Physiological Functions

• Movement

  (a) planktonic or motile at larval stage

  (b) sessile at adult stage

  b.1 ostand erect, branched, lobed, low or encrusting

  b.2 osome bore holes into shells, rocks, corals

  (c) some adults can creep across the seabed at 1-4 mm per day (due to amoeba-like movement of pinacocytes)
• Sponges are generally sessile as adults and spend their lives attached to a fixed substratum. They do not show movement over large distances like other free-swimming marine invertebrates. However, sponge cells are capable of creeping along substrata via organizational plasticity. It has been speculated that this localized creeping movement may help sponges adjust to microenvironments near the point of attachment. It must be noted, however, that this pattern of movement has been documented in laboratories, but it remains to be observed in natural sponge habitats.
• Coordination of Movement

  (a) no nervous tissues

  (b) exhibited by:

  (-) ocontractions of pinacocytes squeezing the water channels, thus expelling excess sediment and other that may cause blockage 

  (-) ocontract osculum independently

  (-) ocontract to reduce the area that is vulnerable to attack by predators

  (c) may involve chemicals similar to neurotransmitters

  (d) myocytes are responsible for closing the osculum and for transmitting signals between different parts of the body
• Respiration and Excretion

  (a) supported by water flow system

  (b) absorbs oxygen and excrete waste products (i.e., ammonia) through diffusion

  (c) archeocytes/amoebocytes remove mineral particles that block the ostia by transporting and dumping into the outgoing water current
• Filter Feeding

  (a) generally feed on suspended particles in the water pumped through the canal system

  (b) filtered food by choanocytes and passed on to archeocytes

  (c) pinacocytes may phagocytosize food particles at the surface followed by intracellular digestion
• Carnivorous Sponge

  (a) mostly from family Cladorhizidae

  (b) techniques:

  • use sticky threads or hooked spicules
  • entangling prey with fine threads
  • possible use of venom
  • inflate balloon-like structures for prey capture

  (c) most lost the water flow system and choanocytes

  (d) food – capturing mostly crustaceans and other small animals
• Chondrocladia Lyra (hard sponge)

  
• Chondrocladia lampadiglobus (ping pong tree sponge)

  
• Host for endosymbionts

  (a) mostly freshwater sponges

  (b) most common in water w/ relatively poor supply of food particles

  (c) have leafy shapes that maximize the amount of light they collect

  (d) host green algae within archeocytes and other cells
• “Immune” System

  (a) do not have a complex immune system

  (b) can reject grafts from other species but accept them from other members of their species

  (c) gray/grey cells reject foreign material

  •produce a chemical that stops the movement of other cells in affected areas

  •concentrate in the areas and release toxins that kill all cells in the area
• REPRODUCTION

  Asexual

  (a) budding (with fragmentation)

  (b) gemmule formation

  Sexual
• Asexual Reproduction: Budding

  (a) fragmentation of body wall; buds appear as an outgrowth on sides of the sponge

  (b) when they reach a certain size, they drop off and settle to the bottom to form a new sponge

  (c) external budding
• Asexual Reproduction: Gemmule Formation

  •occurs only in freshwater sponges

  •gemmules are groups of food-laden amoebocytes that deposit a hard covering of spicules around them

  •formation is triggered by environmental conditions such as decreased temperatures

  •they allow the sponge to pass the winter or periods of drought

  •after which the outer covering breaks open and a new sponge develops
• Gemmules are environmentally resistant structures produced by adult sponges wherein the typical sponge morphology is inverted. In gemmules, an inner layer of amoebocytes is surrounded by a layer of collagen (spongin) that may be reinforced by spicules. The collagen that is normally found in the mesohyl becomes the outer protective layer.
• Sexual Reproduction

  (a) generally monoecious

  •eggs and sperms in one individual (produced at different times to avoid self fertilization)

  •often exhibit sequential hermaphroditism:

  (1) Protandry: male structures develop first

  (2) Protogyny: female structures develop first

  (b) few dioecious

  (c) some populations are mixed
•  In some sponges, production of gametes may occur throughout the year, whereas other sponges may show sexual cycles depending upon water temperature. Sponges may also become sequentially hermaphroditic, producing oocytes first and spermatozoa later. Oocytes arise by the differentiation of amoebocytes and are retained within the spongocoel, whereas spermatozoa result from the differentiation of choanocytes and are ejected via the osculum.
• Sexual Reproduction

  •sperm release is thru osculum

  •sperm entry to another canal system

  •sperm phagocytosized by choanocytes

  •internal fertilization in mesohyl

  •zygote develops into a free-swimming larva within the sponge

  •free-swimming larva is expelled via the osculum

  •settles at the bottom and  begins external development
• Ejection of spermatozoa may be a timed and coordinated event, as seen in certain species. Spermatozoa carried along by water currents can fertilize the oocytes borne in the mesohyl of other sponges. Early larval development occurs within the sponge, and free-swimming larvae are then released via the osculum.
• Three basic larval types have been described in sponges: “coeloblastula” larvae (= “blastula” larvae), parenchymula larvae (= parenchymella larvae), and amphiblastula larvae.
• Most demosponges incubate embryos until a late stage, producing a solid parenchymula larva with an outer surface of monoflagellated cells and an inner mesohyl-like core of matrix and cells.
• Calcareous sponges (and a few demosponges) often release their embryos early, as free-swimming “coeloblastula” larvae. These larvae may undergo one of two developmental processes. In the simplest case, transformation of the larva involves an inward migration of surface cells that have lost their flagella; these same cells subsequently regain their flagella as they metamorphose into choanocytes.
• After a free-swimming period, the amphiblastula larva settles on its flagellated end. Metamorphosis involves a rapid proliferation of the “macromeres” to form pinacoderm that overgrows the flagellated hemisphere.•