Phenol red method for measuring the pH of the gut contents in Lutzomyia longipalpis (Psychodidae:Diptera).

  • 1 January 1998
    • journal article
    • Vol. 16  (1) , 62-5
Abstract
To develop a method to estimate the pH of the gut contents of female sandflies using a microcapillary feeding technique. Female Lutzomyia longipalpis were fed with a small quantity of phenol red solution (indicator range pH 6.8-8.4) before and after a bloodmeal. The colour patterns of the gut contents were recorded by video microscopy immediately after the alimentary canal was dissected out of the sandfly body, and used to determine the pH level. In unfed flies the thoracic mid-gut (TMG) is normally neutral, with the pH ranging between 7.0 to 7.3; and the abdominal mid-gut(AMG) is mildly alkaline from pH 7.1 to 8.4 with the maximum pH observed at the junction with the hind-gut. The presence of sugar in the crop reduced the pH of the TMG to 6.8, and the presence of a recently ingested bloodmeal raised the pH of the TMG to 7.4. However, as bloodmeal digestion proceeded the pH of the TMG was reduced to acidic levels, pH 6.8 or below. The new method could be integrated with the investigation of metacyclogenesis of Leishmania parasites in vivo.

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