Mealworm gregarines: shape, stage and identity

This proposed pilot would examine naturally occurring gregarines in commercially reared mealworms. It would ask how parasite shape and developmental stage relate to molecular identity. Photographs and measurements would be linked to selected DNA sequences where feasible. The intended outcome is a reference atlas that documents variation and supports careful identification of these overlooked invertebrate parasites.

SEPS research concept · 23 October 2026

Research question

When gregarines look different under the microscope, how much of that variation reflects developmental stage, and how much may warrant closer taxonomic study?

Scientific basis

Research on mealworm gregarines has evaluated ribosomal markers for identification and documented substantial variation in reproductive forms. These findings motivate a pilot that records stage and specimen identity alongside shape, rather than treating every size difference as a species difference (Nocciolini et al., 2018; Correa-Espinosa & Pérez-Cordón, 2026).

Starting material and scope

Commercially reared mealworms, Tenebrio molitor, would be acquired and screened before the project proceeds. The initial work would focus on naturally occurring intestinal gregarines. Parasite presence and diversity would remain open questions until specimens are examined.

Proposed laboratory approach

Brightfield microscopy would record individual parasites, including feeding stages and paired reproductive stages when encountered. Measurements would capture body proportions and diagnostically useful features. Host stage, source lot and preparation would be recorded alongside parasite stage and each image.

Selected photographed individuals would be reserved for targeted PCR and external Sanger sequencing of an 18S ribosomal marker. Additional markers would be considered only when they address a specific identification question. Handling and recordkeeping would preserve the link between each image and its molecular sample.

Intended outputs

The intended outputs are an atlas of photographic vouchers, a measurement table with documented methods, and linked sequence records where obtainable. The pilot would establish workable laboratory methods and determine whether the observed variation justifies a larger comparative study.

Interpretation

Mixed or ambiguous sequences would remain unresolved. A single marker would provide supporting evidence rather than a complete test of species boundaries. A small supplier-based sample would not establish the wider distribution of gregarine diversity.

Literature cited

Nocciolini, C., Cucini, C., Leo, C., Francardi, V., Dreassi, E., & Carapelli, A. (2018). Assessing the efficiency of molecular markers for the species identification of gregarines isolated from the mealworm and super worm midgut. Microorganisms, 6(4), 119. https://doi.org/10.3390/microorganisms6040119

Correa-Espinosa, A. J., & Pérez-Cordón, G. (2026). Reproductive morphometric plasticity in Gregarina polymorpha infecting Tenebrio molitor larvae. Journal of Eukaryotic Microbiology, 73(5), e70110. https://doi.org/10.1111/jeu.70110