Seasonal changes in the phospholipid composition in thoracic muscles of a heteropteran,Pyrrhocoris apterus

The fatty acid composition of phospholipids in thoracic muscles of Pyrrhocoris apterus was related to acclimatization temperature and diapause. Two unsaturated fatty acids, linoleic (18:2n-6) and oleic (18:1n-9), and two saturated, palmitic (16:0) and stearic (18:0), dominated at all temperatures. In contrast to most other reports, the proportion of unsaturated fatty acids did not increase with decreasing temperature; there was a positive correlation between the unsaturation ratio and temperature in total phospholipids (r=0.67). The most prominent response to cold acclimatization was an increase in the proportion of 16:0 fatty acid and a corresponding decrease in the proportion of fatty acids with 18 carbons. The negative correlation between the proportion of 16:0 and temperature was stronger in phospholipids with phosphatidylethanolamine (PE) head group (r=−0.85) than in phospholipids with phosphatidylcholine (PC) head group (r=−0.58). Changes in fatty acid profiles associated with photoperiodic induction of diapause had the same trend as changes related to cold acclimatization. Similar to most other reports, the proportion of PE increased, while the proportion of PC decreased with decreasing temperature. In contrast to a general rule, the PE-phospholipids were less unsaturated than PC-phospholipids.     

Regulation of body size in a heteropteran bug, Pyrrhocoris apterus

The determination of body size (length or weight) of teneral adults of Pyrrhocoris apterus L. was investigated. About 50% of size variation was determined already in the egg stage (average egg weight adult length correlations were 0.67 in males and 0.71 in females). During the larval development, starvation, low temperature, and pollution by excreta combined with crowding reduced adult size and usually increased the development length. The effects were directly proportionate to the length of the stress period, and increased with larval age. Photoperiod or intrinsic variation of development time did not affect adult size. The effects of stress were largely compensated when it was followed by a period of compensation growth at optimum conditions. A dramatic reduction of size appeared when last inster larvae starved and moulted to adults without access to food. Average adult weight was then reduced by up to 48%. Threshold weight for adult moulting was 18 mg, being attained after 1–2 day feeding of the last instar.

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Zusammenfassung Die Körpergrösse bei den Imagines eines Wildstammes der Feuerwanze Pyrrhocoris apterus wurde teilweise durch die Veränderlichkeit der Eigrösse determiniert, teilweise auch durch Hungern der Larven, niedrige Temperatur und metabolischen Produkten beeinflusst. Der Effekt letzterer Faktoren stieg mit deren Dauer und war je grösser desto näher sich die Wirkungsperiode zur Imaginalhäutung befand. Unterschiedliche Photoperioden wirkten auf die Körperlänge nicht. Wurden die Larven zwischen der ungünstigen Periode und der Imaginalhäutung noch den optimalen Bedingungen ausgesetzt, kompensierten sich die negativen Einflüsse weitgehend. Zu einer drastischen Verkleinerung der Imagines kam es nur, wenn das letzte Larven-stadium mit Hunger beeinflusst wurde und bis zur Imaginalhäutung keinen Zutritt zum Futter hatte. Minimales Gewicht, wo die Metamorphose der Larven noch möglich war, wurde zu 18 mg festgestellt.

     

始红蝽越冬聚集行为对其能量代谢的影响

聚集行为是动物适应不良环境的一种生态对策。始红蝽Pyrrhocoris apterus在成虫滞育越冬期间具有显著的聚集行为。采用LI-6400型光合仪测定了5种聚集度(分别用1头、5头、10头、20头和50头的群体大小表示)下始红蝽的呼吸量,通过呼吸量计算得到各聚集度始红蝽的呼吸速率(rate of respiration,Rr)及能量代谢速率(rate of metabolism,Rm),旨在明确聚集行为是否能够对始红蝽越冬时的能量代谢产生影响。结果表明： 不同聚集度间始红蝽的Rm值存在显著性差异; 并且随聚集度的增加,Rm值与聚集度呈显著负相关,Rm值依次为0.052,0.044,0.041,0.037和0.033 W/g。结果说明聚集行为可以有效降低始红蝽新陈代谢速率,有利于种群成功越冬。     

Seasonal changes in minor membrane phospholipid classes,sterols and tocopherols in overwintering insect, Pyrrhocoris apterus

Ectotherm animals including insects are known to undergo seasonal restructuring of the cell membranes in order to keep their functionality and/or protect their structural integrity at low body temperatures. Studies on insects so far focused either on fatty acids or on composition of molecular species in major phospholipid classes. Here we extend the scope of analysis and bring results on seasonal changes in minor phospholipid classes, lysophospholipids (LPLs), free fatty acids, phytosterols and tocopherols in heteropteran insect, Pyrrhocoris apterus. We found that muscle tissue contains unusually high amounts of LPLs. Muscle and fat body tissues also contain high amounts of β-sitosterol and campesterol, two phytosterols derived from plant food, while only small amounts of cholesterol are present. In addition, two isomers (γ and δ) of tocopherol (vitamin E) are present in quantities comparable to, or even higher than phytosterols in both tissues. Distinct seasonal patterns of sterol and tocopherol concentrations were observed showing a minimum in reproductively active bugs in summer and a maximum in diapausing, cold-acclimated bugs in winter. Possible adaptive meanings of such changes are discussed including: preventing the unregulated transition of membrane lipids from functional liquid crystalline phase to non-functional gel phase; decreasing the rates of ion/solute leakage; silencing the activities of membrane bound enzymes and receptors; and counteracting the higher risk of oxidative damage to PUFA in winter membranes.     

Enzymatic capacity for accumulation of polyol cryoprotectants changes during diapause development in the adult red firebug, Pyrrhocoris apterus

Abstract. Diapausing adults of the red firebug, Pyrrhocoris apterus, were maintained in the laboratory at constant conditions of 20 °C and short days (LD 12 : 12 h) for 5 months. Spontaneous termination of diapause is seen in 0.4% of adults. At different times of diapause development, groups of adults were exposed to an 8‐week gradual cold treatment ending at 0 °C. Ribitol and sorbitol contents remain very low at constant 20 °C and their rapid accumulation only occurrs at temperatures below 5 °C. The capacity to accumulate ribitol in response to low temperature stimulus remains relatively stable but the capacity to accumulate sorbitol decreases to zero during the 5 months of diapause development. Glycogen (whole‐body and fat‐body reserves) accumulates relatively rapidly during the early phase (up to 1–2 months) and slowly depletes during the late phase of diapause development under constant conditions. Upon cold treatment, part of the glycogen reserve was depleted. The activities of most enzymes involved in polyol metabolism (namely glycogen phosphorylase, glucose‐6‐P dehydrogenase, phosphofructokinase, aldose reductase, polyol dehydrogenase and ketose reductase) increase relatively rapidly during the early phase of diapause development and, in the late phase, they either become stable or slowly decrease. Cold treatment has either no effect or results in a moderate increase in activity when applied in the early phase of diapause development but results in a more or less obvious decrease of enzymatic activity when applied in the late phase.     

Function of the neuroendocrine complex in diapausing Pyrrhocoris apterus females

The role of the brain in inhibiting the action of corpora allata in diapausing short-day females was investigated by transplantation experiments. The function of the transplanted glands was evaluated by oviposition. Active glands from long-day females remained active for a long period of time after transplantation into short-day females, although in situ corpora allata were inhibited shortly after the transfer of females from long to short day. Moreover, inactive glands from short-day females became active after transplantation into other short-day females. In contrast, corpora allata remained inhibited when transplanted together with the brain in the neuroendocrine complex (brain-corpora cardiaca-corpus allatum) where the nervous connections between the brain and corpus allatum remained intact. It is therefore suggested that short-day conditions inhibit corpora allata via nervous connections with the brain.     

A quantitative study of adipokinetic hormone of the firebug,Pyrrhocoris apterus

The development of an enzyme-linked immunoassay (ELISA) for the adipokinetic neuropeptide hormone, Pya-AKH, from the firebug Pyrrhocoris apterus L. is described. The ELISA measures as little as 20 fmol of Pya-AKH. Tested against a range of synthetic peptides, the assay has a high sensitivity for peptides containing the C-terminal motif FTPNWamide. The amounts of Pya-AKH in the brain, corpora cardiaca, suboesophageal ganglia, and fused thoracic and abdominal ganglionic mass are very small, with only the corpora cardiaca containing appreciable levels of the hormone (ca. 4 pmol per bug). Preliminary estimates of the persistence of the hormone in the haemolymph are consistent with values determined for AKHs in other insects, and suggest that Pya-AKH has a rapid turnover with a half-life of ca. 18 min. Measurements of circulating titres of AKH in Pyrrhocoris are only possible in the ELISA described here by using pooled samples of haemolymph, and after preliminary clean-up of the haemolymph samples. The titre of Pya-AKH in resting reproductive female Pyrrhocoris is ca. 1 fmol/μl.     

Seasonal changes in neutral sugars and amino acids of particulate matter in Lake Nakanuma,Japan

Amino acids and neutral sugars in particulate matter were measured weekly from April in 1987 to March in 1988 in Lake Nakanuma, Japan. Changes in concentrations of total amino acids and total neutral sugars corresponded to those of chlorophylla. The composition of amino acids varied little seasonally and vertically. On the contrary, the composition of neutral sugars changed seasonally and vertically. We discuss the relationship between the changes in the biochemical components and environmental factors.     

The effect of allatectomy and photoperiod on the supercooling point in Pyrrhocoris apterus adults

Abstract Adults of Pyrrhocoris apterus (L.) (Heteroptera: Pyrrhocoridae) reared at 26°C had a considerably lower supercooling point (SCP) in diapause-inducing (LD 12:12 h) than in diapause-inhibiting (LD 18:6 h) photoperiodic regimes. Exposure of the insects to diapause-inducing acclimation conditions (LD 8:16 h and a temperature of 20°C during photophase and 5°C during scotophase) for 2–3 weeks had very little effect on the SCP, irrespective of the rearing photoperiod. Allatectomized adults kept continuously at LD 18:6 h and 26°C had high SCP similar to intact or sham-operated insects. In contrast to non-allatectomized insects, the SCP of allatectomized insects decreased after an exposure of from 2 to 3 weeks to diapause-inducing acclimation conditions (see above) almost to the level found in the intact diapausing insects. The relationship between the decrease of SCP and ‘diapause syndrome’ (de Wilde, 1970) is discussed.     

Developmental and diel changes of adipokinetic hormone in CNS and haemolymph of the flightless wing-polymorphic bug,Pyrrhocoris apterus (L.)

We have used an enzyme-linked immunoassay (ELISA) for determination of the AKH content in CNS (brain + corpora cardiaca + corpora allata) and haemolymph of adult macropterous and brachypterous females of the bug Pyrrhocoris apterus. The tests revealed that the AKH content fluctuates between 1 and almost 4 pmol/CNS during the first 14 days of adult life and significantly increased in order diapausing brachypters相似文献   

Voltinism and seasonal changes in haemolymph protein pattern of Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae) in relation to diapause

Abstract. The red firebug, Pyrrhocoris apterus (L.), was shown not to be strictly a monovoltine species in Czechoslovakia. A second generation arises from eggs laid by females emerging between June and the beginning of August. Oviposition takes place before diapause is induced in the females by shortening of photophase. Adults that moult later, enter diapause without having laid eggs.
Electrophoretic patterns of haemolymph proteins of adults collected in the field throughout a year showed a characteristic temporal pattern of changes correlated not only with the stages of ovarian development, but also with the progression of diapause and post-diapause quiescence. The changes mainly concerned vitellogenin and polypeptides of molecular weight 78 and 80 kDa.
Vitellogenin was present only in the haemolymph of reproductive females. The polypeptides of 78 and 80 kDa, belonging to the group of storage proteins, accumulated conspicuously in the haemolymph of adults undergoing diapause and post-diapause quiescence. However, the occurrence of these polypeptides seems not to be connected exclusively with cold, because their titres increased with the length of diapause development, even in diapausing adults reared in the laboratory at a constant 26.C     

Morphological effects of juvenile hormone mimics on embryonic development in the bug,Pyrrhocoris apterus

Summary Embryos ofPyrrhocoris apterus exposed to juvenile hormone mimics (JH) were examined throughout development to determine the progressive effects of treatment. Prior to blastokinesis whole experimental embryos did not differ morphologically from control embryos fixed at the same stage. Treated embryos failed to complete blastokinesis due to abnormal breakage of the extra-embryonic membranes.In the embryo-larva transition, JH exposure interfered with dorsal closure, with the consolidation of the nerve cord, and with the extension of appendages. Yet pigmentation and muscle differentiation occurred.These effects were interpreted and discussed with reference to the role of juvenile hormone in post-embryonic development.This is a portion of a dissertation submitted to the graduate school of Harvard University, in partial fulfillment of the requirements for the degree of Doctor of Philosophy (1973). It was previously reported in abstract (Enslee and Riddiford, 1970). This research was supported by NIGMS Training Grant T01 GM 00036-09, 11, 12, 13 to E.C.E. and NSF grants GB 6730, GB 7966 to L.M.R.     

Effect of thermoperiod on diapause intensity in Pyrrhocoris apterus (Heteroptera Pyrrhocoridae)

The intensity of adult diapause in Pyrrhocoris apterus was measured in two series of experiments as the duration of pre-oviposition period at a constant temperature of 25 degrees C after transfer from short (12L:12D) to long day conditions (18L:6D). Higher diapause intensity was induced with a thermoperiod than at constant temperatures. After the induction throughout larval instars 3-5 and during 4 weeks of adult life at short days and a thermoperiod of 25/15 degrees C the pre-oviposition period was 30+/-4 and 26+/-3 days. After induction at constant 25 degrees C the pre-oviposition period was 22+/-3 and 23+/-4 days, while after induction at constant 20 degrees C it was 17+/-4 and 19+/-4 days. Induction at a lower constant temperature of 20 degrees C was thus followed by a less intense diapause than the induction at a higher constant temperature of 25 degrees C. These counterintuitive results are discussed. The oxygen consumption rate measured at experimental temperatures prior to transfer from short to long days was higher at thermoperiodic conditions than at constant temperatures and it was similar at constant 20 and 25 degrees C. Thus, the oxygen consumption rate measured prior to the transfer was highest (indication of the least intense diapause) in the insects that showed later, after the transfer to long days, the longest pre-oviposition period (indication of the most intense diapause). Within the first two days after transfer to constant 25 degrees C, oxygen consumption rate measured at 25 degrees C decreased in the thermoperiodic insects, while it transiently increased in insects from constant 20 degrees C. Two days and later after the transfer, oxygen consumption rate was similar in all groups. Cold hardiness was not correlated with diapause intensity. The low lethal temperature in diapausing insects was correlated with the night temperature during diapause induction.     

Induction of adult diapause in Pyrrhocoris apterus L. by short cold exposure

Summary The ripening of ovaries in the females of Pyrrhocoris apterus can be inhibited not only by short-day photoperiod but also by cold shocks during the first week of the adult life.Ovaries in a part of the females are prevented from ripening by transferring the bugs from 25° C and long-day photoperiod to substantially lower temperatures for 2 (or 4) days. The oviposition is inhibited at least for 3 weeks after the return to original conditions favourable for reproduction. This effect is achieved when cold treatment is combined either with darkness or with long day. A difference between 2 and 4 days of chilling was not recorded. The effect of cold exposure (evaluated in our experiments by the proportion of mature and immature females) depends on the temperature of the cold exposure and on the age of females at the time of transfer to cold. The incidence of immature females was higher when lower temperatures (+2 to +6° C) were used and when females were transferred to cold early (0–2 days) after the adult moult.     

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.