DEVELOPMENTAL RATES AND DIAPAUSE IN ACHETA PENNSYLVANICUS (BURMEISTER) AND ACHETA VELETIS ALEXANDER AND BIGELOW (ORTHOPTERA:GRYLLIDAE)

1960 ◽  
Vol 38 (5) ◽  
pp. 973-988 ◽  
Author(s):  
R. S. Bigelow
Keyword(s):  
Reproductive Isolation ◽  
High Temperatures ◽  
Cold Hardiness ◽  
Embryonic Diapause ◽  
Geographical Isolation ◽  
Laboratory Rearing ◽  
Nymphal Development ◽  
Developmental Physiology ◽  
Developmental Rates ◽  
Genetically Determined

Tendencies to diapause were not observed in nymphs of Acheta pennsylvanicus (Burmeister), but diapause was noted in a high proportion of the nymphs of Acheta veletis Alexander and Bigelow. On the average, nymphal development was more rapid in pennsylvanicus than it was in veletis nymphs. Embryonic diapause always occurred in pennsylvanicus but never in veletis eggs. These differences in developmental physiology are genetically determined and the failure of the two species to produce hybrids may be due to conflicting lethal interactions of the two genotypes in hybrid embryos. Both species die out after several generations of laboratory rearing at continuous high temperatures, and the evolution of cold hardiness has apparently involved a reduction in tolerance to constant high temperatures. Reproductive isolation may have been achieved by these two species without geographical isolation. Nymphal development is more rapid in northern than in southern veletis populations.

EVOLUTION IN THE FIELD CRICKET, ACHETA ASSIMILIS FAB.

1958 ◽  
Vol 36 (2) ◽  
pp. 139-151 ◽  
Author(s):  
R. S. Bigelow
Keyword(s):  
Sympatric Speciation ◽  
Developmental Differences ◽  
Field Cricket ◽  
Temporal Difference ◽  
Laboratory Rearing ◽  
Field Crickets ◽  
Developmental Rates ◽  
Breeding Seasons ◽  
Incomplete Reproductive Isolation ◽  
Two Populations

Progeny of northern spring field cricket adults lay non-diapause eggs, undergo nymphal diapause, and overwinter as nymphs. Progeny of northern fall adults lay diapause eggs, do not undergo nymphal diapause, and overwinter as eggs. The two populations cannot interbreed freely in the field owing to a temporal difference in breeding seasons; they did not interbreed in the laboratory. Rearing experiments show that the developmental differences are genetically based rather than environmentally conditioned, and it is, therefore, unlikely that hybrids would be viable even if they were produced in the field. Consequently these two populations behave as good species. Field crickets from Virginia developed much more rapidly than did spring crickets from Quebec. Quebec spring males and Virginia females produced hybrids with developmental rates intermediate between those of their parents. More female than male hybrids were produced, and the females developed more rapidly than did male hybrids. Offspring were produced by hybrid females and Quebec spring males, but not by hybrid females and Virginia males. Partial, but incomplete reproductive isolation exists between Quebec and Virginia field crickets. A possible mechanism of sympatric speciation in insects is discussed.

scholarly journals Sound signal of the Himalayan marmot in its insular range

2021 ◽  
Vol 265 ◽  
pp. 01006
Author(s):  
Alexander Nikol’skii ◽  
Elena Vanisova ◽  
Konstantin Belovezhets
Keyword(s):  
Alarm Call ◽  
Sound Signal ◽  
The Loess Plateau ◽  
Geographical Isolation ◽  
The West ◽  
The North ◽  
Ecological Corridor ◽  
History Of ◽  
Genetically Determined ◽  
Himalayan Marmot

The range of Himalayan marmot (Marmota himalayana Hodgson, 1841) has an insular character, as it is limited by ecological and geographical barriers: in the north, northeast and east, these are deserts and the Loess Plateau, in the west - mountain peaks covered with glaciers and rivers, in the south - forests of the southern macro slope of the Himalayas. Only in the northwest of the range there is an ecological corridor. The geographical isolation of populations of marmots provokes the divergence of alarm call, which is one of the obvious genetically determined features. The results of cluster analysis based on a complex of features of the sound signal coincide with the results of analysis using nuclear and mitochondrial DNA. The projection of variability on the structure and history of the landscape contributes to understand the ecological and geographical factors of divergence as the basis for the process of speciation.

A Comparison of the Mating Behaviour Between Populations of the Reptile Ticks Aponomma Hydrosauri and Amblyomma Albolimbatum.

1982 ◽  
Vol 30 (4) ◽  
pp. 635 ◽  
Author(s):  
RH Andrews ◽  
CM Bull
Keyword(s):  
Reproductive Isolation ◽  
Tick Species ◽  
Mating Behaviour ◽  
Geographical Isolation ◽  
Rapid Speciation ◽  
Different Populations

Tests were conducted in Australia to determine the levels of reproductive isolation between geographically separated populations of reptile ticks. Mating behaviour was observed both on and off hosts in the laboratory when males were placed with females of their own or different populations. There was no evidence for reproductive isolation between South Australian populations of Aponomma hydrosauri (Denny) collected from the host lizard Trachydosaurus rugosus, despite one area of geographical isolation. Males of Amblyomma albolimbatum Neum. showed no discrimination between females from populations more than 2000 km apart. This contrasts with earlier reports of reproductive isolation between reptile tick species and contradicts hypotheses of rapid speciation in parasitic taxa.

Intersterility and diapause differences between geographical populations of Teleogryllus commodus (Walker) (Orthoptera: Gryllidae).

1962 ◽  
Vol 10 (3) ◽  
pp. 360 ◽  
Author(s):  
RS Bigelow ◽  
PSA Cochaux
Keyword(s):  
Distinct Species ◽  
Embryonic Diapause ◽  
Northern Australia ◽  
Laboratory Rearing ◽  
Teleogryllus Commodus ◽  
Geographical Populations

Sterile offspring were produced by crosses between strains of Teleogryllus commodus (Walker) from northern Australia (Queensland) and southern Australia (Victoria, Adelaide). If the northern and southern populations are not connected by a series of freely interbreeding populations, they must be recognized as distinct species. Embryonic diapause occurred in none of the eggs of the Queensland strain, and in different proportions of the eggs of the two southern strains, when incubated at 28�C. After several generations of laboratory rearing the proportions of eggs that entered diapause at 28�C decreased in both the southern strains.

Altitudinal adaptation of the life cycle in Allonemobius fasciatus DeGeer (Orthoptera: Gryllidae)

1983 ◽  
Vol 61 (9) ◽  
pp. 1986-1990 ◽  
Author(s):  
Seiji Tanaka ◽  
Victor J. Brookes
Keyword(s):  
Life Cycle ◽  
Genetic Difference ◽  
Adult Emergence ◽  
Growing Season ◽  
Embryonic Diapause ◽  
Nymphal Stage ◽  
Nymphal Development ◽  
Hatching Time ◽  
Photoperiodic Regulation ◽  
Allonemobius Fasciatus

Allonemobius fasciatus DeGeer maintains a univoltine life cycle with an embryonic diapause over an altitudinal gradient of as large as 1100 m. Hatching time differs by more than 1.5 months between the highest and lowest altitudes studied. Little or no genetic difference was detected between populations from different altitudes when physiological traits such as diapause intensity, postdiapause development, and nymphal development were compared in the laboratory. Photoperiod influenced the duration of the nymphal stage and the number of instars, compensating for the shorter growing season at higher elevations. This photoperiodic regulation of nymphal development would also serve as a mechanism synchronizing adult emergence within a population of this species.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

Ultrastructural alterations in the fetal mouse myocardium in response to genetic and environmental factors

1987 ◽  
Vol 45 ◽  
pp. 724-725
Author(s):  
K.C. Feng-Chen ◽  
F.B. Essien ◽  
K.J. Prestwidge ◽  
J.T. Cheng ◽  
C.L. Shen
Keyword(s):  
Fetal Heart ◽  
Perinatal Period ◽  
Primary Energy ◽  
Cardiac Contraction ◽  
Ultrastructural Changes ◽  
Fetal Mouse ◽  
The Subject ◽  
Physiological Adjustments ◽  
Genetic And Environmental Factors ◽  
Genetically Determined

The physiology of the fetal heart differs significantly from that of the mature post-natal organ: e.g., the metabolic supply for adult cardiac contraction relies mainly on fatty acids; whereas, the fetal heart uses carbohydrates as its primary energy source. Limited morphological descriptions of the developing myocardium have appeared. However, additional studies are required to elucidate the ultrastructural changes occuring in the perinatal period when enormous physiological adjustments are made. Although adult animals are most often used in toxocological and pathological analyses, it is also important to investigate fetal cardiac responsiveness to various agents. The vulnerability of the ultrastructure of the fetal mouse myocardium to genetic and environmental assault is the subject of this report. The genetically determined effect on the heart was observed in mouse embryos homozygous for the cab (cardiac abnormality) mutation discovered by Essien.

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