Fungal fauna of Ixodes scapularis say and Rhipicephalus Sanguineus (Latreille) (Acari: Ixodida) with special reference to species-associated internal mycoflora

Abstract

Body contents of the black-legged tick, Ixodes scapularis, and brown dog (or kennel) tick, Rhipicephalus sanguineus, were screened by fungal culturing for more virulent strains to use in biological control and to investigate the propensity of ticks as endosymbiotic hosts. A low incidence of internal fungi was observed in both ticks, averaging < 20% recovery. Noteworthy in R. sanguineus was identification of Scopulariopsis carbonaria Morton and Smith (previously unknown within ticks) among the few internal isolates as well as the common internal associate S. brevicaulis (Sacc.) Bainier. Ixodes scapularis ticks were similarly devoid of fungi except for recovery of Metarhizium anisopliae (Metsch.) that is likely present as a parasite. Compositions of external mycoflora were alike (13 Deuteromycetes and three Zygomycetes) and reflect fungi prevalent in soil, leaf litter and organic debris. Despite this rich external mycoflora, internal fungi appear to be restricted to Scopulariopsis spp. and harboring this fungus is linked to the large wax glands (‘sagittiform sensilla’) that are characteristic of metastriate, but not prostriate (Ixodes), ticks. However, low levels of fungi within R. sanguineus indicate that the prevalence of tick-borne fungi is not as widespread as previously thought. The fact that not all classified entomopathogenic fungi recovered from tick surfaces were found inside the tick suggests that successful parasitism may be limited to a few select fungi (e.g., Metarhizium spp.) in nature, thus affecting potential biological control applications.

Key words:

• Acari
• Ixodidae
• ticks
• entomopathogenic fungi
• biological control
• Ixodes
• Rhipicephalus