Endocrine control of lone star tick, Amblyomma americanum (L.), salivary gland differentiation

Abstract

Salivary glands of female Amblyomma americanum (L.) are stimulated to differentiate by attachment to a host, subsequent feeding and mating. Incorporation of [3H]uridine into ribosomal and transfer RNAs as well as the synthesis of poly(A+)mRNA and protein parallel the pattern of increasing enzymatic activity and secretory ability of the glands. Unfed ticks contained 3.5+0.47 ng poly(A+)mRNA/gland pr. By the second day of feeding this had increased more than 5-fold. The greatest amount of poly(A+)mRNA found in rapid-feeding phase females (body wt)100 mg) was 370+80 ng/gland pr. Poly(A+)mRNA mass doubles on the final day of feeding, just as the ticks exceeded 100 mg in wt. Ticks attached 1 to 10 days had increasingly greater amounts of salivary monosomes, 60 and 40S ribosomal subunits and polysomes. Polysomal mass/gland pr also attained its maximum above 100 mg tick wt at the slow/rapid-feeding phase boundary; exceeding by 20 times that of unfed ticks. Degenerating glands from replete ticks continued to synthesize protein. In vitro incorporation of [3H]leucine was greatest within 24 hr of attachment. Fluorographs of [3H]leucine labeled protein showed that mating caused a drop in incorporation after the 4th day of feeding. Glands from unmated females attached the same number of days continued to incorporate [3H]leucine at higher levels than those from mated females.