Marine Invertebrates of Bermuda Split-Thumb Mantis Shrimp (Gonodactylus bredini) By Lori Lester Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

Taxononmy


Phylum: Arthropoda
  Subphylum: Mandibulata
    Class: Crustacea
      Subclass: Malacostraca
        Order: Stomatopoda
          Family: Gonodactylidae


Habitat


Worldwide, there are approximately 400 different species of mantis shrimp. These creatures can be found throughout all tropical and subtropical marine environments (Cronin et al., 1994). Nearly 250 of these species live in the Indo-West Pacific region (Ahyong, 2003). Approximately 125 of the species located in this region reside in the waters surrounding Australia (Ahyong, 2003). Even now, new species of mantis shrimp are still being discovered. The newest ones have been found off the coast of New South Wales, Australia (Ahyong, 2003). Most commonly, mantis shrimp are found inhabiting the top few meters of water (Marshal and Oberwinkler, 1999). Researchers oftentimes have difficulty finding mantis shrimp because they spend the majority of their time hiden inside the rocks or corals in intertidal and subtidal areas (Sterrer, 1986). This website focuses on the mantis shrimp, Gonodactylus bredini, which is common throughout Bermuda and the Caribbean Sea (Shuster and Caldwell, 1989).



Ecology


Mantis shrimps are not closely related to true shrimps. These organisms branched off from the main line of crustaceans about 400 million years ago, when trilobites were the dominant marine arthropods (Cronin et al., 1994). Today, mantis shrimp are known for their switch-blade like raptorial legs. Two different types of mantis shrimp exist, the spearers and the smashers (Ahyong, 2003). Both of these strike prey or competitive conspecifics by unfolding and swinging their raptorial appendages. The spearers have a claw that is lined with many sharp teeth. These mantis shrimp hunt by impaling prey with these teeth. Most of the time, they feed on animals such as worms, shrimps and fish. On the other hand, smashers have a club-shaped claw. They use this claw to smash their prey. Typically, they feed on hard-bodied animals such as snails and crabs (Ahyong, 2003). G. bredini are a combination of smasher and spearer.

Technically, these raptorial legs are the mantis shrimp’s 2nd maxillipeds (Shuster and Caldwell, 1989). They are capable of delivering extremely powerful blows with these maxillipeds. The raptorial strike lashed out by these creatures is one of the fastest movements made by any animal. Moreover, mantis shrimp can actually break the glass of an aquarium with this strike (Cronin et al., 1994). These creatures use this raptorial leg to attack prey and defend their burrows from conspecifics. During a fight between conspecifics, individuals can be extremely injured or even killed (Shuster and Caldwell, 1989). In addition to the raptorial legs, mantis shrimp can use their telson as a shield. G. bredini have specialized, heavily armored telsons that can be used as a shield to protect the animal from predators and violent conspecifics (Heitler et al., 2000).

Mantis shrimp use their burrows as a place to process hard-shelled prey, molt, mate, and care for eggs and larvae (Steger, 1987). Initially, the breeding pair of mantis shrimp establishes their territory and defends the space around it. However, the territory is typically defended by only one member of the mating pair. Males typically leave the cavity after oviposition and then provide no parental care to the young. After the male leaves, the female is left responsible for the protection of her brood and her territory (Shuster and Caldwell, 1989).

Research has been done to determine what limits the number of mantis shrimp individuals that can live in a certain area. Results suggest that periods without recruitment and the shortage of protective burrows limits the number of individuals that can habituate a specific site (Steger, 1987). Recruitment occurs every month for up to seven months. At that point, recruitment can be absent for up to five or six consecutive months (Steger, 1987). This pattern of non-continuous recruitment limits the local densities of smaller individuals. The number of smaller individuals is then below the capacity of small cavities during parts of the year. Therefore, small individuals are typically not limited by the number of available burrows. On the other hand, large individuals are oftentimes limited by the abundance of available living cavities. Although the pattern of recruitment does not affect the large individuals; overall, large cavities are more difficult to find than small cavities (Steger, 1987). Thus large individuals must search the open ocean for a longer period of time for an appropriate burrow. This leaves the mantis shrimp open to attack from various other forms of sea life. Appropriate burrows are absolutely necessary for the small or large mantis shrimp to survive.

Shuster and Caldwell (1989) studied whether or not male mantis shrimp prefer large females over smaller females (Shuster and Caldwell, 1989). In general, large females are more fecund than small females. This study consisted of a set of experiments in which male or female mantis shrimps were allowed to enter the burrow of a reproducing pair. In a typical mating pair situation, the male takes on the defense role. The males in the mating pair were found to use the same fighting techniques against male intruders as they used against female intruders. Natural selection has favored the mantis shrimp male that defends its reproductive habitat against any intruder, male or female. When evicted from a cavity, both male and female mantis shrimp experience the risk of predation. In addition, they lose energy and waste time trying to locate a new burrow. Therefore, evolutionarily it makes more sense for the male mantis shrimp to remain with the same female instead of opting for a larger and thus more fecund one. When a male remains with the same female for an extended period of time, the chance of him finding a new mate diminishes. The male remaining with the female is also beneficial for the female. When the female mantis shrimp is reproducing, she gains the protection of the male. No evidence was found in this study that suggests that males would exchange their present mate for a larger female (Shuster and Caldwell, 1989).

Other research has studied how G. bredini defend themselves after molting. At this time, the stomatopods lose their body armor and the use of their raptorial appendages (Steger and Caldwell, 1983). This leaves the mantis shrimp extremely vulnerable to attack. However, oftentimes these newly molted stomatopods can bluff conspecific opponents. Although the molted mantis shrimp cannot actually fight, it makes the conspecific believe that it can. For three days after molting, the mantis shrimp’s cuticle is very soft and offers little to no protection from predators and conspecific opponents. New molts can oftentimes protect their cavities by displaying aggressive actions to their competitor. There are five different acts that mantis shrimp use to suggest aggression: appear, lunge, meral spread, strike-cavity, and strike-opponent. The newly molted mantis shrimp tend to use meral spread commonly since they cannot strike. G. bredini perform a meral spread by facing their opponent and leaning out of their cavity. The mantis shrimp then raises and spreads its raptorial appendages. Many times this movement is enough to make the opponent swim away rapidly. A mantis shrimp is more dangerous when it has large raptorial appendages. By raising its raptorial appendages during meral spread, the mantis shrimp is trying to show that it has larger raptorial appendages than the opponent. Since fighting can be costly, in most cases the opponent falls for the bluff and leaves the molted mantis shrimp alone (Steger and Caldwell, 1983).

Many scientists argue that if mantis shrimp continue to successfully bluff to scare off conspecifics then eventually all mantis shrimps will evolve to use the meral spread technique. If all mantis shrimps used the meral spread technique, it would no longer be effective. However, Eldridge Adams has suggested a theory as to why this behavior persists. According to Adams, the meral spread is only cost efficient for certain mantis shrimps (Holden, 1995). This intermittent use of the bluffing behavior leads to the persistence of the behavior. When the molted mantis shrimp performs the bluffing behavior, it takes the risk that the conspecific will attack. Thus animals of just mediocre strength are better off not using the meral spread technique to try to ward off opposing conspecifics. Basically, only the strongest and the weakest mantis shrimp benefit from bluffing (Holden, 1995). Thus the bluffing technique will continue to ward off opposing conspecifics as long as only the strongest and weakest mantis shrimp use the bluffing technique.



Recent Research


Throughout the past decade, researchers have studied the eyesight of Gonodactylus bredini and a variety of other mantis shrimps in depth. The mantis shrimp has an extremely complex, compound eye (Cronin et al., 1994). G. bredini’s eye is made up of thousands of individual units called ommatidia. This eye has an apposition design, which means that each ommatidium is responsible for viewing a single location in the visual field. Honey bees have eyes with the same apposition design. G. bredini can aim individual ommatidia so that receptors in different parts of the eye can inspect the same region of visual space. Another unique feature of their eyes is that the filters are located inside the photosensitive region of the photoreceptive region of the photoreceptive cell. Moreover, a single photoreceptor can have more than one type of filter (Cronin et al., 1994).

Furthermore, the eyes of the mantis shrimp have developed with triply overlapping fields of view (Cronin et al., 1994). Each eye consists of two hemispheres that are separated by a midband. There are groups of ommatidia in each hemisphere that share visual fields with the ommatidia in the midband. This results in a strip where each point is imaged by three sets of receptors. G. bredini have six parallel rows of ommatidia. The photoreceptors in G. bredini are found in the upper four rows of ommatidia and are grouped into three tiers. The light that enters this part of the eye becomes modified because it passes through several levels of photoreceptive cells (Cronin et al., 1994). Evolutionarily speaking, this complex eye developed in order to create more accurate depth perception to allow them more precision when striking predators (Cronin et al., 1994).

Another variety of mantis shrimp, Neogonodactylus oerstedii, also have extremely advanced eyesight (Marshal and Oberwinkler, 1999). These mantis shrimp have four different types of photoreceptors, called R8 cells, for ultraviolet light. In addition, they have excellent color-vision. N. oerstedii evolutionarily developed complex retinae within their apposition compound eye. The top four rows of midband contain eight spectral sensitivities from wavelengths of 400 to 700 nm (Marshal and Oberwinkler, 1999). Three of the R8 cells are found in the midband, and one is located in the periphery. This mantis shrimp have a single color vision system that is sensitive from 300 to 700 nm. They have excellent fine color discrimination and color constancy. Scientists suggest that the eye may be able to examine color space from 300 to 700 nm in the same way that the ear examines auditory space (Marshal and Oberwinkler, 1999). Future research should explore the color vision of G. bredini.

Yet another type of mantis shrimp, Odontodactylus scyallurus, has eyes that are the invertebrate equivalent of the avian eye in vertebrates (Schwab, 2003). In this creature, the ommatidium contains eight separate retinular cells that provide microvilli with photopigments in its membranes. Each of these sets of microvilli is called a rhabdomere and creates the rhabdom at the center of these cells. The rhabdom is the light sensitive portion and it is composed of eight different cells. The rhabdoms in four of the six midband rows are arranged in tiers of two pair of rows. The remaining two rows have specialized ommatidia for analysis of linear polarized light. The most distal of these two is the ultraviolet sensitive portion and is provided by the rhabdomeres of one retinular cell. The remaining seven retinular cells provide rhabdomeres with appropriate orientation. In addition, they provide the animal with a visual pigment for detection of linear polarized light (Schwab, 2003).

In addition to eyesight research, there is experimentation being done on the plume tracking capability of some species of mantis shrimps. So far, no research has been conducted on the tracking ability of G. bredini. However, research has been executed on Hemisquilla ensiguesa californica. Plume tracking is defined as the act of following an odor plume to its source (Mead et al., 2003). Animals use these cues to find food, mates, and suitable habitats. Moreover, they can use these odor plumes to detect predators or conspecifics. Typically, odor plumes consist of fine filaments that contain moderate to high concentrations of odor molecules that are mixed with surrounding fluid. Mantis shrimp sample these odor plumes by moving their antennules through. Overall, the mean available concentration of odor plumes was found to be higher in wave-affected water flow than in unidirectional flow (Mead et al., 2003). The mantis shrimp tended to track odor plumes that were in wave-affected water more consistently than those in unidirectional flow (Mead et al., 2003). Further research would need to be performed in order to determine whether or not G. bredini track odor plumes.



Commercial Importance


In many Asian cultures, mantis shrimp are considered a delicacy and commonly eaten by middle and upper class people. Basically, mantis shrimp are an important commercial species, especially in Hong Kong (Lai and Leung, 2003). Mantis shrimp are served in sushi bars all around the world under the name, shako (Sushi Vocabulary, 2003). A single serving of shako contains 47 kcal. In addition, shako is a great source of vitamin B1 and B2 (Sushi Vocabulary, 2003).

Due to the commercial importance of the mantis shrimp, a trawling survey was recently conducted to study the diversity and abundance of mantis shrimps in the sub-tidal marine environments of Hong Kong (Lai and Leung, 2003). Mantis shrimp were collected by trawling between December 2002 and February 2003. Ten different trawling stations were surveyed. Four of these stations were in Tolo Harbour Waters, three were off the Southern Coast of Hong Kong Island, and three were located in the waters around Lantau Island. Two of the stations produced no mantis shrimps. Overall, eight types of mantis shrimp were collected and identified. G. bredini was not found during this study. However, the mantis shrimp species Miyakea neap, Oratosquilla oratoria, Oratosuillina interrupta, Dictyosquilla foveolata, Clorida decorate, Harpiosquilla harpax, Anchisquilla dasciata, and Erugosquilla woodmasoni were all found (Lai and Leung, 2003).

Bermuda Laws


None.



Personal Interest


My personal interest in the mantis shrimp, G. bredini, began on the day my Marine Invertebrate Zoology class went to Bailey’s Bay, Bermuda to do field work. Our goal was to snorkel around the bay and find a variety of Arthropods among the sea grass habitat. I, along with my wonderful roommate Miranda Hoover (Refer to Portuguese man-o-war page), was turning over rocks and searching for Arthropods when suddenly a lime green colored creature scampered along the sandy ocean bottom. At the time, I did not know that it was a mantis shrimp. I quickly swam after the menacing creature and pulled out a plastic baggie to use to collect the specimen. Quickly and painlessly I captured the mantis shrimp and placed it in the sealed baggie for safe keeping. Everything seemed perfect, I was snorkeling through the bay with our exotic new friend, eagerly awaiting our arrival in the lab later to identify my unique organism.

Unfortunately, several minutes later Miranda found a dead crab. Extremely excited by the dead crab (because we hadn’t seen many other arthropods), Miranda quickly asked me for a plastic baggie. At this point, we had filled all of our baggies so I absentmindedly handed her the one that contained the mantis shrimp. Miranda tore open the bag and the mantis shrimp escaped. My quick thinking roommate and I immediately surrounded the mantis shrimp and tried to scurry it back into the plastic baggie. After several intense minutes of yelling through our snorkels at each other and flopping around in the two feet of water, we managed to collect both the mantis shrimp and the prized dead crab. The field work had been a success.

After arriving back at the lab, Miranda and I collected our plastic baggie in order to identify the then unknown mantis shrimp. Unfortunately, the mantis shrimp had hidden inside a gastropod shell that was also collected for study. Miranda and I then grabbed a hammer, which any reasonable person would do, and went outside the lab to bust open the shell. Once outside, Miranda took the honors of breaking the shell apart bit by bit in order to not harm the mantis shrimp. Finally, the moment we had both waited for arrived and we heard the dreaded clicking sound of the mantis shrimp. The creature climbed out of the shell and lashed out at Miranda, who barely escaped its raptorial claws. Back in the lab, we identified the creature as the mantis shrimp, G. bredini, and my interest in this marvelous species began.

References

Ahyong, S. 2003. Mantis Shrimp – Colorful and Aggressive. Australian Museum. Online. Internet. http://www.amonline.net.au/factsheets/mantis_shrimp.htm Accessed on: 25 February, 2004.

Cronin, T. W., Marshall, N. J., and M. F. Land. 1994. The Unique Visual System of the Mantis Shrimp. American Scientist. 82: 356.

Heitler, W. J., Fraser, K., and E. A. Ferrero. 2000. Escape Behavior in the Stomatopod Crustacean Squilla mantis, and the Evolution of the Caridoid Escape Reaction. Jour. Of Exp. Biol. 203: 183-92.

Holden, C. 1995. The Bluffing Shrimp. Science. 270: 237-9.

Lai, W. C., and K. Leung. 2003. Mantis Shrimp found in Hong Kong waters – A brief look at the Stomatopoda. Invertebrates. 3-4.

Marshall, J., and J. Oberwinkler. 1999. The Colourful World of the Mantis Shrimp. Nature. 401: 873-4.

Mead, K. S., Wiley, M. B., Koehl, M. A. R., and J. R. Koseff. 2003. Fine-scale Patterns of Odor Encounter by the Antennules of Mantis Shrimp Tracking Turbulent Plumes in Wave-affected and Unidirectional Flow. Jour. Of Exp. Biol. 206: 181-93.

Schwab, I. R. Superman on the Reef. 2003. British Journal of Ophthalmology. 87:132.

Shuster, S. M., and R. L. Caldwell. 1989. Male Defense of the Breeding Cavity and Factors Affecting the Persistence of Breeding Pairs in the Stomatopod, Gonodactylus bredini. Ethology. 82: 192-207.

Steger, R. 1987. Effects of Refuges and Recruitment on Gonodactylid Stomatopods, A Guild of Mobile Prey. Ecology. 68: 1520-33.

Steger, R., and R. L. Caldwell. 1983. Intraspecific Deception by Bluffing: A Defense Strategy of Newly Molted Stomatopods. Science. 221: 558-60.

Sterrer, W. 1986. Marine Fauna and Flora of Bermuda. Wilsey-Interscience: New York, 308.

Sushi Vocabulary. Tokyo Food Place. Online. Internet. http://www.bento.com/sushivoc.html Accessed: 25 February 2004.

Links

The Lurker's Guide to Stomatopods
Mantis Shrimp - Colorful and Aggressive
Reef Marine Park Reference Material - Mantis Shrimp
Mantis Shrimp - Shako