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Explaination of characteristics:

Color is a really bad characteristic for shrimp, because it is often determined by what their diet consists of and is not a good trait to look at when dealing with genetics. Overall patterning is usually a bad characteristic as well, but I chose to look at the presence of patterning on the claws since this is definitely a good systematic characteristic of at least some marine shrimp species(1). I also looked at some characteristics suggested by the Shrimp Identification Site, which seemed like a reliable source. However I was only able to create two state names (such as presence and absence, or "short" and "long") for all of my characteristics, rather than counting things like rostrum teeth, because of the very few taxa I was able to get. It would have complicated things if I had created more than two states for my characteristics. There were also some characteristics that were applicable only for the Macrobrachium, such as tail spine number, which I could not observe well in Goby shrimp and was not even a reliable characteristic for the coral banded shrimp.

I acknowledge that my phyogenetic tree is not accurate, but this is the best I could do after trying various combinations of characteristics. For example, even though symmetry or asymmetry of claws is an important feature, I noticed that claws do vary a lot in shape, even when species are closely related, so due to this tendency for the claw shape to be such a mutable characteristic, it might be a bad characteristic especially when comparing a small number of widely-spaced out (phylogenetically) species. If you notice though, I didn't take it out of the character matrix because I thought it was still a pretty important feature for pistol shrimp (in nature, all species of pistol shrimp have assymetrical claws unless a nerve is severed, inducing it to develop another large claw--this has only been seen once in the wild) and taking it out of the matrix didn't affect the tree anyway.

Still, the phylogenetic tree probably SHOULD have looked like this:

Nevertheless, someone with more time, better shrimp-dissecting resources, and more luck with catching shrimp could probably make a really interesting phylogenetic study on freshwater shrimp in Borneo. (I say freshwater shrimp in particular becuase if I didn't have to do ecological notes on the shrimp, I probably could have easily done various marine shrimp by going to the Phillipino market in Kota Kinabalu.)

Questions that came to mind as I consider my taxon:

While I don't recomend for future BOB to do any more taxon studies on shrimp, I do think that more research projects involving freshwater shrimp are needed. Shrimp, especially the small, freshwater ones that do not make up such a big part of our diet, seem to be overlooked. However they are often good indicator species of how the forest around the river is doing, and there are even some studies that show shrimp species being specific to primary or secondary forest streams due to the differences in stream bed composition(2). In addition, some freshwater species are now facing competition pressures and diseases brought on by invasive species, as in the case of Lactococcus garvieae, a virulent bacteriophage originally spread by Thai freshwater shrimp to Taiwanese Macrobrachium(3). Others have their life-long migratory patterns interrupted by river pollution and human development(4).

Also, good phylogenetic studies of shrimp would be useful in biogeography, especially when you can focus on a single widespread genus; the distribution of Macrobrachium is world-wide and they seem to occur in a wide variety of South American, Indian, and African tropical stream habitats(5) in addition to freshwater SE Asian habitats; furthermore, within those regions, many specialized Macrobrachium species have been found in isolated pools such as those in caves(6). Determining how and when they managed to be distributed so far as a freshwater stream species can probably help date the ages of rivers when certain freshwater sources diverged, dried up, or became isolated. It could give us a better understanding about the geographic features that shaped the continents before they separated.

References:

 1. Knowlton, N and Mills, DK. (1992) The systematic importance of color and color pattern: evidences for complexes of sibling species of snapping shrimp (Caridea: Alpheidae: Alpheus) from the Caribbean and Pacific coasts of Panama. Proceedings of the San Diego Society of Natural History. 18: 1-5. 

 2. Iwata, T; Inoue, M; Nakano S; Miyasaka, H; Doi, A; Covich, AP. (2003) "Shrimp abundance and habitat relationships in tropical rain-forest streams, Sarawak, Borneo." Journal of Tropical Ecology 19: 387-395.

 3. Zhang, Z. (2003) "淡水長腳大蝦病害發生情形與可能防治措施 (Freshwater long-legged [Macrobrachium rosenbergii] shrimp, their diseases, and prevention)." 水 產 種 苗 (Fisheries Journal) 66. 20 August 2008. <http://www.fish.org.tw/chinese/magazine/magazine-66b.htm>

 4. Liao, Y and Liu, Y. (2002) "台 灣 的 淡 水 蝦 類 簡 介 (Introduction to Taiwan's freshwater shrimp)." Taiwan Endemic Speices Research Institute 40.  20 August 2008. <http://nature.tesri.gov.tw/tesriusr/internet/natshow.cfm?IDNo=721>

 5. BayScience Foundation, Inc. "Macrobrachium." ZipCode Zoo.18 August 2008. <http://zipcodezoo.com/Animals/M/Macrobrachium_brasiliense/default.asp>

 6. Li, J; Cai, Y; Clarke, A. (2006) "A new species of troglobitic freshwater prawn of the genus Macrobrachium from southern China." The Raffles Bulletin of Zoology. 54: 277-282.

 7. Rosenberry, B. "Anatomy of a Shrimp." Shrimp News International. 19 July 2008. <http://www.shrimpnews.com/AnatomyShrimp.html>

 8. Komai, T. and Matsuura, K. (2005) Shrimp Identification Site. 19 July 2008. <http://svrsh1.kahaku.go.jp/shrimps/index_.html>

(Note: I understood the Chinese articles with much  help from  Google Translate. Please inform me if I misinterpreted them.)


Last updated August 2008. Contact Justine at jschow88[AT]gmail.com.