FMRFamide-like material in the earwig, Euborellia annulipes, and its functional significance

The neurosecretory system of the earwig, Euborellia annulipes, contained material similar to that of FMRFamide, as shown by immunocytochemistry. Within the brain were two pairs of darkly staining perikarya in the medial protocerebrum, and up to four pairs of immunoreactive cells in the lateral protocerebrum. The corpora allata appeared immunoreactive in 10-day females, but not in 2-day-old adults. Additionally, immunoreactive material was detected in midgut endocrine cells of both 2- and 10-day-old females. FMRFamide at 1 to 100 nM did not inhibit juvenile hormone production by earwig corpora allata in vitro. This was true of glands of low activity from 2-day cat food-fed or starved virgin females, 10-day starved females, and those of relatively high activity from 10-day-old, cat food-fed females. In contrast, FMRFamide at 50 and 100 (but not at 1) nM stimulated gut motility in vitro in distended guts from 2-day fed females. Preparations from starved females and those from 10-day fed females (in which feeding behavior is on the decline) did not respond to exogenous FMRFamide with enhanced rates of contraction. Lastly, preparations from females starved for 7 days and subsequently fed for 3 days responded to 10 nM FMRFamide with increases in gut motility.