[Coral-List] Sponges: individual counting

[Janie Wulff]

Dear Catherine,

The paper "Assessing and monitoring coral reef 
sponges: Why and how?"  (J.L. Wulff.  2001. 
Bulletin of Marine Science 69:831-846)  might be 
useful to you.

Number of individuals is not, by itself, a very 
reliable measure of abundance for sponges, 
especially branching and encrusting species, 
because of their propensity to fragment asexually 
and to re-fuse with their fragments.  If partial 
mortality is involved in fragment generation, the 
number of individuals can increase as the actual 
amount of sponge present decreases.  Volume of 
each individual sponge (defined as all the 
physiologically confluent tissue within an 
unbroken surface pinacoderm) can be a better 
measure, because many of the roles that sponges 
play in coral reef systems (e.g., as filter 
feeders, harborers of symbionts, and food for 
spongivores) are played out in proportion to the 
volume of live sponge tissue.  Exhalent apertures 
do not represent individuals in sponges.  This 
very reasonable question has been discussed 
elegantly in a paper by Willard Hartman and Henry 
Reiswig, "The individuality of sponges" (1973. 
In: Animal Colonies, edited by R.S. Boardman, 
A.H. Cheetham, and W.A. Oliver).

Best of luck in your field work.  I can send you 
copies of both papers if they are not readily 
available in Martinique.

Janie Wulff

Department of Biological Science
Florida State University


At 5:17 PM -0400 6/3/04, Catherine Desrosiers wrote:
>Dear Coral-listers,
>
>As I’m beginning my field study on sponges in Martinique, I faced the problem
>of how to realize the determination of the number of individuals. For
>branching forms in particular and some incrusting one, is each exhalant
>operture representing one individual or is the entire colony counted for a
>unique individual?
>If the ones who has already done this type of measures could provide me
>information, I would be grateful for their help.
>
>Catherine Desrosiers
>Marine Environment Observatory of Martinique
>7 avenue Condorcet
>97200 Fort de France
>Martinique (French West Indies)
>ommm at wanadoo.fr
>
>catcat at tzone.org                                              ---+--+--@
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