Porifera Flashcards
How are spicules formed
- Sclerocytes associate to form scleroblast
- Nucelar divison forms central and peripheral nuclei
- Spicule is formed between each pair of nuclei
- Thickener cells from the nuclear division move out along the rays
- Spicule formation is complete the founder cells move out the end of the rays
- cells disintegrate after the spicule is complete
How many valid described species of sponges are there?
-8500
What are the 4 classes of sponges
Demospongiae, Hexactinellids, Homoscleromorpha, Calcarea
Sponge nutrition
Particulate feeding
Water is drawn by beating of choanocyte flagella
Must be slow for exchange of nutrients, gases, wastes between the water and choanocytes
Water leaving the oscules
must be ejected far away enough to avoid recycling
Food particles transferred to ameboid cells called Archaeocytes by phagocytosis for digestion
Sponges are the only metazoans to rely entirely on intracellular digestion
Uptake of DOM
Take up DOM by pinocytosis (vesicle formation at the cell surface). 80% uptake as DOM and 20% as bacteria and dinoflagellates
Sponges main agents of DOM uptake on reefs
Fuels rapid turnover of choanocytes
Old choanocytes and particulate organic matter released by sponges
Uptake of DOM
dissolved organic matter
Take up DOM by pinocytosis (vesicle formation at the cell surface). 80% uptake as DOM and 20% as bacteria and dinoflagellates
Sponges main agents of DOM uptake on reefs
Fuels rapid turnover of choanocytes
Old choanocytes and particulate organic matter released by sponges
Sponge microbiome
The evolution of the meshy skeleton provided a place for the bacterial association
Many sponges therefore have prokaryotic communities in the mesohyl and intercellular matrix
Classed as either high or low microbial abundance
HMA sponges
Microbes can make up to 40% of sponge biomass
High microbial diversity
What is the significance of microbial communities
HMA species show higher mesohyl density than LMA
Pumping rate of LMA species sig. higher than HMA species. HMA lower pumping rate because less reliant on particulate organic matter -> slower passage of water allows for greater time for absorption of DOM, POM, and dissolved chemicals consumed by their microbes
C and N isotope studies indicate that HMA species are receiving nutrients and energy from microbial communities
Benefits of sponge microbiome
- Capable of autotrophic carbon fixation (Poribacteria, and Archaea)
- Nitrogen mtetabolism
Vitamin biosynthesis
Biosynthesis of secondary metabolites
What are carnivorous sponges
Those that live in oligotrophic environments have evolved carnivory because of lack of available nutrients
Spicules have modified to trap small crustaceans and other animals
e.g. Abestopluma
Please describe Abestopluma and how it is different from most other sponges
SEM micrographs of filaments of Abestopluma are covered by raised hooked spicules
Nauplius of brine shrimp are trapped by the hooks and engulfed by body of sponge
No aquiferous system and choanocytes
Filament epithelial cells establish contact with prey in 1 hour and enveloped, digestion complete within a few days
Where is carnivory sponges commonly found
in the deep sea where food is limited
Species pf Chondrocladia have modified aquiferous system to inflate spheres that trap prey (crustaceans) with special spicules
Carnivory evolution
Thought to have evolved once
Cladorhizid sponges have also been found to host chemosynthetic bacteria
- Dense assemblages of cladorihzids found near methane seeps and hydrothermal vents
- Bacterial symbionts are methanotrophic bacteria (methane oxidised to release energy for carbon fixation)
- Symbionts are consumed through phagocytosis by sponge cells in mesohyl
- Sponges reliant on chemosynthesis
