Phylum Porifera: Sponges Chapter 6

Types of Cells Pinacocytes (Epidermal Cell) Porocytes (Water Flow Through Cell) Choanocytes (Collar Cells) Archeocytes (Amoebocytes)

I. Pinacocytes Cells of the external epithelium Main functions: Structure Contraction

II. Porocytes Cells which form pores Function: to allow water flow

III. Chanocytes Line the flagellated canals and chambers. Main function: to create water flow.

Codosiga

Sponge feeding

Diameter of channels influences water flow velocity. Particles that are captured are in the 2-5 µm range.

Cladorhizid carnivorous sponge Predatory sponges Cladorhizid carnivorous sponge

The Harp Sponge, Chondrocladia lyra

IV. Archaeocytes Ameboid cells which can be non-sessile Found in cellular matrix Main function: Digestion Secrete structural components Spongin Spicules

Sponge feeding

Sclerocyte in the process of secreting a spicule

Keeping the mesohyle together Spongin Spines (spicules) Siliceous Calcareous

Spongin Fibers of collagen

Spicules Spines, when placed together form a very rigid skeleton

Megascleres And Microscleres

Main Groups of Sponges P: Porifera C: Calcarea C: Hexactinellida C: Desmospongiae

Calcarea Calcareous sponges Spicules composed of calcium carbonate Small < 10 cm tall

Calcareous sponges

Hexactinellida Glass sponges Some spicules fused to form skeleton Spicules made of glass (Siliceous spicules) six rayed Deep water sponges

Siliceous spicules in Hexactinellida (Triaxon) six rayed spicules.

Desmospongiae Common sponges Skeleton is variable Can be large Spicules Spongin both Can be large

Siliceous Spiculse in Desmospongia Never six-rayed Microscleres Megascleres

Sclerospongiae Sclerosponges were first proposed as a class of sponges, in 1970 by Hartman and Goreau. Sclerosponges are sponges with a soft body that covers a hard, often massive limestone basal skeleton. Because of their long life span (500-1,000 years) it is thought that analysis of these sponges could extend data regarding ocean temperatures, salinity, and other variables farther into the past than has been previously possible. However, it was later found that the sclerosponges are not a monophyletic group (they are polyphyletic) and therefore this class is currently not recognized.

The Big Picture Sponges are metazoans, but don’t have true tissues They are an ancient group Three main groups (taxonomic), which fall into three main structural groups Four types of specialized cells *choanocyte*