Double abdomen induction by UV in Bradysia tritici (syn. Sciara ocellaris, Sciaridae): sensitive stages and conditions for photoreversal

Abstract

The pattern anomaly double abdomen was induced in embryos of Bradysia tritici (syn. Sciara ocellaris) by irradiation of the anterior egg pole with far UV (254 or 285 nm) using low UV fluences. The maximum yield of 18% of double abdomens was obtained when 2.5 h embryos were irradiated (late intravitelline cleavage stage); earlier irradiation failed to yield double abdomens, as did irradiations after the early syncytial blastoderm stage. Exposing irradiated embryos to photoreverting light (366 nm) reduced the yield of malformations. Most double abdomens were symmetrical and the number of segments ranged from 3 to 8 in each set, with the mean value at 6.4 segments.

Sex-determining mechanisms in insects

“…Errors in X-chromosome elimination have been experimentally induced by the UV irradiation of embryos (Perondini et al, 1987;Guatimosin and Perondini, 1994). The UV doses used did not penetrate more than a few micrometers into the cytoplasm and therefore had little effect on egg survival.…”

From egg to pole cells: Ultrastructural aspects of early cleavage and germ cell determination in insects

“…The cytoplasmic architecture of the anterior pole region of the eggs of the dipteran species mentioned above is of special interest, because combined ultraviolet light irradiation and centrifugation experiments, as well as treatments with RNase in Smittia (for review see Kalthoff, 1984;Kalthoff et al, 1977) or appropriate manipulation in Bradysia (Perondini et al, 1987), have led to a conversion which results in the formation of an abdomen with inverted axial polarity instead of a head and a thorax (double abdomen). This change is thought to be due to inactivation of RNP particles located in the anterior of the egg and presumed to be anterior patterning determinants.…”

Female resistance behaviour and progeny sex ratio in two Bradysia species (Diptera: Sciaridae) with paternal genome elimination

“…To ensure virginity, 3rd instar larvae from each population were transferred into individual 5‐mL containers and fed on 2% plain agar, moist peat moss and baker's yeast ad libitum until adult emergence. This is also before the period of development where environmental factors, such as temperature, density or UV radiation, may influence the future brood sex ratio a female produces (Perondini et al ., ; Guantimosin & Perondini, ; Campos et al ., ; Nigro et al ., ). As adult males and females become sexually mature within a few hours (RF unpublished data), experimental females were less than 24 hours old and males were no older than 2 days.…”

“…However, we found no relationship between the proportion of eggs surviving to adulthood and secondary sex ratio, suggesting that this is not the case. It should also be noted that sciarid sex determination occurs post-fertilization and variation in X-chromosome elimination can be induced by environmental conditions before this occurs (Perondini et al, 1987;Guantimosin & Perondini, 1994;Campos et al, 1996;Nigro et al, 2007). We standardized the laboratory environment for our study.…”