Trees and Fish

capman at capman at
Tue Nov 6 01:04:09 EST 2001

>  given the fact that
>many private aquaria are "pan-tropical" and contain organisms from many
>geographic locations.  There would be some chance of introducing a novel
>disease or other undesirable organism if aquarium corals were actually
>used in this way.

Along these lines I would think that in a tank with cnidarians from 
all around the world zooxanthellae from different oceans are possibly 
hopping between corals, with Caribbean zooxanthallae strains 
potentially taking up residence in IndoPacific corals and vice versa. 
If this is the case, then we would risk introducing alien 
zooxanthellae to reefs when reintroducing these tank-raised corals to 
the wild.  To prevent this from happening, our captive corals 
originating from a given area would need to be kept completely 
isolated from organisms collected elsewhere.  Even live rock could 
potentially "contaminate" corals with foreign zooxanthellae, since 
live rock often harbors Aiptasia or Anemonia anemones and other 
cnidaria potentially harboring zooxanthellae.

I have no idea what the effect of this sort of zooxanthellae transfer 
might be on reefs   I'm not an expert on zooxanthellae, but I can 
well imagine potential undesirable consequences.   Or, maybe it would 
be totally benign (especially if the reef had been wiped out 
completely otherwise).  Or, who knows, maybe additional diversity of 
zooxanthellae with different tolerances would increase the resilience 
of corals in a reef?

>My question to the reef research community is what steps the aquarium
>hobby could take to increase the value of our germline holdings?  There
>has been some discussion of this in the hobby for several years.
>Initially, I was somewhat dismissive of the idea.  But things have changed
>substantially over the last few years, both because of the hobby's success
>in captive propagation of several species, and because things seem to be
>falling apart in the wild at an accelerating pace.

I'm not sure can call myself part of the reef research community, but 
I'm a biologist who has thought a fair bit about these issues in 
other contexts (e.g. in the context of terrestrial plant community 
restoration, and in the context of breeding programs to maintain 
freshwater fish such as tropical killifish).

An obvious necessity would be *excellent* record keeping of the sort 
that freshwater killifish breeders in the American Killifish 
Association strive for...the original collection locations of many 
strains of tropical killifish in the hobby are dutifully kept track 
of by killifish breeders.  It is viewed as a sacrilege to lose track 
of such information or to allow strains from different locations to 

Similarly, in the better-quality prairie restoration efforts in the 
Midwestern U.S., great care is taken to use seed stock grown from 
plants originally collected in the general vicinity (e.g. within 50 
miles or maybe even less) of the restoration site.  This complicates 
restoration efforts since it means that a restoration project in 
Illinois, for example, can't simply buy seed from a large native 
plant seed farm in Kansas.  Separate propagation sites need to be 
maintained for each location.

I suspect that it is too late now to figure this information out for 
most of the corals in the hobby at the present time.  However, reef 
aquarists have gotten so good at growing and propagating *many* 
corals that the skills of aquarists could be used to help keep newly 
collected corals with known history (e.g. from small deliberate 
collections made for conservation purposes) going and to propagate 
them for possible reintroductions to the wild.  I think that if we 
were to find ourselves resorting to such drastic measures, a set of 
strict guidelines would need to be developed that aquarists 
maintaining these corals would need to follow.  This begs the 
question of course of how to ensure that the guidelines are actually 

The experiences of those involved in trying to maintain captive 
populations of Lake Victoria cichlids (most species of which are now 
extinct in the wild) would be relevant here.

>The coral strains that we would have to offer are almost without exception
>clonal strains.  So their genetic diversity would be quite low.

Yes and no.  Yes, the Acropora in the hobby known as "Larry Jackson's 
Purple-tipped Monster", for example, is going to be genetically the 
same in everyone's tanks.  However, for many coral species I would 
think the clones in the hobby come from multiple importations and 
thus represent a sampling of the genetic diversity in the original 
wild population.

Furthermore, assuming multiple clones are maintained (and kept 
careful track of), clonal reproduction has some advantages in 
maintaining genetic diversity in captive populations.  Repeated 
rounds of sexual reproduction combined with a small breeding 
population results in a loss of genetic diversity due to the loss of 
heterozygosity  (and the genetic drift) that is hard to avoid when 
there is inbreeding in a small population.  Asexual reproduction, on 
the other hand, maintains the presumably highly heterozygous genomes 
of wild-collected organisms indefinitely (aside from any possible 
effects of somatic mutations).

It seems to me that the important thing in such captive coral 
maintenance programs would be to have multiple clones of a given 
species maintained in as many different aquaria as possible (to 
reduce the risk of total loss of a clone if a given system crashed), 
and to keep very close track of which clone is which and where each 
came from.

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