porifera/cnidaria laboratory phylum porifera laboratory phylum porifera class calcarea...
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Phylum Porifera Class Calcarea (Calciospongiae)
1. Leucosolenia, asconoid body type 2. Scypha, also referred to as Grantia, syconoid body type a) Cross and longitudinal sections with spicules, eggs and different cell types Class Hexactinellida (Hyalospongiae) 1. Euplectella sp. Venus flower basket Class Demospongiae 1. Demonstration specimens of various marine sponges (all leukonoid body type) 2. Commercial sponge spongin fibers 3. Sponge gemmules
Experiments (done per table) 1. skeletal composition and taxonomy Phylum Cnidaria Class Hydrozoa Order Trachylina no representatives Order Hydroidea Suborder Lymnomedusae
1. Hydra a) live, note feeding reaction (use brine shrimp), note nematocyst discharge b) longitudinal and cross-section slides, observe cell organization/tissues Suborder Leptomedusae (Calyptoblastea) no representatives
Suborder Anthomedusae (Gymnoblastea) no representatives Suborder Chondrophora no representatives Order Siphonophora 1. Physalia a) whole preserved colonies b) cross section slide of tentacle, note nematocysts Order Milliporina no representatives Class Scyphozoa Order Stauromeduseae no representatives Order Semacostomeae 1. Aurelia aurita a) whole specimen to observe rhopalia (sense organs) b) scyphistoma stage c) ephyra stage Order Rhizostomeae 1. Cassiopeia live specimens to observe movement Class Anthozoa Subclass Octocorallina (Alcyonaria) no representatives Subclass Zoantharia (Hexacorallia) Order Zoanthidea no representatives Order Actinaria the anemones
1. Metridinum a) whole preserved specimens for dissection b) cross-section and longitudinal slides Order Madreporaria true or stony coral representatives Order Ceriantharia burrowing anemones no representatives Phylum Ctenophora Class Tentaculata ctenophores with tentacles Order Cydippida
1. Pleurobranchia Order Lobota no representatives Order Beroidea no representatives
PHYLUM PORIFERA A. TAXONOMY Class Calcarea - sponges having calcareous spicules with 1 to 4 rays (asconoid, syconoid, leuconoid). Class Hexactinellida - sponges having siliceous spicules with 6 rays. These spicules are often fused to form a beautiful lattice-like cylinder, as in the so-called Venus' flower basket Euplectella (syconoid). Class Demospongiae - contains sponges having siliceous spicules (not 6-rayed) and/or spongin fibers (leuconoid). Class Sclerospongiae - sponges having an internal skeleton of siliceous spicules and spongin fibers plus an outer encasement of calcium carbonate. Only six species from the Caribbean have been described to date (leuconoid) and this class will not be covered in this lab. B. PRINCIPAL FEATURES The sponges are the first metazoans (multicellular animals) that we will study. The principal features of phylum Porifera are listed below.
1. While some sponges are radially symmetrical, the majority of sponges are asymmetrical in body form. Sponges are considered to be at a cellular grade of construction; that is, they have cellular differentiation (tissues) without cellular coordination. 2. The outermost tissue layer of sponges is composed of cells called pinacocytes. In some sponges this outer tissue layer is syncytial while in others the pinacocytes are all distinctly separated from one another by cell membranes. The innermost tissue layer is composed of cells called choanocytes or collar cells with flagella that beat to produce water currents through the sponge body. Between these two tissue layers is a gelatinous layer called the mesohyl or mesoglea. The mesoglea is not considered to be a tissue since it contains a number of different kinds of independently functioning cells. Each cell type in the mesoglea has a specific name, but the general term for all of these wandering cells is amoebocyte. 3. Some of the amoebocytes in the mesoglea are specialized for secreting a skeleton. The sponge skeleton may be composed of mineral spicules, spongin fibers or a combination of these two, depending on the kind of sponge. Spicules may be calcareous (composed of Ca CO3) or siliceous (composed of H2Si2O7). Spongin fibers are composed of a sulfur-containing schleroprotein.
4. Water enters the body of a sponge by way of a number of minute incurrent pores or ostia. Water leaves the body by way of one or more large excurrent pores or oscula. Within the body of the sponge, the water may pass through a large cavity (the spongocoel) through a system of canals and chambers, or through a combination of these two. 5. Movement of water through the sponge body is accomplished by the beating of the choanocyte flagella. The choanocyte cells line either a spongocoel or a number of small chambers, depending on the sponge. A choanocyte cell consists of a nucleus, one or more vacuoles, a long flagellum and a delicate, collarlike structure which surrounds the base of the flagellum. Electron microscope studies show the collar of a choanocyte to be composed of a circular arrangement of microvilli-like structures extending outward from the cell body. The rotary motion of the flagellum forces solid food particles in the incoming water to adhere to the outside surface of the collar. The streaming protoplasm of the collar transfers the food to the collar base where ingestion can occur. C. BODY TYPES Morphologically, the bodies of sponges exhibit three distinct types based on the organization of their internal canal systems. These three morphological types are designated as the ascon, sycon, and leucon types. It is important to recognize that these three body forms represent morphological types and are not directly related to the three classes of sponges. In fact, only a few species of sponges exhibit the ascon and sycon body types. The majority of sponges are of the leucon variety.
I. ASCONOID - Water entering the sponge passes through ostia that are actually openings within doughnut-shaped cells called porocytes, which are found only in asconoid sponges. The water enters the large central cavity called the spongocoel, which is lined with choanocytes. Water exits from the spongocoel Example Leucosolenia Asconoid sponges are the simplest and most primitive sponge architectural type and are all relatively small due to their inefficient filtering system. Their structure is demonstrated in Leucosolenia. 1. Leucosolenia Slides. Examine the prepared slides. The outermost layer is the pinacoderm, which contains the occasional porocytes. In a longitudinal section you will be able to see the cylindrical spongocoel, lined with choanocytes identified by the presence of microvilli. You may also find pinacocytes that form much of the epidermis of sponges and are as close as a sponge gets to having a tissue. The skeletal elements, or spicules, are made of calcium carbonate.
II. SYCONOID - Water enters the sponge through ostia, openings between cells, rather than within cells as in asconoid sponges. Water then passes into radially arranged incurrent canals which lead to flagellated chambers lined with choanocytes. Water leaves the flagellated chambers by way of excurrent canals that lead to the spongocoel, which is lined a simple flat epithelium. Water exits from the spongocoel by way of a single large osculum. Note that the body wall of syconoid sponges is thicker than that of asconoid sponges and that the syconoid spongocoel is not lined by choanocytes as is the asconoid spongocoel. Example Grantia or Scypha (slides only) Syconoid sponges are more complex than asconoid sponges. Syconoid sponges look like large asconoid sponges, having a tubular shape, and each individual has a single excurrent osculum. The body wall is thicker, however, and the spongocoel is lined with pinacocytes. The choanocytes line finger-like chambers (radial canals), which permeate the spongocoel. Because this arrangement provides a more efficient pumping system than the asconoid design, syconoid sponges are larger than asconoid sponges. III. LEUCONOID - The ostia of a leuconoid sponge are like those of a syconoid sponge. These ostia lead into a complex system of canals and flagellated chamgers that penetrate the very thick, dense mesoglea. There is no spongocoel in a leuconoid sponge. Rather, water reaches the oscula by way of large excurrent canals. The complex canal system of leuconoid allows for greater surface area over which water may pass and consequently creates an increased area for food and oxygen uptake and for waste removal. It is not surprising, therefore, that leuconoid sponges are the largest in size of all the types and that the vast majority of sponges are leuconoid.
Leuconoid sponges are by far the most complex architectural-type of sponge. Most leuconoids are colonial, and although individual oscula can be distinguished, it is difficult to separate individual members of the colony. The vast majority of sponges are leuconoid. Examine the anatomy of the leuconoid Chondrilla nuculla available in the laboratory. How do you think its filtration system differ from the asconoid and syconoid sponges you examined? D. SPICULE COMPOSITION AND STRUCTURE The systematics of sponges are based primarily on the composition and structure of spicules rather than on architectural plan. Spicules are composed of either calcium carbonate or silicon dioxide, and the skeleton may consist entirely of collagenous fibers (spongin) or a combination of spicules and spongin. See the poriferan taxonomy for the characteristics of the four classes of Porifera. Each lab table will receive a sample of mystery sponge in order to determine their taxonomy using the following tests: 1. The organic matrix of sponges (spongin) dissolves when boiled in 5% sodium hypochlorite solution. Place small pieces of sponge tissue in 1-2 ml of the sodium hypochlo