Scientists at the Marine Biological Laboratory (MBL) in Falmouth, Massachusetts, USA, have identified sea stars (also known as starfish) as perfect candidates to investigate the processes behind organ development.
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In a study published in the journal Discover Developmental Biology, Margherita Perillo and her colleagues at the MBL looked closely at the Forbes sea star (Asterias forbesi). It’s found in shallow waters of the North Atlantic Ocean, from Maine to the Gulf of Mexico.
Despite being extensively studied for over 70 years, the embryonic and larval development of this sea star hasn’t been clearly described until now.
Many species of sea star develop a hollow tube during the larval stage that expands like a balloon, and acts as precursor to their later organs. Perillo and her team have named this the hydro-vascular organ (HVO).
To find out whether different species build the HVO the same way, the researchers tracked its formation in the Forbes sea star (Asterias forbesi), as well as the bat sea star (Patiria miniata) and the red comb sea star (Astropecten aranciacus).
Sea stars are among the closest invertebrate relatives to humans as fellow deuterostomes: organisms where the first opening in the embryo develops into the anus, while the mouth develops second.
And we share one crucial trait with them: our heart, lungs and kidneys begin as simple tubes during embryonic development. One important difference is that sea stars’ bodies stay nearly transparent through their larval stage, offering a rare look at how the process unfolds. The HVO itself starts as a small tube, then elongates, branches and expands before reaching the final shape.
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Diverging paths
The development of the HVO differs across different species of sea stars. Forbes sea stars extend their tube toward the stomach first, only fusing it into a loop over the mouth later. Bat sea stars work in the opposite order, sealing the first tubal connection early before the tube grows on toward the stomach. Red comb stars take a third path, fusing their tubes near the intestine before the rest of the structure follows.
Yet despite taking these different routes, all three species arrive at a HVO of strikingly similar shape, making the sea star a useful model.
Perillo says the next step for her lab is to understand “how we form organs starting from tubes, how these tubes maintain their proper orientation and shape and – once you have a fully grown, functional organ – how to prevent fibrosis in it.”
Read the full findings here.
Top image credit: Paul Morris from USA, CC BY-SA 2.0, via Wikimedia Commons
