Rädecker, N., Chen, J.E., Pogoreutz, C. et al. Nutrient stress arrests tentacle growth in the coral model Aiptasia. Symbiosis 78, 61–64 (2019). https://doi.org/10.1007/s13199-019-00603-9
This group of researchers was able to identify and induce a “Wurst” phenotype in Aiptasia. This phenomenon is caused by either A) lack of water change or B) lack of feeding. It is called Wurst due to the lack of tentacles and elongated body mimicking a sausage. They found that only non-adult Aiptasia would inhibit the “Wurst” phenotype but when the adult Aiptasia produced asexual offspring the offspring did not feature any tentacles. The cause for the difference is hypnotized that the reason why adults keep their tentacles is that they can self regulate their nitrogen content while younger Aiptasia cannot. The exit causes for this are still largely unknown and this study mainly collected observational-based data; however, alongside this observational state, the Aiptasia does not appear to be less healthy.
To set up the experiment they had a 10L mesocosm with live rock and autoclaved seawater from the Red Sea. I believe that using live rock might cause different results due to the minerals in the rock; however, this still sent the “Wurst” phenotype. Prior to experimentation they had a 3 month control period of weekly feeding with brine shrimp and exchanging of the water. In addition, the climate setting was a 12 h: 12 h light/dark cycle kept at 25C and between 30-35 salinity. To determine the “wurst” state they measure the ratio of the stalks length to the diameter of the oral disk which is the top side of the Aiptasia when the polyp was fully relaxed. This does add some ambiguity to the experiment since the Aiptasia is a very non-rigid animal but is probably the best given the circumstances. While conducting the experiment there were 3 main groups. One group was fed and watch changed another was only fed and the last only had water changed
The “Wurst” phenotype does not make sense because if the Aiptasia lacks nutrients then would it not be more advantageous to keep the tentacles to grab any possible nutrients drifting in the water rather than going into an almost vegetative state where it cannot grab nutrients. In this state, it does retain its symbiosis relationship so it may be more energy-expensive to have the tentacles outward than inward. The only issue with going into this state is that as the paper mentioned the symbionts do not give help obtain nitrogen so they nitrogen especially in non-adult specimens. The researchers also did not isolate the various trace minerals, such as ammonium, nitrate, nitrogen dioxide( which I believe they called nitrate?) phosphate, and silica. Isolating these nutrients could give a more accurate view into what causes this “wurst phenotype.”
This paper provided a potential research idea into looking at what causes the ‘wurst’ phenotype to initiate. Specifically which nutrients are the result of this. It also gave insight into which minerals/nutrients to look for in the study since when they were all of the mentioned nutrients above present. The paper also mentions scleractinian coral which was used in my previous paper as being an ecosystem engineer which helps give greater context to the anemones.