Cell and tissue culture of the red imported fire ant, solenopsis invicta buren

The objective of this study was the establishment of organ and cell cultures \nfrom the red imported fire ant, Solenopsjs jnyjcta Buren. Such culture systems \nwill be invaluable in the development of insect viruses as biological control \nagent for this pest. Ovarian sources were utilized for organ culture, whereas \novarian and embryonic sources were used for cell culture establishment. Organ \ncultures were established in TNM-FH media (pH 7.0, 517 mOsmols) on FalconPrimaria \nsubstrate and survived for 41 days as determined from contractility of \novarian tubules. Cell cultures from ovarian tissue were established in modified \nPTM-1 medium (pH 7.0, 525 mOsmols) on Primaria substrate. Two major cell \ntypes, one fibroblastoid and the other epitheloid, were observed; the latter \nmanifesting cell division with an approximate mean generation time of 72 hours. \nThese primary cell cultures survived in Yi1m for up to 16 days. Primary cultures \nfrom embryonic tissue were set-up in TNM-FH/Schneider's medium (pH 7.0, \n375 mOsmols) on either Primaria or Lux substrate. Cells were viable, but no \ndivision was observed. Persistent contamination of embryonic cultures with a \nfungus led to a systematic study which suggested an intimate relationship \nbetween the fire ant egg and this agent. Whereas incubation of surfacesterilized \nembryos in culture medium resulted in no fungal contamination, \nmechanical disruption or enzymatic treatment (collagenase, 0.5 mg/ml) resulted \nin fungal growth, suggesting that the agent was present in deeper structures of \nthe egg. This fungus was identified as Geotrichum spp., a member of the \nDeuteromycotina Division. This is the first report of the isolation of Geotrichum \nspp. from an insect. Because mycelia were not observed externally and no spores or fungal particles were detected in the haemolymph, a pathogenic role \nis not suggested. However, these facts together with the isolation of the fungus \nfrom ovarian tissue, suggest that an endosymbiotic role for this agent is still \npossible.