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.

UPDATE: Lindsey Dougherty commented below.  Lindsey is graduate student at the University of California, Berkeley whose research I completely missed when I wrote this.  As she mentions below in the comments, the species is actually Ctenoides ales.  Lindsey presented work recently at the Society of Integrative and Comparative Biology meeting both determining the evolutionary relationships of this unique bivalve but how it generates light. As she mentions in her abstract, these are the only known bivalves with a light display.  These critters actually ARE NOT BIOLUMINESCENT.  Part of their mantle is actually iridescent and the clam actually furls and unfurls the reflective bits to cause the light show.  Pretty cool stuff and sorry to Lindsey.

The post Disco Scallops Know How to Boogie Even if They Aren’t Scallops first appeared on Deep Sea News.

It seems that “native” fluorescence like this may not actually serve an adaptive function. Corals aren’t subjected to those UV wavelengths much in nature, so there’s no selective force to promote the evolution of this kind of trait. Instead, it’s more likely a wonderful and beautiful coincidence that can be exploited to make spectacular YouTube videos like this one!  The culprits are different protein pigments in the corals and their symbiotic algae (Symbiodinium spp.) that serve important biological functions for the coral, acting as electron donors in biochemical reactions, as anti-oxidants and other functions. But, they also just happen to fluoresce under the right wavelengths of illumination.  This class of proteins includes the famous GFP, Green Fluorescent Protein, first isolated from jellyfish but these days genetically engineered into a whale range of organisms as a molecular biological tool.

Video link via @DrBondar on Twitter. More about Carin here.

The post TGIF – The spectacular fluorescent colours of Coral Reefs first appeared on Deep Sea News.

More recent stories say that the biolomunescent light show at night is something to behold, but unfortunately I can’t seem to find a good video of that.  Here’s what the critter itself looks like, massively embiggenated, courtesy of Oceana

This particular bloom has been attributed to the predatory dinoflagellate Noctiluca scintillans, which is indeed biolominescent, as this nice image from the Gippsland Coastal Board nicely illustrates.  This species probably blooms in response to blooms of its prey, which are smaller plankton.  These, in turn, respond to pulses of nutrients; in this case as a result of a discrete upwelling event.

I would dearly love to see video of the bioluminescence at Clovelly, Bondi or Stanwell, and I bet I’m not alone.  Perhaps if you are reading this and you live in the Sydney Beaches area you could check it out this evening and snag some video for us. 

The post What’s green and gold and red all over? first appeared on Deep Sea News.

The post TGIF: Edith Widder’s TED talks on Bioluminescence first appeared on Deep Sea News.

Despite the “hunting the giant squid” theme, there is some really cool footage here. some of it I haven’t seen before.

The post National Geographic on Capturing Bioluminescence on Camera first appeared on Deep Sea News.

The red tide that has lit San Diego for several weeks is ending in a microscopic bloodbath. The above photo was taken by Linsey Sala, the manager of the Pelagic Invertebrates Collection at Scripps Institution of Oceanography. She writes:

This image was taken from a collection at the SIO pier this [Friday] morning with a 0.120mm net.  It illustrates a heterotrophic dinoflagellate (Noctiluca, nearly transparent disks) feasting on the autotrophic red tide dinoflagellate (Lingulodinium polyedrum, orange-red cells).

Noctiluca is a dinoflagellate like Lingulodinium, but it can’t photosynthesize. Instead, it makes a living vacuuming up other single-celled organisms. Some Noctiluca are bioluminescent, but the species here in California is not. According to Dr. Peter Franks:

Back in 1995 we had a dense red tide of Lingulodinium polyedrum here, and it collapsed rather suddenly largely through grazing by Noctiluca. Once the Noctiluca had eaten all the L. polyedrum they starved and floated to the surface. There they were swept into lava-colored bands by the underlying internal waves for a few days.

Perhaps we’ll have that to look forward to in the next week or so.

The post San Diego red tide eaten alive by single-celled predator first appeared on Deep Sea News.

This is a guest post modified from two emails by professor of biological oceanography Peter Franks, reprinted here with his permission. Peter is a phytoplankton ecologist who studies how the physical processes in the ocean influence the growth and distribution patterns of phytoplankton, so he’s often the go-to guy on red tides. I have edited the emails slightly for clarity and context.

We’ve got a pretty spectacular red tide going in the waters off San Diego (and farther north and south). The organism is Lingulodinium polyedrum, my favorite dinoflagellate. Why favorite? Because it’s intensely bioluminescent. When jostled, each organism will give off a flash of blue light created by a chemical reaction within the cell. When billions and billions of cells are jostled – say, by a breaking wave – you get a seriously spectacular flash of light.

And the best part? The moon is in its “new” phase. That means that the bioluminescence will not be dimmed by moonlight for the next few days.

So please take the opportunity to go down to the beach tonight or tomorrow night to see one of nature’s most impressive light shows.

Or, if you’re like me (too lazy to get up after the sun goes down) get a clear drink bottle, get a friendly neighborhood surfer to fill it for you (knee-deep water is fine), and take it home. Put it in a cool, dark place – a closet or a bathroom without windows. Then, after the sun goes down go in there and let your eyes adjust to the darkness. Then give the bottle a shake – you’ll see blue sparks from the dinoflagellate’s bioluminescence. Then start experimenting: try your electric toothbrush. Or pour some on your arm, or on the countertop. Let some get sucked up into a towel. Or (this is the best) try adding vinegar. The acid makes the dinoflagellates release their bioluminescence chemicals all at once, giving a show similar to the finale of a 4th of July fireworks display. Unfortunately, like the 4th of July fireworks display, it’s terminal. That’ll be the end of the fun. Until you go and get some more red-tide water…

I’ve received a number of inquiries about the red tide. Frequently Asked Question #1 is (in a nutshell): will it [this red tide] kill me?

The answer?

No.

I know, I know. I’m as disappointed as you are. This species of dinoflagellate is not toxic. If it were, I’d have a lot more funding. It’s possible that it contains low levels of a toxin called “yessotoxin“, but this toxin is not one that’s tested for in the US (as far as I know), and there’s no records of it having any detrimental effects.