Effect of salinity on hatching, survival and infectivity of Anguillicola crassus (Nematoda : Dracunculoidea) larvae

The effect of salinity on hatching, larval survival and infectivity of Angu illicola crassus was studied under experimental conditions using eggs obtai ned from naturally infected eels. Egg hatching rate. second-stage larval su rvival and larval infectivity were maximal in fresh water and declined with increase in salinity. Larvae survived up to 100 d in fresh water, 70 d in 50% sea water and 40 d in 100% sea water. Infectivity experiments demonstra ted that salinity influenced transmission success throughout the Life cycle by decreasing total infectivity of the larval population in utero within f emale A. crassus and when larvae were free-living in the aquatic environmen t. Infectivity was age-dependent in relation to salinity. Larvae were infec tive to intermediate and paratenic hosts for up to 80 d in fresh water, 21 d in 50% sea water and up to 8 d in 100% sea water. The data confirm field observations that infection levels decrease with an increase in salinity. T he study contributes to experimental verification of the colonization abili ties of A. crassus and supports the hypothesis that A. crassus can be disse minated and transmitted in brackish water. The importance of regular monito ring and stringent hygiene practices in the transportation of eels is empha sised.