Lactobacillus rhamnosus will make Nemo stronger!

A Review of : Matteo A Avella, Ike Olivotto, Stefania Silvi, Allen R. Place, and Oliana Carnevali

Effect of dietary probiotics on clownfish: a molecular approach to define how lactic acid bacteria modulate development in a marine fish

Am J Physiol Regul Integr Comp Physiol February 2010 298:(2) R359-R371; doi:10.1152/ajpregu.00300.2009

Probiotics are well known to have a positive effect on fish welfare by reducing general stress response and promoting growth.

This research team focused on the potential use of the lactic acid bacterium Lactobacillus rhamnosus as a probiotic for the clownfish Amphirion ocellaris development and growth.

To this purpose they supplied the L. rhamnosus to clownfish larvae and evaluated the response to probiotic treament through:

• morphometric measurements such as total length and body weight

• molecular measurements of gene expression (real-time PCR) of the biomarkers for:

GR (glucocorticoid receptor strongly correlated with cortisol, the most important index of primary stress response);

IGFs (insuline-like growth factors);

MSTN (myostatin);

HSP70 (heat shock protein as index of stress);

some nuclear receptors such as PPARs (peroxisome proliferator-activated receptors), VDRs (vitamin D receptors)and RARs (retinoid acid receptors) which are known to be important modulators for achieving optimal growth,correct development and proper pigmentation in marine fish.

Briefly, larvae were divided into three experimental groups and fed as follow:

1. in the control group probiotics were not supplied to larvae
2. in the group 2 probiotics were supplied from day 1 post-hatching twice a day via live prey (incubating rotifers and Artemia nauplii in probiotic water) and added to the rearing water
3. in group 3 probiotics were supplied from day 1 post-hatching twice a day via live prey only

Results obtained were great!

Probiotic treatment was able to accelerate development since both in group 2 and 3 metamorphosis occured 3 days earlier than in the control group. Further, body weight of larvae and juveniles was significantly higher in animals supplied with probiotics, while the standard length increased only in juveniles.

The morphometric measurement were supported by changes in transcript abundance for the various biomarkers. A significant reduction was observed in the stress biomarker GR in both groups treated with L. rahmnosus and HSP70 transcripts levels showed a similar response. A significant increase was observed in IGFs, PPARs, VDRs and RARs , whereas MSTN levels decreased, supporting the extreme positive effects of probiotic to development and growth processes.

Clownfish treated with probiotic showed a significantly lower level in skeletal abnormalities compared to the control group, although the hystological section showed deformation of the skull (but not along vertebral column, as usually occurs).

Concluding, L. rahmnosus can significantly improve the clownfish welfare in terms of survivorship, growth and development, especially when the probiotic is supplied via live prey and added to the rearing water.

I think this study is very useful because of the implications in marine aquaculture. Using probiotic can prevent diseases usually affecting fishes in farming, especially in extremely livestock, where the high density of animals per tank has tremendous results on the whole reproduction process and on the organoleptic and nutritional properties of animals sold.

I am really impressed by the findings of this investigation, even because of 2 figures provided in the paper showing the great effectiveness of using probiotics in enhancement fish welfare.