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



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The objective of this study was the establishment of organ and cell cultures from the red imported fire ant, Solenopsjs jnyjcta Buren. Such culture systems will be invaluable in the development of insect viruses as biological control agent for this pest. Ovarian sources were utilized for organ culture, whereas ovarian and embryonic sources were used for cell culture establishment. Organ cultures were established in TNM-FH media (pH 7.0, 517 mOsmols) on FalconPrimaria substrate and survived for 41 days as determined from contractility of ovarian tubules. Cell cultures from ovarian tissue were established in modified PTM-1 medium (pH 7.0, 525 mOsmols) on Primaria substrate. Two major cell types, one fibroblastoid and the other epitheloid, were observed; the latter manifesting cell division with an approximate mean generation time of 72 hours. These primary cell cultures survived in Yi1m for up to 16 days. Primary cultures from embryonic tissue were set-up in TNM-FH/Schneider's medium (pH 7.0, 375 mOsmols) on either Primaria or Lux substrate. Cells were viable, but no division was observed. Persistent contamination of embryonic cultures with a fungus led to a systematic study which suggested an intimate relationship between the fire ant egg and this agent. Whereas incubation of surfacesterilized embryos in culture medium resulted in no fungal contamination, mechanical disruption or enzymatic treatment (collagenase, 0.5 mg/ml) resulted in fungal growth, suggesting that the agent was present in deeper structures of the egg. This fungus was identified as Geotrichum spp., a member of the Deuteromycotina Division. This is the first report of the isolation of Geotrichum spp. from an insect. Because mycelia were not observed externally and no spores or fungal particles were detected in the haemolymph, a pathogenic role is not suggested. However, these facts together with the isolation of the fungus from ovarian tissue, suggest that an endosymbiotic role for this agent is still possible.



Solenopsis invicta -- Cytology, Solenopsis invicta -- Biological control