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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 180 (1957), S. 340-341 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the silver fish (Lepisma) and the fire brat (Thermobia) (Fig. la) there is a triangular-shaped sclerite which is fused to the base of the first gonapophysis and articulates with the ninth tergum (T9) and the second gonocoxa, This sclerite is absent as such in Machilidae (Petrobius). In Thermobia ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Entomology 16 (1971), S. 379-406 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 4 (1974), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gross morphology and ultrastructure of the Malpighian tubules and hindgut in adults of the water bug Cenocorixa bifida (Hung.) is described. These are compared with similar structures in other insects with a view to relating the observed structure with potential function.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Zoomorphology 65 (1969), S. 327-335 
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adult Cenocorixa bifida (Heteroptera: Corixidae) emerging early in the year in British Columbia are all able to fly. Insects emerging in the late autumn look similar externally, but are incapable of flight: the ultrastructure of their indirect flight muscles resembles that of immature tissue, indicating a block in the normal myogenetic sequence.
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  • 6
    ISSN: 1432-234X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The integument of Oncopeltus fasciatus is made up of a vacuolated and a pigmented epidermal cell layer. This double layered integument is present from late embryo to adult in male and female animals reared on milkweed or sunflower seeds. Experiments with a labelled glycoside as well as retrograde ink injections suggest that O. fasciatus concentrates cardiac glycosides, normally derived from the host plants, within the vacuolated epidermal cell layer throughout its life cycle. In the adult, droplets of glycoside-rich fluid appear at precise points along the dorsolateral margins when external pressure is applied to the thorax and abdomen. This pressure causes separation of cuticular flanges in the metathoracic epimeral lobe and rupture of the cuticle in restricted areas in the mesothorax and abdomen. In addition the pigmented epidermal cell layer and the distal membranes of the vacuolated epidermal cell layer rupture with the result that the contents of the vacuolated cell layer are eliminated onto the surface of the animal where they are retained as discrete droplets by the cuticular morphology. Release of cardiac glycosides into the haemolymph is prevented by a thick basal lamina on the haemolymph side of the vacuolated epidermal cells. No specialized muscles involved with fluid release were observed. The vacuolated epidermal cells do not show ultrastructural features characteristic of actively transporting tissues, i.e., abundant mitochondria and elaborate membrane infoldings. This suggests that glycoside sequestration is essentially a passive process and should not be associated with any physiological cost. Large concentration gradients of cardiac glycosides are maintained across the basal lamina, basal plasma and vacuolar membranes of the vacuolated epidermal cell layer. Possible mechanisms by which O. fasciatus is able to concentrate cardiac glycosides as well as the possible function of this phenomenon are discussed.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 30 (1977), S. 23-41 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The parameters influencing food consumption in larvae and adults of five species of Gerris were studied. An experimental components analysis was utilized with emphasis placed on measurements of the length of time the insects spent handling food items, and the amount of food in the gut at any one time. The following characteristics were noted: (1) The maximum feeding time required to achieve satiation was 2–2.5 h for all gerrids above 10 mg wet weight. For gerrids below this weight, feeding time declined at a logarithmic rate. (2) Body size had little influence on the duration of the feeding period after food deprivation; only with the first and second instar larvae was a significant difference noted. (3) The average duration of the feeding and non-feeding periods was 10.4 and 24.6 min respectively for satiated adult G. remigis in the presence of excess food. (4) Signifcant differences in relative digestive rate existed between adult and larvae irrespective of species. (5) The smaller the gerrid, the greater the volume relative to its body weight that could be consumed at a single feeding, and for all gerrids, the amount consumed per day was greater than the maximum amount that can be ingested at a single feeding, this difference being larger in the larvae than in the adults. (6) The relationship between daily amount consumed and temperature was linear for four species, increasing with increasing temperature; food consumption in G. remigis, however, peaked at about 19°C, and declined linearily at temperatures both above and below this value. (7) Irrespective of instar and stadium duration, food consumption for G. notabilis peaked within a stadium about 40% of the way through the stadium.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 44 (1979), S. 13-20 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two of the parameters which determine the rate at which prey are encountered by a predator, i.e. the distance at which a predator responds to a prey and its rate of movement relative to the prey's, were determined for all the stages of five species of Gerris using gerrids and Drosophila as prey. These parameters allowed calculation of the swath, or “encounter path”, a gerrid would cover as it moved across the water surface. Gerris species prefer to attack live prey in front of them, and tend to ignore prey if the attack requires a turn of more than 100°. Hunger was found to affect the responsive angle required to clicit an attack by G. remigis, and regardless of species, smaller gerrids required the prey to be closer before an attack was initiated. The rate of movement in Gerris was measured as a function of stride length and the number of strides made per unit time. Stride length varied according to the length of the mesothoracic leg, and the frequency of movement was observed to be species specific. G. remigis, a stream species, moved 4–6 times as often as the four other species studied, all of which are characteristically found on non-moving water surfaces. Within a species, gerrid size had no significant effect on the frequency of movement, although there was a tendency for smaller gerrids to move less.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 105 (1983), S. 143-154 
    ISSN: 1573-5117
    Keywords: saline lakes ; ecology ; physiology ; Hemiptera ; Corixidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two closely related species of Cenocorixa inhabit saline lakes in British Columbia. C. bifida lives in lakes with a conductivity of 20 to 20 000 µS cm-1, while C. expleta occurs in lakes with a conductivity ranging from 5 000 to 30 000 µS cm-1. The factors limiting the differential distribution of these species in higher salinities, and those governing the exclusion of C. expleta in low salinities have been studied. Mortality experiments, and an investigation of osmotic and ionic balance, indicate that the two species differ in their ability to tolerate high salinity: these data correlate with the limits computed from field data and suggest that the differential distribution in the high saline lakes is because of physiological differences. However, these same data indicate that both species have a similar ability to live in low salinity lakes. Although C. expleta does not occur in such lakes, it is physiologically capable of doing so and has been reared in freshwater. It is proposed that ecological rather than physiological factors exclude C. expleta from low salinity waters. Competitive exclusion by C. bifida might be suggested, but available data do not support this. A study of life cycle phenology, fundamental food niche and realized feeding niche of the two species shows that these are not significantly different. No interactive segregation is evident in sympatry, and so competitive exclusion of C. expleta in freshwater is unlikely. Hence, other biological factors in fresh and low salinity water have been investigated. A marked difference in susceptibility to mite parasitism of the species has been discovered. Although both C. bifida and C. expleta are parasitized by larval Eylais and Hydrachna, C. expleta appears unable to survive such parasitism. It is suggested that this is the biological factor that excludes C. expleta in the fresh and low salinity lakes where water mites are abundant.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of chemical ecology 12 (1986), S. 1171-1187 
    ISSN: 1573-1561
    Keywords: Hemiptera Heteroptera ; Lygaeidae ; Oncopeltus fasciatus ; Asclepiadaceae ; cardenolides ; sequestration ; morphological adaptations ; physiological adaptations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The morphological and physiological adaptations associated with sequestration of cardenolides by the lygaeidOncopeltus fasciatus are summarized and discussed. Cardenolides are efficiently accumulated inO. fasciatus; however, the insect does not appear to suffer any physiological cost as a result of handling large amounts of these plant toxins. Morphological adaptations of the insect include a modified integument composed of a double layered epidermis with an inner layer (the dorsolateral space) specialized for cardenolide storage. Special weak areas of the cuticle are found on both the thorax and abdomen, which rupture when the insect is squeezed, resulting in the cardenolide-rich contents of the inner epidermal layer being released onto the body surface in the form of discrete spherical droplets. Physiological adaptations include selective sequestration of food plant cardenolides, concentration of cardenolides in the dorsolateral space, passive uptake of cardenolides at the gut and dorsolateral space requiring little energy output, reabsorption of secreted cardenolides by the Malpighian tubules, high in vivo tolerance to cardenolides, and the presence of cardenolide-resistant Na,K-ATPases.
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