Juvenile hormone effects on polymorphism in the pea aphid, A cyrthosiphon pisum

Abstract

When reared in short days (LD 12:12) at 15 °C, apterous Acyrthosiphon pisum gave birth to sexual females (oviparae) exclusively for the first eight days of larviposition. After this time they switched to the production of parthenogenetic females (viviparae). Topical application of juvenile hormones I, II and III to fourth instar or adult ovipara‐producers induced the precocious appearance of parthenogenetic females in the progeny sequence. Various forms intermediate between oviparae and viviparae were also produced and repetitive JH — I treatments resulted in a few alatiform progeny. However, many of the JH induced apterous, parthenogenetic females appeared to be normal viviparae and were capable of reproduction. Thus, prenatal treatment of oviparous embryos with JH diverts development towards the viviparous form. JH‐I treatment of long‐day reared A. pisum had no effect on the type of progeny produced. RÉSUMÉ Effets de l'hormone juvénile sur le polymorphisme d'Acyrthosiphon pisum Quand il est élevé sous jours courts (LN 12/12) à 15 °C, le type anglais vert d'Acyrthosiphon pisum ne donne naissance qu'à des femelles sexuées (ovipares) pendant la première partie de sa période de reproduction. Ensuite quelques types intermédiaires ovipares/vivipares peuvent apparaitre avant que les pucerons ne bifurquent spontanément vers la production de femelles parthénogénétiques (vivipares). L'application cutanée d'hormones juvéniles (JH I, II, et III) aux larves de quatrième stade ou à des adultes producteurs d'ovipares provoque l'apparition prématurée d'intermédiaires et de vivipares dans la descendance. Les différentes formes intermédiaires produites par des applications répétées de J. H. comprenaient des types ailés ou partiellement ailés. Cependant, les vivipares aptères induits par J.H. étaient morphologiquement normaux et beaucoup étaient capables de se reproduire. Des traitements semblables aux J.H. de vivipares élevées en jours longs (LN 16/8) n'ont pas eu d'effets sur le type de la descendance. On ne sait pas si l'action de JH exogène sur l'induction des vivipares est direct ou indirect. La reprogrammation des embryons, autrement destinés à se développer comme ovipares, est examinée en relation avec notre connaissance du contrôle endocrine du polymorphisme des pucerons.

Transcriptomic profiling of the reproductive mode switch in the pea aphid in response to natural autumnal photoperiod

“…More interestingly, several transcripts involved in Juvenile Hormone (JH) synthesis and signalling appeared to be down-regulated by the autumnal photoperiod, while they have not been detected in controlled conditions. It has been shown in earlier studies that JH was required for the switch of the reproductive mode (Corbitt and Hardie, 1985). These authors indeed ectopically applied kinoprene (a homologue of JH) on parthenogenetic individuals placed under short day conditions (also called sexuparae) that normally produce sexual individuals in their offspring.…”

Juvenile hormone titre and related gene expression during the change of reproductive modes in the pea aphid

“…As measurements were performed on whole body extracts, we did not track the hemolymphatic JHIII titer. In some aphid species, ectopic applications of JHs or JH analogues to aphids under short-day lengths induces the production of parthenogenetic females, instead of oviparous females (Hardie, 1981;Mittler et al, 1979;Corbitt & Hardie, 1985;Hardie & Lees, 1985a;Hardie & Lees, 1985b). In addition, topical application of Kinoprene, one of the JH analogs, prevented photoperiod-induced male production in the green peach aphid Myzus persicae (Mittler et al, 1979).…”

“…In addition, topical application of JH or juvenoids under short-days leads to the production of parthenogenetic females instead of sexual morphs in several aphid species (Lees, 1981;Mittler et al, 1976;Mittler et al, 1979;Corbitt & Hardie, 1985;Hardie & Lees, 1985a;Hardie & Lees, 1985b). Finally, treatment with the anti-JH agent precocene induces male production in the green peach aphid Myzus persicae (Hales & Mittler, 1983;Hales & Mittler, 1988).…”

“…aphids, on sexual-morph production (Corbitt & Hardie, 1985). One previous study used GC-MS to investigate the JHIII level difference between aphids reared under long-and short-day length in Megoura viciae .…”

Sex versus parthenogenesis: A transcriptomic approach of photoperiod response in the model aphid Acyrthosiphon pisum (Hemiptera: Aphididae)

“…Hereafter, involvement of endocrine glands like corpora allata and the juvenile hormone are usually invoked (Hales et al, 1997;Tagu et al, 2005). The capacity of juvenile hormone administered to aphids reared under short days to induce the development of their embryos (at least partially) as parthenogenetic females, instead of the expected fully sexual phenotypes (Hardie, 1981;Corbitt and Hardie, 1985), would support its participation in the process. Finally, the hormone melatonin has been shown to mimic the effect of short photoperiods to some extent by promoting the sexual response in Acyrthosiphon pisum (Gao and Hardie 1997).…”