Are little brown bats (Myotis lucifugus) impacted by dietary exposure to microcystin?✰
Devin N Jones1, Gregory L Boyer2, Julia S Lankton3
1Department of Biology, Grand Valley State University, 1 Campus Drive, Allendale, Michigan, 49401 USA; Department of Microbiology and Immunology, Montana State University, Bozeman, Montana, USA.
Abstract:
The cyanobacterium, Microcystis aeruginosa, can produce the hepatotoxin microcystin. When toxic M. aeruginosa overwinters in the sediments of lakes, it may be ingested by aquatic insects and bioaccumulate in nymphs of Hexagenia mayflies. When volant Hexagenia emerge from lakes to reproduce, they provide an abundant, albeit temporary, food source for many terrestrial organisms including bats. Little brown bats, Myotis lucifugus, feed opportunistically on aquatic insects including Hexagenia. To determine if microcystin moves from aquatic to terrestrial ecosystems via trophic transfer, we combined a dietary analysis with the quantification of microcystin in bat livers and feces. In June 2014, coincident with the local Hexagenia emergence, bat feces were collected from underneath a maternity roost near Little Traverse Lake (Leelanau County, Michigan, USA). Insects in the diet were identified via molecular analyses of fecal pellets from the roost and from individual bats. Livers and feces were collected from 19 female M. lucifugus, and the concentrations of microcystin in these liver tissues and feces were measured using an enzyme-linked immunosorbent assay (ELISA) and liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We show that the majority of the bats' diets consisted of aquatic insects and that microcystin was detected in high concentrations (up to 129.9 μg/kg dw) in the bat feces by ELISA. Histopathological examination of three bat livers with the highest concentrations of microcystin showed no evidence of phycotoxicosis, indicating that M. lucifugus may not be immediately affected by the ingestion of microcystin. Future work could examine whether bats suffer delayed physiological effects from ingestion of microcystin.
Insights
Microcystin, a toxin from cyanobacteria, transfers to terrestrial ecosystems through aquatic insects eaten by bats. High microcystin levels were found in bat feces, but immediate harm was not observed.
Area of Science:
- Ecotoxicology
- Environmental Science
- Wildlife Biology
Background:
- Cyanobacteria like Microcystis aeruginosa produce microcystins, a potent hepatotoxin.
- Toxic M. aeruginosa overwintering in lake sediments can be ingested by aquatic insects, such as Hexagenia mayflies.
- Emerging Hexagenia provide a food source for terrestrial animals, including bats (Myotis lucifugus).
Purpose of the Study:
- To investigate the trophic transfer of microcystin from aquatic to terrestrial ecosystems.
- To determine if microcystin bioaccumulates in bats that consume contaminated aquatic insects.
Main Methods:
- Dietary analysis of bat feces using molecular methods.
- Quantification of microcystin in bat livers and feces using ELISA and LC-MS/MS.
- Histopathological examination of bat livers.
Main Results:
- Bat diets predominantly consisted of aquatic insects during Hexagenia emergence.
- Microcystin was detected in high concentrations (up to 129.9 μg/kg dw) in bat feces.
- No immediate signs of phycotoxicosis were observed in bat livers, even at high microcystin concentrations.
Conclusions:
- Microcystin can be transferred from aquatic to terrestrial food webs via insectivorous bats.
- Little brown bats (Myotis lucifugus) accumulate microcystin from their diet.
- Further research is needed to assess potential delayed physiological effects of microcystin on bats.
