Postembryonic development of leucokinin-like immunoreactive neurons in the moth Spodoptera litura.

摘要

Antiserum to leucokinin I, a neuropeptide originally isolated from the cockroach Leucophaea maderae [Rhyparobia maderae], was used for immunocytochemical labelling of neurons in the brain and ventral ganglia of Spodoptera litura during postembryonicdevelopment. In the ventral ganglia, leucokinin-like immunoreactivity begins to occur in the abdominal ganglion A3 to A7 of the 1st-instar larva. One to two weakly labelled pairs of bilateral LK-LI cell bodies are located in the suboesophageal ganglionof 4th- to 6th-instar larvae and in the abdominal ganglia A1 to A7 of 2nd- to 6th-instar larvae. The abdominal ganglion A1 of 4th- to 6th-instar larvae and A8 of 6th-instar larva each contain one weakly labelled pair of median LK-LI cell bodies. Two strongly labelled pairs of bilateral LK-LI neurons are found in A3 to A7 of 3rd- to 6th-instar larvae. Abdominal ganglia A1 to A8 of the prepupa, pupa and adult contain one to three weakly labelled pairs of bilateral LK-LI cell bodies, whereas A2 to A7 in the same developmental stages have two strongly labelled pairs of bilateral LK-LI neurons. Two strongly labelled pairs of bilateral LK-LI neurons in each of the abdominal ganglia of the larva, prepupa, pupa and adult send axons to the neuropil, and then each axon bifurcates into two axonal branches. These axonal branches form two bundles. From each of the two pairs of neurons an axon exits through the posterior ventral nerve (N2) which runs to the transverse nerve of the next posterior segment. In larvalbrains, 2-16 pairs of bilateral LK-LI cell bodies can be found together with LK-LI processes in the central neuropil. The larval brains show great changes in the number of LK-LI neurons throughout postembryonic development. The number of LK-LI cell bodies are reduced in number from 6th instar larval brain. Therefore, prepupal, pupal and adult brains contain a smaller number of LK-LI cell bodies. Two pairs of LK-LI median neurosecretory cells located immediately beside the pars intercerebralis in larvalbrains increase to three pairs in the 7-day-old pupal brain. In the adult brain, however, LK-LI median neurosecretory cells decrease to one pair.