New insights into the amphibious life of Biomphalaria glabrata and susceptibility of its egg masses to fungal infection

• Aquatic B. glabrata egg masses mature, and juveniles eclose in stable water films.
• New test devices offer test conditions in simulated transitory habitat.
• Entomopathogenic fungi, B. bassiana and M. anisopliae, can attack B. glabrata eggs.
• Hyphal bodies of these fungi are more virulent against snail eggs than their conidia.
• Host range of these entomopathogens is not restricted to arthropodous invertebrates.

The air-breathing snail Biomphalaria glabrata proliferates in stagnant freshwater, and nothing is known about the survival of eggs in intermittently (rather than perpetually) wet habitats. In the present study their egg masses matured, and juveniles subsequently eclosed and were mobile in a stable water film of transitory habitats simulated by two different simple test devices described here. The viability of eggs maintained in an unstable film however, was diminished. The maturation of egg masses in a water film or in water was significantly prevented by the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae. The efficiency depended on the fungal propagule and test environment. Hyphal bodies were more effective against egg masses than conidia. This appears to be a first report of activity of either entomopathogen against a mollusc. Both devices offer accurate and reproducible conditions to test both biological questions and the effects of substances or pathogens against B. glabrata egg masses in water films.

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