Positive Correlation of Body Length with Innate Immune Status and Resistance to <i>Aeromonas hydrophila</i> Infection In Rohu, <i>Labeo rohita</i>

Abstract

Full-sib families of rohu (Labeo rohita) of four year-classes viz., 2003 (906 numbers of fish), 2004 (1208 nos.), 2008 (2000 nos.) and 2009 (1355 nos.) were subjected to intraperitoneal Aeromonas hydrophila challenge. The fingerlings were tagged individually with passive integrated transponder (PIT) tag and total length was measured prior to challenge. The mortality was recorded on an hourly basis for up to 24 h and later over a period of 10 days post-challenge. Mean body length of survived and dead fish were significantly different (p<0.05) in the year-classes 2004, 2008 and 2009, whereas for 2003 there was no marked difference. Positive correlations of 0.004, 0.115 and 0.108 were found between length and survival for 2004, 2008 and 2009 year-classes, respectively. However, the length of 2003 year-class showed a negligible negative correlation (-0.065) with survival. The serum immune parameters viz., haemolysin titre, ceruloplasmin and myeloperoxidase activities analyzed from naïve individuals of each family showed positive correlations with body length of the same family (0.135, 0.290 and 0.109, respectively) in three year-classes i.e., 2003, 2004 and 2009. The positive correlation of length with survival and immune response indicated its possibility to be used as a co-trait for selection for improved resistance to A. hydrophila infection.