Rarely reported, widely distributed, and unexpectedly diverse: molecular characterization of mermithid nematodes (Nematoda: Mermithidae) infecting bumble bees (Hymenoptera: Apidae:Bombus) in the USA

Abstract

Mermithid nematodes (Nematoda: Mermithida: Mermithidae) parasitize a wide range of both terrestrial and aquatic invertebrate hosts, yet are recorded in bumble bees (Insecta: Hymenoptera: Apidae: Bombus) only six times historically. Little is known about the specific identity of these parasites. In a single-season nationwide survey of internal parasites of 3646 bumble bees, we encountered six additional instances of mermithid parasitism in four bumble bee species and genetically characterized them using two regions of 18S to identify the specific host-parasite relationships. Three samples from the northeastern USA are morphologically and genetically identified as Mermis nigrescens, whereas three specimens collected from a single agricultural locality in the southeast USA fell into a clade with currently undescribed species. Nucleotide sequences of the V2-V6 region of 18S from the southeastern specimens were 2.6-3.0% divergent from one another, and 2.2-4.0% dissimilar to the nearest matches to available data. The dearth of available data prohibits positive identification of this parasite and its affinity for specific bumble bee hosts. By doubling the records of mermithid parasitism of bumble bee hosts and providing genetic data, this work will inform future investigations of this rare phenomenon.

Report of a mermithid nematode infecting Amyna axis, Chrysodeixis spp. and Spodopteraspp.from India

“…obtained from lepidopteran insects in India grouped into "lineage 1" along with other unknown mermithids. However, use of additional mermithid 18S rDNA sequences (Bik et al, 2010;Villemant et al, 2015;Tripodi and Strange, 2018) resulted in generation of a new clade that we propose as "Lineage 3" in this study (Fig. 3).…”

Three Aedes species infested by mermithids in France

“…The paucity of available data prohibits positive identification of the parasites we processed as previously encountered in the mermithid parasitism of bees or black flies [19,21]. Considering the importance of these nematodes in the biocontrol of mosquitoes, our work will, however, provide some information for future investigations on mermithids.…”

Amphimermis enzonin. sp. (Nematoda: Mermithidae) parasitizing damselflies and dragonflies in Argentina

“…Photographs were taken with an Olympus DP-71 camera and a Leica DM 500 microscope; drawings were made using an Olympus CX-31 with drawing tube. For the examination of the hypodermal chords, a 0.3 to 0.5 cm portion of the midbody region of two specimens was removed and slide-mounted in a glycerin-lactic acid stain for observation at 10-100 x according to Tripodi and Strange (2018).…”