Marine Invertebrates of Bermuda Squat Shrimp (Thor amboinensis) Genna Ruzanski and James B. Wood (Ed) Abstract Taxonomy  Habitat  Ecology  Recent Research  Commercial Importance  Bermuda Laws  Personal Interest  References  Links

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©1997-2005 Jeffrey N. Jeffords.



Abstract


      The Squat shrimp, Thor amboinensis is a small, spotted shrimp found in shallow coral reef areas throughout Bermuda, the Caribbean and the Indo-Pacific region. Thor amboinensis is one of the most common species of shrimp seen throughout the Indo-Pacific, but is rarely seen in Bermuda or the Caribbean. These shrimp are distributed with respect to available host habitat. Thor amboinensis shares a symbiotic relationship with several species of anemones by living within their tentacles. Some Squat shrimp have even been observed providing cleaning service to Mantis shrimp, Lysiosquillina lisa . Thor amboinensis is sometimes nicknamed the sexy shrimp due to its tendency to vibrate its abdomen while walking. Even though Thor amboinensis is a very commonly sold decapod in the aquarium industry, it is still poorly understood.

Taxonomy


Phylum: Arthropoda
  Subphylum: Crustacea
    Class: Malacostraca
      Subclass: Eumalacostraca
        Order: Decapoda
          Suborder: Pleocyemata
            Infraorder: Caridea
              Superfamily: Alpheoida
                Family: Hippolytidae


      Thor amboinensis are usually less than 1.3 cm in size (Boyer 2002). Being a member of the Hippolytidae family, these shrimp have short-stalked eyes that are not covered by their carapace (Sterrer 1986). The rostrum is well developed and does not overreach the eyes or expand ventrally (Sterrer 1986). Thor amboinensis are a deep brown color with bright white splotches outlined in blue. The abdomens and tails of these shrimp typically arch upwardly towards their heads (Boyer 2002).

Habitat


      Squat shrimp are found on anemones in shallow waters throughout the Caribbean and Indo-Pacific. These shrimp, although sparse are also located in Bermuda among inshore patch reefs to the terrace reefs (Sterrer 1986). Thor amboinensis lives protected from predators within an anemone’s tentacles which serve as protection and food for the shrimp, while the host anemone is unaffected (Wirtz 1997, Boyer 2002).

      These shrimp are typically found in groups within a single anemone (Khan et. al 2004). Within host anemones, Thor amboinensis feed primarily on mucus-covered tentacles and on the planktonic organisms that are trapped upon them (Guo 1996). Thor amboinensis has been found on the Carpet anemone, (Stichodactyla haddoni) Telmatactis cricoids (no common name), the Adhaesive anemone (Cryptodendrum adhaesivum) and the Stinging anemone, (Lebrunea danae), as well as several other anemone species (Guo et. al 1996, Sterrer 1986).

Ecology


       To avoid predation, Thor amboinensis relies on host anemones to keep them sheltered from predators. The shrimp select their host by visual distinction and chemical cues (VandenSpiege et. al 1998). In one study of crustacean symbionts in anemones in Madeira and the Canary Islands, Thor amboinensis was the most common shrimp found (Wirtz 1997).

       Thor amboinensis does not commonly interact with other species, however, it is not unusual for many Squat shrimp to congregate on a single anemone (Khan et. al 2004). When Thor amboinensis was kept in an enclosed aquarium environment with other organisms, it showed no hostility towards its own species or other aquarium dwellers (Dunder 2007). Vibrant camouflage colors are displayed on Thor amboinensis’ body to blend in with its environment. Squat shrimp are found typically in shallower waters with little wave disturbance (Wirtz 1997).

       Thor amboinensis uses sexual reproduction to produce larvae. After intercourse, the female shrimp holds the fertilized eggs until they are ready to hatch before releasing them into the water column (Firemouth 2007). Thor amboinensis larvae are vulnerable, slow-growing and require ample protection during maturation (Firemouth 2007). Thor amboinensis displays sexual dimorphism with the females being significantly larger than the males (VandenSpiege et. al 1998).

       In the wild, the diet of the Squat shrimp consists of the host anemone’s mucus-covered tentacles and the planktonic organisms trapped upon them. However, when kept in saltwater aquariums, they consume algae and brine shrimp (Khan et. al 2004, Dunder 2007).

Recent Research


       Research by Khan et. al (2004) using three shrimp: the Holthuis cleaner shrimp, Periclimenes holthuisi, Periclimenes brevicarpalis (no common name) and Thor amboinensis to display the spatial distribution of symbiotic shrimps on the sea anemone, Stichodactyla haddoni. It was found that all the shrimp highly depended on the anemones for shelter and food and preferred the outer tentacles of their hosts (Khan et.al 2004). This preference could be due to the increase in food availability (Khan et. al 2004). This information is important to know about the shrimp in order for them to survive if their host is lost.

       In order to determine what type of anemones Thor amboinensis selects for its hosts, Guo (1996) performed an experiment on host selection using symbiotic shrimp and anemones. The data revealed that Thor amboinensis exhibited no specific preference in anemones, however, it was inferred that the shrimp were able to chemically and visually select their host (Guo 1996). Many shrimp displayed a chemical reaction to an anemone of a particular species (Guo 1996). This result was inferred because none of the shrimp in the experiment were able to locate their host anemone with vision alone, but all of the specimens were able to locate their host with both visual and chemical cues (Guo 1996). Many shrimp also displayed a chemical attraction to an anemone of a particular species (Guo 1996).

       Wirtz (1997) researched crustacean symbionts of the sea anemone Telmatactis cricoids in Madeira and the Canary islands. Thor amboinensis was the crustacean symbiont found most frequently in all the tested anemones (Wirtz 1997).

       Increasing interest in maintaining salt water tanks has heightened the demand for collectable aquarium fish and invertebrates (Calado et. al 2006). A recirculation system on shrimp breeding was studied by Calado et. al (2006) to improve the aquaculture of Thor amboinensis and other marine decapods.

Commercial Importance


      Thor amboinensis is popularly sold around the world for use in personal aquariums because of its beauty, abundance, and easy maintenance (Calado et. al 2006). The Squat shrimp is considered one of the most heavily collected marine ornamental decapods (Calado et. al 2006). Because of its popularity, it is important to ensure that this species is not over-collected.



Bermuda Laws


       No shrimp are listed as protected on the 2007 Convention on International Trade in Endangered Species of Wild Fauna and Flora. However, in Bermuda, three shrimp: Typhylatya iliffei, Procaris chacei and Mitocaris halope were listed under the protected species order for 2007 (Bermuda Law Database 2007)

Personal Interest


       I chose the Squat Shrimp because photography and painting have been hobbies of mine for years, and it has been one of my goals to capture some photos of shrimp. Thor amboinensis are particularly fascinating because of their vibrant colors and peculiar tendency to wiggle their abdomen. Thor amboinensis are also intriguing because very little research has conducted regarding their behavior or feeding in the wild even though they are extremely common in marine aquaculture. Overall, this was a very interesting research assignment, despite the fact that these shrimp are quite difficult to find information about. Also, throughout completing this assignment, I learned more about Decapods and shrimp both of which were topics that I previously knew very little about.

From my experience in SCUBA diving and snorkeling in Bermuda, these shrimp seem to be very rare. I have not seen one yet! They will not allude me for long though! Photos will be captured!!!!

References

Boyer, M. 2002. Squat Shrimp: Thor amboinensis.Life at the Edge of the Reef. Available at: http://www.edge-of-reef.com/macruri/MACThoramboinensisen.htm. Accessed November 9th, 2007

Calado, R., Vitorino, A., Dionisio, G. and Dinis, M.T. 2006. A recirculated maturation system for marine ornamental decapods. Aquaculture. 263: 68-74

2007. Customs Tariff Amendment Act 2007- First Schedule. Available at: http://www.laws.gov.bm/. Accessed November 9th, 2007.

Debelius, H. 1984. Crustacea- Guide of the World: Shrimps, Crabs, Lobsters, Mantis Shrimps, Amphipods. New York. TMC Publishing

Guo, C.C., Hwang, J.S. and Fautin, D.G. 1996. Host Selection by shrimps with sea anemones: A field survey and experimental laboratory analysis. Journal of Experimental Marine Biology and Ecology. 202:165-176

Inskip and Gillett. 2005. Checklist of CITES Species and Annotated CITES Appendices and Reservations. Available at: http://www.cites.org/common/resources/2005_CITES_Checklist.pdf. Accessed November 8th, 2007.

Jeffords, Jeffrey. 2005. Jeff’s Nudibranch Site and Coral Reef Gallery. Available at: http://www.divegallery.com/shrimp_ambonian.htm. Accessed October 24th, 2007.

Khan, R.N, Becker, J., Crowther and A., Lawn, I. 2004. Spatial distribution of symbiotic shrimps (Periclimenes holthuisi, P. brevicarpalis, Thor amboinensis) on the sea anemone Stichodactyla haddoni. Journal of the Marine Biological Association of the United Kingdom. 84: 201-203

Sterrer, W. Marine Fauna and Flora of Bermuda: A Systemic Guide to the Identification of Marine Organisms.USA: John Wiley & Sons Inc.

VandenSpiege, Eeckhaut, I. and Jangoux, M. 1998. Host selection by Synalpheus stimpsoni (De Man), an ectosymbiotic shrimp of comatulid crinoids, inferred by a field study and laboratory experiments. Journal of Experimental Maine Biology and Ecology. 225: 185-196

Wirtz, P. 1997. Crustacean symbionts of the sea anemone Telmatactis cricoids at Madeira and the Canary Islands. Journal of Zoology. 242: 799-811 Links

Fishkeeping Care Sheets: Sexy Shrimp
CITES
Laws of Bermuda
Squat shrimp Thor amboinensis