The Ancient Asexual Reproductive Strategy of the Six-Armed Brittle Star

The fossil record of planet Earth is a treasure trove of information that stretches across vast expanses of time. Each fossil serves as a snapshot in time, capturing the moment when a living organism was buried and slowly turned to stone. In a recent discovery in Germany, scientists have unearthed a remarkable fossil of a six-armed brittle star in the midst of regenerating one half of its body. This unique find sheds light on the evolutionary roots of asexual reproduction in star-shaped echinoderms.

The fossil of the six-armed brittle star, known as Ophiactis hex, was excavated in 2018 from a limestone deposit in southern Germany. The area, once a deep lagoon teeming with coral meadows and sponge beds, is now a fossil garden filled with remnants of ancient creatures from the late Jurassic period. This particular specimen of Ophiactis hex is the first of its kind and has been identified as a new species of brittle star by scientists.

Many modern-day brittle stars and some starfish engage in a reproductive process called fissiparity, where the organism splits in half and regrows its missing parts. This method of reproduction, also known as clonal fragmentation, results in two identical clones of the original organism. While fissiparity is observed in various lineages of starfish and brittle stars, its evolutionary origins have remained largely unknown. The six arms on stars that reproduce through fissiparity are believed to facilitate an even split during reproduction.

The fossil of Ophiactis hex, dated to 155 million years old, provides compelling evidence that clonal fragmentation in star-shaped echinoderms dates back to ancient times. This discovery challenges previous assumptions about the history of asexual reproduction strategies in echinoderms. The well-preserved fossil clearly shows the hook-shaped arm spines of the brittle star, offering a glimpse into its ancient reproductive process.

While fossils of ophiuroids with individual regenerating arms are relatively common, instances of organisms with regenerating body halves are exceedingly rare. The specimen of Ophiactis hex is only the second known case of a fossil displaying regenerative properties tied to six-fold symmetry and clonal fragmentation. This discovery highlights the importance of studying ancient fossils to unravel the mysteries of evolutionary history.

Despite the significance of the discovery of Ophiactis hex, researchers acknowledge that much remains unknown about this ancient species. With only one specimen found so far, it is impossible to determine the appearance of the species before it engaged in clonal fragmentation. The scarcity of fossils displaying ancient reproduction in brittle stars underscores the need for continued research in paleontology to further our understanding of evolutionary processes.

The fossil of Ophiactis hex offers a rare glimpse into the ancient asexual reproductive strategy of the six-armed brittle star. This remarkable discovery sheds light on the deep evolutionary roots of clonal fragmentation in star-shaped echinoderms and underscores the importance of studying fossils to unravel the mysteries of Earth’s history.