The 18 species of Histioteuthid squids, the biggest no larger than a football, are often strawberry colored, with dark photophores resembling black seeds adding to the sweet fruit-like appearance.   All the species live in the mesopelagic, that region in the ocean between 200 and 1000 meters that goes from dimly lit to a full on dark habitat.  Light comes from above in the form of attenuated sunlight and below in the form of bioluminescence.  Given the drastic changes in light with depth, the mesopelagic is filled with a cornea-copia of truly amazing, dare I say monstrous, visual adaptations.  The Histioteuthid squids are no expectation.  The left eye can be twice the diameter of the right eye, a trait only acquired with adulthood.  The left eye can gain such proportions it actually pushes the head out of alignment with the squid’s body in some species.

New work by Kate Thomas and colleagues reveals why these strawberry squid’s different eyes have made such a spectacle of themselves.  The group found that the squids oriented the enlarged left eye upward and the smaller right eye slightly downward.   The squids often held a slanted angle with their body so the eye looking upward was near 45˚ and the downward near 120˚.  Given the field of view of the eyes, the large eye would receive light from directly above to 90˚ horizontal on the left side.  The small eye from 43-198˚ or from directly below to horizontally on the right side.

To keep these eyes aimed in the right area, the strawberry squids also demonstrate a peculiar behavior.  Squids would ratchet themselves, turning the body while the head maintain the same orientation.  The head would, at a precise stopping point, suddenly snap around to match the body orientation. “This may allow histioteuthids to compensate for the unbalanced fields of view created by [different sized] eyes and rapidly change which direction each eye is facing, or to scan their environment.”

But why two different eyes?  Thomas explains, “Eyes are metabolically expensive to grow, maintain, and use, so while larger eyes can improve both sensitivity and resolution, selection probably favors an eye just large enough to perform a necessary visual task but no larger.”  It is actually cheaper, in the total calories needed sense, to have the eyes perform to unique functions and allow one of them to be itty bitty.

And with that, my friends, eye take my leave.

The post The Little Strawberry Squid with the Big Eye first appeared on Deep Sea News.

Nearly every group of animals has a transparent brethren that lives in the well-lit open ocean.  In darker deeper water, a majority of denizens are red or black.  In both cases, this coloration or lack of serve to cloak the animal.  But what’s an animal to do if they are in between these zones, not a sharp boundary but a grey area full of scoundrels  or needs to migrate between the two.  A red or black creature in ligher shallower waters easily contrasts against the light coming from above.  A transparent animal, finding itself in the deep, would be easily distinguishable from the direct light cast from another organism’s bioluminescence.  If only like a Bird of Prey an organism could shift between cloaking and no cloaking.

Two such creatures the octopus Japetella heathi (right) and the squid Onychoteuthis banksii (left) can do exactly this.  When you shine a direct light on the normally transparent Japetella heathi or Onychoteuthis banksii, mimicking a bioluminescent beam, its chromatophores are triggered turning the animal opaque. But the octopus, like a crafty Klingon,  is strategic in triggering the chromatophore response.  Objects or shadows near the octopus did not trigger a response.  Yet tactile, i.e. poking it with a probe, a big stick, or whatever is nearby, or blue light did activate the cloaking device.

Both animals consistently reflected 2x as much light when in the transparent mode compared with the pigmented mode. Indeed in the cloaked state, the octopus was able to achieve the same reflectance of the red and black fishes and invertebrates of the deep.

These cephalopods seem to understand the ancient Klingon proverb tugh qoH nachDaj je chevlu’ta’ or A fool and his head are soon parted.  Best be no fool and cloak often***.

Sarah Zylinski, Sönke Johnsen (2011) Mesopelagic Cephalopods Switch between Transparency and Pigmentation to Optimize Camouflage in the Deep. Current Biology Vol. 21, Issue 22, pp. 1937-1941)

*I would also note that early Klingon Bird of Preys also had sweet submarine style periscopes

**I’m not referring to young emo vampires either although maybe cloaking is useful agains them as well

***not really related to this post but I feel compelled to say KKKKKKKHHHHHHAAAAAANNNNNN!!!!!!!

The post Cloaking Klingon Cephalopods first appeared on Deep Sea News.

Great informative video from MBARI:

“This video shows some adaptations animals have for camouflaging themselves in the deep sea. Many of the animals in the deep-sea use red pigments to hide themselves because red light is one of the first wavelengths of visible light to be absorbed by the ocean (at approximately 100 meters), rendering any animal using it invisible. The red coloration is visible in these images because high-intensity lights shining from the ROV illuminate the scene.”

The post Hide and Seek in the Deep Sea first appeared on Deep Sea News.

One thing you should know about DSN is that Craig keeps real strict rules on his definition of the deep-sea, so I work to find a way around this when something interesting pops up in shallow waters. For instance, Craig will use his (very awesome) “25 Things You Should Know” series to tell you 200m is a minimum depth cutoff for the deep-sea. However, many sea creatures (like squid) ignore this boundary, so I try to navigate through this barrier with “depth certified” asides that fly under Craig’s 200m radar. See the “extended entry” below. You’ll see more of this tomfoolery in future posts about sea turtles, whale sharks, and waterspouts.

Jellyfish are one of the most unexpected and delightful encounters in deep-sea surveys. They cast shadows on the seafloor big enough to frighten you, and fly at the video cameras to fill the frame in spectacular displays.

Jellyfish are attracted to light through primitive eyes called rhopalium, but the most deadly jellyfish, the cubozoans, have sophisticated visual systems. New research on cubomedusans investigates these elaborate eyes that can see a burning match meters away, navigate around dark objects, and actually see people.

This month’s Journal of Morphology reports visual processing and integration in a diffuse system spread throughout the rhopalium of the toxic box jellyfish Tripedalia cystophora (Skogh et al. 2006). These and other results (Nilsson et al 2005, Parekfelt et al 2005) show that a major part of the rhopalial nervous system is bilaterally symmetrical. One website reports at least 8 human deaths from box jellies. So beware, my friends, if the carnivorous sponges don’t get you, the jellyfish will.

References

Nilsson DE, M Coates, L Gislen, C Skogh, A Garm. 2005. Advanced optics in the jellyfish eye. Nature 435:201-205.

Parkelfelt L, DE Nilsson, P Ekstrom. 2005. A bilaterally symmetric nervous system in the rhopalia of the radially symmetric cubomedusa. J Comp Neurol 492:251-262.

Skogh C, A Garm, DE Nilsson, and P Ekstrom. 2006. Bilaterally symmetrical rhopalial nervous system of the box jellyfish Tripedalia cystophora. J Morph. 267: -13911405

The post The Jellyfish are Watching first appeared on Deep Sea News.