Lecture 9 MARB 435 Outline of Last Lecture 1 Stauromedusae 2 Class Hyrdozoa 3 Hydroids 4 Hydroid Colonies 5 Siponophores 6 Hydrocorals 7 Class Anthozoa 8 Hexacoralia Zoantheria 9 Sea Anemones 10 Stony Corals Scleractinia 11 Octocorals Alcyonaira 12 Alyconarian Examples 13 Gorgonians 14 Introduction to Ctenophores 15 Kleptocnida 16 Ctenophore Tissue 17 Metazoan Musculature 18 Ctenophore Nervous System 19 Locomotion 20 Gastrovascualr System 21 Feeding Outline of Current Lecture 1 Ctenophore Morphological Terms 2 Ctenophore Symmetry 3 Fossilized Ctenophores 4 Invasive Ctenophores 5 Mnemiopsis Ctenophores blossoms 6 Introduction of Bilateria 7 Types of Symmetry 8 Unusual types of Symmetry 9 Bilateria Adaptive Significance of Bilateral SymmterY 10 Cephalization 11 Germ Layer Table 12 Body Cavities 13 Coelom Functions 14 Genreal Excretion 15 Nitrogenous Waste Products 16 Urine 17 Steps of Excretion 18 Excretory Organs in Bilateria Current Lecture Ctenophore Vocabulary 1 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 Symmetry Ctenophores 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 Ctenophores Fossil 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 Ctenophores Mnemiopsis ledyi is a native ctenophore that s native to North America s east coast They were 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 they compete 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 ledyi Mnemiopsis 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 of them from continous water currents Introduction of Bilateria These 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 body regions They have planes of symmetry in which they can be cut but this will be discussed throughout the notes Types of Symmetry The main two types of symmetry defined in lecture are radial and bilateral Radial symmetry has multiple 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 Symmetry There 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 Symmetry There 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 Cephalization The 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 Table This table defines what each germ layer consists of Ectoderm Outer covering of the animal and has the CNS Endoderm Digestive tract liver and lungs Mesoderm Muscles gonads nephridia blood vessels and endoskeleton Body Cavities Three 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 or less solid mesodermal tissue Coelom Functions The coelom has four main functions as followed 1