Jan Šula

Physiology of drought tolerance and cold hardiness of the Mediterranean tiger moth Cymbalophora pudica during summer diapause.

Prepupae of the arctiid moth Cymbalophora pudica spend spring and summer months in a summer diapause (aestivation), the duration of which is photoperiodically controlled. Cold hardiness, drought tolerance and some physiological and biochemical parameters were measured in aestivating prepupae. Large amounts of metabolic reserves, in the form of lipids and glycogen, accumulated prior to aestivation. Glycogen served as the main metabolic fuel for aestivating prepupae. Metabolic rate decreased rapidly after the onset of the inactive prepupal stage and remained low (5-15% of the level in active larva) during aestivation. A spontaneous increase of the respiration rate occurred before pupation. Neither low mol. wt sugars or alcohols (polyols) accumulated nor the haemolymph osmotic pressure changed during aestivation. Drought tolerance of aestivating prepupae was high (no decrease in survival after exposure to r.h.<10% at a temperature of 23 degrees C for a substantial part of diapause) owing to their extensive capacity to stabilize the relative body water content irrespective of the r.h. of surrounding air. Cold hardiness was low (>90% decrease in survival after exposure to -7 degrees C for 24h). Cold and drought acclimations did not lead to significant changes in the measured physiological and biochemical parameters but cold (not drought) acclimation caused a significant increase in cold hardiness. Neither drought tolerance nor the increase in cold hardiness after cold acclimation appear to be related to presence/accumulation of polyols in aestivating C. pudica prepupae.

Feeding, drinking and digestive enzyme activities in long- and short-day females of Pyrrhocoris apterus (Heteroptera)

Abstract. .Reproducing females of the firebug, Pyrrhocoris apterus (Linnaeus) (Heteroptera: Pyrrhocoridae), reared under long‐day (LD 18:6h) photocycle (long‐day females), and diapausing females reared under short‐day (LD 12:12h) conditions (short‐day females) were analysed for temporal patterns of feeding, drinking and gut digestive enzyme activities. In long‐day females the highest activities of feeding and drinking were found at the beginning of each reproductive cycle. Significant correlation between feeding and drinking activities in both reproducing long‐day females and short‐day females during pre‐diapause state was found. In pre‐diapausing short‐day females the cyclical pattern of feeding and drinking was maintained despite the inhibition of reproduction. After entering the diapause their feeding activity became very low. Analysis of five gut enzymes revealed that short‐day females differ significantly from long‐day females in higher protease, amylase and esterase activities, in case of lipase only at certain times of their adult life; no significant difference was found in the aminopeptidase activity. Positive correlations between intensity of feeding and gut enzyme activities were observed in short‐day females. Using several protease inhibitors most protease activity in the gut of P.apterus was identified as cysteine and aspartyl proteases, and only a small part of the activity could be caused by some serine proteases.

Hexameric haemolymph protein related to adult diapause in the red firebug, Pyrrhocoris apterus (L.) (Heteroptera)

Abstract A hexameric storage protein was electrophoretically isolated from the haemolymph of diapausing adults of the red firebug, Pyrrhocoris apterus. This protein (Mrmr ~ 480,000, glycoprotein) was found to be a monohexamer. During the penultimate and last larval instar (both in diapausing and non-diapausing bugs), its concentration increased from about 1 mg/ml up to 8 and 13 mg/ml, respectively, and declined to almost zero value during ecdysis. In diapausing adults, the titre of the protein rose steeply from day 3 and reached a level of about 21 mg/ml in females and 24 mg/ml in males. In non-diapausing adult females there was an initial rise in the protein titre during the first 6 days but subsequently it stabilized to a level of about 3 mg/ml. In males the hexameric protein content reached only 1 mg/ml after imaginal ecdysis; an increase on day 21 and 30 was observed. In 14-day-old diapausing and non-diapausing bugs the hexameric protein constitutes about 15 and 4% of all haemolymph proteins, respectively. An amino acid analysis showed that the hexameric protein is neither an arylphorin nor a methionine-rich protein.

Wing morph-related physiological differences in adults of temperate population of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae).

The reproductive and diapausing adult females of brachypterous morph and macropterous females with reproductive arrest of non-diapause type, originating from the laboratory cultures of Pyrrhocoris apterus, were studied for their feeding and drinking behaviour, digestive enzyme activities, and carbohydrate and lipid contents. The highest feeding and drinking activities were observed in reproductive brachypters, the lowest in macropters. Macropters also differed from brachypters by lower activities of gut lipase, peptidase and protease, lower concentration of haemolymph sugars, and lower weight of fat body, which probably reflects their low feeding activity. The total content of fat body lipids was also lower in macropters (0.6 mg) than in reproductive and diapausing brachypters (4.6 and 7.5 mg, respectively) on day 14. A very high amount of glycogen was found in the fat body of diapausing brachypters, 363 micrograms on day 14, as opposed to 15 and 80 micrograms in macropterous and reproductive brachypterous females, respectively. The obtained data indicate that the most important difference between macropterous and brachypterous females with different types of reproductive arrest consists of an enhanced mobilization of lipids for dispersal in macropters and accumulation of energetic reserves for hibernation in brachypters.