Phylum Porifera (Sponges) body consists of just 4 kinds of cells arranged ~9,000 living species; >2200 fossil forms around a system of pores and canals abundant fossil record though multicellular, no true organs or even tissues eg. first signs of multicellular life are in 750 MY old rock, in this same rock are unique chemical signatures of sponges sponges are closely related to the group of eg. newly discovered(2010) fossils that may be sponges have protozoan protists called the been found in 635-659 MY old rocks choanoflagellates whose cells very closely eg. 400 MY ago sponges dominated the oceans as reef builders resemble the collar cells of sponges eg. some fossil sponge reefs are much larger than the great th ~ 1/4 of their genes are shared by all other animals barrier reef à covered an arc across most of N Europe 200 MY ago about 1000 of those are absent from protozoa and other protists fossilized into hard rock used to build castles and other buildings in the Middle ages à may hold key to origin of multicellularity genetic analysis indicates that sponges are the most while multicellular their structure is unlike any other primitive animal group alive today animal group ancient spongelike ancestors were the first early biologists thought they were some kind of plant animals all are aquatic, mostly marine all other animal groups descended from this ancestor found at all depths from intertidal to the abyssal zone - the earliest sponges in symbiosis with bacteria may have significantly helped to aerate the ancient oceans making them more suitable for animal diversification a few (~150 sp./27 US) occur in freshwater sponges are some of the simplest animals most range from <1/2 inch to over 6 feet tall (=loggerhead sponges) all sponges are sessile Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 1 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 2 some are round, flat, grow as crusts or vaselike but only of its own species (if 2 blended together) most are assymetrical sponges need only very small amts of oxygen and, as some of the some are radially symmetrical earliest animals, may have played a role in helping to raise earths oxygen levels by feeding on dead or dying bacteria that often brightly colored: yellows, reds, greens, would deoxygenate the water oranges, lavenders Body Plan à pigments in surface cells body is a network of pores, canals and passageways most are colonial – colonies formed by budding no “mouth” all are sessile (non motile) , most are filter feeders water is pumped through these passageways and the but larvae are free swimming (motile) animals filter nutrients from the water currents very simple in structure small openings are pores or ostia where water is drawn into the sponge though multicellular, they function largely like a colony of unicellular organisms water exits the sponge through larger openings = oscula (sing. = osculum) Aristotle thought they were an intermediate between plants and animals natural selection favored an increase in surface area cellular level or organization leading to more complex “folding” of the sponge: à no true tissues or organs; loose aggregate of cells simple to more elaborate canal systems à masses of cells in gelatinous matrix= mesophyll à only a few cells have specialized for a particular function a. asconoid (6 kinds of cells in sponges; simplest type humans have >250 kinds of cells) very small tube shaped sponges large central cavity = spongocoel eg. can force sponge through fine sieve to separate cells in via small openings called ostia and individual cells will reform a sponge out through single osculum Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 3 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 4 functions b. syconoid derived from asconoid pattern by folding most cells are “totipotent” (ie. can change form more branching has incurrent canals and side passages and function – probably an important key to still have main spongocoel their success) single osculum 1. Choanocytes (= collar cells) c. leuconoid most complex consists of many small flagellated chambers probably the most distinctive and most important no longer a central spongocoel but almost unlimited of sponge cells ability for sponge to grow in size generally larger colonial forms each mass has its own osculum each collar cell has a flagellum incurrent and excurrent canals surrounded by a sieve-like collar that acts as a a typical sponge can pump water equivalent to its own strainer volume in ~ 8 seconds “collar” is made of microvilli and microfibrils a sponge must pump >1 ton of water to get 1 oz of the flagellum beats to draw the water currents into food the sponge and then to strain particles through the collar they can also control the flow by constricting osculum at night and opening in day when food is more food is absorbed (phagocytosis) by the collar cell plentiful and then sent to other cells in the sponge also can reverse the flow to clean out canals after a choanocytes line major cavities depending on canal system: storm a. spongocoel on asconoid types b. radial canals on syconoid types like cleaning pool filters c. flagellated chambers on leuconoid types Cell Types collar cells are almost identical to the cells of choanoflagellates only a few cells have been specialized for certain Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 5 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 6 genetic analysis indicates a very close relationship between these protists and can differentiate into any other type of cell sponges different kinds à choanoflagellates are ancestors of animals sclerocytes à secrete spicules spongocytes à secrete spongin 2. Pinacocytes collencyotes à secrete collagen form outer “epithelium” and sometimes lines Support inner passages the cells in gelatinous matrix of a sponge are arranged nearest thing to tissues around a skeleton of spicules thin flat cells spicules maintain its shape and keep pores and canals open some are contractile = myocytes in circular bands around oscula to regulate water flow spicules may be composed of: 3. Porocytes a. calcium carbonate tubular cells form the pores of asconoid sponges b. silica 4. Archaeocytes à spicules often united to form a rigid network that looks like fiberglass amoeboid type cells (eg. Venus Flower Basket) c. spongin (a form of collagen – a protein only move about in mesophyll matrix found in animals) receive particles from choanocytes for digestion à flexible protein fibers related to keratin phagocytize old cells (eg. common commercial sponge and most sponges Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 7 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 8 normally encountered on reefs) within days other “tentacles” grow around victim and engulf Feeding and Digestion and digest it 1. all but a few sponges are filter feeders 3. a small number of sponges are “parasites” feed on detritus, plankton, bacteria = boring sponges (demospongiae) pinacocytes, archaeocytes and choanocytes can all phagocytize excavates hollow tubes and passageways into shells and food corals (living or dead host shells) or limetone rock archaeocytes can eat larger particles choanocytes can eat smaller particles the animal grows into the canals and holes it creates when boring into live animal shells the host will either die sponges can also absorb dissolved nutrients outright or be much more susceptible to predation directly from the water may have significant impacts on coral reefs and oyster reefs digestion is all intracellular important in recycling shells and corals = “bioerosion” each cell is responsible for getting its own food in some areas bridge supports are no longer constructed of limestone because it is attacked by these sponges 2. one sponge is a predator No respiratory or Excretory Systems until 90’s all sponges were thought to be filter feeding omnivores take in O2 and get rid of wastes and CO2 by simple diffusion one sponge from Mediterranean is now known to be a predator = Cladorhiza corona a few have contractile vacuoles in choanocytes and archaeocytes found in Mediterranean caves lives in stagnant water à not much to filter No Nervous System or Sense Organs has developed a tentacle like appendge covered with velcro-like hooks sponges can react to local stimuli the hooks snag shrimplike crustacea some produce electrical signals Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 9 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 10 specialized sex cells in mesenchyme form egg sponges do produce some hormones for chemical or sperm control sperm released into water Reproduction & Development eggs are retained in mesenchyme reproduce both sexually and asexually sperm are drawn into female sponge Asexual through ostia or pores and fertilize a. regeneration egg b. asexual buds: most sponges are viviparous may break off or remain attached to form =retain and nourish embryo colonies free swimming ciliated larvae hatch and are c. fw & a few marine forms produce internal released buds = gemmules unique larval form = amphiblastula à dormant masses of encapsulated swims in plankton for a while then turns cells inside-out and settles to become a sessile adult usually produced during harsh conditions may be retained inside “parent” sponge or as original sponge dies, they fall to bottom Sexual some sponges are monoecious, some are dioecious Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 11 Animals –Animal Phyla: Porifera; Ziser Lecture Notes, 2015.9 12 Sponge Classification [not current taxonomy] Phylogeny of Sponges A. Class Calcarea (calcareous sponges) origin dates to cambrian small, vase shaped, primitive group related to flagellate protozoans mostly drab coloried; a few are yellow, red, green, lavender all marine, especially shallow waters à choanoflagellates show all 3 types of canal systems; mostly asconoid canals spicules of CaCO , needle shaped or 3-4 rayed 3 sponges diverged early new genetic analysis (2010) indicate that sponges B.