Fish Gut Endophyte: A Source of Organic Insecticide

Abstract

Mosquito-borne diseases such as dengue, Zika, and chikungunya constitute a significant global public health concern, particularly in tropical and subtropical regions. Conventional vector control methods that rely heavily on chemical insecticides have resulted in environmental degradation and have facilitated the emergence of insecticide-resistant mosquito populations, thereby diminishing the efficacy of these interventions. The investigation suggests that the intestinal bacteria of guppy fish (Poecilia reticulata) have the larvicidal potential to control Aedes aegypti. The mosquito larvae suffered fatal damage when exposed to the extract isolated bacteria Lysinibacillus pakistanensis J20M5LARS by high mortality rate. The research demonstrates an environmentally responsible biological mosquito control system which operates as an organic replacement for chemical insecticides in pest management.

Introduction

Stagnant water bodies are major breeding sites for mosquitoes responsible for diseases such as malaria, dengue, Zika, and chikungunya. Conventional chemical insecticides, while commonly used, create environmental pollution and lead to mosquito resistance, highlighting the need for eco-friendly alternatives.

This study explores biological mosquito control using guppy fish (Poecilia reticulata). Guppies are small, hardy freshwater fish known for their ability to survive in varied conditions and reproduce rapidly. They naturally feed on mosquito larvae, making them a promising sustainable vector control agent.

In addition to direct larval predation by guppies, the research also investigates intestinal bacteria isolated from guppy fish. These bacteria were cultured, identified through biochemical tests and 16S rRNA sequencing, and tested for larvicidal activity. Results showed strong mosquito-killing potential, with bacterial supernatants causing rapid larval death and significant mortality observed under dilution-based assays.

The methodology involved:

• Collecting guppies and isolating gut bacteria
• Culturing and characterizing bacterial strains
• Extracting secondary metabolites from bacteria
• Testing larvicidal effects on mosquito larvae in controlled conditions

Key findings include successful isolation of motile Gram-positive bacteria with biochemical activity consistent with larvicidal properties. The bacterial extracts demonstrated strong effectiveness, with mosquito larvae dying within hours in certain conditions.

Overall, the study concludes that guppies provide a dual mosquito control mechanism:

1. Direct feeding on mosquito larvae
2. Indirect control through larvicidal gut bacteria (e.g., Lysinibacillus pakistanensis)

Conclusion

This research investigated the potential of guppy fish (Poecilia reticulata) in controlling the mosquito larvae especially Aedes aegypti and as an effective biological control agent. The research proved that guppies feed on mosquito larvae actively and bring down their population in an efficient manner without the use of chemical insecticides. Moreover, there is successful isolation of bacterial strains with the property of larvicidality from the guppy’s intestine. Biochemical and morphological characterization of these bacteria discovered them as natural mosquito control agents, a further justification of the role of guppies in curbing the transfer of vector borne diseases.

References

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Copyright

Copyright © 2026 Darsha S, Seethal K. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.