Shmuel Perl, Dani Elad, Michael Samish - Kimron Veterinary Institute, P.O.B. 12, Bet-Dagan, 50250 Israel

Metarhizium anisopliae chlamydospores were rarely described previously and the
conditions needed for their development were not identified. For the first time, the presence of M.
anisopliae chlamydospores in the tick eggs and the ambient conditions influencing its formation are
reported. The infection of tick eggs by M. anisopliae involves the common events such as adhesion,
conidia germination, penetration of the egg chorion and development of hyphae in the egg cytoplasm.
However, the final fungal developmental stage in egg differs according to the ambient conditions. At
high humidity (100%) and moderate temperature (25°C) the fungus emerges out of the dead eggs and
forms conidiophores with conidia. Stress conditions, in which the temperature was elevated to 30 °C or
the humidity was reduced to 55 – 75 %, induced the production of chlamydospores inside the eggs
without emergence of fungi on the eggs surfaces. When eggs with chlamydospores were transferred to
favorable conditions (25oC / 100 % RH), conidiogenesis was observed. Observations were done by
means of histology and TEM.