On the visually evoked head nystagmus of Tenebrio molitor and other beetles

Head movements of different species of walking beetles elicited by rotating stripe patterns have been investigated. They are of the usual type in contrast to an inverted nystagmus reported forTenebrio molitor in similar experimental situations. Reexamination of theTenebrio records revealed that the sign of the stimulus was interchanged by a mistake while plotting the results. Thus, the head nystagmus inTenebrio is also of the usual type, consisting of a smooth pursuit head movement followed by a faster returning phase.     

Klinokinetic and klinotactic humidity reactions of the beetles Hylobius abietis and Tenebrio molitor

ABSTRACT. The effects of spatially uniform but temporally changing air humidity stimuli on the orientation behaviour of the large pine weevil ( Hylobius abietis L.) and the flour beetle ( Tenebrio molitor L.) were studied in a specially constructed vertical air flow chamber. Moist-acclimatized but hygronegative pine weevils were exposed for 10 s to a moist air stream ( c. 85% R.H.) and then for 10 s to a dry air stream ( c. 50% R.H.). The Tenebrio were divided into two groups acclimatized to moist and dry air respectively. For each group the humidity during the initial 5 s in the air stream was the same as during acclimatization, and then changed to the alternative level. In Hylobius the change from moist to dry air caused a decrease in spatial displacement brought about by a decrease in walking speed and an increase in the amount of turning per unit time. In Tenebrio the change from dry to moist air caused a decrease of walking speed and a turning-back reaction based, presumptively, on idiothetic information about the insect's previous walking direction. The average angle turned during 2 s after the humidity change was 165°. In moist-adapted beetles the dry air stream caused an identical orthokinetic arrestment, but no klinokinetic or klinotactic reaction. Klinokinesis is redefined as a change in the circular variance of turning angles per unit time, which does not change the mean direction (or directions in cases of multimodal distributions) of the circular distribution. Accordingly, klinotaxis consists of a change in the mean directions) of the circular distribution of angular velocities. In both species the turning frequency was more constant than turning per unit distance, suggesting a temporal control in the nervous system of klinokinetic and klinotactic behaviour.     

Lack of preference for infective faeces in Hymenolepis diminuta-infected beetles (Tenebrio molitor)

The beetle-tapeworm life cycle provides a convenient system to study how host behaviour influences the probability of re-infection because initial and secondary infections can be tracked. The beetle, Tenebrio molitor, is infected with the tapeworm Hymenolepis diminuta when it ingests rat faeces containing tapeworm eggs, which upon hatching undergo five morphologically distinct stages while developing inside the beetle. In a series of preference trials, both individual and groups of previously infected beetles were exposed to baits of infective (faeces with eggs) and uninfective faeces. Beetles did not differ in the amount of time spent or in the number of occurrences at each bait type, suggesting that infected beetles show no preference for infective faeces. This may be a host adaptation to avoid further infection, parasite manipulation to avoid competition for host resources, or both. Further, once infected, beetles are no more or no less likely to become re-infected than uninfected beetles. An analysis of the mean and variance of infection suggests that some individuals are highly susceptible to and some are highly resistant to infection, with males being more variable than females. This could explain the higher load of cysticercoids observed in males.     

Effect of hydrocortisone on the growth and development of larvae Tenebrio molitor

Hydrocortisone administered with the food causes inhibition of growth in larvae Tenebrio molitor. Hydrocortisone together with the reduction in the rate of growth retards the moulting cycle in larvae T. molitor. The action of hydrocortisone does not influence greatly the number of larvae moulting cycles.     

泰山虫草对黄粉虫的侵染特性研究

报道了用泰山虫草分生孢子悬浮液接种活体黄粉虫,提取被侵染的黄粉虫体液,并测定不同侵染时间虫体液中酶活性的动态变化。结果表明:泰山虫草分生孢子能成功的侵染黄粉虫并长出子座;接种第2~4 d后即可导致黄粉虫体内活性发生不同程度的变化,说明黄粉虫具有独特的防御病原微生物的侵染机制。     

Structure of the apical cells of the testis of the tenebrionid beetles: Tenebrio molitor and Zophobas rugipes

The developmental cytology of the apical tissue of the testis of Tenebrio molitor and Zophobas rugipes was studied with light and electron microscopy. In the early larvae of both species the tisue was found to be a thickened protrusion of nongerminal cells appearing at the apical end of each testis follicle following gonadal differentiation. The cells persist through pupal and adult stages in both species, becoming more prominent at these stages in Z. rugipes, despite tracheal invasion in both species. In older adults the apical tissue regresses and ultimately distintegrates. Ultrastructurally the apical cells are distinguished from adjacent germinal cells by their (1) small, rounded or oval nuclei, (2) highly convoluted plasma membrane, (3) electron-opaque cytoplasm, (4) profuse concentrically-stacked, granular endoplasmic reticulum, (5) large aggregates of glycogen-like granules, (6) numerous small, tubular mitochondria, (7) well-developed Golgi centers and (8) striking arrays of microtubules. These cells have many cytological features in common with the androgenic gland cells of crustaceans, but not with the steroidogenic cells of vertebrates. Evidence for the formation of protein granules is also lacking. As yet, experimental procedures have not indicated an endocrine function for these cells in tenebrionids. However, their cytology is consistent with secretory activity of some kind.     

Effect of light wavelength spectrum on magnetic compass orientation in Tenebrio molitor

In many animal species, geomagnetic compass sensitivity has been demonstrated to depend on spectral composition of light to which moving animals are exposed. Besides a loss of magnetic orientation, cases of a shift in the compass direction by 90 degrees following a change in the colour of light have also been described. This hitherto unclear phenomenon can be explained either as a change in motivation or as a side effect of a light-dependent reception mechanism. Among the invertebrates, the 90 degrees shift has only been described in Drosophila. In this paper, another evidence of the phenomenon is reported. Learned compass orientation in the Tenebrio molitor was tested. If animals were trained to remember the magnetic position of a source of shortwave UV light and then tested in a circular arena in diffuse light of the same wavelength, they oriented according to the learned magnetic direction. If, however, they were tested in blue-green light after UV light training, their magnetic orientation shifted by 90 degrees CW. This result is being discussed as one of a few cases of 90 degrees shift reported to date, and as an argument corroborating the hypothesis of a close connection between photoreception and magnetoreception in insects.     

Cytodifferentiation of the accessory glands of Tenebrio molitor

Summary Spermathecal accessory glands from pupae of Tenebrio molitor were cultured in vitro in Landureau S-20 medium with or without ecdysterone at a concentration of 5 g/ml medium. Morphological changes were examined by electron microscopy. Tissue taken from pupae that have not been exposed to a peak of ecdysterone in vivo is only able to differentiate in medium with hormone, and then only partially, while tissue taken from pupae that have experienced an endogenous peak of ecdysterone is able to develop maximally irrespective of the presence or absence of hormone. The specific ultrastructural changes that occur in vitro correspond to those occurring in the gland in situ during the normal course of differentiation, and are: the formation of the pseudocilium, cell retraction and formation of an end apparatus, and cuticulogenesis in the ductule and main lumen of the gland. Pseudocilium formation does not appear to be ecdysterone-dependent, while cuticulogenesis requires ecdysterone for initiation of the process. Deposition of cuticle is an expression of an earlier commitment of the cells to this process, and is initiated by elevated levels of ecdysterone. Ecdysterone is not required for completion of cuticulogenesis.This study was supported by grants from the National Institutes of Health (NIAMD 15662 and NIGMS 26140)     

Effect of weak combined magnetic fields on the metamorphosis of the meal-worm beetle Tenebrio molitor

The effects of weak combined magnetic fields adjusted to the parametric resonance for Ca2+ and K+ and extremely weak alternating magnetic field on the metamorphosis of the meal-worm beetle Tenebrio molitor have been studied. It was shown that the exposure of pupas of insects to all above-indicated types of fields stimulates the metamorphosis. However, after the exposure to weak combined magnetic fields adjusted to the parametric resonance for Ca2+ and K+, the number of insects with anomalies increases, which is not observed by the action of the weak alternating magnetic field.     

Effect of weak combined magnetic fields on the metamorphosis of the mealworm beetle Tenebrio molitor

The effects of weak combined magnetic fields adjusted to the parametric resonance for Ca²⁺ and K⁺ and extremely weak alternating magnetic field on the metamorphosis of the mealworm beetle Tenebrio molitor have been studied. It was shown that the exposure of pupas of insects to all above-indicated types of fields stimulates the metamorphosis. However, after the exposure to weak combined magnetic fields adjusted to the parametric resonance for Ca²⁺ and K⁺, the number of insects with anomalies increases, which is not observed by the action of the weak alternating magnetic field.     

Head movements of the mealworm beetle Tenebrio molitor

Tethered walking imagines of the mealworm beetle Tenebrio molitor wave their heads in random fashion. If a periodic pattern of vertical black and white stripes is rotated around the animal a regular nystagmic head movement is superimposed upon the random waving, the frequency of the latter equals the contrast frequency within large ranges of the angular velocity of the pattern. The nystagmus is inverted: After a short period of tracking, during which the angular velocity of the head is the same as that of the panorama, the head returns slowly toward its normal position according to an exponential-like function. Resting animals do not wave their heads. However, if the above panorama is rotated, the beetle turns its head in the direction of the movement of the panorama and holds it in a side-way position, as long as the rotation is maintained. The angular position reached depends in the same manner on the angular velocity of the panorama as the turning tendency of walking animals established in open loop experiments using the spherical Y-maze method.     

Effect of ecdysone agonist RH-0345 on reproduction of mealworm,Tenebrio molitor

RH-0345 belongs to a new group of insect growth regulators (IGRs) with a benzoylhydrazine structure that mimic the action of the natural insect molting hormone 20-hydroxyecdysone. After topical application on female adult beetles of mealworm, Tenebrio molitor L. (Coleoptera: Tenebrionidae), first oviposition was delayed, the number of eggs per female was reduced by 32%, the follicular epithelium was thinner (-33%) during sexual maturation, the size of deposited eggs was reduced, and egg viability was lost by 68%. Treatment with RH-0345 had also reduced the ovarian protein content and two protein bands were missing in the ovaries. Ultrastructural observations of the ovaries at the end of vitellogenesis in treated females, however, showed no evident differences with the fine structure of both follicular cells and oocytes in controls. In addition, we measured the amount of ecdysteroids in the medium of treated ovary cultures in vitro and in the eggs deposited by treated females. Possible action sites with the reproductive system at different levels in T. molitor are discussed for this novel group of IGRs.     

Sequence-induced curvature of Tenebrio molitor satellite DNA

Single satellite DNA constitutes about 50% of the Tenebrio molitor genome. Electrophoresis of 142 base pair long satellite monomers on nondenaturating polyacrylamide gel shows retarded mobility, a characteristic of fragments with sequence-induced DNA curvature. Migrational analysis of circularly permuted satellite monomers revealed the existence of 2 bend centers in the monomer sequence. We calculated the trajectory of DNA helix axis according to the algorithm of De Santis et al. This model predicts that T molitor naked satellite DNA forms a solenoid structure with left-handed superhelix. One turn of the superhelix has approximately 310 base pairs and a 33 nm pitch. Point mutations found in the satellite DNA (1.8%) influence bending characteristics, but do not distort the general geometry of satellite superhelix.     

黄粉虫幼虫对硒的生物积累

在饲料中添加含硒化合物喂养黄粉虫Tenebrio molitor L.幼虫,测定幼虫硒含量、粪便硒含量和体重的变化,计算黄粉虫幼虫特定生长率及幼虫对硒生物积累系数,分析黄粉虫有效积累硒的条件。结果表明,饲料硒含量在15~20mg/kg时,幼虫硒含量明显提高,对硒的生物积累系数高于其它试验组水平,饲料硒含量过高,幼虫硒含量降低,正常生长受到抑制。黄粉虫幼虫特定生长率、取食量、排粪量、干物质含量随着饲料硒含量的增加而降低,死亡率、粪便硒含量随着饲料硒含量的增加而增大。饲料硒含量为15～20mg/kg时黄粉虫幼虫对硒的生物积累效果最好。     

Effect of temperature on production of fungal metabolites toxic to larvae of Tenebrio molitor

Larvae of the yellow mealworm, Tenebrio molitor, were fed diets containing rye seed on which five fungal isolates had been cultured at temperatures of 10°, 15°, 20°, and 25°C in complete darkness. Larval growth and survival were influenced by the fungal isolate contained in the dietary substrate, by the temperature at which the fungus was grown, and by an interaction of these factors. Evidence is presented suggesting that different fungal metabolites are involved in regulating rates of growth and mortality of these larvae.