Exploring the hidden communities of helminth parasites in Arapaima gigas and Colossoma macropomum in Acre's aquaculture systems
In the heart of the Amazon, where waterways pulse like arteries through the world's largest rainforest, a silent drama unfolds in the region's growing aquaculture industry. Here in the state of Acre, southwestern Amazon, fish farmers face an invisible adversary: diverse communities of helminth parasites that thrive in the gills and tissues of their prized fish. These parasites represent an often-overlooked dimension of biodiversity, one that threatens both the economic viability of fish farming and the health of aquatic ecosystems.
Aquaculture has emerged as a crucial economic activity across the Amazon region, with native fish species standing as the most valuable in this industry.
Recent studies reveal that understanding parasite biodiversity is fundamental to developing sustainable aquaculture practices.
One of the world's largest freshwater fish, reaching lengths of 3 meters and weights of 200 kilograms. This air-breathing giant had nearly disappeared from many Amazonian markets due to overfishing until aquaculture emerged as an important conservation tool 6 .
| Parasite Species | Prevalence (%) | Mean Abundance | Mean Intensity | Total Number |
|---|---|---|---|---|
| Anacanthorus spathulatus | 50.0 | 17.1 | 34.1 | 2,082 |
| Notozothecium janauachensis | 44.3 | 8.6 | 19.4 | 1,046 |
| Mymarothecium boegeri | 20.5 | 3.9 | 18.9 | 474 |
| Linguadactyloides brinkmanni | 9.0 | 0.2 | 2.0 | 22 |
Source: 2
Studies have documented significant tissue damage including displacement of gill epithelium, focal hyperplasia of epithelial cells, lamellar fusion, congestion, and shortening of the secondary lamellae of gills 2 .
These physiological impacts translate directly to economic losses through reduced growth rates, lower feed conversion efficiency, and increased susceptibility to secondary infections.
| Location | Key Hematological Findings | Interpretation |
|---|---|---|
| Iranduba and Novo Airão | Variations in hematocrit, hemoglobin concentration, and erythrocytes | Signs of anemia and dehydration |
| Manacapuru | Elevated triglycerides and cholesterol | Unsuitable diet |
| Multiple farms | Similarities in leukogram and thrombogram | Significant intraspecific variation despite similar environments |
Source: 4
Variations in hematocrit and hemoglobin indicate blood disorders
Elevated triglycerides and cholesterol reveal dietary issues
Physiological assessments distinguish healthy from diseased conditions
| Research Tool | Function | Application Example |
|---|---|---|
| Stereomicroscope | Initial examination and detection of parasites | Scanning gill filaments and body surfaces for monogeneans 2 |
| 70% Ethanol | Fixation and preservation of parasite specimens | Preserving monogeneans for morphological study 2 |
| 4% Formalin | Alternative fixative for parasite preservation | Used when different morphological features need highlighting 2 |
| Gomori Trichrome Stain | Differentiating tissue structures in parasites | Enhancing visibility of internal structures for identification 2 |
| Canada Balsam | Permanent mounting medium for microscope slides | Creating durable specimens for reference collections 2 |
| Berlese or Hoyer Medium | Clearing agents for transparent specimens | Making internal structures of parasites visible under microscope 2 |
| α-MSH Hormone Solution | Experimental induction of stress response | Demonstrating hormonal control of skin coloration in stressed fish 1 |
| Deep Learning Algorithms | Automated analysis of fish coloration | Assessing stress levels through image analysis of skin darkness 1 |
"Understanding how genes are turned on and off opens the opportunity to develop gene-based vaccines to control these economically significant fish pathogens" 3 .
Stress tolerance in tambaqui is a "moderately to highly heritable trait" 1 , paving the way for selective breeding programs.
A recent study described five new species of Cosmetocleithrum parasites , highlighting how much remains unknown about these complex ecosystems.
The hidden world of helminth parasites in Amazonian fish reminds us that biodiversity exists at all scales—from the majestic pirarucu to the microscopic monogeneans that inhabit its gills. As aquaculture continues to grow in economic importance throughout the Amazon region, understanding these complex parasite-host relationships becomes increasingly vital.
The research emerging from Acre and other Amazonian states provides both warning and hope. It reveals the vulnerabilities of intensive fish farming while simultaneously pointing toward innovative solutions—from AI-based monitoring to selective breeding and potential vaccines. By respecting the complexity of Amazonian ecosystems and investing in scientific research, we can work toward aquaculture practices that support both human communities and the extraordinary biodiversity that makes the Amazon unique.