Morphology and Morphometry of Aedes aegypti Larvae
Ananya Bar *
Department of Zoology and School of Entomology, St. John's College, Agra, 282002, India.
J. Andrew
Department of Zoology and School of Entomology, St. John's College, Agra, 282002, India.
*Author to whom correspondence should be addressed.
Abstract
Aims: To observe the morphology of the larva of A. aegypti in detail and to evaluate their morphometry.
Place and Duration of Study: Place – St. John’s College, Agra. Duration – June, 2011 to May, 2012.
Methodology: Morphology of larval head, antennae, compound eyes, median brush (palatum), lateral brush; neck; thorax; abdomen, comb spine, siphon, siphon teeth and anal papillae were observed and photographed under an image documentation system and their size (length/width) measured by using image J software for morphometric study. Dyar’s rule was also applied to see the increase in width of head, neck, thorax and abdomen of A. aegypti larvae.
Results: Morphology and morphometry of various instars of Aedes aegypti (dengue vector) larvae collected from Agra city were studied. Larval key characters of head, antenna, compound eye, palatum, lateral brush, neck, thorax, abdomen, comb spine, siphon, pecten teeth and anal papilla are studied by morphometry. The head capsule grows in size (length/width) to attain globular shape. The width of head, neck, thorax and abdomen were measured and the Dyar’s rule was applied to find out the growth rate. The width of the head doesn’t follow the Dyar’s rule. The factors between I-II, II-III and III-IV larval instars increase by a constant factor. The increase in size of antennae, compound eye, median and lateral brush of larvae in every instar of larval development were observed. In A. aegypti larvae the size of the neck, thorax and abdomen were also studied. The number of comb spine varied from 4.4 -10.6 from I-IV instar. The mode in I instar stage is 4 and from II-IV instar is 10. In the respiratory siphon of A. aegypti larvae the ratio of its length and width measure approximately less than the double of its width. The number of pecten teeth and their length increase in each instar. Four anal papillae increase in length and width during larval development.
Conclusion: This study reveals the morphologic features of A. aegypti larvae in Agra for better understanding of the key characters.
Keywords: A. aegypti, dengue vector, morphology, morphometry