Phylum Porifera sponges

1

• Phylum Porifera (sponges)
• Living water pump composed of cells, lacking true
  tissues.
• Sponges are just masses of totipotent cells (can
  move and change form).
• Most cells are in direct contact with their
  environment.
• Sessile, benthic, aquatic some endolithic.
• Have skeleton made of organic fibers (spongin)
  and/or SiO2, or CaCO3 spicules.

2

• Morphology
• Ostia incurrent pores.
• Incurrent canals.
• Spongocoel or atrium main cavity on interior of
  sponge. In complex sponges, not always able to
  differentiate a distinct atrium.
• Osculum excurrent opening of sponge
• Branch has osculum.
• Bud osculum has not developed

3

• Morphology (continued)
• 3 grades of sponges
• Ascon relatively straight path from ostia
  through incurrent canals to atrium to osculum.
• Sycon water goes from ostia through incurrent
  canals, to single chambers through atrium to
  osculum. Like a cluster of ascon sponges.
  Simple folding of sponge walls.
• Leucon water goes from ostia through incurrent
  canals, to complex network of chambers through
  excurrent canals and atrium (if one is
  recognizable) to osculum. Many modern leucon
  sponges have complex branching or encrusting
  forms.
• Note that sponge grades are really a response
  (convoluting structures) to the area-volume
  problem.

4

• Morphology Three Layers of Cells
• Ectosome or Pinacoderm
• Pinacocytes leathery cells which form the tough
  exterior of sponges and also help line the
  interior (atrium) in most sponges
  (endopinacocytes).
• Porocytes (in ascon grade) tube shaped cells
  which line incurrent canals and control amount of
  water allowed in the sponge. Expand during
  respiration and feeding contract during times of
  disturbance.
• Endosome or Choanoderm
• Choanocytes (collar cells) each has whip-like
  flagellum which is used to create currents for
  feeding and respiration. Also traps food
  particles. Line the atrium in ascon and sycon
  grades of sponges. Occur in distinct chambers in
  leucon grade of sponges (which lack well
  developed atrium).
• Endopinacocytes leathery cells.
• Mesophyle or Mesenchyme
• Sclerocytes and spongocytes secrete spicules and
  spongin, respectively.
• Myocytes contractile cells which help control
  the diameter of excurrent canals and the osculum.
• Archaeocytes ( amoebocytes) contain digestive
  enzymes and are important in digesting and
  transporting food. Can alter to become any kind
  of cell. (Think The Terminator.)

5

• How a Sponge Works
• Essentially just a very efficient plumbing
  system.
• Choanocytes help create feeding currents, but
  general morphology of sponges is critical.
• Sponges living in relatively turbulent water or
  in areas of strong currents cause a vacuum effect
  due to their construction.
• Make sure that everyone understands
  velocity-diameter-pressure relationships.
• Show flow path. That means you folks should look
  at the overhead!
• Water increases in velocity as it goes over a
  sponge, causing a pressure drop and an upsuction
  of water from ostia to the osculum.
• Notice that the excurrent opening (osculum) for
  most sponges is raised and thus causes waste
  material to be carried up and away from sponge.

6

• How a Sponge Works (continued)
• Water flow is also a function of the total
  cross-sectional diameters of the channels in
  which water flows
• Cross-sectional diameters go up, velocity of
  water decreases.
• Cross section goes down, velocity increases.
• Water needs to move slowly over choanoderm so
  there is time for ingesting nutrients, exchanging
  gases, wastes, etc.
• Combined cross sectional area of all the
  incurrent canals is much less than that of the
  atrium or choanocyte chambers (in leucon grades).
  So, water slows as it enters the chamber(s).
  This allows time for metabolic activities.
• Oscular diameter is less than that of the atrium
  or combined diameters of choanocyte chambers.
  So, water velocity increases. Helps to send
  waste water far from sponge.

7

• Sponge Reproduction Sexual
• Eggs develop from arcaheocytes or choanocytes.
  Sperm cells develop from choanocytes.
• Most sponges are sequentially hermaphroditic. In
  some species, there are permanent males and
  hermaphrodites.
• Sperm released form osculum. Smoking sponges.
• Captured by choanocytes of another sponge. There
  is some sort of recognition factor that keeps
  sperm of same species from simply being ingested.
  
• Embryo develops in parent and is released as a
  larvae through osculum or through split in
  parents body wall.
• In general, shallow water sponges produce
  planktonic larvae, while deeper water sponges
  produce benthic larvae.

8

• Sponge Reproduction Asexual
• Buds Buds and branches may pinch off by a
  process of cellular reorganization. Pieces
  regenerate.
• Gemmules Cyst-like, nutrient rich arcaeocytes
  which form during times of environmental stress.
  Especially common in fresh water sponges, but
  also in marine sponges. Very resistant can dry
  up to 10 years.
• Regeneration following fragmentation.

9

• Spicules
• Calcareous or opaline silica
• Sufixes
• Axon axises
• Actine rays

10

• Classification
• Class Demospongea
• Spongin and/or silica spicules
• Monaxon or tetraxon (but none with 90o angles)
  spicules
• Marine and fresh water.
• Massive, many fall to spicules upon death.
• Cambrian to Recent
• 390 fossil genera, 600 living

11

• Class Hexactinellida
• Silica hexactine spicules
• Marine, prefer cooler water
• Massive, some use tufts composed of spicules to
  anchor in muddy substrate.
• Cambrian to Recent
• 295 fossil genera

12

• Class Calcarea
• Calcareous spicules or asphicular calcareous
  walls
• Marine
• Massive, bead-like (sphinctozoans) or branched.
• Cambrian to Recent
• 115 fossil genera.

13

• Class Sclerospongea
• Skeleton of silica spicules and spongin
• Massive layered aragonite base.
• Many have mamelons and astrorhizae.
• Marine.
• Modern ones are cryptic (hidden)
• Triassic to Recent

14

• Class Stromatoporata
• Laminated, aspiculate calcareous skeleton.
• Have laminae and latilaminae.
• Pillars.
• Astrorhizae and mamelons.
• Marine
• Massive, encrusting, less commonly branching
• Ordovician to Cretaceous
• 70 fossil genera.

15

• History
• During the Paleozoic and the Triassic, there were
  lots of sponges in shallow water.
• Important reef builders (esp. stromatoporoids) in
  Ordovician through Devonian. Stromatoporoids are
  rare in late Paleozoic make moderate comeback in
  Triassic and peak again in Jurassic.
• Stromatoporoids suffered major extinctions during
  Frasnian-Famenian (Late Dev.) mass extinction.
• In Devonian, abrupt increase in abundance of
  hexactinellids has been used to suggest ocean
  cooling at this time.
• Sphinctozoans (calcareous sponges) were important
  reef organisms in late Paleozoic and Triassic
  reefs.
• In Jurassic, hexactinellids invaded deeper water,
  possibly with opening of the Atlantic. Today,
  most live deeper than 200 m some even in
  trenches.

16

• Phylum Archaeocyatha
• Conical cone shaped calcareous fossils
• Unknown affinity.
• Skeletal plan is somewhat similar to a sponge.
• Seems to have a body plan designed as a water
  pump.
• Solitary and colonial forms.
• One- and two-walled forms.

17

• Morphology
• Fossil called cup.
• Tip of cone called tip.
• Many had holdfasts.
• Walls are porous.
• Region between inner and outer walls called
  intervallum.
• Intervallum can be divided by vertical septa into
  loculi.
• Some have horizontal tabulae or slanting
  dissepiments.

18

• 2 classes
• Class Regulares
• 1-wall forms lack dissepiments.
• 2-wall forms typically lack dissepiments.
• In ontogeny of 2-wall forms, inner wall appears
  earlier than dissepiments, tabulae or septa.
• 173 genera
• Class Irregulares
• All have dissepiments.
• Dissepiments start to form before inner wall in
  2-wall forms.
• 1-wall forms also have irregularly spaced
  calcareous bars and rods, which apparently acted
  like struts for skeletal support.
• 60 genera

19

• History
• Early to Mid Cambrian
• Show up in the Tommotian along with small
  shellies.
• Calcareous to mixed calcareous/siliciclastic
  settings.
• Shallow marine
• Important early reef builder in conjunction with
  cyanobacteria.
• Great Siberian Barrier Reef 800 km long, up to
  300 km wide, only a few meters of relief above
  seafloor.