Abstract

Amyna axis (Lepidoptera: Erebidae), Chrysodeixis spp. (C. acuta and C. eriosoma) and Spodoptera spp. (S. exigua and S. litura) (Lepidoptera: Noctuidae) are important polyphagous insect-pests of leguminous crops. A mermithid (Nematoda: Mermithidae) nematode was found parasitizing the larval stages of these insects in the western Indian state of Rajasthan. Morphological and molecular analysis suggests that the nematode might be a species of the genus Hexamermis. The average length of post-parasitic nematode juveniles was 15 cm, and the average greatest body width was 1.5 mm. The vulva was median (V% = 48) without vulval flap. Approximately 100-125 μm long caudal appendages were present on tail. The cross-section revealed the presence of six hypodermal chords at the mid body region, and stichosome was present. The 18S rDNA sequence showed 99% similarity to mermithid nematode. A phylogenetic analysis of 18S rDNA sequences of mermithids resulted in identification of a new clade “Lineage 3” which included representatives of Mermis sp., Isomermis sp., Limnomermis sp., and Pheromermis sp. This is the first report of natural mermithid parasitism of A. axis and Chrysodeixis spp. along with its molecular characterization.

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