[Coral-List] test tube corals in Brazil

[Nikolas Zuchowicz]

Hi Doug & all,

 

"Also, I think sperm are easy to freeze.  Eggs and larvae are hard to freeze
and survive thawing . "

 

You have it right, and I can offer some detail to expand on the work in
Brazil. The coral cryopreservation community can freeze and recover viable
sperm of most coral species that have been attempted, mainly using
techniques that originated in Dr. Mary Hagedorn's group. Of course, a thing
is easy once it has been worked out - that took a good few years! Over 40
species in total are now represented in the CryoDiversity Bank in Sydney and
Dubbo [1], the National Animal Germplasm Program repository in Colorado, and
smaller repositories elsewhere. Proof-of-concept has been shown for assisted
gene flow between regions [2] to enhance diminished populations with few
genetically distinct individuals.

 

No coral eggs have been cryopreserved and recovered to my knowledge.
Cryopreserving and warming larvae has been possible for a few years, first
by laser warming [3] and more recently with a rapid heat transfer substrate
called cryomesh [4]. The difficulty with larvae is that they likely cannot
be slow-frozen in the presence of crystalline ice, a simpler method that
works well for sperm. Instead, they must be loaded with a high concentration
of cryoprotective chemicals such as dimethyl sulfoxide and propylene glycol,
have much of their water evacuated, and be both cooled and warmed extremely
rapidly so as to outrun nucleation and growth of ice crystals. Dr. Chiahsin
Lin's group in Taiwan is also pushing the larval work forward, having
recently reported production of adult corals from cryopreserved larvae that
were recovered with laser warming [5].

 

Recent successes have been reported in the cryopreservation of whole adult
tissue [6, 7], though I am not closely familiar with that work.

 

Much of the problem now is in scaling up methods, in agreeing on the best
practical applications such as enhancement of broodstock, and in finding the
skilled people and resources to cryopreserve a breadth of species and
allelic diversity that will be of greatest utility in the decades to come.
On a note of great personal interest, there is also the question of
diversity of larval size among species. Small larvae such as those of
Fungiidae are considerably easier to cryopreserve than those of (say)
Acroporidae - an ongoing effort! More to follow soon, no doubt.

 

Cheers,

 

Nikolas Zuchowicz

Doctoral candidate

Department of Mechanical Engineering, University of Minnesota - Twin Cities

 

[1] https://doi.org/10.3389/fmars.2022.960470

[2] https://doi.org/10.1073/pnas.2110559118

[3] https://doi.org/10.1038/s41598-018-34035-0

[4] https://doi.org/10.1002/advs.202303317

[5] https://doi.org/10.3389/fmars.2023.1172102

[6] https://doi.org/10.1101/2023.03.05.531199

[7] https://doi.org/10.1101/2023.03.16.533048