Presentation on theme: "Phylum Porifera Sponges Ancient group of animals that dates back to the late Precambrian about 600 million years ago."— Presentation transcript:
Phylum Porifera Sponges Ancient group of animals that dates back to the late Precambrian about 600 million years ago
Phylum Porifera (sponges) Sessile, aquatic, benthic, suspension feeders on bacteria and protists Mainly marine (~7000 species), but some in freshwater (~300 species). ~27 freshwater species in North America.
Phylum Porifera Filter feeders (a few are carnivorous) –Water current produced by choanoflagellates delivers particles and dissolved organic material to all the cells –Food enters cells by Phagocytosis (particles) Pinocytosis (dissolved organic materials) –Digestion is intracellular Wastes are eliminated by diffusion Gas exchange is by diffusion
Defining Characteristic of Phylum Cellular level of organization –No true tissues –Cells are not connected to each other by basement membrane as seen in true tissues Cells are totipotent –Can change form and function No true embryological germ layers –3 types of embryological germ layers in animals Ectoderm Endoderm Mesoderm Not all animal phyla have all 3 layers
Defining Characteristic of Phylum Body covered in holes (ostia) –Pores - hence the name Porifera “Pore bearer” –Skeleton made of spicules Silica CaCO 3 Spongin – organic material No fixed body shape No plane of symmetry –Some have radial symmetry
Defining Characteristic of Phylum Adults are sessile (immobile) Suspension feeders Flagellated cells called choanocytes circulate water through canal system No nerves or muscles Larvae are flagellated and free swimming
Defining Characteristic of Phylum Microvillae form collars around flagella of Collar cells = Choanocytes Functions of choanocytes –Generate currents that maintain water flow throughout sponge. –Capture small food particles. –Capture sperm for fertilization. nucleus microvillus Flagellum Collar
Sponge Cells Pinacocytes – form the pinacoderm, the outermost layer of sponge Choanocytes – flagellated collar cells that pump water through the sponge, form the choanoderm Amoebocytes (or Archaeocytes) are amoeba-like cells that are totipotent, in other words each is capable of transformation into any other type of cell. They also have important roles in feeding, reproduction and in clearing debris that blocks the ostia. Amoebocytes wander through the central jelly or mesohyle Porocytes – line the pores (or ostia) of the sponge; provide channels to spongocoel
Pinacocytes (“tablet cells”) form outer epithelium
Other types of cells within the mesohyl Sclerocytes secrete the mineralized spicules ("little spines") that form the skeletons of many sponges and in some species provide some defense against predators. Spongocytes secrete spongin. Lophocytes are amoeba-like cells that move slowly through the mesohyl and secrete collagen fibres. Collenocytes are another type of collagen-producing cell. Rhabdiferous cells secrete polysaccharides that also form part of the mesohyl.
Other types of cells within the mesohyl In addition to or instead of sclerocytes, demosponges have spongocytes that secrete a form of collagen that polymerizes into spongin, a thick fibrous material that stiffens the mesohyl. No specialized communication cells. Cells signal each other by DIFFUSION of chemical messages Myocytes ("muscle cells") regulate the opening and closing of the porocytes. "Grey cells" act as the equivalent of an immune system for the sponge. Oocytes and spermatocytes are reproductive cells.
Sponge Skeletal Materials Spicules and spongin fibers areSpicules and spongin fibers are –Structural –Used in defense against predators Also important for identification of spongesAlso important for identification of sponges
Sclerocytes - derived from amoebocytes; produce spicules
Growth of a sponge spicule Spicule Founder cell Thickener cell Sclerocytes - derived from amoebocytes; produce spicules
Leuconoid Body Plan Most common and most complex type of sponge body Water: flows in through pores into inhalant canals. It then enters choanocyte lined chambers… …and finally travels the excurrent canals to the osculum.
Detailed organization of the leuconoid sponge Prosopyle Apopyle
Hexactinellida Glass sponge community in Antarctica's eastern Weddell Sea, in an area not covered by ice shelves
Major component of the body is the trabecular syncytium. Flagellated cells lack nuclei, and are called collar bodies. Produced by nucleated choanoblasts.
Trabecular Syncytium Is the largest example of a syncytium known in the animal kingdom. Comes from fusion of early embryonic cells. Embryos are cellular until gastrulation SO - Hexactinellid sponges may have evolved from cellular sponges
Syncytium –Is Cytoplasmic –Lacks cell walls –Possesses multiple nuclei –Is bilayered –Extends through the entire body of the sponge. Syncytium –Connects through cytoplasmic bridges to various cells in the sponge, such as choanocytes and archaeocytes.
Trabecular Syncytium Primary reticulum, encloses and supports the collar bodies and the choanoblasts Secondary reticulum, branches from the primary reticulum and forms a kind of barrier around the collars of the collar bodies. Nuclei are scattered within the two reticula. Water is drawn through openings, or prosopyles, and moves through the microvilli of the collar bodies then through the excurrent canals to the outside through apopyles. Some water passes directly through the prosopyles into the flagellated chamber
Classification 2 subphyla –Symplasma –Cellularia 4 Classes based on type of spicules –Hexactinellida –Calcarea –Demospongiae –Homoscleromorpha
Classification Based on type of skeleton –Class Hexactinellida Spicules made of silica (glass) Maybe should be separate phylum –Class Calcarea Spicules made of calcium carbonate – Class Demospongiae Siliceous spicules in some Spongin fibers only in some Both spicules and spongin fibers One family lacks a skeleton entirely
Classification Subphylum: Symplasma –Class: Hexactinellida Acellular syncitium –Trabecular syncitium (discussed later) Spicules made of silica (glass sponges)
Euplectella Venus’ Flower Basket Sponge A deep water species. Often contains a pair of shrimp that entered as juveniles and remain trapped inside their entire lives. Usually many small shrimp arrive and the first pair to achieve sexual maturity kill off the rest. Often given to Japanese couples as a wedding present symbolizing fidelity and long life together. Hmmmmmm – prisoners and murderers?
Spongicoloides Unusual eyes. –In contrast to the sensitive optics used in the eyes of almost all other adult decapod shrimps, spongicolids retain the less sensitive optics used by larval decapods. (We’ll talk about this later with discussion of arthropods.) –These eyes are derived by neoteny, possibly reflecting the limited value of more specialised eyes within the body cavity of the sponge at depths of 100 – 1500 m.
Freshwater sponges are useful for monitoring pollution. In addition, they produce an antibiotic that may have important biomedical and ecological functions. Read article on East Chicago Sanitary District Wastewater Treatment Plant – sponges and salmon http://www.chicagowildernessmag.org/ issues/fall2007/sponges.html http://www.chicagowildernessmag.org/ issues/fall2007/sponges.html Watch the video!
Classification Subphylum: Cellularia –Class: Homoscleromorpha (newly separated from Demospongiae) Very simple structure- once considered to be “primitive” sponges
Homoscleromorpha –Reduced skeletons; some lack spicules entirely –Spicules are all the same (homoschleromorpha) –Spicules are siliceous –Spicules tend to be very small, don’t form a well- organized skeleton.
Classification Subphylum: Cellularia –Class: Homoscleromorpha (newly separated from Demospongiae) Small group (<100 described species in 2 families) of exclusively marine sponges Generally located in shallow waters from 8 to 60 m, but also at more than 1000 m depth Dwellers of hard substrate communities often in semi-dark or dark caves
Homoscleromorpha Reproduction is viviparous Larva = amphiblastula. Suspension feeders Chemical defense producers Builders of substrate Bioeroders of calcareous concretions
Homoscleromorpha Characters shared with Eumetazoa –True epithelium: basement membrane with collagen –zonula adhaerens cell junctions –Acrosomes in sperm Character shared with calcareous sponges –Cross-striated rootlets in the flagellar basal apparatus of larval cells –(Also found in at least one demosponge)
(f) Oscarella viridis TEM micrograph showing basement membrane (arrow heads) (h) Plakina trilopha TEM micrograph of the cross-striated ciliary rootlet (i) Oscarella microlobata TEM micrograph of cell junctions (zonula adhaerens)
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