Phylum Porifera

Phylum Porifera

1. What do sponges do?

   • Sponge cells can communicate (CELL phones amirite)
   • you can chuck a sponge in a blender and eventually all of the cells would reaggregate into a new, functional sponge
   • produce variety of chemical compounds
   • Primary metabolites produced for day to day fxning
   • Secondary metabolites
     • often serve defensive purpose
     • Cacospongia sp. - alkaloid concentration highest @ tips, nudibranch eats tips and stores toxins to use for defense
     • competition for space, defending territory, prevents overgrowth and fouling
   • Biomonitoring of pollutants
     • filter great volumes of water and accumulate heavy metals and other pollutants

2. Types of canal systems/body types

   • Leuconoid
     • most common
     • folded, very thick body walls
     • many channels and many flagellated chambers
     • lack an atrium
     • water flow: ostium --> incurrent canals --> flagellated chambers --> excurrent canal --> osculum
   • Synconoid
     • folded body wall, intermediate thickness
     • more channels for water to flow through (increased feeding opportunity)
     • series of flagellated chambers connected by canals
     • water flow: ostium --> incurrent canals --> radial canals --> spongocoel --> atrium --> osculum
   • Asconoid
     • simple, small, tube shaped
     • body wall not folded
     • choanocytes only on inside
     • rarely exceed 10cm
     • water flow: ostium --> spongocoel --> atrium --> osculum

3. Reproduction

   • Sexual
     • no organized reproductive system
     • hermaphrodites
     • no self fertilisation, produce eggs and sperm, switching each year
     • some gonochoristic (separate sexes)
     • Gametes turned on by enzymes
     • Release of gametes:
       • collar cells collect and transfer sperm to amoebocytes which then transfer sperm to ripe eggs
       • Larvae develop in sponge and then released
       • Planktonic larvae swim for a few days then settle onto substrate and grow
       • Vivipary = live young produced
   • Asexual
     • Fragmentation and regeneration
       • missing body parts regrown, growth from fragments
     • Budding
       • new sponge grows from older one, breaks off and grows into new individual
     • Gemmules
       • food filled ball of archaeocytes surrounded by protective coat w spicules
       • can survive harsh conditions, break open when conditions improve to form new sponges

4. Classes of Porifera

   • Class Calcarea
     • calcium carbonate spicules with 1, 3, or 4 rays
     • <15cm
     • contains all asconoid forms, mostly synconoids
     • NEVER contain spongin
   • Class demospongiae
     • silica spicules and spongin fibres
     • 85% of all species
     • ALL freshwater sponges are demo
     • leuconoids
     • skeleton is variable - some spicules only, some spongin only, or both
   • Class Hexactinellida
     • silica spicules, 6-rayed
     • mostly deep water (2km)
     • all marine
     • some spicules fused to form skeleton

5. General Features

   • Porifera = pore bearing
   • adults sessile (non-motile)
   • Mostly asymmetrical but some radial
   • Sponge = collection of different specialized cells arranged in a gelatinous matrix

6. General Morphology

   • Body is mass of cells embedded in gelatinous matrix and stiffened by spicules of calcium carbonate or silica and collagen
   • Choanocytes
     • feeding cells
     • flagella creates water current, pulls water in through ostia
     • collar traps food, which is ingested and digested
   • Skeleton
     • spongin fibres and collagen
     • spongin protein is endoskeleton, allows structure and shape
     • spongin secreted by spongocyte cells
     • 90% use spongin as major component, 10% use collagen
   • Spicules
     • calcerous or silicon based secreted by sclerocyte cells
     • serve as skeleton support
     • deter predators
     • used to ID sponges
   • Archaeocytes
     • totipotent (change fxn)
     • ingest and digest food
     • transport nutrients
     • excrete wastes
     • differentiate into gametes for sexual reproduction
     • secrete spongin and spicules

7. Common ancestor of all animals

   • Animals probably evolved from colonial, flagellated protists
   • Last Eucharya Archaea Common Ancestor (LEACA)
   • Choanoflagelidda