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Schayer's Brittle Star

The species Ophionereis schayeri, more commonly known as Schayer’s Brittle Star, belongs to the Ophionereididae family. The Schayer’s Brittle Star can grow up to an average of 18 cm (7.1 inches) and resides under rocks in the rocky intertidal and coastal waters of Sydney, Victoria, South Australia, Western Australia, and Tasmania. Another name for the Schayer’s brittle star is Snake Star, due to its snake-like resemblance. This animal possesses long, flexible arms held together by muscle. Its center is gray with white spots, while its arms are black, gray, and white. Brittle stars, belonging to the same phylum as sea stars (Echinodermata), share similar feeding habits to their counterparts. Their mouths can be located on the bottom side of their bodies, and because they have only a stomach without an intestine nor an anus, waste is eliminated through the mouth as well. In order to feed, brittle stars filter detritus out from the sand and mud of the benthic zone. (Australian Museum, 2020).

           Schayer’s brittle star undergoes a process of metamorphoses throughout their life cycle, starting from planktotrophy and moving to brooded lecithotrophy. The larva of a Schayer’s brittle star is bilaterally symmetrical, with a ciliated band around the body. The next developmental form is a vitellaria larva, bordered by ciliary ridges. The vitellaria larva soon develops juvenile tube feet and ventral skeletal plates. This metamorphosis results in a full body transformation from bilateral to radial symmetrical form, the last of which resembles other members of the Echinodermata phylum. (Selvakumaraswamy & Byrne, 2004). This evolutionary adaptation from planktotrophic to lecithotrophic development can be associated with an increased maternal reliance. The lecithotrophic development evolved along with a larger egg. Both of these evolutionary adaptations led to an increase in triglyceride present in the eggs. The effect of this increase in triglyceride levels on the eggs is still currently undergoing research (Inke et al, 2006).

           A study conducted by Barker et al, examined the luminescence of Schayer’s brittle star along with another species of brittle star, the Ophionereis fasciata. The two species of brittle star were captured along the Australian coastline and observed in lab for light emission levels. The experiment used potassium chloride in order to provoke a luminescent response. For every test, Schayer’s brittle star was seen to shine brighter. The light sources found in Schayer’s brittle star were in the arm, banded and distributed throughout the ligament. The bioluminescence is produced as a warning method to predators. It is hypothesized that this behavioral phenomenon requires extra-cellular calcium, associating with the radial nerve chord in order to trigger the luminescence. The experiment indicated that the fluorescent cells of Schayer’s brittle star are photocytes, which can be found under the ventral, dorsal, and lateral arm plates. The true functional purpose of this bioluminescence has yet to be studied (Heinzeller & Nebelsick, 2004).

           The increased atmospheric CO₂ and its effects induced by climate change has affected Schayer’s brittle star and many other marine animals. The acidification and rising temperatures of the ocean has modified communities globally. As stated before, Schayer’s brittle star resides underneath rocks, these of which may cause the brittle stars to remain trapped in tide pools during low tides. These tide pools are susceptible to extreme temperatures, oxygen levels, and acidification, all of which can be deathly to those brittle stars trapped in the tide pool. Although there are some animals who are able to adjust to the novelties climate change is bringing, according to the study conducted by Christensen et al, the Schayer’s brittle star is not likely to survive these oceanic changes (Christensen et al, 2011).  

         

Literature Cited

The Australian Museum. (n.d.). Schayer’s Brittle Star. https://australian.museum/learn/animals/sea-stars/schayers-brittle-star/

Christensen, Ana B, Nguyen, Hong D, & Byrne, Maria. (2011). Thermotolerance and the effects of hypercapnia on the metabolic rate of the ophiuroid Ophionereis schayeri: Inferences for survivorship in a changing ocean. Journal of Experimental Marine Biology and Ecology, 403(1), 31–38. https://doi.org/10.1016/j.jembe.2011.04.002

Heinzeller, T., & Nebelsick, J. H. (2004). Echinoderms: Munchen: Proceedings of the 11th International Echinoderm Conference, 6-10 October 2003, Munich, Germany (1st ed.). CRC Press.

Inke Falkner, Maria Byrne, & Mary A. Sewell. (2006). Maternal Provisioning in Ophionereis fasciata and O. schayeri: Brittle Stars With Contrasting Modes of Development. The Biological Bulletin (Lancaster), 211(3), 204–207. https://doi.org/10.2307/4134542

Selvakumaraswamy, P., & Byrne, M. (2000). Vestigial Ophiopluteal Structures in the Lecithotrophic Larvae of Ophionereis schayeri (Ophiuroidea). The Biological Bulletin (Lancaster), 198(3), 379–386. https://doi.org/10.2307/1542693