Vein Angle Research Articles

Heritability of morphological characters used to distinguish European and Africanized honeybees

Identification of "Africanized" honeybees (Apis mellifera) is usually achieved by measuring an array of morphological characters. Discriminant functions exist that allow determination of subspecies similarity on the basis of these measurements. Here we compute the heritabilities of the standard character set for ten eco-types (Table 1) of bees. Heritability is extremely high for body size characters and there is greater genetic variance among ecotypes than within. Heritability is lower, but still very high, for the vein angle characters and hamuli number (Table 3). Heritability was also computed for the same character set for a group of 20 colonies in Venezuela (Table 4). Heritabilities declined by an average of 41% when specimens were reared in nonmaternal environments, but were still extremely high for the body size characters. These results support the continued use of morphological characters as a tool for identifying Africanized bees. They also suggest that multivariate analysis of morphology is useful in evaluating changes in the honeybee genome, and is therefore an effective means of studying the population genetics of honeybees.

Lymphsystem und Lymphdrainage im Hoden des Pekingerpels (Anas platyrhynchos, L.)

SummaryLymph system and lymphatic drainage in the testis of the Peking drake (Anas platyrhynchos, L.)After perfusion fixation the lymph vascular system can be distinguished sharply from the blood vascular system because the formation of lymph proteins is a reliable distinguishing criterion. Prelymphatic spaces without endothelial lining among seminiferous tubules partially communicate with lymph capillaries that are continuous with lymph sinusoids. Lymphatic vessels whose walls as yet contain no muscle are already present between the seminiferous tubules. The lymph then flows to the tunica albuginea in which it was possible to demonstrate, by injection of Prussian Blue, an narrow‐mesh lymphatic network. Collecting vessels converge on the hilus and carry the lymph to the thoracoabdominal trunk. Right and left trunks, singly or after joining, enter the blood vascular system close to the left angle of veins.

POSITIONAL AND SEASONAL VARIATION IN OAK (QUERCUS; FAGACEAE) LEAF MORPHOLOGY

Within‐tree and seasonal variation in quantitative characters of oak leaves were evaluated by factorial analysis of variance. All linear and areal measurements illustrate marked within‐tree and seasonal variation. Numbers of lobes and bristle tips and primary vein angle appear relatively stable within trees and among seasons. In many instances, size‐correction reduces both within‐tree and seasonal variance to nonsignificant levels. However, all characters do not illustrate the same trends either within trees or across the seasons. The results have important implications for those attempting to evaluate among‐tree and among‐population variation.

Positional and Seasonal Variation in Oak (Quercus; Fagaceae) Leaf Morphology

Within-tree and seasonal variation in quantitative characters of oak leaves were evaluated by factorial analysis of variance. All linear and areal measurements illustrate marked within-tree and seasonal variation. Numbers of lobes and bristle tips and primary vein angle appear relatively stable within trees and among seasons. In many instances, size-correction reduces both within-tree and seasonal variance to nonsignificant levels. However, all characters do not illustrate the same trends either within trees or across the seasons. The results have important implications for those attempting to evaluate among-tree and among-population variation.

Pleiotropic effects in the four jointed mutant of Drosophila melanogaster.

Studies of the adult morphology of male D. melanogaster suggest that a shortening of body parts is the common aspect of the pleiotropic effects of fj (four jointed tarsi) on the development of the leg, wing, scutellum, distal parts of antenna, and one of three tergite segments measured. In the scutellum and distal antenna the only detected effect of fj is overall shortening, whereas local effects appear in leg and wing. Shortening of the leg is maximal (44%) at the proximal tarsal segments and absent at the distal two, confirming earlier studies. In the wing, total length is reduced 10% and maximum shortening (50%) occurs in the area between the anterior (ACV) and posterior (PCV) cross veins, while the proximal longitudinal veins are longer or unchanged. The effect of fj on wing width is small. Observations on cell density and bristle spacing also indicate that the strongest effect of fj is in the central area, between the ACV and PCV. We interpret the primary effect of fj to be a general reduction in the longitudinal growth pattern of many different imaginal discs. Secondary effects in the leg include a change in tarsal segmentation, followed by a bristle pattern change. In the wing, the angle of veins, bristle pattern on the subcosta vein, positions of ACV and PCV, and cell density variations are secondary effect of fj. A decrease in cell density on the wing surface between ACV and PCV may be related to a final stretching of wing tissue after the process of vein formation. Local effects are not seen in other discs which lack sequential regional patterning mechanisms emphasizing the effects of general shortening. The similarities in developmental aspects between leg and wing are discussed in relation to homoeotic changes by certain mutants.

Heterosis, Inbreeding Depression, and Combining Ability in Diallel Crosses of Cigar‐Wrapper Tobacco1

Seven varieties and breeding lines of cigar‐wrapper tobacco (Nicotiana tabacum L.) and the 21 possible hybrids between them, excluding reciprocals, were evaluated in terms of 8 important characters. Heterosis above the midparent was observed for number of 40‐cm (16‐in) leaves, total leaf number, lateral vein angle, yield, No. 1 string, grade index, crop index, and blue mold index. One hybrid, 1128✕5058, yielded significantly more than the highest‐yielding parent, ‘Florida 20.’ Inbreeding depression was observed for number of 40‐cm leaves, lateral vein augle, yield, crop index, and blue mold Peronospora tabacina Adam) index.Estimates of general combining ability were significant for all characters investigated; specific combining ability was significant for number of 40‐cm leaves, total leaf number, and lateral vein angle. The data indicate the predominance of additive genetic variance in the material investigated, but also suggest that nonadditive components may be important, especially for certain leaf characteristics. Inferences from the data are that development of pure lines from segregating material would, in general, be preferable to the development of F1 hybrids as a breeding procedure to produce commercial varieties. If F1 hybrids are to be used commercially for any reason, intensive development of inbreds for specific contributions to particular F1 hybrids and evaluation of combining ability could result in superior hybrids for specific situations.

Vascularization of Fern Leaves

The subject of fern leaf venation is a very old topic and it has been dealt with by many authors during the nineteenth and twentieth centuries. Most of the discussions of fern leaf venation concentrate on its qualitative aspects resulting in descriptions of various types of leaf venation. Considerably less attention has been devoted to the quantitative aspects of fern leaf vascularization. This report will give a brief summary of some of the measurable aspects of the vascular system within the leaves of certain rather common ferns. The collections of the ferns used in this study came from two sources. Those collected out-of-doors came from Giant City State Park or from Jackson Hollow, six miles northeast of Simpson, Illinois. Material was taken with the permission and under the supervision of Dr. Robert H. Mohlenbrock of Southern Illinois University. Other ferns were obtained from the Department of Botany greenhouse at the University of Nebraska. The fern leaves were studied from slides made of cross sections of the material which had been stained with Delafield's hematoxylin and safranin. Whole mounts of cleared leaves or leaflets or parts of these were also studied to obtain vein patterns and angle of branching. All measurements recorded in this study were made by means of an ocular micrometer. All those listed in Table I are averages of many separate measurements. Leaf thickness was measured at veins rather than between veins. Intervascular interval was measured from the vascular tissue of one bundle to the vascular tissue of the next adjacent bundle; thus it includes any specialized parenchyma or bundle sheath cells. Vein width includes only the width of the conductive tissues of a vascular bundle. Angle of branching refers to the branching of vascular bundles from the midvein of the leaf or segment and not to the ultimate branchings in the lamina. It was measured in linear units and the angle 87