student profile: Mr Mohammad Sadequr Rahman Khan


Thesis work

Thesis title: Evolution of Viviparity in marine invertebrates

Supervisors: Maria BYRNE , Camilla WHITTINGTON , Michael THOMPSON

Thesis abstract:

Matrotrophic brooding in aplacental viviparous animals involves a diverse range of maternal-fetal relationships in different phyla, and includes intragonadal lecithotrophic brooding in the Echinodermata. The evolution of viviparity requires internal fertilization and retention of offspring, but evolution of matrotrophy requires extra embryonic nutrition to be provided to offspring within mother’s body by adopting specialized physiological and morphological mechanisms. Therefore, the brooding strategy, nutrient transfer and genetic network responsible for advanced brooding require a thorough investigation to understand the evolution of reproductive strategies in invertebrates. I will describe the brooding mechanisms, gonadal morphological changes and molecules involved in evolution of viviparous matrotrophic and broadcast spawning echinoderms to understand the morphological changes associated with viviparity in sea star. In my PhD project, I aim to identify which maternal-fetal relationships evolved in a intragonadal viviparous matrotrophic invertebrate Parvulastra parvivipara. Advanced non-invasive imaging techniques (μCT), microscopy, laboratory observation and transcriptomics will be used to describe the cellular and molecular mechanisms that enable matrotrophic brooding in viviparous sea stars. Brood arrangement will be characterized by using micro-computed tomography (μCT) of the whole sea star, which has previously been applied successfully to study echinoderms in situ. Any morphological modification in the gonadal epithelial cell that may be required for viviparous larval development will be studied using Transmission Electron Microscopy. I will also locate membrane molecules in different stages of birth through immunofluorescence microscopy and western blotting to confirm the presence of specific membrane molecules in P. parvivipara. RNA-Seq will be applied to identify and quantify differences in the genes expressed in the reproductive tissues between broadcasters and viviparous sea stars. I will compare viviparous and oviparous congeners to determine whether similar mechanisms are responsible for the evolution of matrotrophy in other invertebrates.

Note: This profile is for a student at the University of Sydney. Views presented here are not necessarily those of the University.