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Divers measuring height of a moderate size Cloud Sponge
Divers placed markers next to 8 Cloud Sponges and then
measured their height and photographed them periodically over a
period of one year.
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We reported in a paper last
year (Austin et al 2007) on Growth over a 3 ½ year
period
(for the
complete paper click
HERE,
go into Table of contents and scroll down to Research
Articles; second paper)
Growth
in surface area is perhaps most meaningful, but except
for juveniles, can’t be measured
without killing the sponge.
Here is the size of the sponge with corresponding
surface areas at year 1(1A), 2 (1B), and 3 ½ (1C)
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At year 4 ½ (1D) the sponge was too convoluted to
get an approximation of surface area
Note that the “phallus”
part of the sponge, which has a skeleton of fused glass,
does not grow at
all
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The phallus like part of the sponge is roughly cylindrical so that an
estimate of the surface area is best determined as that of a cylinder closed at
one end. The
non-growing phallus is 18.3 cm long and 3.3 cm in diameter,
resulting in a surface area of 160 cm
2.
The mitten like part of the sponge is comprised of 2 broad fairly flat surfaces
together forming a flattened sac.
Areas of the broad surfaces were determined graphically by Bill Austin,
Khoyatan Marine Lab, and electronically by Sheri Ward, Coastal and Ocean
Resources. The two methods of calculating area were in close agreement (within 1
sq. cm.). The initial surface area on one side (excluding the “holdfast” ) was
about 107 square cm while the surface area after one year had increased to 253
square cm., a 136 % increase in size.
No direct measurements of thickness were made as removing samples might affect
subsequent growth. Measurements on another similar sized sponge were taken at 5
cm, 10 cm, 15cm and 20 cm from the growing edge. The thickness for this sponge was 6mm for all but the lowest (20 cm) which was 5.5 mm. |
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Where
does growth occur?
Measurements of the phallus sponge over time
indicates that growth is apical rather than throughout the sponge.
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To independently verify where growth occurs
•Divers
drilled two holes and measured the distance between the
holes, as well as, between the osculum, or sponge vent, and
the closest hole
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They returned 2 ½ and 3 ½ months later and
re-measured these distances.
Note the
regeneration can occur at the broken edges of fused
skeleton.
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•The
results for 2 sponges are shown in the table above
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•The
distance between 2 bored holes is unchanged
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•While
the distance between the osculum and the near hole has
increased significantly
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•Growth
is limited to the soft parts where the mainframe
skeleton hasn’t fused together
Regeneration can also occur at the broken edges
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