Date: 6 April 1998
From: OCEANRICH@aol.com
To: AQUA-L@killick.ifmt.nf.ca
QUESTION:
There is much controversy surrounding probiotics in shrimp biology because they do not have an immune responsive system per se. How can you stimulate an immune response in a species as primitive as shrimp?
What do the experts say?
I say that you can improve water quality, you can improve nutrition and you can certainly improve management.
However, I am sceptical of "off the shelf" remedies either chemical or biological that will stop environmental stress and ultimately disease.
Ray DeWandel
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COMMENTS 1:
I guess it depends on how you define a probiotic: apart from the stimulation of possibly non-specific as well as specific defence mechanisms, is not this also taken to include the addition of competitive bacteria, which may occupy surfaces which could otherwise be colonised by pathogenic bacteria/create a normal flora etc?
Judith Handlinger
Judith Handlinger@dpif.tas.gov.au
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COMMENTS 2:
As an biotechnologist with interest in mixed microbial systems and aquaculture I see the term probiotic as general term for a substance that promotes the growth of microorganisms.
To my opinion many probiotic substances do not stimulate the immune system, but influence the mixed culture of microbes in the gut, promoting the growth of "beneficial" organisms. With the help ot the probiotic substance the "good" microbes can outgrow "bad" organisms, which produce byproducts being harmful to the host. This may be true for example for shrimp feeding on glucan enriched diets.
Although my opinion somehow denies the immune system stimulation, I still believe in a positive effect of these feed additives.
Dr. Peter Goetz
goet1534@mailszrz.zrz.tu-berlin.de
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COMMENTS 3:
Here are some of the differences between immune systems of vertebrates and crustaceans:
Crustaceans lack 1) adaptive resistance improved by repeated exposure; 2) antibody; 3) T and B cells.
As do vertebrates, crustaceans have lysins, opsonins, lectins, phagocytic capability and killer cells. Interferon is unknown. They have a PPO system (short for propolyphenyloxidae) which is hemocyte based, responds readily to tissue trauma and foreign agents and produces clotting, activates phagocytosis, causes nodule formation and encapsulation, and causes healing in the form of quinones & melanin (like scabs in humans). In short, crustaceans have an immune system.
Re vaccination: crustaceans do lack adaptive resistance improved by repeated exposure to a foreign agent. Therefore, vaccination has limited application. Some protection is provided by vaccination; however, it is of short duration. Lobsters vaccinated against Gaffkemia developed some protection, and phagocytosis was enhanced in vaccinates. Vaccination tests of shrimp often show protection; however, the cost is generally couterproductive because vaccination must be done every few weeks.
Re probiotics: Some growers have introduced non-pathogenic vibrios, which, I understand, effectively compete with pathogenic ones and avert disease.
For more information, you might contact:
Dr. Don Lightner
aquapath@ccit.arizona.edu
Kent Hauck, Fish Pathologist
agmain.khauck@state.ut.us