The fine structure of the light organ of the New Zealand glow-worm Arachnocampa luminosa (Diptera: Mycetophilidae).

Thc ruullen dlr t r l lips 01 !he Ma lp igh~rn lubuler 01 the glou-norm Aro~llnoco,rlpo Inrrri,ru\rr con5liluie the Ilghc organ. The \enIra1 and lateral rurlacer are co\ered hy a tracheal 'refleclor' and the nenour supply l o the light organ comer rrom the g'anglion in [he penul~imale segment. Ftne n e r w lerminalr. arons. and glial cellr can he seen i n close pro\imily lo $he haral rurlacc a( the cellr 01 the l i g h ~ o rgan The eptlhelial cells a1 Ihe light organ are large. the c)~loplrrm dense. homogeneous and acadophllic. The cymplarm gi\er a 5trong porll l\e reactwan l o r protein. The cy~oplarm cantillnr r high den,ily or lree rihoromer. pacther 01 dense ma~erial, smooth endcplrrnllc reliculum, glyco~en and scatrered m~crotubuler. Mktochondria are numerous: lhey arc large. randomly dtslrihuted and packed u i t h tine crirtse. There cellr lack the lealures characlerirlic o r Malp~ghian tubule epithelial cells: inlotding 01 the apncal and basal cell rurCacer is reduccd and the cyloplarm contains leu organelles Thcre cellr do no, contain recrelory or pho,ocyce granules and !he grainy cell m a ~ r i x is thought to be [he lucilerin ruhrlrale. O\ygen ir upp plied via Ihe tracheal layer luh lch may hare secondary reflectnng prapertlcsl and light production controlled hy neurorecretory encicalion eilher d~rer l ly \la s)nrp<ei. or hy hormones. There are no other reports o r Matpiphian tubules or lnrecls producing light and [he tine ruuclure 01 there cells IS dirlincl. Thus. the mol len dlsldl 1np5 01 the Malpighian tubules 01 the glou-norm undouhledly canrlitute 3 unique lum~nercent organ. Introduction Thcir taxonolny and belia\iour have been THE New Zealand glow-worm Arurbrocu~i~po Irtni;,rosa is the larva o f a midge-like insect of the Mycetophilidae or fungus fly family (Order: Diptera) and is well knoun from the early descriptions of its habirsand life history (Meyrick, 1886: Hudson, 1886. IRS7). Edwards (1924) described the spectacular display by the glow-worm population in the Waitomo Caves as 'the radiance of such a massed body o f glouj-worms as cannot be found anywhere else in the u,orld. u t~er l j incalculable as 10 numbers and merging their individual lights in a nirvana of pure sheen'. treated in more recent works (Richards. 1960; Harrison. 1966: Stringer, 1967). As a result a reasonably good account of the habits and behaviour of the glow-worm now exists. A number of b~ological studies o f ihis inscct have been reported (Edwards, 1914: Harvey. 1952; Norris, 1970) and accounts of the anatomy and histology o f the larva were presented by Gatenby (1959, 1960) and Ganguly 11960) respectively. Wheeler and Williams (1915) were the first to identify the terminal ends o f each of the four Malpigllian tubules as being the source of the characteristic lumtnescent glou,. They suerested that this In mel f was o f interest -De~ar lmen l ~ ~ Z o o l o ~ y . Uni\erslly 01Aucll;lnd. both morpho~og~ca~~y and physiologically. P r n a ~ e Bag, Auckland, Neu Zealand. Present address: Department olLoolagy. South There are rep0rrs of 'he h'alpighian Parks Road, University or OIroi d 0x1 3ps. tubules of insects other than A~~uclr~~ocanlpa England. Receired 20 March 1979. producing light. The histology and ultrastructure of the