Natural History : Growth & Age                                                                                               Page 2 >>

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.

   

Divers measuring height of a small Cloud Sponge

Height is only one parameter of growth and parallax and viewing angle may have resulted in some degree of error.    

   
Next 5 photos of same sponge over a period of one year.

The best results to date are from measurements of a flattened mitten-like form of a small sponge by divers Mike Miles and Joe Doiron.

Photo taken Sept. 13, 2002.  

   
Photo taken February 2, 2003,   Osculum is in upper side of mitten on right
   
Photo taken March 8, 2003.   Mitten damaged on the right side on or before this date
   
Photo taken May 24, 2003.   Note that edges of damaged area appear to have regenerated.
   
Photo taken Sept. 13, 2003.  Note osculum walls are now fully regenerated (opening on right).

The mitten has clearly increased in size over the year by 6 cm in width and 6 cm in length (the scale numbers are in decimeters).  
   
Photo taken Sept 13, 2003.   In this view one can see the flattened form of the mitten (left and back) and the tubular form of the finger (right and front).
   
 
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)
                                                             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

 

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.
 

Where does growth occur? 

Measurements of the phallus sponge over time indicates that growth is apical rather than throughout the sponge.    

 

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
 

 

 
 

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.

 

 

 

  • The results for 2 sponges are shown in the table above
  • The distance between 2 bored holes is unchanged
  • While the distance between the osculum  and the near hole  has increased significantly
  • 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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