Traditionally conservation of mega wild animals has been based on their increase in number in a given habitat. This was the basis of India's conservation strategy for tigers when their number had dwindled from 40,000 (in 1900 AD) to a mere 1872 (in 1972). The fallacy of stressing only increase in number of such animals was shattered when it was found that cheetah, a very aggressive species in Africa, is genetically only a single genotype in its entire distributional range. Such a species runs a very high risk of being wiped out of existence on account of its vulnerability to a breakout of a disease for which it may not have any resistance. Thus, the genetic-evolutionary approach to the conservation of mega-animals has become very important.

Wild life experts in India are still not convinced about the foregoing approach to conservation. They find it esoteric. However, the present author (Curr. Sci., 1997, 73, 830 -842; 1998, 74, 13 -14) stressed the need to adopt molecular approach to conservation of mega animals. In the meantime, CCMB has taken a lead in this direction. Such an approach has to be the very foundation of any long-range conservation strategy for tiger and lion.

DNA studies of Asian lion and Indian tigers done at CCMB have led to some very useful results. Mitochondrial DNA has been used to distinguish different big cats and their hybrids. The studies reveal that there has been a material contribution of African lions in hybrid populations. It is surmised that African and Asian lions diverged about 80 -100,000 years ago. These studies also revealed that in Dhudhwa tigers there are Siberian tiger alleles: Asian lion and tiger show a degree of genetic polymorphism. Corroborative studies on spermatozoa, their motility and level of testosterone have also been done. It is hoped that the importance of such studies in evolving conservation strategies will be realized and ultimately will catch the attention of wildlife experts at large.

Success in genetic-evolutionary approaches outlined above has led to another problem. The wildlife experts and animal lovers object to tranquilization of the mega animals for purposes of collecting blood samples and/or tissues or semen. They regard this as cruelty to animals. Scientists are also already locked in a controversy regarding use of laboratory animals. A problem regarding mega animals was foreseen by Khoshoo (Curr. Sci., 1998, 74, 13 -14). He suggested that instead of blood and tissues, scats (excreta) of these animals be used for purposes of estimating genetic variability by extracting DNA from the large number of epithelial cells present in scats. CCMB scientists (page 883) have already perfected a technique using DNA in epithelial cells from scats. This is truly a non-invasive method of estimating genetic vari a- bility in these animals. The DNA profiles thus prepared give us an idea about the extent and nature of genetic variability in these animals. Such data can be used to chalk out proper conservation strategies rather than base the same on mere replication of same or similar genotypes. It should now be possible to bring genetic-evolutionary considerations in the conservation of mega animals. These techniques can also be used to understand the extent and nature of genetic variability in not only endangered species but also those with disjunct, sympatric and allopatric distribution. Such simple molecular techniques also offer possibility of discovering new genetic-evolutionary and biogeographic pathways of evolution of India's flora and fauna.

T. N. Khoshoo

Planet Earth is fast approaching a celestial extravaganza with the shower of meteoroids dissipated by the short-period comet 55P/Tempel-Tuttle. This event was christened `Leonid shower' as the meteors seem to radiate from the constellation Leo. The Leonid shower of current interest has dominated the contemporary storm record with seven of them since 1799. The consistency with which it appears every 33 years and the awe-inspiring fireworks of about 1,50,000 meteors per hour recorded during its last appearance, generates a great interest among astronomers and the spacecraft owners/operators, of course with contrasting reasons.

The profuse sprinkling of the meteoroids with a relative velocity o f about 71 km/s is inevitable, when the earth plunges head-on through the d ebris track, thickened by the recent perihelion passage of the comet. The sojourn through this belt of rubbles lasts for a week's duration during 14 -20 November 1998, with the peak reserved for 17th midnight. When these particles made a heavenly descent during the last encounter (1965 -1966), it was not of much interest to the space industry as there were only few spacecraft in orbit. But, now with more than five- hundred satellites serving the humanity in different fronts, this event attracts utmost attention with the probability of satellites suffering mechanical and electrical damages from the hyper velocity meteoroid impact.

Though the probability numbers are quite low and in favour of the uninterrupted service from space, no stone is left unturned as a measure of abundant caution. ISRO, with twelve satellites operating from the Geostationary and Low Earth orbits, is gearing up for this celestial event armed with contingency plans to face any eventuality. T. Parimala Rangan et al. (page 889) provide a brief account of the phenomenon as well as a risk assessment for ISRO satellites.

S. Rangarajan

The malarial parasite spends a critical stage of its lifecycle in residence in the red blood cell (erythrocyte), which is largely a reservoir of hemoglobin. The imperative of survival dictates that the parasite must use hemoglobin as a nutrient source, breaking it down into peptides and amino acids using a cascade of proteases. Hemoglobin degradation, releases the heme cofactor, which is highly toxic in its free form. Necessity again dictates that the parasite must find a way of defusing heme toxicity to ensure its survival in the erythrocyte. Rather than use known mechanisms for heme breakdown, parasites have developed a strategy for converting heme to a novel (malarial) pigment known as hemozoin, which poses no threat to the parasite. The structure of hemozoin and the process of its formation have been active subjects of investigation. On page 911, Pandey and Chauhan review the area of heme polymerization and consider the possibility of using the process of hemozoin formation as a possible site for targetting the therapeutics of the future.

P. Balaram