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Unformatted text preview: Lab # 5 – Invertebrate Lab I: Porifera to Annelida Invertebrates • Phylum Porifera – Sponges o “Pore bearer” o Least complex Posses multiple cell types but no truly defined tissues o 1 st truly multicellular organisms in animal kingdom o Nonmotile o Filter feeders Feed on particles in the water o Mostly marine, few FW o Body plan Simple Several cell types arranged into a loose aggregation that do not form true tissues Some are amorphous (no distinct body shape) Others are radially symmetric around a central axis Choanocytes • A collection of flagellated cells lining a series of chambers • Located within body of sponge • Beat their flagella moving water through sponge body and collecting particles as they contact a modified region of the cell termed the collar o This makes sponges one of the more effective filter feeders b/c they are able to consume tiny particles smaller than a cell Sponges have an outer layer of epidermal cells w/ interspersed porocytes Porocytes allow water to pass through the epidermal layer into a central spongocoel The spongocoel walls are lined w/ choanocytes that help pull water though the prorcytes into the spongocoel and out a center exit, the osculum Amoebocytes • Embedded in the walls of the sponge • Transport nutrients obtained from the choanocytes to other cells in the sponge Spicules • Also in walls of the sponge • Composition varies by species • Spicule type is a major tool used to classify taxa of sponges • Three types: o Calcium Carbonate (CaCO ) Sharp Vary in shape from a simple rod to multi-branched shape o Silica Dioxide (SiO ) Glass-like skeleton o Spongin Consist of a protein that gives sponges their “spongy” feel Commercial sponges are species of sponge containing sponging fibers Three body designs: • Asconoid o Basic body plan o Consists of a central osculum lined w/ choanocytes and a simple linear channel system of porocytes • Syconoid o More complex morphology o Consists of a more complex inner channel w/ choanocytes located inside the canals and not the central osculum • Leuconoid o The most complex morphology o Consists of a complex series of inner channels and often lacks a central osculum o The choanocytes are localized to specialized chambers called flagellated chambers o Allows for greater filtering ability and a larger body size o All the sponges on demo exhibit this morphology o Observe: Cross section through Grantia slide Grantia , a syconoid sponge Consists of a central chamber (a spongocoel ) w/ a number of radial canals extending outward These canals are line w/ flagellated choanocytes that circulate water through the sponge Btw radial canals are incurrent canals that are connected to the surrounding water How it works: • Due to beating of choanocytes, water is pulled into the incurrent canals and passes through specialized cells called porocytes into the radial canals...
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This note was uploaded on 10/06/2008 for the course BIOL 10514 taught by Professor Horner during the Spring '08 term at TCU.
- Spring '08