist the cnidarians with digesting its prey. Food is also absorbed by gastrodermal cells.Photosynthetic symbionts in CnidariaCnidarians harbor photosymbionts such as zooanthellae and chloroellae in their gastrodermal cells. 90% of the host nutrition may be derived from the photosynthetic activity of the symbionts.ReproductionCnidarians can either reproduce sexually or asexually. The following table represents characteristics of both.Asexual Reproduction Sexual ReproductionIncreased capacity for healing and regenerationGonochoric (When one of at least two sexes like male and female are produced)Budding of fusion is a result of asexual reproductionGerm cells originate in the gastrodermisCloning is a type of asexual reproduction and is common in polyps than in medusaExternal fertilization occursPolyp form of cnidarians way of reproducing The zygote develops into a planula larvaeMedusa form of cnidarians way or reproducing Development and Life CycleThe student must understand four main stages of the cnidarian development and life cycle. First, holoblastic cleavage occurs; which is where the zygote separates equally producing equal blastomeres. Followed by gastrulation, which is when the two germ layers (endoderm and ectoderm) are formed. Followed by the planula larvae which is the larvae produced after successful cleavage has occurred. Then finally the planula larvae presumes a primitive life cycle and grows to be an adult.Cnidarian Taxonomy- Class Scyphoza (Jellyfish)- Class Cubozoa (Box Jelly)- Class Hydrozoa(Scyphoza, cubozoa and hydrozoa are all medusozoan)- Class Anthozoao Subclass Hexacoraliao Subclass OctocoraliaMedusozoaMedusozoa are the cnidarians which are either in the class Scyphoza, Cubozoa of Hyrdozoa. They spend their entire life cycle in the medusa form. They have tetramerous symmetry which isa specialized form of radial symmetry. There structures are in multiples of 4. For