Production of the Sesquiterpenoid, Juvenile Hormone-1 (JH-I), and of Vitamin E in the Accessory Sexual (colleterial) Glands of Adult Male Moths, <i>Hyalophora cecropia</i> (Linnaeus, 1758), (Lepidoptera: Saturniidae)

Abstract

The content of the sesquiterpenoids, juvenile hormones (JH), JH-I, JH-II, JH-III and Vitamin E (α-, β-, γ- and δ-Tocopherols) was investigated in mated and unmated adult Cecropia silkworms, Hyalophora cecropia (Linnaeus, 1758), using combined chromatography/mass spectrometry methods. The relatively most abundant derivative of Vitamin E was α-tocopherol, the highest concentrations of which were found in the fat body of unmated males (30 ng/organ), and which was substantially decreased after mating. Conversely, the content of α-tocopherol increased more than twice in female abdomens after mating. This suggests that Vitamin E was transferred from the male to the female reproductive systems during courtship. Chromatographic analysis of extracts prepared from female abdomens, male fat bodies, and male reproductive organs revealed that separate fractions of Vitamin E (α-tocopherol, β- + γ-tocopherols and δ-tocopherol) were evenly distributed in quantitative proportions of 18400 : 550 : 100, respectively. These results suggest that sesquiterpenoid derivatives of Vitamin E play important functions in insect reproduction, in analogy with similar functions of Vitamin E during reproduction of vertebrate animals. The sesquiterpenoid 10,11-epoxy-homofarnesoate ester known as JH-I, which is thought to be the true hormone of insect corpus allatum, was virtually absent or undetectable in abdomens of virgin females of Cecropia moths. In contrast to Vitamin E, JH-I was also absent or occurred below the detectable limits in fat body/haemolymph fractions of adult males. Actually, the sesquiterpenoid JH-I was found exclusively in the lumen of the exocrine, accessory sexual (colleterial) glands of unmated males (50 ng/organ). Smaller amounts of this JH-I excretory product occurred also in the associated parts of the male reproductive system (testes, vas deferens and ejaculatory ducts), which are directly connected with the colleterial gland by the connecting ducts. The content of JH-I in the colleterial glands and ejaculatory ducts decreased to 9 ng/organ after courtship, when JH-I conversely appeared in the female abdomens (20 ng/abdomen). We conclude, therefore, that both these sesquiterpenoid compounds, JH-I and Vitamin E, become translocated from males into the female reproductive system by ejaculate during the courtship. A possibility that both Vitamin E and JH-I serve important physiological functions (antioxidant, sperm survival, fertilisation, stabilisation of egg chorion) has been suggested. The relative contents of JH-I to JH-II to JH-III in the colleterial glands revealed proportions of 64000 to 100 to 20, respectively. According to these data, the most abundant and widespread JH analogue of other insect species, methyl epoxyfarnesoate, commonly known as JH-III, was present only in traces. The real physiological status of JH-I in adult Cecropia has been defined as the excretory product of the exocrine colleterial gland. The presence of JH-I only in the exocrine colleterial glands of males and not in the females, combined with the secretory inactivity of the corpora allata, led us to formulate several physiological reasons why JH-I, as an excretory product of exocrine glands cannot be considered an insect hormone. A possibility that the true hormone of insect corpus allatum is still unknown has been emphasized.