Invisibility versus camouflage in cephalopods: Part 1

Who here has not considered the infinite possibilities with the power of invisibility? How you could improve your life, and sift through it unseen. So have the cephalopods of the animal kingdom considered the possibilities. And being equipped with their highly evolved pigmentation (known as chromataphores, which are in a sense pigmented muscles connected to the brain) (Mäthger & Hanlon 2012), certain cephalopods managed what men only can dream of. Invisibility.

Actually, what it really is, is transparency. By completely contracting their chromataphores they reveal the transparent muscle tissue, and basically turn their whole body invisible (Mäthger & Hanlon 2012). Like this little weirdo:

 

(https://www.youtube.com/watch?v=M-0V1xJJR58)

This is but one way cephalopods can become invisible. Many cuttlefish, octopi and squids can camouflage against complex backgrounds, like coral reefs or kelp forests (Hanlon et al 2009).

 

(https://www.youtube.com/watch?v=q8xJ13pAZNw)

There have been some speculations into the different ways cephalopods camouflage, with there being three found so far; uniform (adapting color of background), mottle (adapting color, pattern and texture of background), and disruptive (additional input in mottle and/or uniform camouflage) (Hanlon et al 2009). Disruptive is the most interesting one, where the individuals seem to add a distinct feature within the camouflage (Figure 1), as if adding a personal touch. An example could be black spots in the middle of their camouflage.

Flower_flounder_in_Kona_may_2010

Figure 1: Cuttlefish camouflaging against heterogeneous substrate using the disruptive method

What is really interesting is how these animals can distinguish the different colors when, in fact, they have been proven to be colorblind (Hanlon 2007). In an experiment to see the extent to which cephalopods could hide in plain sight, Hanlon (2007) found that the cephalopods would camouflage against a checkerboard made of highly contrasting shades of yellow and blue, using the uniform tactic. However, when set in a natural environment, they seem like the ultimate masters of disguise. With regards to their color blindness, going transparent would seem like the go-to technique, with limited effort put into trying to decipher the color spectrum of the intended background.

So, to address the initial title of this post, what really is the best approach for invisibility? Transparency or camouflage? To answer this question properly, and allow more room for discussion, I have decided to split this piece into two parts, where this post works as an introduction into the discussion.

This piece is taking a slightly different path than I intended when I initially started this blog, meaning it diverges slightly from looking into the evolution of this particular defense mechanism. However, I found in the end that discussing what tactic is the ultimate invisibility technique would be more interesting and challenging.
Hope to see you back next week when we will try to find the answer.

Here is some food for thought until next week.

 

(https://www.youtube.com/watch?v=0wtLrlIKvJE)

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The Iron Fist, also known as the Mantis Shrimp

Lets talk about the mantis shrimp, a crustacean equipped with a super power like punch. The second thoracapod appendages (second arthropod leg) is powered by a three part system; engine, amplifier and tool, all of which are present in every mantis shrimp (Claverie and Patek 2013). However, there are many versions of the claw, where the two most polar versions are the club and the spear (Anderson and Patek 2015).

Here is a video to illustrate:

(https://www.youtube.com/watch?v=E_mbnXJh2Dk)

The mantis shrimps use their claws primarily for predatory behavior (Claverie and Patek 2013). However, it is also often observed to be used for defending territory, and against predators. They are also exceptionally unique and intriguing animals, which is why I chose to start with them.

In addition to its famous punch, the mantis shrimp is renowned for its binocular vision (Haug et al 2010). Each of its eyes are two parted, being able to see two places at the same time with the same eye. Consider the chameleons, with the ability to move each eye separately enabling them to look at two things at the same time. Then top that with two way split vision in each of these eyes, looking at four different things at the same time. How would one even process this much information simultaneously? That would be a different conversation in an entirely different blog.

To redirect the attention back at the defense mechanism, what is the current view on how these iron fists evolved? Anderson and Patek (2015) hypothesized that it may be related to energy , supported by deVries et al (2012) by adding that they store energy in their skeletal springs to create the catapult mechanism in their raptorial appendage . However, Claverie and Patek (2013) found that this energy is different in smasher (mantis shrimps with club-claws) from non-smashers (mantis shrimps with other versions of the claw) . It seems the non-smashers redirect some of the energy budget from amplifiers to muscle elasticity, similarly to the grasshopper and its hind legs. Claverie and Patek (2013) also stated that non-smashers evolved quicker than the smashers , indicating that smashers might be the latest branching on the mantis shrimp evolutionary tree. Apparently, Clavier and Patek (2013) found that the smashers morphological adaptation to create a punch of the equivalent power as a bullet leaving a gun, is of lower modularity. The question still stands for me though, why evolve the iron fist? It seems further research need to be conducted.

Lastly, I would like to just leave this video here for anyone who is interested in learning about the Mantis Shrimp with a laugh. Let me introduce to you the man who first introduced me to the Mantis Shrimp.

(https://www.youtube.com/watch?v=F5FEj9U-CJM)

Next week we will be talking about our next super power, being invisible.

 

The sea, once it casts its spell, holds one in its net of wonder forever. -Jacques Yves Cousteau

Truer words could not be said, as those by Jacques Cousteau on the ocean. To those not already in awe of the fantastical world known as the sea, I welcome you.

The aim of this blog is to shed light on the creatures dwelling in the sea, to investigate the evolution of certain characteristic defences to selected species. There may be even more intriguing predatory strategies in aquatic species, however, I would like to focus on the underdogs of the sea. To see how some species have evolved unique ways to defend themselves against sea monsters. Some examples are:

The invisible squid and octopus 
Onychoteuthis banksii & Japetella heathi

(https://www.youtube.com/watch?v=VpUKk-DrWGw)

Morphological defence mechanism to avoid being seen by turning invisible with predators lurking above, and pigmented when predators hunt from below. More details on this later.(Zylinski & Johnsen 2011)

The pom pom crab
Lybia edmondsoni

(https://www.youtube.com/watch?v=tKMxRBYQs5k)

Behavioural defence mechanism to fend off predators using stinging sea anemone as boxing gloves, hence the second common name “boxing crab”. However, when seen with the sea anemone while performing the sexual attraction dance, it may resemble a dance routine for a cheerleading squad. (Schnytzer et al 2013)

The hagfish
From the family Myxinidae

(https://www.youtube.com/watch?v=pmaal7Hf0WA)

Physiological defence mechanism where the fish secretes a slime that evolves into an intricate network of mucus, enveloping the threat and allowing the fish to escape by strategically wriggling the slime off. (Bernards et al 2014)

These are but an excerpt of the defence mechanism I will talk about. There will be coverage of superhero like super powers, adaptations that befuddle scientists, and remembrance of certain characteristic species and their defence mechanisms. Simultaneously I will try to unveil where these unique adaptations came from, still recognizing there are certain things we do not know yet. Like which species I will cover next week, stay tuned.