Compensation for solar UV damage by solar radiation of longer wavelengths (Smittia spec., Chironomidae, Diptera)

Abstract

Photobiological experiments and laboratory observations on the egg deposition behaviour of Smittia were undertaken to assess the effect of different spectral ranges of solar radiation on inactivation and photoreactivation of the eggs.The egg deposition of Smittia is not confined to certain periods of the daily cycle, nor are the eggs hidden away even from bright laboratory light. Both the egg shells and the jelly of the clusters absorb UV poorly.An action spectrum was established for inactivation of eggs by exposition to ultraviolet radiation (UV) during intravitelline cleavage. It shows a pronounced peak at 295 nm and overlaps with the spectrum of the sunlight between 300 and 310 nm wavelength.The inactivating range of solar UV was substituted for by 305 nm radiation of 5 nm band with and a dose rate of 0.28 W/m, obtained from a monochromator. This "solar UV equivalent" caused inactivation of 50% of exposed eggs within 12 min, whereas exposition to full overhead sunlight produced the same effect only within 3 hrs.It is concluded that the inactivating effect of solar UV (300-310 nm) is counteracted by repair mechanisms requiring light of longer wavelengths (320-480 nm) which are also emitted by the sun.The type of photoreactivation described is difficult to understand within the established framework of nucleic acid repair. However, it seams to play a vital rôle in the survival of Smittia eggs under sunlight without need for pigmentation or shading.

PHOTOSENSITIZED FORMATION OF RNA‐PROTEIN CROSSLINKS IN AN INSECT EGG (SMITTZA SPEC., CHIRONOMIDAE, DIPTERA)*

“…The significance of RNA--protein crosslinks for inactivation of Sinitria eggs is small as compared with 'the role of pyrimidine dimers. since in the latter c;isc the photoreactivable sector of the biological dam;igc is 0.75 or higher (Kalthoff. 1975;1976) and correlates with the amount of pyrimidine dimers formed (Jilcklt.…”

The Bunsen–Roscoe reciprocity law in ultraviolet-B-induced mortality of the two-spotted spider mite Tetranychus urticae

“…The potential mechanism causing such variation in LD 50 values between laboratory and field studies may be the photoenzymatic repair of UVB-induced DNA damage (Kalthoff, 1975;Sinha and Häder, 2002;Macfadyen et al, 2004). In fact, Santos (2005) has suggested such a function of photoreactivation in T. urticae adult females.…”

PHOTOREACTIVATION OF RNA IN UV‐IRRADIATED INSECT EGGS (SMITTIA SP., CHIRONOMIDAE, DIPTERA) I. PHOTOSENSITIZED PRODUCTION AND LIGHT‐DEPENDENT DISAPPEARANCE OF PYRIMIDINE DIMERS*

“…In fact Srnittia eggs are rapidly inactivated by solar UV; only 12min exposure killed 50% of the eggs (Kalthoff, 1975). However, the deleterious effects of solar UV upon the eggs was effectively counteracted by solar radiation of longer wavelengths; 50% of the exposed eggs survived full sunlight for about 3 h (Kalthoff, 1975). Thus the photoreactivating light from the sun, if received simultaneously with the solar UV, caused PR of Srnittia eggs with a PRS of about 0.93.…”

“…The presence of physiological photosensitizers may create serious problems in cells exposed to solar radiation because they transfer the energy of solar UV which is not directly absorbed by nucleic acids. In fact Srnittia eggs are rapidly inactivated by solar UV; only 12min exposure killed 50% of the eggs (Kalthoff, 1975). However, the deleterious effects of solar UV upon the eggs was effectively counteracted by solar radiation of longer wavelengths; 50% of the exposed eggs survived full sunlight for about 3 h (Kalthoff, 1975).…”