Td. Jarvis et al., ECDYSTEROID BIOSYNTHESIS IN LARVAL TESTES OF SPODOPTERA-LITTORALIS, Insect biochemistry and molecular biology, 24(5), 1994, pp. 531-537
The ability of testes of the last larval instar of the cotton leafworm
, Spodoptera littoralis to synthesise ecdysteroids was investigated. T
he endogenous ecdysteroid titres of both the testes and the haemolymph
differed in their composition and times of peak concentration during
this instar. At two developmental stages, one at the start of the risi
ng titre concentration and one in the middle of the rising concentrati
on (65 and 89h into the instar, respectively; the final instar lasts 5
days under our conditions), the ratios of 20-hydroxyecdysone to ecdys
one were similar (1.8.1) in the testes. However, at the same stages, t
he ratios in the haemolymph were 5:1 (65h) and 11:1 (89h). Incubation
in vitro of [H-3]2-deoxyecdysone or [H-3]2,22,25-trideoxyecdysone with
various larval tissues (prothoracic glands, testes, gut, carcass, fat
body, Malpighian tubules) from last instar larvae (65 and 89h into th
e instar for [H-3]2-deoxyecdysone, 57h for [H-3]2,22,25-trideoxyecdyso
ne) showed that the testes were capable of the greatest rates of conve
rsion of the precursors into ecdysone and 20-hydroxyecdysone. Further
investigation of the conversion of [H-3]2,22,25-trideoxyecdysone in te
stes throughout the final instar showed that the production of ecdyste
roids varied with time. The significance of these results is discussed
in relation to the likelihood of testicular ecdysteroid synthesis.