Mantis Shrimp

General Information

Kingdom: Animalia

Phylum: Arthropoda

Class: Crustacea

Sub-class: Malacostraca

Super-order: Hoplocarida

Order: Stomatopoda

There are 400 species of the extraordinary mantis shrimp, or the stomatopod, that span 12 families. It really is not a shrimp, but a shrimp like crustacean. They are also split into two other different groups determined by their claws. There are the smashers and the spearers. The smashers have a clubbed claw to smash their prey while the spearers have sharper appendages to kill their prey. Below is a smasher mantis shrimp attacking its prey.

The Eye

The mantis shrimp has a apposition compound eye with many different ommatidia each with their own photoreceptor. The apposition part of the name means that this eye creates an inverted image. Typically a compound eye uses a combination of all the inputs from the ommatidia to create an image. The eye of the mantis shrimp has four times as many cone types as a human eye. This is a whopping 12 cones! Four of these cones allow mantis shrimp to visualize ultraviolet (UV) light.

The upper third of the eye is the dorsal hemisphere while the lower third of the eye is the ventral hemisphere. In the midband of the eye pictured above, there are six rows. The top four rows convey color information while the bottom two rows deal with light polarization. Each of the rows has two tiers. The first tier is made up of UV detecting cones. The second tier has two levels of cones within them, this is why the top four layers can each have a sensitivity to two colors. The first level of the second tier has one color sensitivity cone while the bottom level of the second tier has another color sensitivity cones. These UV cones in the first tier of mantis shrimp eye cones expand the mantis shrimp's vision spectrum from a typical 400-700nm range to 300-700nm (Marshall and Oberwinkler, 1999). But, it has been found that mantis shrimp do not visualize colors, UV or otherwise, in the way that other animals possessing UV cones do. They actually are quite bad at distinguishing colors that come between 15nm within each other. In a study done by Thoen et al., the mantis shrimp were trained to pick a specific wavelength within an optic fiber via food reward enforcement. When trained and put in front of two fibers that projected wavelengths within 15nm of each other, they were unsuccessful in choosing the correct colored fiber. Their discrimination threshold was a 60% success rate. In contrast, some people can distinguish colors 1-2nm apart (Milius, 2012). They use scanning movements to create temporal signaling to enable color recognition instead of color discrimination (Thoen et al., 2015). This has been attributed to the mantis shrimp's fast paced life-style where basic color recognition is sufficient for survival.

The use of light polarization in the mantis shrimp is also interesting because of how developed their eye is. The use of light polarization cones is also found in animals like the cuttlefish and other cephalopods. But they do not have color vision like the mantis shrimp do so the use of light polarization techniques to visualize their environment is not peculiar. In the other cephalopods and cuttlefish, polarized light was believed to be use to navigate and orient themselves (Cronin et al., 2003). But the mantis shrimp actually recognize this polarized light and use it as it does color cues. This was shown by an experiment conducted by Marshall et al., that used much the same technique as the one that showed mantis shrimp could learn color preference. They were presented with multiple types of polarized light and chose the light that was similar to the one they were trained on with food reinforcements.

Fluorescents

Mantis shrimp have strong fluorescent yellow markings on their antennae and upper shell. In a study done by Mazel et al., it was shown that the mantis shrimp uses these spots for signaling. This had not yet been done before, fluorescent color signaling had not yet been seen in the sea. When male mantis shrimps are in threat display, the fluorescent coloring can make them seem bigger to predators and other males when they move in on other mantis shimp's territory to mate. These marking also clearly illuminate and show off the mantis shrimp's claws or weapons.

Sexual Role Reversal

In the common mantis shrimp, pseudosquilla ciliata, there is precopulation sex role change. In this instance, the female pursues and shows off for the male. The males then often mate with females larger than themselves. While role change during sex is noteworthy in itself due to the low occurrence rate in nature, it is especially interesting in the example of the common mantis shrimp. This is because there is no reversal in the male to female breeding costs. Usually this type of behavior, where the female pursues the male counterpart, evolves when there is a higher price of reproduction for the male than female. But this is not the case for the mantis shrimp. There is no parental care, nuptial gifts, or female guarding in the instances of the mantis shrimp, these often spur the sex role change (Hatziolos and Caldwell, 1983).

Fun Facts

• Many species of the mantis shrimp are eaten in Asian cultures

• The peacock shrimp is very beautiful and colorful, it is kept in many marine tank collections

Bibliography

Cronin, T. W. "Polarization Vision and Its Role in Biological Signaling." Integrative and Comparative Biology 43.4 (2003): 549-58. Web.

Hatziolos, Marea E., and Roy L. Caldwell. "Role Reversal in Courtship in the Stomatopod Pseudosquilla Ciliata (Crustacea)." Animal Behaviour 31.4 (1983): 1077-087. Web.

Marshall, Justin, and Johannes Oberwinkler. "Ultraviolet Vision: The Colourful World of the Mantis Shrimp." Nature 401 (1999): 873-74. Web.

Marshall, Justin, Thomas W. Cronin, Nadav Shashar, and Mike Land. "Behavioural Evidence for Polarisation Vision in Stomatopods Reveals a Potential Channel for Communication." Current Biology 9.14 (1999): 755-58. Web.

Mazel, C. H. "Fluorescent Enhancement of Signaling in a Mantis Shrimp." Science 303.5654 (2004): 51. Web.

Milius, Susan. "Life: Mantis Shrimp Flub Color Vision Test: Results Suggest Alternate Way of Detecting Wavelengths." Science News 182.6 (2012): 11. Web.

Thoen, H. H., M. J. How, T.-H. Chiou, and J. Marshall. "A Different Form of Color Vision in Mantis Shrimp." Science 343.6169 (2014): 411-13. Web.