Cephalopod Eyes and Light Sensing Skin

[DWhatley]

Pioneering studies on cephalopod’s eye and vision at the Stazione Zoologica Anton Dohrn (1883-1977)
Ariane Dröscher 2016 (full provisional article)

From the late nineteenth century onwards, the phenomena of vision and the anatomy and physiology of the eye of marine animals induced many zoologists, ethologists, physiologists, anatomists, biochemists, and ophthalmologists to travel to the Zoological Station in Naples. Initially, their preferred research objects were fish, but it soon became evident that cephalopods have particular features which make them particularly suited to research. After the first studies, which outlined the anatomical structure of cephalopods’ eyes and optic nerves, the research rapidly shifted to the electrophysiology and biochemistry of vision. In the twentieth century these results were integrated with behavioral tests and training techniques. Between 1909 and 1913 also the well-known debate on color vision between ophthalmologist Carl von Hess and zoologist Karl von Frisch took place in Naples. Largely unknown is that the debate also concerned cephalopods. A comparative historical analysis of these studies shows how different experimental devices, theoretical frameworks, and personal factors gave rise to two diametrically opposing views.

 

[DWhatley]

Color Richness in Cephalopod Chromatophores Originating from High Refractive Index Biomolecules
Sean R. Dinneen†, Richard M. OsgoodIII‡, Margaret E. Greenslade†, Leila F. Deravi 2016 (subscription The Journal of Physical Chemistry Letters)

Abstract

Cephalopods are arguably one of the most photonically sophisticated marine animals, as they can rapidly adapt their dermal color and texture to their surroundings using both structural and pigmentary coloration. Their chromatophore organs facilitate this process, but the molecular mechanism potentiating color change is not well understood. We hypothesize that the pigments, which are localized within nanostructured granules in the chromatophore, enhance the scattering of light within the dermal tissue. To test this, we extracted the phenoxazone-based pigments from the chromatophore and extrapolated their complex refractive index (RI) from experimentally determined real and approximated imaginary portions of the RI. Mie theory was used to calculate the absorbance and scattering cross sections (cm2/particle) across a broad diameter range at λ = 589 nm. We observed that the pigments were more likely to scatter attenuated light than absorb it and that these characteristics may contribute to the color richness of cephalopods.

 

[DWhatley]

Testing the Optomotor Response in Sepia bandensis
Lauren Thompson 2017 Honors Thesis Georgia Southern University (full PDF)

ABSTRACT Cephalopods (octopus, squid, and cuttlefish) have commonly been used as models to test visual function and camouflage due to their similarity in eye morphology with humans and because of their readily observable changes in body color in response to visual stimuli. Most studies have used a single species, Sepia officinalis, to make broad conclusions about camouflage and vision. However, these generalizations may not be applicable to all species. Here, I have examined visual function of the dwarf cuttlefish (Sepia bandensis), which differs from S. officinalis in habitat, geographic range, and size. Using the optomotor response, I quantified the minimum separable angle (MSA) of resolution, a behavioral measure of visual acuity, by recording cuttlefish movement in response to rotating black and white stripes of decreasing stripe width. The threshold of visual acuity for these experiments was a stripe width of 5mm and a MSA of 3.76°. These results indicate that S. bandensis has poorer visual acuity than S. officinalis (MSA 0.57°), and therefore, may be less able to resolve fine details in the environment. The ability to perceive these fine details enables animals to navigate, forage, and communicate with conspecifics. Future work should examine the behavioral ecology of S. bandensis to understand the biological and physical environmental context in which visual cues are used by this species.

 

[DWhatley]

Visual ecology and the development of visually guided behavior in the cuttlefish
Anne-Sophie DARMAILLACQ, Nawel Mezrai, Caitlin E. O'Brien, Ludovic Dickel 2017(subscription Frontiers inf Physiology)

Cuttlefish are highly visual animals, a fact reflected in the large size of their eyes and visual-processing centers of their brain. Adults detect their prey visually, navigate using visual cues such as landmarks or the e-vector of polarized light and display intense visual patterns during mating and agonistic encounters. Although much is known about the visual system in adult cuttlefish, few studies have investigated its development and that of visually-guided behavior in juveniles. This review summarizes the results of studies of visual development in embryos and young juveniles. The visual system is the last to develop, as in vertebrates, and is functional before hatching. Indeed, embryonic exposure to prey, shelters or complex background alters postembryonic behavior. Visual acuity and lateralization, and polarization sensitivity improve throughout the first months after hatching. The production of body patterning in juveniles is not the simple stimulus-response process commonly presented in the literature. Rather, it likely requires the complex integration of visual information, and is subject to inter-individual differences. Though the focus of this review is vision in cuttlefish, it is important to note that other senses, particularly sensitivity to vibration and to waterborne chemical signals, also play a role in behavior. Considering the multimodal sensory dimensions of natural stimuli and their integration and processing by individuals offer new exciting avenues of future inquiry.

 

[DWhatley]

Vision in Cephalopods Frontiers research collection 2018 Ebook available

This Research Topic is aimed to focus on current advances in the knowledge of cephalopod vision. It is designed to facilitate merging questions, approaches and data available through the work of different researchers working on different aspects of cephalopod vision. Thus the research topic will create mutual awareness, and will facilitate the growth of a field of research with a long tradition - cephalopod vision, visual perception and cognition as well as the mechanisms of camouflage.

 

[DWhatley]

Vision and Bioluminescence in Cephalopods
Thomas, Kate Nicole 2018 (dissertation Duke University)

In the deep pelagic ocean, there are no structures to serve as hiding spots, and visual interactions among animals are potentially continuous. The light environment in the midwater habitat is highly structured due to light scattering and absorption. Downwelling sunlight becomes exponentially dimmer, bluer, and more diffuse with depth. This optical structure means that an animal’s depth and viewing direction greatly affect the distances at which it can see visual targets such as potential prey or approaching predators. Additionally, this light environment mediates the visibility of bioluminescent camouflage and signals. My dissertation examines how the midwater light environment affects the ecology and evolution of vision and bioluminescence through an examination of cephalopods, a highly visual group that exhibits a broad diversity of eye adaptations and multiple evolutions of bioluminescence. My research investigates (1) vision and behavior in a deep-sea squid with dimorphic eyes, (2) depth-dependent patterns in cephalopod eye size and visual range, and (3) evolutionary dynamics in bioluminescent cephalopods.

 

[DWhatley]

Polarisation signals: a new currency for communication
N. Justin Marshall, Samuel B. Powell, Thomas W. Cronin, Roy L. Caldwell, Sonke Johnsen, Viktor Gruev, T.-H. Short Chiou, Nicholas W. Roberts, Martin J. How

ABSTRACT
Most polarisation vision studies reveal elegant examples of how animals, mainly the invertebrates, use polarised light cues for navigation, course-control or habitat selection. Within the past two decades it has been recognised that polarised light, reflected, blocked or transmitted by some animal and plant tissues, may also provide signals that are received or sent between or within species. Much as animals use colour and colour signalling in behaviour and survival, other species additionally make use of polarisation signalling, or indeed may rely on polarisation-based signals instead. It is possible that the degree (or percentage) of polarisation provides a more reliable currency of information than the angle or orientation of the polarised light electric vector (e-vector). Alternatively, signals with specific e-vector angles may be important for some behaviours. Mixed messages, making use of polarisation and colour signals, also exist. While our knowledge of the physics of polarised reflections and sensory systems has increased, the observational and behavioural biology side of the story needs more (and more careful) attention. This Review aims to critically examine recent ideas and findings, and suggests ways forward to reveal the use of light that we cannot see.

 

[DWhatley]

The Extraordinary Secret of Cephalopod Vision
2016 article by Ines Dawson

 

[DWhatley]

Octopuses Can Feel Light with Their Arms Live Science

Octopuses can "see" light with their arms, even when their eyes are in the dark, researchers have found. When the arms of the octopus detect light, the eight-armed creature pulls them close to their body.

Because octopuses generally have a poor sense of where their body is in space, this complex instinctive behavior might help protect their arms from the pincers of predators nearby that they might otherwise not sense.

Scientists have long known that octopus arms react to light. Their skin is covered in pigment-filled organs called chromatophores that reflexively change color when exposed to light. These chromatophores are responsible for the octopus's color-changing camouflage superpowers. In fact, it was while studying these light-induced chromatophore responses that Tal Shomrat and Nir Nesher of the Ruppin Academic Center in Israel noticed something odd. ...

 

[Feder]

Heard that we could observe octopuses with red lights without being noticed. Is there any research basis for the statement that octopuses can‘t sense red light?

 

[pkilian]

Is there any research basis for the statement that octopuses can‘t sense red light?

From what I can tell after a very brief amount of googling, is that octopus likely only have photoreceptors. This means that they likely wouldn't be able to perceive the red-color from the light. Depending on the kind of light you have and whether the light is actually emitting wavelengths in the proper spectrum or just a white light with a red filter you may have mixed results. Octopus are incredibly light sensitive and if you have a poor quality light that "leaks" white light you may be unknowingly disturbing your animal.

Generally my stance is that if you can best mimic the animals natural environment (no lights at night) you will have the happiest animal. This isn't to say that you can never use red light to observe your animal without bothering them at night, but I wouldn't leave them in the red light overnight just in case the light is poor quality or it turns out they actually are able to perceive red light and we just don't know it.

I have done some hunting behavior experiments in full white light, red light (with actual red lights, not a red filter) and total darkness with an infrared light and camera. Typically in white light the animal hunts using a "distance pounce", the common type of prey capture method (for bimacs at least) where the animal pounces on the prey and balloons the mantle to surround and capture it. In red light or total darkness the animal never does a distance pounce, and relies on a "contact pounce" to predate. They do not capture they prey until after they have made contact with it with the arm. The predatory behavior is triggered by the chemoreceptors on the sucker cups, rather than input from the visual system.

I'm not making any claims about whether or not the animal is able to "see" in red light or not, and from my understanding we don't quite know for sure or not. Please correct me if I am mistaken. I just thought it was interesting that the predation strategy in white light relies on the visual system most likely, while the predation strategy in red light and total darkness shifted to a more contact-dependent method (likely no longer relying on the visual system, and instead relying on the chemotactile system in the arm suckers).

It could be interesting to hear if anyone else has experiences with their animals reacting to a red light being turned on or off near the tank when in total darkness (which is relatively difficult to achieve if not in a specialized space). Typically seeing how the pupil dilates or any changes in body posturing is a good metric for their ability to perceive the light. I can spend more time experimenting with my dark room setup and red lights and see if I can get them to react to a red light or not.

 

[DWhatley]

I have experimented with red lights of varying types (filter lens, red LED, filter paper over the tank top). For diurnal animals, I agree with @pkilian, don't disturb the slumber as they do detect the light but are not at bothered as with white light (there are thoughts that blue light, aka moon light, might actually be worse than white light but most reports are that they become accustomed without obvious stress).

However, with nocturnals, I have found that leaving a red light (I never detected a better or worse red but the brightness does seem to be a factor) on all night and providing good daytime caverns will allow observation of natural (or as natural as an aquarium can be) night time activity. The light is definitely still observed but seems to be accepted (perhaps as moon light?) as night time. I have noted that if you turn off the light at some point in the evening, nocturnal/crepuscular animals will learn wait until the light goes out (my reason for saying they definitely see the light) before coming out to hunt. Note that red light all night does not seem to change the natural hunting time. O. mercatoris seems to come out at about 9:00 if the room is dark but true nocturnals will still hunt at 3:00 AM.

As for not seeing you, that is more dependent on the ambient light behind you than the light in the aquarium.