APHID FEEDING, AS INFLUENCED BY DISRUPTION OF THE SYMBIOTIC BACTERIA - AN ANALYSIS OF THE PEA APHID (ACYRTHOSIPHON-PISUM)

Pea aphids (Acyrthosiphon pisum) whose symbiotic bacteria were disrupt ed with the antibiotic chlortetracycline over the first 5 days after b irth (i.e, aposymbiotic aphids), were able to feed from the host plant Vicia faba, as indicated by the regular production of honeydew drople ts and by electrical penetration graph (EPG) recordings of stylet pene tration through the plant tissues to the sieve elements, No difference was identified in the time taken by adult symbiotic and aposymbiotic aphids [24 +/- 2.4 and 24 +/- 3.0 min (mean +/- SE), respectively] to penetrate the plant tissues and puncture the sieve elements during the probes which resulted in sustained phloem feeding, 7/8-day-old aposym biotic larvae produced less honeydew (0.43 +/- 0.038 mg/aphid) over 24 h than symbiotic aphids (0.79) +/- 0.079 mg/aphid), but this differen ce was attributed primarily to the greater body size of the symbiotic aphids, suggesting that feeding by these larval aphids was not substan tially impaired, The aposymbiotic larvae produced smaller honeydew dro plets more frequently than symbiotic larvae, and no difference between the number of droplets produced in the first and second 12 h in the 2 4 h recording period was found, Aposymbiotic adults, in contrast, fed relatively poorly, Both EPG and honeydew production studies indicated that all symbiotic adults, but only 60-66% of aposymbiotic adults, had initiated phloem ingestion within a 10 h test period, It is proposed that the deleterious effects of bacterial disruption may be cumulative , and become increasingly severe and nonspecific with time since antib iotic treatment, It is recommended that studies on the nutritional phy siology of aposymbiotic aphids are conducted with recently-generated a posymbionts, whose feeding responses are not impaired.