Uricolityc fungi symbionts of nopal cochineal Dactylopius spp. (Hemiptera: Dactylopiidae)

Interactions between fungi and plant feeding insects as ants, termites, bark beetles and some hemipterans have been widely studied. It is suggested, that this kind of association between fungi and insects is mutualistic, where fungi presumably supply enzymes, essential amino acids, vitamins and sterols. Fungi may help with nitrogen recycling from uric acid wastes in insects, while insects provide a habitat for fungi. Our interest is on cochineals of the genus Dactylopius (Costa), scale insects that spend their life cycle on Cactacea plants feeding on the sap. All insects of the genus Dactylopius produce a red dye called carminic acid which is used for production of cosmetics, drugs, food and textiles. To our knowledge nor yeasts neither molds associated with Dactylopiushave been reported. The aim of this work was to identify some fungi inside cochineals and analyze their role in uric acid recycling in the host.

We have cultivated and isolated 35 fungi from different species of Dactylopius. These fungi were identified by ITS gene sequences as: Cryptococcus satoi, C. diffluens, C. flavescens, Rodhodotorula mucilaginosa, R. glutinis, R. minuta, Trametes polizona, Phanerochaete sordida, Penicillium griseofulvum, Penicillium chrysogenum, Penicillium citrinum, Penicillium bevricompactum, Debaryomyces coudertii, Irpex hydnoides, Stereum sp. and Periconia sp. Only Crytococcus, Rhodotorula, Penicillium, Trametes, and Debaryomyces have been documented in association with insects. Basydiomicetes like Phanerochaete, Phlebiopsis and Irpexhave been reported from high lignin plants but there are no reports of these kind of fungi in insects.

We tested the ability of some isolates to use uric acid as only carbon and nitrogen sources in vitro. Cryptoccocus, Rhodotorula and Penicillium can grow using this molecule as only carbon and energy source. Furthermore, these fungi use uric acid as nitrogen source albeit growth is reduced in comparison to other nitrogen sources. Additionally we detected uric acid in guts of D. coccus, D. ceylonicus and D. opuntiae (3.466 ± 0.87; 4.719 ± 0.82 and 10.13 ± 2.5 µg gut^-1; respectively) and in the whole male body of D. coccus (4.493 ± 0.3879 µg insect^-1).  It is know that, in brown planthopper Nilaparvata lugens some yeast like symbionts recycle uric acid from host to essential amino acids. These data suggest that in Dactylopius their fungi symbionts use the uric acid from their guts, and maybe produce some metabolites beneficial to the insects.