Lecture 9 MARB 435Outline of Last Lecture1. Stauromedusae2. Class Hyrdozoa3. Hydroids4. Hydroid Colonies5. Siponophores6. Hydrocorals7. Class Anthozoa8. Hexacoralia (Zoantheria)9. Sea Anemones10. Stony Corals (Scleractinia)11. Octocorals (Alcyonaira)12. Alyconarian Examples13. Gorgonians14. Introduction to Ctenophores15. Kleptocnida16. Ctenophore Tissue17. Metazoan Musculature18. Ctenophore Nervous System19. Locomotion20. Gastrovascualr System21. FeedingOutline of Current Lecture1. Ctenophore Morphological Terms2. Ctenophore Symmetry3. Fossilized Ctenophores4. Invasive Ctenophores5. Mnemiopsis (Ctenophores) blossoms6. Introduction of Bilateria7. Types of Symmetry8. Unusual types of Symmetry9. Bilateria: Adaptive Significance of Bilateral SymmterY10. Cephalization11. Germ Layer Table12. Body Cavities13. Coelom Functions14. Genreal Excretion15. Nitrogenous Waste Products16. Urine17. Steps of Excretion18. Excretory Organs in BilateriaCurrent LectureCtenophore Vocabulary1. The location of the nucleus is defined as being in between two poles, the animal pole and the vegetal pole.2. Animal pole- (Nearest to the nucleus) The animal pole becomes the oral pole.3. Vegetal Pole- (Opposite side of the Animal Pole). The vegetal pole becomes the aboral pole.4. The oral-aboral pole is a region commonly when discussing Cnidarians. For example, in the medusa form of Cnidarians the oral part defines the region nearest the mouth (bottom) and the aboral region is on top of the mouth. Ctenophore SymmetryCtenophores can be divided two planes, the pharyngeal plane which runs vertically and horizontally runs the tentacular plane. They divide by pleurobranchia cleavage and they later undergo gastrulation. After cleavage oral and aboral meres are made and they can be either macro or micro. Ctenophores are hermaphrodites who are free spawners that reproduct through external fertilization. External fertilization is when an organism can reproduce offspring without having the embryo grow inside the mother’s stomach to receive nutrients. A common example of organism that reproduce through external fertilization are frogs.Fossilized CtenophoresFossil records extend to the before the “Cambrian Explosion” which is part of the Ediacara fauna (635-541 million years ago). There fossils showed them to have no tentacles and to have octomerous radial symmetry. There fossils didn’t represent them as having biradial symmetry.Invasive CtenophoresMnemiopsis ledyi is a native ctenophore that’s native to North America’s east coast. Theywere introduced with ballast (heavy particles/material like gravel) water in the Black Sea until the late 1980’s. Mnemiopsis ledyi was first introduced in the Caspian Sea in 1998 and there theycompete with fish for zooplankton. The Herring and Kilka populations suddenly declined when the Mnemiopsis ledyi arrived. Other types of Ctenophores such as Beroe’ were categorized as natural predators.Mnemiopsis ledyiMnemiopsis ledyi began to bllom everywhere else as well as in the Caspian and Black Sea. TThey spread to the North and Baltic Sea but the populations had limited growth due to the fact the that there were low temperatures and gelatinours predators. They were probably reintroduced to the Mediterranean Sea from the Black Sea by ballast water and the spreading ofthem from continous water currents.Introduction of BilateriaThese are animals whose symmetry can be defined as being biracial. This means that they can be spilt into two mirror images of themselves. They have a front, back, left and right bodyregions. They have planes of symmetry in which they can be cut but this will be discussed throughout the notes.Types of SymmetryThe main two types of symmetry defined in lecture are radial and bilateral. Radial symmetry hasmultiple planes of symmetry that intersect at the oral-aboral axis. Bilateral symmetry has a single plane of symmetry that transects the animal from anterior to posterior and dorsal to ventral. The midsagital plane can runs vertically and seperates the organism into mirror like half images. Radial symmetry breaks down into three additional subgroups, hexamerous, octamerous, and pentamerous. Hexamerous radial symmetry is when the body parts are in multiples of six. Octamerous radial symmetry has bosy parts I mulpties of eight. Pentamerous radial symmetry has body parts in multiples of five. An example of a pentamerous organism would be a sea star.Unusual Case of SymmetryThere are two unusal cases of symmetry discussed n lecture, superficial radial symmetry and secondary bilateral symmetry. Superficial radial symmetry is a case of extreme radial symmetry but internal bilateral symmetry occurs. (Examples: Tube-dwelling worms, bryozoans and moss animals) Secondary bilateral symmetry occurs when bilateral symmetry is superimposed on radial symmetry. (Examples: Sea dollars, many sea cucmbers.Bilateria: Adaptive Significance of Bilateral SymmetryThere are numerous beneficial reasons for Bilateria organisms to have bilateral symmetry. The environment relatively uniforms on all sides, body parts are distinguished regularly around the circumference of the animal, unidirectional currents are present. Unidirectional currents mean that there’s a divergence from radial symmetry. For motle animals there are other benefits such as being dorso-ventrally polar and having anterior-posterior polarity.CephalizationThe process of cephalization is the formation of a head. The evolutionary process concentrates nervous tissue and seansory organs to the anterior end of the body. The formation of a central nervous system (CNS) occurs which consists of a brain ad longitudinal nerve cords. The mouth usually is located at the anterior end of the organism with the sensory organs. The sensory organs are also usually paired.Germ Layers TableThis table defines what each germ layer consists of.Ectoderm Outer covering of the animal and has the CNSEndoderm Digestive tract, liver and lungsMesoderm Muscles, gonads, nephridia, blood vessels, andendoskeletonBody CavitiesThree main types of body cavities are discussed, coelomates, pseudocoelomates, and acoelomates.Coelomates- Coelom is present which is a fluid-filled body cavity completely lines by mesodermal epithelium.Pseudocoelomates- Pseodocoelomates are fluid-filled body cavity not completely lined by mesodermal tissue.Acoelomtes- Have no secondary body cavity and the digestive tract is the only body cavity. The body is filled with more