I wanted to find out whether the bioluminescent ability of Ctenophora helped them communicate with each other, but apparently there is not much info on it, so this is the research project I came up with for my senior English class. It'd be great if anyone could shed more light on the communication theory.
Bioluminescence and the Refraction of Light through Cilia Movement
An Expert Project in Marine Biology
October 7, 2015
Auburn High School
Word Count: 1,893
Table of Contents
GENERAL INFORMATION/ CONTEXT 3
Different types of ctenophores 3
Bodily Functions 4
In General 6
Light Colors 6
Theory of Communication 7
REFRACTION OF LIGHT 8
MORE FACTS 8
A ctenophore, also known as a comb jelly, is a simple marine organism that has the ability of bioluminescence and the ability to refract light. Bioluminescence is caused by special cells called photocytes. In those cells, a chemical reaction occurs when the specimen senses physical contact, and that chemical reaction causes the comb jelly to glow. The bioluminescence colors that ctenophores are able to create are blue, green, and red. Studies have shown that this glowing ability is used to frighten potential danger, such as predators, away, and attract meals such as plankton and other jellies. Recent studies have provided information that theorizes the possibility of communication between the species through bioluminescence; however, a lot more research is needed in order to prove that theory.
Refraction of light is when light enters a prism, thus scattering the light and creating rainbows. Ctenophores have this ability, but scientists are unsure of why. The cilia of a comb jelly acts as a prism, so when light enters the moving cilia, it scatters and makes it appear as if there are tons of tiny rainbows circulating throughout the system of the ctenophore.
Abstract Word Count: 189
Ctenophores, also known as comb jellies, are often mistaken for jellyfish, due to the fact that its species is gelatinous and, from the outside, look similar to medusa. The majority of comb jellies is almost transparent and has the ability to glow through light producing cells and/or refract light through movement of their cilia to produce a rainbow effect. It has been observed that the comb jelly uses its unique abilities as a defense tactic and a way for it to lure food. A ctenophore can ward off predators and attract prey by glowing either blue or green due to bioluminescence. There are also theories that the species is able to communicate through the light emissions, however, more studying is needed in order to completely confirm or deny this theory. Scientists have not yet come to a conclusion as to why they refract light. So, through the use of cilia and special cells, a comb jelly is able to attack prey, defend itself, and possibly communicate, all while appearing mesmerizing and majestic at the same time.
GENERAL INFORMATION/ CONTEXT
Different types of ctenophores
There isn’t a wide variety of types in the phylum ctenophore, however, with so many new species being discovered lately, it is difficult to separate the different breeds into separate subgroups and keep track of how many specific kinds there are. In general, there are only about a hundred to one hundred and fifty species which can be organized into five orders, and those five orders can be organized into two classes. These orders include Beroida, Cestida, Cydippida, Lobate, and Platyctenea (Banister). The two classes are tentaculata, which have two sticky tentacles, and nuda, which lack tentacles but have a large mouth (“Jellyfish and Comb Jellies”).
Cestida are flat, long, and are shaped like a belt, which often contributes to their more familiar name of Venus’s girdle; they have two tentacles (Figure 1). Platyctenea are often mistaken for flatworm sea slugs, because they have the same flat, bacon-like shape; although, some of them look like splats of clear gel. The Beroida species are sack-shaped and do not have tentacles, but have large mouths with which they capture prey and tightly clamp shut. Cydippida have globular bodies, and look similar to the Beroida species, but with two branched tentacles. Lobates have “two flattened lobes that extend from the typical rounded ctenophore body down below their mouths” (Ramel).
Ctenophores are best known for being the largest organism to use cilia as a means of mobility. Each one has “eight rows of plates of cilia (comb rows) whose activities serve to propel the animal” (Banister). Unfortunately, the combs are no match against the powerful currents, so ctenophores usually use the currents to guide them towards a food source within the strong courses of water and use the cilia to point them in the right direction of their meal.
They have a nearly transparent gelatinous body with muscles that aid it to harden its figure on physical impact as a defense mechanism. The basic anatomy of a ctenophore is made of two major cell layers. The outside layer is called the epidermis and contains nerve cells which are used to sense potential danger, prey, and/or fellow comb jellies. The inner layer is called the gastrodermis and contains its guts, mouth, and waste passage (Figure 2). Ctenophores that occupy the deeper open waters don’t have to endure the violence of the waves, therefore, they are extremely fragile, and scientists are unable to collect certain specimen without damaging them. Because of this, the lifespan of ctenophores is uncertain (Ramel).
All ctenophores are carnivorous and feed on two specific types of pretty, crustacean grazers and other gelatinous animals. Otherwise, they are pretty harmless, except for one species that has the ability to sting (“Jellyfish and Comb Jellies”). The Beroida class feeds on other jellies as well as other ctenophores. The Cydippida and Lobate classes are more passive and trap crustaceans in their tentacles, and then wipe the tentacles over their mouths in order to feed on their prey (Robison).
Ctenophores are unique in the aspect that they can reproduce asexually. They have a male half which releases sperm into the ocean and a female half that releases eggs into the ocean. When both are released, they float around until they find each other and combine to create a new ctenophore. They have been around for at least 500 million years, but their lifespan is unknown due to their fragility (“Jellyfish and Comb Jellies”).
Bioluminescence is the most widespread form of communication in the abysmal parts of the ocean. There are many organisms that have the ability of bioluminescence. A couple of examples are jellyfish and plankton. The majority of the ctenophore phylum has the ability to light up or glow either blue or green. The ninety percent that has the ability of bioluminescence can either be used as a way to scare of predators, or be used as a way to entice prey into their awaiting tentacles (Robison). One species, the bathyctenid ctenophore, has the ability to illuminate red (Haddock). Ctenophores can produce their glow through light-producing cells called photocytes. What’s curious about these cells, though, is that they can only be found on the male side of the species (Schnitzler).
Ctenophores swim with their mouth facing upwards, or in the direction they want to swim towards. They are sensitive to light and tilting (Banister). After some observation and experimentation, it was discovered that coastal species, usually the juveniles, glow green while oceanic species, usually the adults, glow blue. The younger ctenophores tend to glow more brightly, relative to body size, than the older ones. However, after being exposed to light for an elongated period of time, ctenophores soon lose their bioluminescence (Haddock). In a lab, it is hard to recreate the nutrients and other substances in the surrounding water which are needed by the ctenophores in order to glow (Moss).
At the deeper depths where certain ctenophores live, the only light visible is blue (Robison). This is because it has a shorter wavelength and a higher frequency than other wavelengths of the light spectrum. Since red, which has a longer wavelength and a shorter frequency than other wavelengths in the spectrum, can’t be seen in the dark deep area of the ocean, the bathyctenid ctenophore is practically invisible to predators in the area (Ramel). Because red light cannot be seen in the parts of the ocean where sunlight does not reach, comb jellies that have the ability to glow this pigment are camouflaged from predators and prey alike which aids them in their survival (Figure 3). For now, all that is known is that this special ability is used as a defense and survival tactic.
Theory of Communication
There are theories pertaining to the possibility of communication between the species through bioluminescence, however, not enough research has been conducted in order to prove this theory right or wrong. A ctenophore lacks a brain, as well as other organs typically found in more complex creatures, but past experimentation has led to a hypothesis stating that, “light production and light reception may be functionally connected in ctenophore photocytes” (Schnitzler). Based on this finding, a theory can be created which describes the possibility of communication between ctenophores based on light transmission and reception.
REFRACTION OF LIGHT
If you observe a ctenophore closely, it will look as if it has rainbows circulating through its system. That is, in fact, its cilia causing a rainbow effect through the refraction of light. These rainbows are not bioluminescence, but are caused by light refracting through the beating of a ctenophore’s eight combs of cilia (Schnitzler). Scientists are unsure of what to make of this ability. As far as anyone knows, it is just there to make them look pretty.
Surprisingly, comb jellies can be found quite frequently, however many people aren’t aware of its species and mistake them for jellyfish. At the beach, when it is dark, they can be found illuminating the shoreline in a blue haze. They can be found in the open waters as well, but may be harder to find due to their propensity to seek darker conditions. Most species enjoy warmer bodies of water, however, a smaller variety can be found near the Arctic (“Jellyfish and Comb Jellies”). Some types of ctenophores can be from less than a centimeter long to over a meter (Banister).
Ctenophores are fascinating creatures, but little is known about them. They are capable of basic functions, but use extraordinary ways to survive. Comb jellies can radiantly gleam blue, green, and red in the night due to cells specially structured for chemical reactions to occur. This protects them from potential predators and bait prey into their snares of tentacles. When they aren’t busy displaying a light show, they are scattering light by moving the cilia in their combs to create streams of rainbows within themselves. Scientists have yet to explore their full potential and whether or not they are able to communicate with each other through bioluminescence, but for now, they can be safely admired by almost anyone near warm waters and who is interested in seeing this unique creature of the ocean.
Banister, Keith Edward., and Andrew C. Campbell, eds. "Comb Jellies." The Encyclopedia of Aquatic Life. New York, NY: Facts on File, 1985. 182-83. Print.
Barathieu, G. Venus's Girdle. N.d. Tumblr, Réunion.
Griswold, R. Ctenophore off New England with Long Ciliated Tentacles. 1984.
AquaCare, Boreal Atlantic Ocean, Southern New England.
Haddock, S. H. D., and J. F. Case. "Bioluminescence Spectra of Shallow and Deep-sea Gelatinous Zooplankton: Ctenophores, Medusae and Siphonophores." Marine Biology 133.3 (1999): 571-82. Web. 25 Sept. 2015.
"Jellyfish and Comb Jellies." Smithsonian Ocean Portal. Ed. Allen Collins. The Ocean Portal Team, n.d. Web. 29 Sept. 2015.
Moss, Anthony G. "Auburn University Biology Department Tour." Personal interview. 10 Sept. 2015.
Ramel, Gordon. "The Phylum Ctenophora." Earth Life. Gordon Ramel, n.d. Web. 4 Oct. 2015.
Robison, Bruce H. "Deep Pelagic Biology." Journal of Experimental Marine Biology and Ecology 300.1-2 (2004): 253-72. Web. 25 Sept. 2015.
Schnitzler, Christine E., Kevin Pang, Meghan L. Powers, Adam M. Reitzel, Joseph F. Ryan, David Simmons, Takashi Tada, Morgan Park, Jyoti Gupta, Shelise Y. Brooks, Robert W. Blakesley, Shozo Yokoyama, Steven Hd Haddock, Mark Q. Martindale, and Andreas D. Baxevanis. "Genomic Organization, Evolution, and Expression of Photoprotein and Opsin Genes in Mnemiopsis Leidyi: A New View of Ctenophore Photocytes." BMC Biology BMC Biol 10.1 (2012): 107. Web. 25 Sept. 2015.
Dr. Stan Arington has been a great inspiration to me and is one of the main reasons I am studying Marine Biology and Geology at Auburn University today. There has been talk about Auburn City Schools shutting down his program, but many of us find that unacceptable…Continue