Cytogenetic Analysis in Trigona spinipes Fabricius (Hymenoptera, Meliponina) Reveals Intraspecific Variation

The stingless bee Trigona spinipes (Hymenoptera: Apidae) is at risk from a range of insecticides via direct ingestion and trophallactic exchanges

BACKGROUND

The stingless bee, Trigona spinipes, is an important pollinator of numerous native and cultivated plants. Trigona spinipes populations can be negatively impacted by insecticides commonly used for pest control in crops. However, this species has been neglected in toxicological studies. Here we observed the effects of seven insecticides on the survival of bees that had fed directly on insecticide-contaminated food sources or received insecticides via trophallactic exchanges between nestmates. The effects of insecticides on flight behavior were also determined for the compounds considered to be of low toxicity.

RESULTS

Imidacloprid, spinosad and malathion were categorized as highly toxic to T. spinipes, whereas lambda-cyhalothrin, methomyl and chlorfenapyr were of medium to low toxicity and interfered with two aspects of flight behavior evaluated here. Chlorantraniliprole was the only insecticide tested here that had no significant effect on T. spinipes survival, although it did interfere with one aspect of flight capacity. A single bee that had ingested malathion, spinosad or imidacloprid, could contaminate three, four and nineteen other bees, respectively via trophallaxis, resulting in the death of the recipients.

CONCLUSION

This is the first study to evaluate the ecotoxicology of a range of insecticides that not only negatively affected T. spinipes survival, but also interfered with flight capacity, a very important aspect of pollination behavior. The toxicity of the insecticides was observed following direct ingestion and also via trophallactic exchanges between nestmates, highlighting the possibility of lethal effects of these insecticides spreading throughout the colony, reducing the survival of non-foraging individuals. © 2023 Society of Chemical Industry.

The Satellite DNAs Populating the Genome of Trigona hyalinata and the Sharing of a Highly Abundant satDNA in Trigona Genus

Among Meliponini species, c-heterochromatin can occupy large portions of chromosomes. This characteristic could be useful for understanding evolutionary patterns of satellite DNAs (satDNAs), although few sequences have been characterized in these bees. In Trigona, phylogenetically represented by clades A and B, the c-heterochromatin is mostly located in one chromosome arm. Here we used different techniques, including restriction endonucleases and genome sequencing followed by chromosomal analysis, to identify satDNAs that may be contributing to the evolution of c-heterochromatin in Trigona. Our results revealed a highly abundant ThyaSat01-301 satDNA, corresponding to about 13.77% of the Trigona hyalinata genome. Another seven satDNAs were identified, one corresponding to 2.24%, and the other six corresponding to 0.545% of the genome. The satDNA ThyaSat01-301 was shown to be one of the main constituents of the c-heterochromatin of this species, as well as of other species belonging to clade B of Trigona. However, this satDNA was not observed on the chromosomes of species from clade A, demonstrating that the c-heterochromatin is evolving divergently between species of clade A and B, as a consequence of the evolution of repetitive DNA sequences. Finally, our data suggest the molecular diversification of the karyotypes, despite a conservated macrochromosomal structure on the genus.