Porifera

Question 1

Porifera - sponges

Answer 1

-Porifera = Latin ‘bearing pores’
-Sponges (phylum Porifera) are among the oldest,
simplest, and most primitive of all metazoans
-They are found in all oceans at all depths, from the
Artic to the Southern Ocean and the coastal waters
of the Antarctic
-Sponges are sessile: except for the tiny filter-feeding
flagella located inside them, they are unable to move
-Sponges differ from other metazoans in that they do
not have true tissues

Question 2

Porifera - anatomy

Answer 2

-Sea water pumped into the sponge through small
inhalant openings (ostia) by the beating of
flagellated choanocyte cells
-Near-sterile water (up to 96% of microbial cells are
removed) discharged via the exhalant opening
(osculum)
-The choanocytes capture food particles from
seawater, including bacteria, unicellular algae and
even viruses
-From the choanocyte chambers, microorganisms
are transferred to the inner mesohyl layer, where
they are engulfed by archaeocyte cells

Question 3

Porifera - spicules

Answer 3

-Some sponges synthesise mineralised siliceous
skeletal elements
-Spicules are divided into two categories according
to size and function (megascleres and microscleres)
-Microscleres display diverse 3D morphologies
-All spicule branches harbour a proteinaceous axial
filament
-The protein silicatein forms the template for
spiculate construction

Question 4

Porifera - microbiomes

Answer 4

-Despite their simple body plans, sponges harbour
enormously dense and diverse communities of
symbiotic bacteria, archaea and unicellular
eukaryotes in their tissue
-These microorganisms constitute up to 35% of total
sponge biomass, at densities exceeding 109
microbial cells per cubic centimetre of sponge tissue
-Marine sponges and their microbiomes boast an
impressive metabolic and chemical repertoire that
contributes to their nutritional ecology