Late Larval Development and Onset of Symbiosis in the Scleractinian Coral Fungia scutaria by JODI A. SCHWARZ, DAVE A. KRUPP, AND VIRGINIA M. WEIS.
Schwarz, Jodi & Krupp, Dave & Weis, Virginia. (1999). Late Larval Development and Onset of Symbiosis in the Scleractinian Coral Fungia scutaria. Biological Bulletin. 196. 10.2307/1543169.
This study looked at how larval development in the coral Scleractinian affected the adoption of zooxanthellae, also known as dinoflagellates. Throughout their testing, they found that even with adding brine shrimp into the tanks larval were able to adopt zooxanthellae once a mouth was developed. This is because the coral was born azooxanthellate meaning they did not come with any zooxanthellae and the only way to adopt zooxanthellae is through the mouth because it is absorbed in the gastric cavity where it is then consumed by endodermic cells. A note to be had is that the coral would consume any particulate including brine shrimp and the zooxanthellae, but when brine shrimp were present there was a higher proportion of larvae that were infected by the dinoflagellates. Another interesting find from their experiment was that the consumption of zooxanthellae may have caused the larvae to mature into a polyp acting as a “settlement cue.”
The specimens were obtained from breeding 75 adult specimens from Hawaii. To obtain the zooxanthellae they were washed off from F. scutaria and then separate using a centrifuge. The brine shrimp were obtained from frozen Artemia and then put through a mess. It would be interesting to see if live brine shrimp would cause a change in the development of the larvae since the brine shrimp would be moving. To researches then made 3 out of 9 groups brine shrimp fed either kept the feeding mixture in for 4 hours or 24 hours. To see the introduction of particulars into the larvae they used electron microscopy and light micrographs. This was done over a 10 to 14 day period.
During the introduction, the paper mentions that the host gives the symbiont nutrients but never specifies or cites a paper that mentions what type of nutrients. Granted this may be not applicable for this paper but this may give more information into the relationship between symbiont selection as it may have to give different nutrients or all the same nutrients. The paper does mention little is known about the mechanisms of infection of the initial symbiosis and today this is still a bit foggy but the Guse Lab has helped provide a more genetic/molecular understanding behind this.
This paper gave plenty of information into the cnidarian and Symbindium symbiotic relationship as well as how cnidarians mature. It first distinguished that animals like Scleratinian Coral and Aiptasia are bornt without algae and it through an idea where the symbionts a re transferred horizontally, picked up through the environment, rather than vertically, born with the algae. It then detailed how different methods the zooxanthellae could be adopted First is through the embryo, second is through the ectoderm and then the endoderm, and finally is through the mouth and then phagocytosed by endodermal cells in the gastric cavity. The paper also mentioned an interesting point that settlement may not be a favorable mode for the cnidarians as the larvae are typically not exposed to food which only comes in small bits of animal issues. You can see how the health of the organism is altered when put in an environment where settlement is not allowed (such as bubbled walls.) The paper also addressed an idea that needs to be kept in mind when designing experiments is that until the specimen develops its mouth it cannot obtain dinoflagellates or brine shrimp and therefore if over looked could be a confounding factor. To have naturally occurring zooxanthellae the “[c]nidarians hosts can expel mucus containing high concentrations of zooxanthellae.” Which might be good to know when designing experiments.