Mermithid nematode (Nematoda: Mermithidae) parasites of a fossil black fly (Diptera: Simuliidae) in Baltic amber

Abstract

Summary A new species of fossil mermithid, Heydenius simulphilus sp. n. (Nematoda: Mermithidae), is described from two parasitic juvenile specimens adjacent to a male black fly (Diptera: Simuliidae) in Baltic amber. It is proposed that the nematodes emerged from their developmental sites in the haemocoel of the black fly host through a wound in the abdomen of the latter, as indicated by the release of a droplet of haemolymph and damaged cuticle. Various internal structures of the nematodes are identified and related to those found on extant developing mermithids. This is the first fossil record of mermithid parasitism of a black fly.