Archive for the 'Crustaceans' Category



It Came from the Reef Tank #1: Ostracod

I am going to start a running catalogue of the diverse arthropod microfauna of my reef tank. Here is my first attempt to capture one of these tiny animals. This is a sediment-dwelling ostracod, about 250 microns in carapace length.

Ostracod, the white stuff around him is detritus.

I know, ugly photo, but this was a first attempt. Can anyone ID it further? The rubble in the tank was aquacultured on the gulf coast of Florida, but this little guy could have hopped on at the fish store.

More about Ostracods in my next post.

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Neogonodactylus bredini

I haven’t had much time to write this week on account of wanting to graduate someday. Here is one of the animals that I’m working on at the moment.

Neogonodactylus bredini

N. bredini is the easiest mantis shrimp to find on the east coast since they commonly hitch-hike on reef rubble, cultured in Florida for the aquarium trade. The photo above shows the ‘smasher’ raptorial appendage nicely, as well as the black pseudo-pupil (the facets of the eye that are directly facing the camera). These guys come in a bunch of different color morphs including the rusty color above, green, and grey mottled.

I’m trying to improve my photography skills, but the old Olympus C-5050 I’m using isn’t cutting it any more. It’s no fun trying to manually focus on a moving critter using a 1.8″ 110,000-pixel screen.
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Edit: Correction, this animal is actually N. wennerae. This species is physically indistinguishable from N. bredini. The only reliable determinant other than genetics is habitat depth.

Mantis Shrimp glow in the dark

Mantis shrimp use a variety of visual signals in order to communicate with one another. One set of commonly used signaling structures are the antennal scales; flattened, paddle-like structures derived from the second antennae and set on either side of the mantis shrimp’s head. They have a wide range of motion and can be directed at other mantis shrimp as part of intraspecific threat and mating displays. The antennal scales are often adorned with attention grabbing color and polarization patterns that stand out to other visually adept mantis shrimp.

Attenuation of light in water. Adapted from Levine and MacNichol, 1982

However, the deep ocean is not kind to color contrast. As you move deeper, the absorptive and refractive properties of water attenuate the spectrum of available light. Longer and shorter wavelengths are filtered out until eventually the only available light is blue-green, around 480 nanometers in wavelength (left). Despite this limitation, some deep water mantis shrimp have found a way to preserve their color signals in an essentially monochromatic environment.

Lysiosquillina glabriuscula has bright yellow spots on its antennal scales and the underside of its carapace. This species is found in the shallows as well as at greater depths. It turns out that the yellow spots contain fluorescent materials that are stimulated by blue light and emit yellow light, similar to the yellow reflected light that the spots produce in white lighting. Therefore, these mantis shrimp are able to preserve their yellow spot signals at depths where there is only blue light available.

L. glabriuscula in white light (left) and blue light (right). Blue light is filtered out in the second picture in order to better show the green and yellow fluorescence on the animal. Adapted from Mazel et al., 2004

References:

  • Mazel CH, Cronin TW, Caldwell RL, & Marshall NJ (2004). Fluorescent enhancement of signaling in a mantis shrimp. Science (New York, N.Y.), 303 (5654) PMID: 14615546

Arthropoda ID (#2)

Can anyone ID this little guy?

I’m working up a post about these bizarre animals and I’ll post it shortly after someone IDs it.

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Correct ID by Christopher Taylor.
Answer: Ostracod, Alacia valdiviae (highlight)
Photo from Russ Hopcroft.

Arthropod Roundup: Amphipods under the ice, high octane isopods, and the pea aphid genome

Quick blurbs about arthropod research and news:

  • NASA climate researchers have discovered animal life deep below the Pine Island Glacier Ice Shelf in Antarctica. The researchers drilled a hole six-hundred feet deep and eight inches wide into the glacial ice sheet about twelve miles from the open ocean. When they lowered a camera below the ice sheet, the scientists were surprised to see a Lyssianasid amphipod crustacean swim up and park on the cable. The researchers were only expecting to find microbial life under the ice sheet this far in from the open ocean. It is unknown what the primary energy source for animals living here could be. The presence of a three-inch amphipod, however, suggests a much more elaborate and dynamic ecosystem than hypothesized in this poorly understood habitat. (DSN has a video of the amphipod)
  • Limnoriid isopods, commonly called gribble worms for some reason (they neither are, nor resemble worms), have a ravenous appetite for wood. This is not unusual among arthropods; many diverse groups including termites, millipedes, and squat lobsters are capable of digesting woody plant matter. However, all these creatures process the wood with the aid of gut-dwelling symbiotic bacteria. A new study finds that the Limnoriid isopod, Limnoria quadripunctata is special in that it doesn’t rely on bacteria-produced catalysts to break down wood, but rather has the necessary glycosyl hydrolase enzymes incorporated into its genome. These enzymes are evolutionarily related to similar proteins found in arthropods, but their derived function for wood digestion in Limnoriid isopods is completely novel. The researchers, or their over-excitable university PR department, think the study of these enzymes could aid in bio fuel synthesis.
  • The gemone of the pea aphid, Acyrthosiphon pisum, has been sequenced. This is the first Hemipteran (true bug) genome and will provide clues about the evolutionary history of certain hexapod groups. This new genome could also help agriculturalists develop new techniques to control aphid pests and the spread of aphid-borne plant viruses. Researchers are also interested in the pea aphid’s, apparently, scaled down immune response system and their ability to easily switch specialization from one plant species to another.

Arthropod on arthropod violence

How does a swarm of army ants take down a heavily armored fresh water crab? Let’s find out…


That’s gotta be a pretty terrible way to go.

Red in mandible and pincer…

Mantis Shrimp Vision Preview

I haven’t been able to post any hard science this week since I’ve been working on a presentation for my department’s annual symposium. So far, this is the largest audience I have presented my work to.

I thought I might quickly share one of my slides from that presentation as a preview for a much larger future post about the ridiculously complicated mantis shrimp visual system.

Click to embiggen. Stomatopod Photo: Roy Caldwell

This is a comparison of photoreceptor classes in human and mantis shrimp retinas. Each photoreceptor class has a distinct wavelength sensitivity curve. On the human plot, you can see our three cone photoreceptor classes; blue, green, and red. These receptors cover the electromagnetic light spectrum between 400 nm (violet) and 700 nm (red). Our brains are able to process relative stimulation between the three cone photoreceptor classes, allowing us to differentiate many colors.

Mantis Shrimp don’t have the advantage of a large brain for downstream processing, so they take another approach to seeing many colors: They have 16 distinct photoreceptor classes, packed via optical filtering into tight slivers of the spectrum. Of these, five classes are sensitive to UV light, below our visual range (these are the receptor classes that I am attempting to characterize). In addition, not shown in this slide, mantis shrimp can discriminate linearly and circularly polarized light.

Stay tuned for an in depth mantis shrimp vision post at some point.


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I have moved.
Arthropoda can now be found here.

Michael Bok is a graduate student studying the visual system of mantis shrimp.

Flickr Photos