Lecture 7 MARB 435 Outline Last Lecture 1 Phylum Porifera Sponges Introduction 2 Sponge Cells Body Wall Structures and Functions 3 Sponge Tissues 4 Levels of Complexity of Sponges 5 Sponge Taxonomy 6 Class Calcarea 7 Class Demospongiae a Demosponge Diversity 8 Class Hexactinellida 9 Feeding and Nutrition 10 Cladorhizidae Carnivorous demosponges 11 Bioactive Metabolites 12 Sponge Natural Products 13 Bioerosion 14 Sponge Symbionts 15 Gemmules 16 Sexual Reproduction 17 Development 18 Sponge Reefs 19 Reef Building Sponges 20 Conservation Outline of Current Lecture 1 Introduction of Cnidaria a Cnidaria Diversity Examples 2 General Morphology 3 Cnidaria skin cell layer Structure and Function table 4 Cnidocytes 5 Prey Capturing and Feeding of Cnidaria 6 Photosynthetic symbionts in Cnidaria 7 Cnidaria Reproduction 8 Development and life cycle 9 Cnidaria Taxonomy 10 Medusozoa 11 Class Scyphozoa 12 Rhopalia 13 Scyphoza 14 Class Cubozoa box jellies Box Jelly Diversity Current Lecture Introduction of Cnidaria Cnidarians 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 Diversity Six types of cnidarians are sea anemones corals sea pens sea fans hydroids and jellyfish General Morphology Cnidarians 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 layers Structure Epidermis Mesoglea Gastrodermis Cnodocil Nematocyte Ciliary receptor Epitheleomuscular cells Function The outermost layer of skin and acts as a protective barrier to the outside environment Middle layer between epidermis and gastrodermis Assists cnidarians with buoyancy and transparency Lines the gastrovascular cavity and has glandar cells which produce digestive enzymes and assist in digestion The trigger located on a cnidoblast which activates the discharge of nematocyst when touched A cell which are located on the outer surface of a cnidarians and is used to capture prey or defend themselves A primary cilia A cell that has fibrils which assist in Interstitial cell Receptor Cell sensory neuron Motorneuron Longitudinal muscle filaments Basal Lamina Circular muscle filaments Nucleus Secretion vesicles Enzymatic gland cells Forming vacuole Cilium locomotion and muscle contractions The cells that represents the space between cnidarians structures They also give rise to sperm and egg The cells that allow cnidarians to gather information rather it be reproduction or defense and react Assists in locomotion and movement Assists in locomotion and movement Anchors the epidermis and mesoglea to the gastrodermis Assists in locomotion and movement Regulate all cell activity Used to move cell inside of the body and from the inside to the outside of the cell Assist in initial digestion Helps with breaking down of food prior to digestion Assists in digestion Assist in locomotion Cnidocytes Cnidocytes 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 Feeding Nematocyst 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 Cnidaria Cnidarians 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 Reproduction Cnidarians can either reproduce sexually or asexually The following table represents characteristics of both Asexual Reproduction Sexual Reproduction Increased capacity for healing and Gonochoric When one of at least two sexes regeneration like male and female are produced Budding of fusion is a result of asexual reproduction Cloning is a type of asexual reproduction and is common in polyps than in medusa Polyp form of cnidarians way of reproducing Germ cells originate in the gastrodermis External fertilization occurs The zygote develops into a planula larvae Medusa form of cnidarians way or reproducing Development and Life Cycle The 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 Anthozoa o Subclass Hexacoralia o Subclass Octocoralia Medusozoa Medusozoa 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 is a specialized form of radial symmetry There structures are in multiples of 4 For example they can have 4 tentacles 8 tentacles etc Class