Study of filament, thorax and other genes of peculiar interest in drosophila

I. "FILAiMENT" A MUTANT IN DROSOPHILA. (1). Filament forms the first dominant eggs mutation to be reported in Drosophila. As yet, no satisfact - ory means of determinigg its genotype from the study of the external morphology of the fly has been dis - covered. Like many known dominant mutations, it is lethal when homozygous. When present in the hetero zygous condition, it lowers the total fecundity of the females and the size of the eggs they produce. Its main visible effect however, is on the two filaments - causing a variable amount of their fusion and reduction in size. Hatchability tests show that aging of the females lessens the viability of the eggs produced - the older the females the less viable are their eggs. When the effect of age is practically nil, namely, during the first 3 or 4 days of laying, the viability of the Filament eggs is conditioned by the structure of the eggs. The more extreme the departure of the egg structure from the normal, the lest viable the eggs become. Viability of the eggs with no filaments is zero. (2). A comparison of the hatchability percentages with the fertility (no. of adult flies obtained) percentages as also the larger number of adult flies obtained when Filament female was fertilised by wild type male than when it is fertilised by Filament male, suggest that possibly Filament is lethal when homozygous; 51 and that the lethal effect acts probably during the larval or pupal stages. (3). The shape of the egg is not necessarily determined by the genetic possibilities of the embryo. filament flies have been obtained from apparently .normal Filament eggs. The gene for Filament is on the second ¡ chromosome. (4). A study of the fecundity and ovarian rhythm in the normal and Filament indicates the presence of a rhythm (periods of high laying with periods of little or no laying) in both; but fewer number of eggs per wave are developed in Filament. The curve for the average number of eggs produced per batch with successive waves is one of first rapid increase followed by a gradual decrease, the usual curve for egg -production. The curve for the average time taken to lay these eggs in terns of 12 -hr units with successive waves, follows on the contrary, a linear trend. These results substantiate s the assumption made by Donald and Lamy (1937) that egg -production is due to the inter -action of, two factors - one determining the number of egg- primordia formed at the apices of the egg - strings, the other, influencing the rate at which these priinordi a develop into eggs ready for fertilisation and laying. The different nature of the two curves show these factors to be independent. (5). The presence of the ovarian rhythm, lower number o eggs produced per wave and the longer time taken to lay them, point to the conclusion that the effect of Filament on egg- production, is one of lowering the normal activity of the ovary; in other words, reducing the efficiency of the mechanism of egg -production and laying. As this mechanism, as already shown, is dependent on two factors, say factor A (determing the number of eggs produced per wave) and factor B (deter mining the rate of development into ripe eggs), a cor responding repercussion in their normal rate of activity is also expected. Thus there will be a reduction in the rate of activity of the two factors. fieduction in factor A activity will lead to the production of lower number of eggs per wave; reduction in facto B activity will lead to the lowering of the rate of laying- lengthening the total period taken for laying. This has been shown to be exactly the case in Filamen. (6). The study of Filament has established at least 2 processes that went to evolve the number of filaments in insects, esp., Drosophiladae. One is "total fus and the other is "reduction" of the filaments. II. THORAX - A MUTANT IN DROSOPHILA PSEUDO-OBSCURA. A full morphological description of a new autosomal gene in Drosophila pseudo - obscura - thorax (th) - that partly overlaps wild type and affects the thorax and its appendages, along with its linkage data is given. It is found to be situated on the third chromosome, 22.4 units to the right of orange (or). III. STERILITY MUTATIONS IN DROSOPHILA MELANOGASTER. In an attempt to test Berg's hypothesis namely that there are "much more numerous sterility mutations in the X- chromosome than in the secon 1chromosome and possibly more than in all the autosomes taken together ", experiments were deviced to find out the frequency of the male "specific" (producing sterility of the males only, leaving females fertile) and female "specific" (producing sterility in the females only while leaving the males fertile) dominant sterility mutations produced in the autosomes, as these were not considered by Berg. Our results show that such dominant sterility mutations are either very rare or do not occur. Berg's original conclusion therefore, holds good. Localisation of ;S,,of the X- steriles show 5 to be located between the garnet and forked region, which lends support to Berg's suggestion that there are found in the X- chromosome, greater number of genes per unit of length of the active region, affecting sex and is in agreement with the unpublish ed data of Berg dealing with the location of 17 X- steriles

The AGN and Gas Disk in the Low Surface Brightness Galaxy PGC045080

We present radio observations and optical spectroscopy of the giant low surface brightness (LSB) galaxy PGC 045080 (or 1300+0144). PGC 045080 is a moderately distant galaxy having a highly inclined optical disk and massive HI gas content. Radio continuum observations of the galaxy were carried out at 320 MHz, 610 MHz and 1.4 GHz. Continuum emission was detected and mapped in the galaxy. The emission appears extended over the inner disk at all three frequencies. At 1.4 GHz and 610 MHz it appears to have two distinct lobes. We also did optical spectroscopy of the galaxy nucleus; the spectrum did not show any strong emission lines associated with AGN activity but the presence of a weak AGN cannot be ruled out. Furthermore, comparison of the H$\alpha$ flux and radio continuum at 1.4 GHz suggests that a significant fraction of the emission is non-thermal in nature. Hence we conclude that a weak or hidden AGN may be present in PGC 045080. The extended radio emission represents lobes/jets from the AGN. These observations show that although LSB galaxies are metal poor and have very little star formation, their centers can host significant AGN activity. We also mapped the HI gas disk and velocity field in PGC 045080. The HI disk extends well beyond the optical disk and appears warped. In the HI intensity maps, the disk appears distinctly lopsided. The velocity field is disturbed on the lopsided side of the disk but is fairly uniform in the other half. We derived the HI rotation curve for the galaxy from the velocity field. The rotation curve has a flat rotation speed of ~ 190 km/s.Comment: Paper contains 14 figures and 4 tables. Figures 8, 10 (color) and 13 supplied separately. Accepted for publication in MNRA

Studies on the interference of wings and propeller slipstreams

The small disturbance potential flow theory is applied to determine the lift of an airfoil in a nonuniform parallel stream. The given stream is replaced by an equivalent stream with a certain number of velocity discontinuities, and the influence of these discontinuities is obtained by the method of images. Next, this method is extended to the problem of an airfoil in a nonuniform stream of smooth velocity profile. This model allows perturbation velocity potential in a rotational undisturbed stream. A comparison of these results with numerical solutions of Euler equations indicates that, although approximate, the present method provides useful information about the interaction problem while avoiding the need to solve the Euler equations

Linearized potential solution for an airfoil in nonuniform parallel streams

A small perturbation potential flow theory is applied to the problem of determining the chordwise pressure distribution, lift and pitching moment of a thin airfoil in the middle of five parallel streams. This theory is then extended to the case of an undisturbed stream having a given smooth velocity profile. Two typical examples are considered and the results obtained are compared with available solutions of Euler's equations. The agreement between these two results is not quite satisfactory. Possible reasons for the differences are indicated

Preliminary observations on the biology of Chirocentrus dorab Forsk

The flourishing dorab fishery along the coasts of Palk Bay and Gulf of Mannar in Ramnad District in South India is constituted chiefly of Chirocentrus dorabJ probably the only clupeoid fish growing to a size of nearly 100 crn

A modified lifting line theory for wing-propeller interference

An inviscid incompressible model for the interaction of a wing with a single propeller slipstream is presented. The model allows the perturbation quantities to be potential even though the undisturbed flow is rotational. The governing equations for the spanwise lift distribution are derived and a simple method of solving these is indicated. Spanwise lift and induced drag distribution for two cases are computed

The Oil Sardine

In the marine fisheries map of India pelagic fishes dominated by clupeoids undoubtedly occupy an important place by virtue of the relative magnitude of their fishery. Clupeoids, in general, constitute about a third of the marine fish caught in India and within this group oil sardine {Sardinella longiceps Valenciennes) known as "Mathi" in Malayalam "Boothai" in Kannada and "Tarali" or "Haid" in Marathi, ranks first. Out of a total of 815,120 tonnes of marine fishes landed in 1965, oil sardine alone accounted for 253,302 tonnes forming 31. 69