The present study was conducted to evaluate the effects of two commercial yeast products (Y1 and Y2) that were
administered via Artemia sp. enrichment on the survival, growth, histomorphometry, immunohistochemical and
stress tolerance of pejerrey larvae. The larvae received enriched Artemia for 20 days. After 20 days post-hatch
(dph), a saline stress test was conducted with 10 larvae tank−1. The remaining larvae were kept for ten days
(until 30 dph) being fed with dry feed without yeast supplementation. The samples were taken at 0, 10, 20
and 30 dph for weight, length, histological and immunohistochemical analysis. The results showed that the larvae
fed with hydrolyzed yeast presented a higher weight and specific growth rate than did those fed Artemia without
yeast. However, there was no effect on survival or condition factor. Regarding the histological analyses, no difference
was observed on intestinal morphology. Hydrolyzed yeast appears to have a positive influence on the area
and diameter of the kidney and thymus. The specific label of CD3 for kidney, spleen and thymus revealed that Y1
and Y2 have a significantly higher percentage of labeled cells. The kidney and thymus of larvae that received yeast
displayed significantlymore CD4-labeled cells. The control and Y2 groups were significantly more sensitive when
subjected to salinity of 60‰. Our findings indicate that Artemia enriched with yeast may promote growth and
immunity and the persistence of these parameters for ten days after the last hydrolyzed yeast supplementation.
Furthermore, enhanced stress tolerance of pejerrey larvae was observed.
Statement of relevance: The larviculture is a very sensitive moment, since the immune system is not fully developed,
resulting in a greater vulnerability to diseases. In this study we found that, besides presenting performance
improvement, hydrolyzed yeast supplementation also improves the marine pejerrey larvae immune response
and resistance to salinity stress