RESUMO
The developmental stages of nematode generally comprise an egg, four larval stages, an adult and four moults. The moulting sometime occur within the eggshell. In Gnathostoma spinigerum, the newly hatched free living larvae were called “the first stage larvae” by many authors. However, the mewly hatched free living larvae of Gnathostoma procyonis was found to be the second stage larvae. This finding raised a guestion about the actual stage of the free living larvae of Gn. Spinigerum. Therefore, the present experiments were made. It was found that eggs of Gn. spinigerum developed into the first stage larvae between 4 and 5 days in freshwater. The first stage larva was delicated and cylindrical shape with rounded anterior end and pointed tail. The whole body was filled with coarse refractile granules. The first mouth occurred within the eggshell between one and two days after becoming the first stage and still retained water where they move actively. In the Cyclops intermediate host, after being swallowed, the second stage larvae shed off their sheaths in the intestinal lumen and penetrated into the haemal cavity where the second moult took place. The larvae then became the third stage larvae. The present studies revealed that the first stage larva, the second stage larva and the first moult of Gn. spinigerum occurred within the eggshell. Therefore, the previously called “free living first stage larvae” were in fact the second stage larvae within the sheath of first stage.