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Syconoid sponge A radially symmetrical sponge that has a body wall folded into radially oriented canals. Symbiosis An intimate, long-term, physical interraction between two species, in which at least one of the species is dependent, to various degrees, upon the other. Symmetrogenic Producing mirror image daughter cells as a result of fission. Synanthropic Living with humans. Syncytium Tissue in which nuclei are not separated by cell membranes. Synkaryon Zygotic nucleus of ciliates. Systole The contraction phase of a heart beat. Tagma (pl. Tagmata) An arthropod body region of arthropods (i.e., head, thorax, abdomen). Tanned Stabilization of the arthropod exocuticle by the formation of cross linkages. Tapetum A reflective layer within an eye. Tan To increase the strength, and darken the color, of protein by establishing crosslinks between adjacent polypeptides. Tarsal organ Cuplike spider chemoreceptor for detecting pheromones. Taxodont Hinge dentition and consisting of uniform alternating teeth and sockets in a row. Taxon A group of organisms with a common ancestor. Tegmen Membranous oral wall of the crinoid disc. Tegument The nonciliated outer syncytial layer of the body wall of parasitic platyhelminths and acanthocephalans. Telolecithal Type of egg in which the yolk material is concentrated to one side (vegetal) of the egg. Telopodite The movable part of an appendage extending outward from an immovable protopod. Telotroch A ring of cilia encircling the anus at the posterior end of a trochophore larva. Tensilium The outer portion of a bivalve hinge ligament. Tentacle Evagination of the body wall surrounding the mouth which aids in the capture and ingestion of food. Tentacle sheath In Bryozoa, the part of the withdrawn body wall that encloses the withdrawn tentacles of the lophophore. See vestibula. Tergite The dorsal, sclerite of each arthropod segment. Tergum (pl. Terga) The combined tergites. A plate contributing to the barnacle operculum. Terminal At the end. Terminal anchor Anchor at the leading end of a burrowing animal. Terminal cell Tubular flagellated cell attached to the inner end of the protonephridial tubule. Test An encasing or shell like skeleton, typically covered externally by cytoplasm or living tissue. Theca (pl. Thecae)··The nonliving cuticle around the hydranths of thecate hydroids. Hydrotheca. Thecate Refers to hydroids with a hydrotheca surrounding the polyp proper. Tetramerous Radial symmetry in which a basic pattern is repeated in multiples of four. Thigmotactic Responding to touch or surface contact. Thoracopod Any thoracic appendage of an arthropod. Tiedemann’s body One of the interradial outpockets of the ring canal of many echinoderms. Removes unwanted particulates from the water vascular system. Tongue bar A downgrowth of pharyngeal tissue that divides a developing gill opening into two side-by-side slits. Tornaria Transparent, long lived, planktotrophic larva of enteropneusts. Torsion The counterclockwise twist of the gastropod visceral mass over the head and foot. Toxicyst A vesicular organelle in the pellicle of gymnostome ciliates which discharges long threads with bulbous bases; used for defense or capturing prey. Transmitted light In microscopy, light, from a source below the stage, which passes through the plane of the stage to reach and pass through the object. Trichobranchiate Having filamentous gills. Trichocyst A bottle shaped extrusible organelle of the ciliate pellicle. Trilobite larva Horseshoe crab larva that superficially resembles trilobites. Triploblastic Embryos possessing all three germ layers: ectoderm, endoderm, and mesoderm. Triturate To grind or masticate. Trochophore Type of larva found in molluscs, annelids, and other groups in which the larval body is ringed by a girdle of cilia, the prototroch. Trochus The anterior band of cilia of the divided corona of some rotifers. Troglobitic, troglodytic Dwelling in caves or otherwise underground. Trophi Cuticular hard parts of the rotifer mastax. Trophosome Central mass of tissue in the trunk of the pogonophore that is packed with symbiotic bacteria. Trophozoite Apicomplexa. Feeding stage that occurs when the sporozoite invades the host. Trophozooid Nutritive or feeding zooid of doliolid urochordates. Tropic hormone A hormone whose target is an endocrine cell. Tube tracheae Simple branched or unbranched trachea. Tubicolous Tube dwelling. Tubules of Cuvier Eversible toxic or sticky tubules associated with the bases of the respiratory trees of some holothuoid echinoderms. Tubulus (pl. Tubuli) Sensory papilla on the trunk of some aschelminths. Tunic Special cuticular covering of the body of ascidians. Tunicate A urochordate. Tunicin A kind of cellulose that forms structural fibers in ascidian tunics. Typhlosole A ridge projecting internally from the intestinal wall to increase its surface area. Ultrafiltration Passage of fluid across a fine-mesh filter to retain proteins and larger particles. Umbo (pl. Umbos, Umbones) A dorsal protuberance of a bivalve valve rising above the hinge. Uncinus (pl. Uncini) A minute seta modified into a hook. Undulating membrane Type of ciliary organelle that is a row of adhering cilia forming a sheet. Uniramous Having one branch. Ureotelic Producing urea as the end product of nitrogen metabolism. Uricotelic Producing uric acid as the end product of nitrogen metabolism. Uropods Sixth abdominal appendages of most malacostracans but the 4 th, 5 th, and 6 th of amphipods. Vanadocytes Yellowish green ascidian blood cells that contain high concentrations of vanadium. Vascular plug Specialized nemertean exchange site across which an ultrafiltrate passes from the blood to the rhynchocoel. Vegetative nucleus Macronucleus. Velarium Velum like structure of cubozoans. Veliger Planktotrophic molluscan larva that follows the trochophore. Velum Shelf formed by the margin of the umbrella projected inward which is characteristic of most hydromedusae. One of the two ciliated flaps with which a veliger larva swims and feeds. Vermiform Having the shape of a worm. Vermiform embryo Asexually produced young of dicyemids that has the same form as the parent; formed within the axial cell of the parent. Vessel A small tubular blood channel. Vestibule Preoral chamber. In Bryozoa, a space enclosed by the withdrawn body wall of a retracted zooid distal to the withdrawn tentacles and tentacle sheath. Vestigial Reduced to a non-functional remnant. Vestimentum The collar like body region of a vestimentiferan that helps to secrete the animal’s tube. Vibraculum (pl. Vibracula Bristle like heterozooid found in some cheilostome bryozoans. Visceral mass One of three primary parts of the molluscan body; contains the internal organs. Viscous drag Friction that results from the tendency of the polar water molecules to stick to each other and to surfaces. Vitellarium (pl. Vitellaria) Specialized part of the ovary for the production of yolk filled nurse cells. Nonfeeding barrel shaped larval stage of some echinoderms. Viviparous Embryos gestated internally within the female where supplemental nutrition is supplied. Whorl Any complete turn (360 ° ) of a coiled molluscan shell. Xylophagous Feeding on wood. Zoarium (pl. Zoaria) The form of a bryozoan colony. Zoea (pl. Zoeae) Penultimate larval stage of many decapod crustaceans, preceding the postlarva. Zoochlorella (pl. Zoochlorellae) Unicellular green algal symbiont of certain animals, especially freshwater sponges and freshwater and marine cnidarians and turbellarians. Zooecium (pl. Zooecia) The cuticle, or exoskeleton, of a bryozoan zooid. Zooflagellate A flagellate that has one to many flagella, lacks chloroplasts, and is heterotrophic. Zooplankton Microscopic animals suspended in the water of oceans and freshwater lakes. Zooplanktivore Feeding on zooplankton. Zooxanthella (pl. Zooxanthellae) A golden brown alga, usually a dinoflagellate, symbiotic with various marine animals, especially cnidarians.
2 LECTURE Leturw #1. Animal kingdom. Subkingdom - celled animals Protozoa. Species diversity and structural features of Sarkomastigofora.
1. Simple as a whole organism. Similarity in the structure of cells and the simplest multicellular animals. General characteristics of subkingdoms. The protozoa are a heterogeneous assemblage of some 50,000 single-cell organism s possessing typical (eukaryote) membrane-bound cellular organelles. Because most are m otile and many are heterotrophic, this assemblage was treated in the past as a single phylum within the Anim al Kingdom— the phylum Protozoa. They are now known to consist of a number of different unicellular phyla, which together with m ost algal phyla are placed in the Kingdom Protista. Some of these protozoan groups are related to each other, some probably evolved independently from remote eukaryote ancestors, and some are m embers of various algal groups. The unicellular level of organization is the only characteristic by which the protozoa as a whole can be described; in all other respects they display extreme diversity. Protozoa exhibit all types of symmetry, a great range of structural complexity, and adaptations for all types of environmental condi tions. As rganism s, the protozoa have remained at the unicellular level but have evolved along numerous lines through the specialization of parts of the protoplasm (organelles) or of the skeletal structure. Thus, sim plicity and com plexity in protozoa are reflected in the num ber and nature of their organelles and skeletons in the same way that simplicity and com plexity in m ulticellular anim als can be reflected in the development of tissues and organ system s. A protozoan cell may be far more com plex than a m etazoan cell, but a protozoan cell is an entire organism , not part of an organism, as is a m etazoan cell. Protozoa occur wherever m oisture is present—in the sea, in all types of fresh water, and in the soil. There are com m ensal, m utualistic, and many parasitic species. Although m ost protozoa occur as solitary individuals, there are numerous colonial forms. Some colonial form s, such as species of Volvox, attain such a degree of cellular interdependence that they approach a true m ulticellular level of structure (Fig. 2-6). Both solitary and colonial species may be either free moving or sessile.
The protozoan body is usually bounded only by the cell membrane, which possesses the typical bilayered lipid ultrastructure of cells in general. The rigidity or flexibility of the protozoan body is largely dependent on the nature of the underlying cortical cytoplasm, called ectoplasm , which is rather gelatinous, in contrast to the more fluid, internal cytoplasm called endoplasm. Nonliving external coverings or shells occur in many different groups. Such coverings may be sim ple gelatinous or cellulose envelopes, or they may be distinct shells, com posed of various inorganic and organic m aterials, or sometimes foreign particles cemented together. Depending on the species, there are one to many nuclei. The locomotor organelles may be flagella, cilia, or flowing extensions of the body called pseudopodia. Since the type of locom otor organelle is important in the classification of the phylum, discussion of the structure of these organelles is deferred until later. All types of nutrition occur in protozoa. Some are autotrophic or saprozoic; many ingest food particles or prey and digest this food intracellularly within food vacuoles. Food reaches the vacuole by engulfment, or phagocytosis, often through a mouth, or cytostome. Soluble food may enter by pinocytosis. Intracellular digestion has been most studied in amebas and ciliates. The food vacuoles undergo definite changes in hydrogen ion concentration (pH) and in size during the course of digestion. Following ingestion, the vacuole contents become increasingly acid and smaller, as excess wateris removed. Lysosomes deliver hydrolytic enzymes (Fig. 2-1), and the vacuole increases in size and becomes alkaline. The enzymes digest the vacuole contents, and products of digestion then pass into the cytoplasm by pinocytosis. The undigestible remnants are egested. Protozoa that live in water where there is active decomposition of organic matter or in the digestive tract of other animals can exist with little or no oxygen present. Some protozoa are facultative anaerobes, utilizing oxygen when present but also capable of anaerobic respiration. Changing availability of food supply and of oxygen associated with decay typically results in a distinct succession of populations and protozoan species (see Bick, 1973). Metabolic wastes diffuse to the outside of the organism. Ammonia is the principal nitrogenous waste, and the amount eliminated varies directly with the amount of protein consumed. Characteristic of many protozoa is an organelle system called the contractile vacuole com plex (Fig. 2-2). The complex is com posed of a spherical vesicle— the contractile vacuole proper— and a surrounding system of small vesicles or tubules termed the spongiome. The complex functions primarily in water balance (osmoregulation), pumping excess water out of the organism . The spongiome provides for the collection of water, which is delivered to the contractile vacuole. The latter expels the fluid to the outside of the organism through a temporary or perm anent pore. In some protozoa (some amebas and flagellates) the vacuole completely disappears following contraction and is reformed by fusion of small vesicles. In others (many ciliates) the vacuole collapses at discharge and is refilled by fluid from the surrounding tubules of the spongiome. Reproduction and Life C ycles The protozoan reproductive processes and life cycles are varied. Only a few of the more common term s are described here. Asexual reproduction occurs in most protozoa and is the only known m ode of reproduction in som e species. Division of the animal into two or more daughter cells is called fission. When this process results in two similar daughter cells, it is termed binary fission; when one daughter cell is much smaller than the other, the process is called budding. In some protozoa, multiple fission, or schizogony, is the rule. In schizogony, after a varying number of nuclear divisions, the cell divides into a number of daughter cells. With few exceptions, asexual reproduction involves som e replication of missing organelles following fission. Sexual reproduction may involve fusion (syngamy) of identical gametes (called isogametes) or gametes that differ in size and structure. The latter, called anisogam etes, range from types that differ only slightly in size to well-differentiated sperm and eggs. Meiosis commonly occurs in the formation of gametes, but in many flagellate protozoa and sporozoans meiosis is postzygotic, that is, it occurs following the formation of the zygote as in most algae (Fig. 2-3). In ciliate protozoa there is no formation of distinct gametes; instead, two animals adhere together in a process called conjuga conjugation, and they exchange nuclei. Each m igrating nucleus fuses with a stationary nucleus in the opposite conjugant to form a zygote nucleus (synkaryon). Less com m on is a process called autogamy, in which two nuclei, each representing a gamete, fuse to form a zygote, all within a single individual. Encystment is characteristic of the life cycle of many protozoa, including the m ajority of freshwater species. In form ing a cyst, the protozoon secretes a thickened envelope about itself and becomes inactive. Depending on the species, the protective cyst is resistant to desiccation or low temperatures, and encystment enables the animal to pass through unfavorable environmental conditions. The simplest life cycle includes only two phases: an active phase and a protective, encysted phase. However, the more complex life cycles are often characterized by encysted zygotes or by for mation of special reproductive cysts, in which fission, gametogenesis, or other reproductive processes take place. Protozoa may be dispersed long distances in either the motile or encysted stages. Water currents, wind, and mud and debris on the bodies of water birds and other animals are com m on agents of dispersion.
1 Protozoa are unicellular organism s that are animal-like in being heterotrophic and motile. In all other respects, protozoa are a very diverse assemblage, and the major groups are now commonly treated as separate phyla of eukaryote protistans. The old phylum name Protozoa can be used as a convenient term of reference for any member of these phyla.
a protozoon is a single cell, it is also a complete organism . 4 Digestion occurs intracellularly within a food vacuole, and food reaches the vacuole through a cell mouth or by engulfment. 5 Excess water is usually eliminated by a contractile vacuole. 6 Most of the members of the protozoan phyla are distinguished, in part, by their type of locomotor organelles: flagella, pseudopodia, or cilia. 7 Reproduction by fission occurs at sometime in the life history of almost all protozoa. Meiosis, gamete formation, and fertilization have been observed in many species, but the nature of these events and their occurrence in the life cycle of the organism is highly variable. Encystment is common. 2. Type Sarcomastigophora. Organelles of Sarсomastigophora movement. Reproduction process Phylum Sarcomastigophora These protozoa possess flagella or pseudopodia as locomotor or feeding organelles and a single type of nucleus. The 18,000 described species constitute the largest phylum of protozoa, which is composed of two principal groups subphyla), the flagellates and the sarcodines. SUBPHYLUM MASTIGOPHORA The flagellates, or mastigophorans, include those protozoa that possess flagella as adult organelles. They can be conveniently divided into phytoflagellates and zooflagellates. The phytoflagellates usually bear one or two flagella and typically possess chloroplasts. These organism s are thus plantlike, and phycologists treat most species in this division as algae. The phytoflagellate division contains most of the free-living members of the class and includes such common forms as Euglena, Chlamydomonas, Volvox, and Peranema. The zooflagellates possess one to many flagella, lack chloroplasts, and are either holozoic or saprozoic. Some are free living, but the majority are commensal, symbiotic, or parasitic in other animals, particularly arthropods and vertebrates. Many groups have become highly specialized. It is generally agreed that this division does not represent a closely related phylogenetic unit. Locomotion The presence of flagella is the distinguishing feature of flagellates. The phytoflagellates usually have one or two flagella, the zooflagellates one to many. When two or many flagella occur, they may be of equal or unequal length, and one may be leading and one trailing, as in Peranem a (Fig. 2 - 5 B) and the dinoflagellates. The ultrastructures of flagella and cilia are fundamentally similar in all eukaryote organisms. A single flagellum (or cilium) is constructed very much like a cable. Two central microtubules form a core that is in turn encircled by nine double outer microtubules (Fig. 2 -4A). One microtubule of each doublet bears two rows of projections (arms) directed toward the adjacent doublet (Fig. 2-4B). The entire bundle is enclosed within a sheath that is continuous with the cell membrane. The flagellum always arises from a basal body, sometimes called a blepharoplast in flagellates, that lies just beneath the surface. Like a centriole, the basal body has an ultrastructure somew hat like a flagellum, except that the central fibrils are absent and the nine fibrils in the outer circle are in triplets, two of the three being continuous with the doublets of the flagellum. Arms are absent and the inner microtubule of each triplet is connected by a radial strand to a central ring for part of its length (Fig. 2-4B). A fibrillar root system connecting the basal body with various organelles, especially the nucleus, characterizes m any flagellates. In some species the basal body functions as a centriole in mitosis. Flagellar propulsion in most astigophorans essentially follow s the same principle as that of a propeller, the flagellum undergoing undulations in one or two planes that either push or pull. The undulatory waves pass from base to tip and drive the organism in the opposite direction (Fig. 2-4C ), or the undulations pass from tip to base and pull the organism (Fig. 2-4D ). In many species with two flagella, the actual path of movement is determined by the flagellar orientation. Other types of beat have been described for flagella besides undulatory. The relationship of flagellar (or ciliary) ultrastructure to movement has received much attention, and the sliding tubule model is now widely accepted. According to this theory, the microtubules do not change length but adjacent doublets slide past each other, causing the entire organelle to bend. Sliding involves the establishment of cross bridges and utilization of adenosine triphosphate (ATP), as in muscle contraction (see Sleigh, 1974). Mastigophorans that have thin, flexible pellicles are often capable of am eboid m ovem ent; some forms, such as chrysomonads, may cast off their flagella and assume an ameboid type of locomotion entirely.
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