The last breath of the octopus, and this blog

There are many ways in which to defend yourself against predation, where the main bulk of my posts have been about self-pursued protection either actively, by force for example (eg. Mantis shrimps), or passively, through camouflage (eg. Cephalopods). However, the ultimate defense mechanism can be said to be one that involves altruism, where your active participation is limited close to none. The altruistic behavior I will talk about in this post is in the form of parental care, seen in the deep sea octopus (Graneledone boreopacifica). They demonstrate the most sacrificial parental care where their progeny survival outweighs their own, this to the extent where the parents consistently dies of starvation as they protect their genetic heirs (Ed Yong, 2014).

(https://www.youtube.com/watch?v=3ehHQOziuF0)

Parental care is rarely seen so extreme (Ed Yong, 2014). Usually, energy expenditure is also allocated to future prospects of reproduction and not only to current reproductive status (Kolliker et al 2012, pp. 41), meaning most of the energy acquired goes into self-maintenance to ensure future reproduction. However, these deep sea octopi only reproduce once, whether this is a result of the altruistic behavior or the altruistic behavior a result of its reproductive behavior is not well discussed in the scientific literature. Although ensuring all progenies survive the egg life cycle does have a significant increase in ensuring your genetics are passed on to the next generation, which is ultimately the motivation for reproduction, to starve in order to make this assurance is quite extreme. Could there not be a middle path to take between complete sacrifice and no parental care? There is the possibility that the starvation is to avoid attracting parasites and predators because of debris from eating. Additionally, it is thought that octopi generally cease or greatly reduce consumption after their initial brood have hatched (Robison et al 2014). Therefore, Robison et al (2014) proposed, the starvation seen in boreopacifica might be a result of weighting an increased brood size when hatched (by lengthening the caring time) to a short life with starvation in the cards anyway. Which is yet another evidence that supports the incredible intelligence these creatures have, and is why there should be conducted more research into understanding them.

Octopus den

Figure 1: Image of a deep sea octopus protecting her eggs in her lair (Picture by Stuart Westmorland/Corbis).

It saddens me to say that this will be the last post on this blog, however, here are some honorable mentions that did not make the cut. Use these videos, and the posts I have produced in this blog to inspire you to give back to the sea for what life it has allowed us to make on this Earth.

 

Some honorable mentions

The Porcupine fish

(https://www.youtube.com/watch?v=KhRbYOQXpNM)
Similar to the Pufferfish

 

The flying fish

(https://www.youtube.com/watch?v=9uFjmeWnFZ4)

The electric eel

(https://www.youtube.com/watch?v=7UWgtrCzLw0)
Technically a riverine species and not marine.

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The slimy bastard, also known as the Hagfish

When discussing the topic of mucus, as one does on a daily basis, the species that by far produces the most amount of mucus has to be the Hagfish. The mucus produced by the Hagfish is more known as slime, produced in massive quantities when provoked.

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

These eel-like creatures can mass produce slime due to the fact that there are several mucus glands spaced evenly across their whole bodies (Downing et al 1981) and that the mucus is three times as diluted as typical mucus (Fudge et al 2005). Additionally, it is a two part compositional mucus of coiled slime threads (‘skeins’) and mucin vesicles that are thought to erupt in contact with seawater (Fudge et al 2005). Whether or not there is the potential harm of vesicles erupting in the Hagfish tissue before release is unknown.

There is also little knowledge of how these two components interacted with each other, where initially it was thought that the skeins were predominately the basis of the slime, in striated alignment held together by the mucin to produce a sheathing arrangement (Fudge et al 2005). However, in 2005 Fudge et al produced a study that concluded the slime is most likely is a “discontinuous fibre-reinforced composite”, illustrated to them by the fact that the skeins were tapered at both ends, and produces a very fine sieve like structure.
In addition to answering parts of the question of how these components work together, they unintentionally answered mine, of why this adaptation came to, hypothesized to be to constrain gill breathing for potential predators when threatened or attacked, as illustrated by this video.

(https://www.youtube.com/watch?v=Bta18FdkVcA)

How it evolved is a little trickier to answer. Compared to typical mucus it is, as mentioned before, highly evolved slime. To be able to answer this question there needs to be further research into the historic progression of how the Hagfish evolved this very specific adaptation, and increase knowledge regarding the components of the slime. At the moment most research is increasing understanding of the proteins within the mucus, which has been thought to be a source to produce fabric, while not so much on the evolutionary aspect of it.

Next week we will have a look on altruism as a form of defense mechanism.

Blowing bubblegum bubbles sans bubblegum, performed by the Parrotfish

Spitting on your enemy just got a whole new meaning when considering the defense mechanism adopted by the Parrotfish. As a preemptive defense strategy they cocoon themselves in a spit bubble when at their most vulnerable, while sleeping. This spit cocoon envelopes the Parrotfish completely and is thought to mask olfactory cues unintentionally sent out to their predators (Grutter et al 2011).

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

However, a recent paper published by Grutter et al (2011) found that there is little evidence to support the claim that the cocoon does protect them against predation. One paper did comment on the observed behaviors of Parrotfish in the wild (Sazima & Ferreira 2006), saying that they fled when their cocoon was touched by an outsider. Sazima & Ferreira (2006) suggested that this cocoon might work as an early warning system. One major counterargument to this is the energy expenditure on this defense mechanism, estimated to be at 2.5% of their daily energy budget (Grutter et al 2011). This indicates that the mechanism is of high value by not being selected against in nature. Therefore, functioning purely as an early warning system is highly unlikely. Still, there would have to be a use for it.

Grutter et al (2011) found statistically sound proof of the cocoon being an outstanding parasitic preventive tool, especially towards the Gnathiid parasite, which has been found to be a vector for blood transmitted parasites (Grutter et al 2011). Therefore, the cocoon is more likely to have evolved to prevent parasitism than predation.

Another thing to note is that Parrotfish are not the only fish that can produce these mucus bubbles, as seen in this video showing a Wrasse performing the same defensive strategy.

(https://www.youtube.com/watch?v=uskvo4RUYjw)

Once again we are presented with the very rare homoplasy situation where two different species, however, of the same suborder (Labroidei), have evolved the same defensive strategy. Of the Parrotfish only the genus Scarus seems to be able to produce this mucus cocoon (Sazima & Ferreira 2006), which would be phylogenetically distant from the Wrasse. This increases the likelihood that this cocoon is of great importance for improved fitness, however, with lacking research it is impossible to say why it is of such high importance. Quite possibly it could be a wide range of applications.

Regardless of what use the mechanism is for, what question usually interests me is how these impressive and interesting defense mechanisms evolved. There is a known wide range of application of mucus within the fish “community” in general, for example the Clown fish that cover themselves in it in order to protect themselves against the nomatocysts of the sea anemones. However, to specifically blow up a mucus bubble, that, in addition to imaginably being complicated to make, takes a long time to create, suggests that the first individual would not have accidentally made one and discovered its potential. At the moment this is an extremely under explored subject, which is interestingly enough, seeing as it has some medical prospects as discovered by Videler et al (1999). Apparently, the mucus cocoons Parrotfish produce hold antibiotics, which at the moment does not seem to be of use for humans. However, with more research it could hold a great deal of potential for aquaculture for example., while simultaneously providing some much needed insight into the rare adaptation, which at the moment there is close to none.

Next week we will look into some more mucus production, this time produced by the infamous Hagfish.

The kleptomaniac, aka the Nudibranch

From a morphological perspective, these sea slugs might seem quite similar to the sea cucumber. However, they couldn’t be more different. These are actually molluscs that have shed or are in the process of losing their shell. Additionally, their food source is quite different from the sea cucumbers, or any of the marine inhabitants for that matter. Nudibranchs, mainly the Aeolidiidae, feed on the phyllum cnidaria (Farley 2017), which entails animals such as sea anemones and jellyfish, known for their defensive strategy using nematocysts. Nudibranchs have this amazing adaptation that allows them to ingest and digest cnidarians without getting hurt from the released nomatocysts. Even more impressively, they can single out these nomatocysts in the digestive process and bring them into their own tissue to use as their defensive strategy (Schlesinger et al 2009).

Nomming-nudibranch-2

Figure 1: Illustration of Nudibranch anatomy highlighting the organs devoted to kleptonidae adaptation (Illustration credit: Sara Mynott)

This kleptomaniac adaptation is brilliant, it means that what energy and time was spent on evolving these specific adaptations could be spent on a generalist approach to steal other species specialization. By generalist approach I mean that not only can Nudibranchs steal nomatocysts, they can also cross over trophic levels by stealing chloroplasts, thereby turning into primary producers (McFarland & Muller-Parker 1993). Consider how incredible that could be for you if you had that adaptation, you had only to eat some plant tissue and then you would be able to produce your own energy with the power of sunshine. So the question is, can we evolve this kleptonidae adapation? Also, can I please have it. To start answering that question we have to understand where this adaptation came from.

The first thing that comes to mind is the similarity with the endosymbiotic theory that explained the evolution of eukaryotic cells from prokaryotic organisms. However, this theory postulates that two prokaryotic cells combined where the smaller evolved into complex organelles such as the mitochondria and chloroplasts (The editors of the American heritage dictionaries 2015). Whereas kleptonidea revolves around the one absorbing the other, intentionally. Additionally, that these are multicellular organisms, in contrast to the procaryotic organims, which severly complicates things.
In all, what scientific literature I have found on the Nudibrnachs and kleptonidea has not given any further insight into the evolutionary pathway of the adaptation. Nor did I find any research into the selective digestion or the adaptation of utilizing something digested for protection or divesting from predation. However, I did find that certain flatworms have a similar adaptation of kleptonidae towards nematocysts (Greenwood 2009). And as these species are within a seperate phyllum, this means that this adaptation has evolved twice. Which is quite rare in itself, but with the added rareness of the adaptation in question, it makes the whole thing so extremely rare. I am both surprised and frustrated that this has yet to be researched further and promptly urge all biologists to get on with it.

To calm your nerves, if you got frustrated by the bottomless pit of no answer like me, have a look at this incredible assortment of Nudibranchs to a calming melody.

(https://www.youtube.com/watch?v=HC1v02Rmnww)

Next week I will talk about a surprising adaptation found in Parrot fish.

The ugly duckling, aka the sea cucumber

seacucumber

Figure 1: Drawing of a sea cucumber by lupiloops.

The sea cucumber might not be the prettiest creature of the sea, especially compared the pom pom crab. However, the ones found in the Aspidochirotida order are equipped with the most fascinating  defense mechanism. A behavioral adaptation that involves literally spewing their guts out, however, through their rectum. When I first read this I questioned why? Where did this adaptation come from?

It seems they actually eject an internal organ, called cuvierian tubules, and spend up to five weeks to regenerate it (Vandenspiegel et al 2000). These tubules expand upon ejection and deter any predators attempting to attack them.

I have been searching for the answer of when this adaptation arose, but there seems to be struggles in the phylogeny of this species as traditional taxonomic identification based on morphology is not as relevant, seeing as they are quite cryptic species, as noted by Byrne et al (2010). The order Aspidochirotida is from Late Ordovician according to Reich (2010), but is that clade in general based on their distinct defense mechanism or on other traits of that order? There seems to be little research into how this defense mechanism came to be, did the first sea cucumber just get so scared it pooped its pants and subsequently scared the predator off? Initially I would not think so, because these are specifically designed organs used to entangle and confuse predators (Flammang et al 2002). But the species could not have specifically designed a new organ to deter predators out of the blue, there must have been a step before. It seems most research is focused on the regeneration of these tubules, and not the origin of them. However, I did find one article that went into some of the evolution of this defense mechanism. Lanterbecq et al (2008) expressed in their abstract that using a reconstruction of a phylogenetic tree, the ancestor of the Aspidochirotida had ramified, nonadhesive, nonexpellable and nonstretchable tubules.

Overall, however, there does not seem to be a lot of research put into these creatures. Funding to do so might be hard seeing as they are far from any typical flagship species. That does not mean they are not important. They do play an important role in the marine ecosystem as detrivores, which is exactly why these sea cucumbers should receive more attention.

To hopefully increase any further interest in you, I leave you with this dramatic “World’s weirdest” youtube video.

(https://www.youtube.com/watch?v=wXf_YodWw40)

Next week let us diverge from this subject you would not want to be reading about, nor see for that matter, while eating. Trust me, I know.
Let us talk about the incredibly surprising animal that made me interested in marine biology in the first place, Nudibranchs.

The Pom pom crab: Cheerleaders of the sea

The Pom pom crabs are of the genus Lybia, nicknamed Pom pom crabs due to their tendency to sway around holding sea anemones in their claws, as seen in this video.

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

The Lybias have a symbiotic relationship with these sea anemones (Schnytzer et al 2017). By swaying with the sea anemones they catch food debris floating in the water and feed off the sea anemones, the anemones get a meal as well as by the crabs leftovers. However, the amount of food intake is controlled by the crabs, thereby maintaining a small sized ‘bonsai’ anemone.

There are other crabs that show similar interspecific behavior, like the carrier crab, which has a tendency to pick up whatever it can find and carry it above its back as protection against predators, sometimes these things can be alive. Take the crab in this video as an example, carrying an unwilling sea urchin on its back.

(https://www.youtube.com/watch?v=BL-CxvyVLds)

The adaptation of utilizing other species as a shield against predators does not seem uncommon in the decapod crustaceans. However, when it comes to the Pom pom crabs, there is the specific question of where they got the anemones from, as asked by Schnytzer et al (2017). They found that these crabs actively propagate the anemones asexually by slowly splitting them in half. This behavior was observed in situations where the crab was only left with one anemone due to another crab stealing the other. Thought, the question still stands, where did they originally get the anemones from? If the species the crabs hold have not been observed in the wild, have they created a new species with the asexual reproductive chain from intraspecific competition?

Another curious aspect of the Pom pom crab was found by Karplus,et al (1998). They observed that during intraspecific competition, the crabs would not use the anemones, but rather their pereiopods to inflict harm. They noted that the anemones were used in intraspecific interactions as a method of threatening the other individual, that they would extend their claw to be in close range, but with the arm furthest away from their competitor. They had three possible explanations for this half hearted competition technique. The first being that the implications of being hurt in a fight from the serious harm these anemones can inflict outweighed the possibility of winning a fight if they were used on their competitor. The second is a bit contradictory to the first hypothesis, where they suggested that the effect of an anemone attack would not be enough to win a fight. The third possible explanation was that they were avoiding any damage to their sea anemones. Either way, this behavioral adaptation is quite unique and entertaining. Though in desperate need of more research.

Next week we will try to retrace the evolutionary history of the extreme defense mechanism where the organism ejects its internal organs on its predators.

Invisibility versus camouflage in cephalopods part 2

In an alternate universe, where someone for some reason would present me with the choice of being able to go invisible or to camouflage myself, I would always chose invisibility. In my head this has always been a superior power to camouflage. Is it actually though?

There are limitations to both. The most obvious one being for camouflage, where the setting is crucial. Without any background to camouflage against, say in the middle of the ocean, they would be easy prey. However, the cephalopods who live in these areas, in the deep oceans, are usually colored red or black (Figure 1) (Mäthger and Hanlon 2012). This serves them as an invisibility cloak, as these colors absorb more light than those in other wavelenghts.

redoctopus

Figure 1: A coconut octopus showing off the red skin used in deep waters for camouflage

However, a limitation here is that their heavy coat makes them throw a shadow with light from above. A similar issue is there for transparent cephalopods.
For transparency, the issue is to do with light scattering. When direct light hits these transparent bodies, it is absorbed more so than the background, making them stand out (Zylinski and Johnsen 2011). This direct light can for example come from predatory fish equipped with light emitting organs, known as ‘searchlights’. However, two species have been found to respond to this direct light with color pigmentation, thereby reducing the amount of scattered light and remain in disguise. These two species are the Onychoteuthis banksia (squid) and Japetella heathi (octopus) (Zylinski and Johnsen 2011).

 

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

 

One possible limitation to this adaptation is that essential organs, like digestive tracts, are still exposed inside the transparent body. Whether these give them away, as Tasmin asked in the comment section in my last post, is an interesting question, but was not covered in Zylinski and Johnsens (2011) report. Considering where the two species live (in the lower pelagic areas with low light penetration), the size of them (squid mantle length = 140 mm, octopus mantle length = 80 mm), and the fact that they use pigmentation as a form of disguise against predators with searchlights (Zylinski and Johnsen 2011), makes me assume that some visibility of organs would not regularly give them away. However, without proper research it is hard to say for sure.

Another interesting notion is the fact that the two species respond more slowly than the camouflaged species. Mäthger and Hanlon (2012) redirected the attention onto response time reported in Zylinski and Johnsens (2011) paper and highlighted that these two species reacted in ‘seconds’, while camouflage species have a response time frame of about 300–800 ms. Mäthger and Hanlon presumption is that these two species do not have a direct neural control of their chromataphores (2012), and suggested a new experiment that analyzes the ability of the cephalopods to presumably ‘see with their skin’, performed on Onychoteuthis banksia and Japetella heathi. The idea is to see whether their skin will respond with pigmentation when subjected to bioluminescent light without letting the individual see the light with its eyes. More about this is covered in their paper, if there is any additional interest in the matter.

So who is the winner? At the moment I wish to deliver the prize to the highly adapted Onychoteuthis banksia and Japetella heathi, who have found a way of merging transparency and camouflage. This way they get the mobility entailed in transparency and the ultimate invisibility entailed in camouflage. However, whether response time has any effect on the invisibility, as well as what the cause is for the delayed response, has yet to be studied.

Due to this post being a little late, there will be two posts this week. In the next post we will diverge from the superhero theme and have a look at the cheerleaders of the sea. Yes, you read that right, let’s talk about those pom poms.