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Wild femaleAedes aegyptiandAe.albopictuswere allowed to lay eggs in (i) ovitraps with different concentrations of NaCl, (ii) different coloured ovistrips, (iii) water from different sources, (iv) larva holding water, and different sized ovitraps for oviposition preference. Oviposition cycle was also studied in different photoperiod regimens. The number of eggs laid was observed to gradually decrease with increase in NaCl concentration in both the species. Experiments were conducted to determine egg laying preference for any specific colour of the ovistrip and black ovistrip was found to be most preferred by both the species. For oviposition preference, eight water samples collected from different sources were used and it was observed that the maximum number of eggs was laid in ovitraps containing distilled water followed by tap water. In addition,Aedesmosquitoes laid more number of eggs in ovitraps containing larval holding water than ovitraps containing distilled water. Further, both the species did not lay any egg in the smallest used ovitrap although the number of eggs was maximally deposited in the largest ovitrap used. In the present studies, both theAedesspecies laid the maximum number of eggs in the 4th quarter of the light period with normal 12 h light and dark phases (LD 12 : 12).

The enzyme catalase breaks down H(2)O(2), a potentially harmful oxidant, to H(2)O and O(2). Besides oxidase activity, the enzyme also exhibits peroxidase activity. Therefore, it plays an important role in maintaining health and regulating pathophysiology of the organisms. However, 3D structure of this important enzyme in invertebrates particularly in crabs is not yet available. Therefore, an attempt has been made to predict the structure of the crab catalase and to envisage its catalytic interaction with H(2)O(2). A three dimensional model of crab catalase was constructed using the NADPH binding site on Beef Liver catalase from Bos taurus (PDBID: 7CAT) as template by comparative modeling approach. Backbone conformation of the modeled structure by PROCHECK revealed that more than 98% of the residues fell in the allowed regions, ERRAT results confirmed good quality of modeled structure and VERIFY3D profile was satisfying. Molecular docking has been used to know the binding modes of hydrogen peroxide with the crab catalase protein. The receptor structures used for docking were derived from molecular dynamics (MD) simulations of homology modeled structure. The docking results showed that the three important determinant residues Arg68, Val70 and Arg108 in catalase were binding with H(2)O(2) as they had strong hydrogen bonding contacts with the substrate. Our analysis provides insight into the structural properties of crab catalase and defines its active sites for binding with substrate. These data are important for further studies of catalase of invertebrates in general and that of crabs in particular.

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