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.)
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.
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>