User:EasyBlakeOven/sandbox

Evolution of the Eye (Emphasis on Box Jellyfish)
Hi Blake,

This is a well thought-out outline, and it is an exciting sneak peek into the article you are working on! Here are some comments on each of the sections you are proposing.

1.	The start with an evolutionary perspective from jellyfish in general, to box jelly fish to more derived visual systems provides a nice comprehensive background for why it is important to study box jelly fish eyes. 2.	What you have proposed in this section looks like it will flow nicely from the preceding section – you have set it up well! I wonder if you should save the comparison to eyes like humans for after you discuss the more in depth makeup of jellyfish visual systems. You’ll have to see how things flow when you start writing. FYI be careful saying modern, because box jelly fish eyes are also modern. I would use the terminology “more derived” meaning they have evolved later on in the tree of life) 3.	I really like the discussion of adaptations to the specific environment. This looks like it will be a very interesting section!

Overall, you have thought out a nice flow of ideas and cover a wide variety of topics that will be of interest to the general public and scientists alike. Looking forward to seeing how your article develops! (5/5)

Kasey Evol&#38;Glass (talk) 17:53, 4 March 2021 (UTC)

Outline
My overall plan is to discuss the early visual systems seen in jellyfish and then narrow down to the cubozoans (box jellyfish) and give information on their eyes and how they differ from other organisms.


 * 1) Jellyfish visual systems from an evolutionary perspective:
 * 2) Focus on general examples of jellyfish visual systems
 * 3) Transition towards discussion of box jellyfish specifically, and emphasizing their complexity in comparison to other jellyfish visual systems
 * 4) Potential common ancestor of visual systems
 * 5) References: Nilsson 2013, Hiroshi et al. 2008, Anders et al. 2010, Hiroshi et al. 2010.
 * 6) Box jellyfish eyes as a microcosm of highly evolved visual systems
 * 7) Structure of cubozoan eyes and visual systems as a whole (models and structure/function descriptions)
 * 8) More in depth makeup of jellyfish visual systems such as histology, role of opsins, crystallins, and synapses
 * 9) Multiple photosystems
 * 10) Touch on comparison to more derived eyes such as humans
 * 11) Jellyfish eyes as Evo/Devo model of all eyes
 * 12) References: Nilsson et al. 2005, Gray et al. 2009, Berger 1898, Piatigorsky et al. 1989, Piatigorsky et al. 2004, O' Connor et al. 2009, Hiroshi et al. 2008, Anders et al. 2010
 * 13) Evolution of jellyfish eyes in response to environmental stimuli
 * 14) Discussion of the significance of blurred vision
 * 15) Comparing niche specialization of different species of box jellyfish to thrive in their natural habitat
 * 16) Pupillary responses to light and its underpinnings
 * 17) Dark/light adaptation
 * 18) References: Nilsson et al. 2005, Seymour et al. 2020, O' Connor et al. 2009, Anders et al. 2010.

Peer Review
Hey Blake, so, uh, wow. I'm not going to lie, I may or may not be a little concerned about the length of my own article after reading yours. I was really impressed by how in-depth you went on jellyfish visual organs and how much you had to say on the subject.

Throughout your article, you use the terms box jellyfish and cubomedusae interchangeably. I would suggest choosing one and sticking with it throughout the article to prevent confusion. I would also recommend placing more emphasis on the results of the research that was used rather than the process of the experiment, since the results are what the readers would be looking at for information, whereas the process is more individual to the specific experiment used.

On a smaller note, I would suggest adding a diagram or two, especially at the parts where you are discussing the structure of the jellyfish eye. I was unable to picture what you were discussing in my head, and as a result it didn’t make much sense to me as someone with no previous experience with jellyfish anatomy. I also noticed that in several places throughout the article there are phrases like ‘it is believed/argued’ and ‘it is evident’ which can imply a level of uncertainty of validity and bias respectively. I would recommend removing those phrases entirely unless uncertainty is a notable aspect of the subject in question.

-Hannah

Evolution of the Jellyfish Eye
The study of jellyfish eye evolution is an intermediary for a better understanding of how visual systems evolved on Earth. Ranging from photoreceptive cell patches seen in simple photoreceptive systems to more highly derived complex eyes seen in box jellyfish, jellyfish exhibit immense variation in visual systems across multiple evolutionary stages. Major topics of jellyfish visual system research (with an emphasis on box jellyfish) include: jellyfish vision in an evolutionary sense (covering the evolutionary steps towards more complex visual systems), box jellyfish eye morphology and molecular structures (including how they compare to more derived eyes seen in organisms such as vertebrates), and the implications of vision including task guided behaviors and niche specialization as a result of visual/environmental stimuli.

Jellyfish Visual Systems from an Evolutionary Perspective
Experimental evidence for photosensitivity and photoreception in cnidarians antecedes the mid 1900’s, and research has provided further insight into the evolution of visual systems in jellyfish. Jellyfish visual systems range from simple photoreceptive cells to complex eyes. More ancestral visual systems incorporate extraocular vision (vision without eyes) that encompass numerous single function behaviors. More derived visual systems comprise perception that is capable of multiple task guided behaviors.

Although they lack a true brain, cnidarian jellyfish have a “ring” nervous system that plays a significant role in motor and sensory activity. This net of nerves is responsible for muscle contraction and movement, and culminates the emergence of photosensitive structures. Across Cnidaria, there is large variation in the systems that underlie photosensitivity. Photosensitive structures range from non-specialized groups of cells, to more “conventional” eyes similar to those of vertebrates. Intricacy of jellyfish visual systems gradually evolved in response to natural selection. These selective pressures favor high-resolution vision in response to changes in habitats and task complexity. The general evolutionary steps to develop complex vision include (from more ancestral to more derived states): non-directional photoreception, directional photoreception, low-resolution vision, and high-resolution vision.

Basal visual systems observed in various cnidarians exhibit photosensitivity representative of a single task or behavior. An example of this is extraocular photoreception (a form of non-directional photoreception), which serves as the most basic form of light sensitivity for organisms and guides a variety of behaviors among cnidarians. It can function to regulate circadian rhythm (as seen in eyeless hydrozoans), positive phototaxis, and other light-guided behaviors. Extraocular photoreception in cnidarians allows for them to be influenced by ambient forms of light that create rhythmic contractions in their bodies that vary based on the intensity and spectrum of the light. These contractions create movements that assist in spawning events timed by moonlight, as well as shadow responses for potential predator avoidance. Extraocular photoreception can function in daily rhythms (as seen in eyeless hydrozoans) and positive phototaxis (movement toward light as seen in planula larva of hydrozoans). Extraocular systems can also be witnessed in organisms that use photoreception to avoid harmful amounts of UV radiation. Light-guided behaviors are additionally observed in numerous scyphozoans including the common moon jelly, Aurelia aurita, which migrates in response to changes in ambient light and solar position even though they lack proper eyes. The aforementioned cnidarians are representative of directional photoreception (ability to perceive direction of incoming light) which allows for phototaxis responses to light, and likely evolved by means of membrane stacking.

In more highly derived cnidarians, like cubomedusae (box jellyfish), more complex visual systems are responsible for guiding multiple tasks or behaviors. These behaviors include phototaxis based on sunlight (positive) or shadows (negative), obstacle avoidance, and control of swim-pulse rate. The significant difference between box jellyfish visual systems and lesser derived ones is the ability to conduct multiple task-guided behaviors within one system and not be limited to a single function. Box jellyfish lie in the category of low-resolution vision, which represents the most basic form of true vision in which multiple directional photoreceptors combine to create the first imaging and spatial resolution. This is different from the high-resolution vision that is observed in camera or compound eyes of vertebrates and cephalopods that rely on focusing optics.

Though they have significantly more complex visual systems and eyes in comparison to other cnidarians, it is important to consider how box jellyfish eyes stand on an evolutionary scale. Box jellyfish are representative of low-resolution vision because they possess “proper eyes” (similar to vertebrates) that allow them to inhabit environments that lesser derived medusae cannot, and are considered the only class in the clade Medusozoa that have behaviors necessitating spatial resolution and genuine vision. Box jellyfish are not considered to have high-resolution visual systems because the lens in their eyes are more functionally similar to cup-eyes exhibited in low-resolution organisms, and have very little to no focusing capability. This is due to the focal length exceeding the distance to the retina, meaning that box jellyfish eyes produce considerably unfocused images along with poor spatial resolution. Though this would not be ideal in even higher task oriented (more derived organisms such as vertebrates) eyes, it is sufficient for box jellyfish in fulfilling its role in producing an image that helps with tasks such as object avoidance.

Box Jellyfish Eye as a Microcosm of Highly Evolved Visual Systems
Box jellyfish eyes are a visual system that is sophisticated in numerous ways. These intricacies include the considerable variation within the morphology of box jellyfishes' eyes (including their task/behavior specification), and the molecular makeup of their eyes including: photoreceptors, opsins, lenses, and synapses. The comparison of these attributes to more derived visual systems can allow for a further understanding of how evolution may have occurred, and puts into perspective how box jellyfish can play the role as an evolutionary/developmental model for all visual systems.

Box Jellyfish Visual Systems Overview
Though they are less derived than those seen in vertebrates, box jellyfish visual systems are both diverse and complex. This diversity is seen within box jellyfish visual systems because they comprise multiple photosystems. It is important to consider that variances in visual properties exist between species of box jellyfish given that their eyes tend to differ in size and shape, along with number of receptors (including opsins), and physiology.

Box jellyfish have multiple photosystems that comprise of different sets of eyes. Subsets of box jellyfishes' 24 eyes are each specific to a different task. Evidence includes immunocytochemical and molecular data that show photopigment differences among the different morphological eye types, and physiological experiments done on box jellyfish to suggest behavioral differences among photosystems. Each individual eye type constitutes a different photosystem that ultimately controls separate visually guided behaviors. The ability for these organisms to exhibit extraocular photoreception is representative of another photosystem in of itself.

Box jellyfish have a series of intricate lensed eyes that are similar to those of more derived multicellular organisms such as vertebrates. Their 24 eyes fit into four different morphological categories. These categories consist of two large, morphologically different medial eyes (a lower and upper lensed eye) containing spherical lenses, a lateral pair of pigment slit eyes, and a lateral pair of pigment pit eyes. The eyes are situated on rhopalia (small sensory structures) which serve sensory functions of the box jellyfish and arise from the cavities of the exumbrella (the surface of the body) on the side of the bells of the jellyfish. The two large eyes are located on the mid-line of the club and are considered complex because they contain lenses. The four remaining eyes lie laterally on either side of each rhopalia and are considered simple. The simple eyes are observed as small invaginated cups of epithelium that have developed pigmentation. The larger of the complex eyes contains a cellular cornea created by a monociliated epithelium, cellular lens, homogenous capsule to the lens, vitreous body with prismatic elements, and a retina of pigmented cells. The smaller of the complex eyes is said to be slightly less complex given that it lacks a capsule but otherwise contains the same structure as the larger eye.

Box jellyfish eyes primarily use c-PRCs (ciliary photoreceptor cells) similar to that of vertebrate eyes. These cells undergo phototransduction cascades (process of light absorption by photoreceptors) that are triggered by c-opsins. Available opsin sequences suggest that there are two types of opsins possessed by all cnidarians including an ancient phylogenetic opsin, and a sister ciliary opsin to the c-opsins group. Box jellyfish could have both ciliary and cnidops (cnidarian opsins), which is something not previously believed to appear in the same retina. Nevertheless it is not entirely evident whether cnidarians possess multiple opsins that are capable of having distinctive spectral sensitivities.

Box Jellyfish Visual Systems Comparatively
Significant research has gone into the genetic and molecular makeup of box jellyfishes' eyes and how they compare to more derived eyes seen in vertebrates and cephalopods. The primary focuses of this research include: lenses and crystallin composition, synapses, and Pax genes and their implied evidence for shared primordial (ancestral) genes in eye evolution.

Although the structure of the lenses of box jellyfish appears very similar to those of other organisms, the crystallins are very different in both function and appearance. The large lens of Carybdea marsupialis box jellyfish contained two crystallin polypeptide bands with molecular masses of 20000 and 35000 daltons, while Tripedalia cystophora have three bands with two masses of 20000 and one of 35000 daltons. T. cystophora are deficient in lower molecular weight proteins in comparison to the other species. Weak reactions were seen within the sera and there were very weak sequence similarities within the crystallins among vertebrate and invertebrate lenses. This is likely due to differences in lower molecular weight proteins and the subsequent lack of immunological reactions with antisera that other organisms’ lenses exhibit.

Identification of the synapses and their characteristic differences were witnessed among four box jellyfish species (Carybdea marsupialis, Chiropsalmus quadrumanus, Tamoya haplonema and Tripedalia cystophora). All four species have invaginated synapses, but only in the upper and lower lensed eyes. Density measurements suggest that there are differences between the upper and lower lenses, and between species. Four types of chemical synapses have been discovered within the rhopalia which could help in understanding neural organization including: clear unidirectional, dense-core unidirectional, clear bidirectional, and clear and dense-core bidirectional. The synapses of the lensed eyes could be useful as markers to learn more about the neural circuit in box jellyfish retinal areas.

Box jellyfish eyes are said to be an evolutionary/developmental model of all eyes based on their evolutionary recruitment of crystallins and Pax genes. Research done on box jellyfish including Tripedalia cystophora has suggested that they possess a single Pax gene, PaxB. PaxB functions by binding to crystallin promoters and activating them. PaxB in situ hybridization resulted in PaxB expression in the lens, retina, and statocysts. These results and the rejection of the prior hypothesis that Pax6 was an ancestral Pax gene in eyes has lead to the conclusion that PaxB was a primordial gene in eye evolution, and that it is highly likely that all eyes share a common ancestor.

Evolution of Box Jellyfish Eyes in Response to Environmental Stimuli
It is probable that certain box jellyfish species’ eyes evolved to have lesser focused vision as an evolutionary response to their habitat. The primary responses to environmental variation observed in box jellyfish eyes include pupillary constriction speeds in response to light environments, as well as photoreceptor tuning and lens adaptations to better respond to shifts between light environments and darkness.

Pupillary contraction appears to have evolved in response to variation in the light environment across ecological niches. Three species of box jellyfish (Chironex ﬂeckeri, Chiropsella bronzie, and Carukia barnesi) were used to compare pupillary responses to light. The pupils of Ca. barnesi contracted most rapidly, followed closely by ''Ch. fleckeri, and lastly Ch. bronzie'' which contracted the slowest when exposed to direct sunlight. The same pattern was suggested for each of the light intensities within each species. The variation of pupillary contraction between the differing species lies in the ecological niches of the species. ''Ch. bronzie'' inhabit shallow beach fronts that have low visibility and very few obstacles, meaning faster pupil contraction in response to objects in their environment is not of much importance. Ca. barnesi and ''Ch. fleckeri'' are found in more three dimensional environments and mangroves with an abundance of natural obstacles, so pupil contraction is more significant in order to thrive in their natural habitats. Niche specialization is further supported by ''Ch. bronzie'' displaying poor ability to avoid obstacles in a simulated light environment with natural conditions, while the other two species rarely came in contact with any obstacles.

Light/dark adaptation via pupillary light reflexes is an additional form of an evolutionary response to the light environment. This adaptation relates to the pupillary response to switches between light intensity (generally from sunlight to darkness). In the process of light/dark adaptation, the upper and lower lens eyes of different box jellyfish species vary in specific function. The lower lens-eye contains pigmented photoreceptors and long pigment-cells with dark pigments that migrate on light/dark adaptation, while the upper-lens eye play a much more significant role in light direction and phototaxis given that they face upward towards the water surface (towards the sun or moon). Considering ''Ch. bronzie and Tr. cystophora (a box jellyfish species that tends to live in mangroves), the upper lens of Ch. bronzie does not exhibit any considerable optical power while Tr. cystophora'' does. This suggests that the ability to use light to visually guide behavior is not of as much importance to ''Ch. bronzie'' as it is to species in more obstacle filled environments. Such differences in visually guided behavior serves as evidence that species that share the same number and structure of eyes can exhibit differences in how they control behavior.