Unit 4.1 Phylum Porifera

Phylum Porifera Multicellular Body with pores (ostia) No organs or true tissues. No nervous system Adults sessile & attached to substratum. Skeleton of calcareous spicules, siliceous spicules, spongin made of collagen or a combination. No respiratory, circulatory, or nervous systems All aquatic, mostly marine.

Phylum Porifera Composed of 3 layers outer layer of flattened contractile cells (pinacocytes) inner non-living mesenchyme containing a variety of specialized cells collar cells (choanocytes) which capture food, etc. from water flowing through channels. Exhibit asymmetry or radial symmetry.

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Spicules Skeleton of sponge Calcium carbonate Silicon Collagen

Sclerocytes Produce spicules

Mesenchyme (Mesoglea) Gelatinous matrix that holds all the living cells of a sponge in place

Pinacocytes Comprise the outer surface of a sponge Contractile – can regulate the amount of water that is able to enter the sponge

Porocytes Forms the walls of the pores (ostia) through which water is able to enter the sponge

Choanocytes Flagellated cells Rear end anchored in the mesenchyme, collar and flagellum exposed to the inner sponge cavity Flagellum creates water currents Collar traps food Passes food to archeocyte

Archeocytes Amoeboid cells Receive food from choanocytes Able to move throughout the mesenchyme to deliver food to all other cells in the sponge Able to differentiate into other cell types

Fig. 12.5 Three Sponge Body Types Fig. 12.5

Asconoid Sponges Asconoid sponges have a stalk-like shape and a large, central atrium Choanocytes are only located along the inner walls of the atrium Asconoid sponges are often small, many no larger than 1mm in diameter, due to limits on nutritional uptake caused by simple choanocyte orientation

Syconoid Sponges Syconoid sponges possess folded walls that increase the surface area of the animal Water passes through radial canals located in these folds which also contain much higher numbers of choanocytes than is seen in asconoid sponges No choanocytes are anchored to the inner walls of the atrium May grow up to several centimeters in diameter

Fig. 12.7 Fig. 12.7

Leuconoid Sponges The most common type of sponge body plan Inner atrium is almost non-existent Inner sponge is filled almost entirely with mesenchyme crisscrossed by by a network of chambers that all contain large numbers of choanocytes Largest surface area to volume ratio of any sponge allows leuconoid sponges to grow to over a meter in diameter

Three Sponge Body Types Asconoid Syconoid Leuconoid

Class Calcarea Small – 4 inches or less Vase shaped Found in shallow waters around the world Asconoid, Syconoid, or Leuconoid Spicules of calcium carbonate Straight or 3-4 rays

Class Hexactinellida Vase-like Delicate Glass sponges Found in deep, tropical waters Leuconoid only Spicules Siliceous 6 rays

Class Hexactinellida Euplectella

Class Demospongiae Largest number of sponges are in this class Bath sponges Found in shallow, warm waters to abyssal waters 5 miles deep Only type of sponge possible to find in fresh water Leuconoid Spicules Siliceous (rounded) Spongin (cellulose)

Fig. 12.11a

Sexual Reproduction Monoecious Sperm and egg derived from choanocytes Both male and female gametes produced by a single sponge Sperm and egg derived from choanocytes Reproduce en-masse during certain times of the year when the moon and water temperature are at a specific point Once fertilized, the larvae grow cilia and swim to a new location to grow

Asexual Reproduction Sponges are able to reproduce asexually by two different methods Fragmentation Similar to cloning plants A small portion may be severed from the rest of the body and it will grow as a new sponge on its own Gemmule formation When conditions become harmful to a sponge, it can produce a type of seed that may lie dormant for years until conditions become more favorable

Precambrian Before 670 MYA Porifera Platyhelmithes Mollusca Arthropoda Echinodermata Hemichordata Cnidaria Nemertea Annelida Lophophores Chordata Precambrian Before 670 MYA Protozoans

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The End CO 12 Fig. 12.CO