POSTEMBRYONIC DEVELOPMENT OF LEUCOKININ-LIKE IMMUNOREACTIVE NEURONS IN THE MOTH SPODOPTERA-LITURA

Antiserum to leucokinin I, a neuropeptide originally isolated from the cockroach Leucophaea maderae, was used For immunocytochemical labelin g of neurons in the brain and ventral ganglia of the moth Spodoptera l itura during postembryonic development. In the ventral ganglia, leucok inin-like immunoreactivity begins to occur in the abdominal ganglion A 3 to A7 of first instar larva. One to two weakly labeled pairs of bila teral LK-LI cell bodies are located in the subesophageal ganglion of f ourth to sixth instar larvae and in the abdominal ganglia A1 to A7 of second to sixth instar larvae, The abdominal ganglion Al of fourth to sixth instar larvae and A8 of sixth instar larva each contain one weak ly labeled pair of median LK-LI cell bodies, Two strongly labeled pair s of bilateral LK-LI neurons are found in A3 to A7 of third to sixth i nstar larvae, Abdominal ganglia Al to A8 of prepupa, pupa and adult co ntain one to three weakly labeled pairs of bilateral LK-LI cell bodies , whereas A2 to A7 in the same developmental stages have two strongly labeled pairs of bilateral LK-LI neurons. Two strongly labeled pairs o f bilateral LK-LI neurons in each of the abdominal ganglia of larva, p repupa, pupa and adult send axons to the neuropil, and then each axon bifurcates into two axonal branches. These axonal branches form two bu ndles. From each of the two pairs of neurons an axon exits through the posterior ventral nerve (N2) which runs to the transverse nerve of th e next posterior segment, in larval brains, 2-16 pairs of bilateral LK -LI cell bodies can be found together with LK-LI processes in the cent ral neuropil, The larval brains show large changes in the number of LK -LI neurons throughout postembryonic development, The number of LK-LI cell bodies are reduced in number from sixth instar larval brain, Ther efore, prepupal, pupal and adult brains contain a smaller number of: L K-LI cell bodies, Two pairs of LK-LI median neurosecretory cells locat ed immediately beside the pars intercerebralis in larval brains increa se to three pairs in the 7-day-old pupal brain. in the adult brain, ho wever, LK-LI median neurosecretory cells decrease to one pair.