Research Projects

Sperm flagellum is an active polymer whose motility is essential for species survival. The length of this flagellum varies widely across the biological world. Among this diversity, Drosophila, a fruit fly, stands out with the longest sperm flagellum of few millimetres which is comparable to the body size of the fly itself. In vivo, Drosophila sperm cells are often present as entangled active matter. This raises the question how such a long polymer moves within the reproductive system both as an isolated cell as well as collectively. A handful of previous studies have qualitatively established that the Drosophila sperm flagellum shows arc line waveform instead of the conventional sinusoidal waveform. Here, we propose to quantitatively measure the waveform and motility of isolated Drosophila sperm cells in vitro and collective motion of Drosophila sperm cells in-vivo within the female reproductive tract using high speed video microscopy and image analysis. We will further establish the active mechanics of these cells by measuring active forces at the ends of the flagellum as a function of end-to-end distance. We will use laser ablation to cut precise segments of sperm tail and measure how the motility changes as a function of length. Finally, we will study a few hypomorphic mutants of motility apparatus to uncover the molecular processes leading to those motility features. The outcomes of this set of experiments will lead to achieving three important goals, namely 1) quantitative understanding of motility of long insect sperm cells, 2) an experimental platform and analysis framework to monitor reproductive fitness of ecologically important insect species and 3) uncover specific roles of key motility apparatus in the process.