Research Interests

C. vittatus under UV light.

My current research revolves around the population genetics of the bark scorpion Centruroides vittatus. Populations of this scorpion encompass a large geographic range that includes southern Colorado, eastern New Mexico, several of the states in northern Mexico, Texas, western Louisiana, western Arkansas, southern Missouri, Oklahoma, and much of Kansas.

This is the range of C. vittatus in the midwest and C.hentzi in the east. Shelley, R.M. and W.D. Sissom. 1985. Distributions of the scorpions Centruroides vittatus (Say) and Centruroides hentzi (Banks) in the United States and Mexico (Scorpiones, Buthidae). JOA 23:100-110.

My lab is working to develop genetic markers to conduct an analysis that will show the phylogeographic relationship among populations of this scorpion. We are investigating RAPDs (Random Polymorphic DNA), DNA sequences, AFLP's (Amplified Fragment Length Polymorphisms), and microsatellities (with Dr. Douglas Rhoads, UA-F) for this project.


Most recently, I have become interested in the differentiation of venom toxin genes among C. vittatus populations and how these toxin genes have evolved in this less toxic sister species to C. exilicauda. To investigate these genes, I plan to obtain genetic markers (microsatellities and SNP's) that will allow allow a comparison of genetic diversity among scorpion populations and diversification of toxin genes. Here I plan to understand if genetic divergence among populations can be correlated with toxin gene diversification. In addition, I plan to compare toxin genes in C. vittatus to homologous genes in C exilicauda to determine how changes have occurred in protein coding sequences.


We are also isolating select toxin genes for eventual over expression of toxin proteins. We plan to then study the structural characteristics of these proteins and experiment to determine their action against select channel proteins. We are collaborating with Drs. Kumar and Jayanthi (UA-F, Dept of Chemistry and Biochemistry)


These rocky glade areas in Arkansas are the habitat of C. vittatus.


Arkansas populations of this scorpion show reduced densities as compared to western Texas populations [AR populations: 0.818 individuals/100m2 (2000 estimate), 0.456 individuals/m2 (2003 estimate); Texas estimate: 7.36 individuals/100m2]. Arkansas scorpions were not active on the surface during December, January, February, and March but Texas scorpions were active all year. Arkansas scorpions exhibited lower biomass than Texas scorpions 0.133 kg/ha (2001) and 0.111 kg/ha (2003); TX- 0.31 kg/ha. Average female mass in Arkansas was 0.49 gm; male mass was 0.41 gms. Texas scorpions exhibited similar male mass (0.419 gms) but markedly larger female mass (0.765 gm). Lastly, Arkansas populations exhibited high cannibalism rates comparable to the sand scorpion (9.1% versus 9.52%, AR striped scorpions). These findings suggest Arkansas scorpions exhibit food stress. This stress may result from a recent expansion into eastern areas from western regions during a warming trend approximately 8,000 to 4,000 years before present. This scorpion maybe exhibiting incomplete adaptations to recent climatic changes in this region. The Texas estimates stem from Brown et al. 2002.

I plan to use this scorpion to show Arkansas' unique biogeographic history. The Ozarks and Ouachita mountains appear to possess a unique biogeographic history because many habitats show plants and animals representative of eastern forms but may also show species more common in the western United States.

Other projects with students at Tech include population genetic analysis of the Stargazing Darter (P. uranidea), Fatmucket mussell (L. hydiana) DNA sequencing analysis, ladybeetle RAPD analysis and the morphological analysis of C. vittatus populations.



Curriculum Vitae

PROFESSIONAL INFORMATION
Academic Degrees:

1993 Ph.D. Department of Biology, Vanderbilt University, Nashville, TN 37235 1985 B.A. Hendrix College, Conway, AR 72032

Professional experience:

2014-present

Professor, Department of Biological Sciences
Arkansas Tech University

2003-2014

Associate Professor, Department of Biological Sciences
Arkansas Tech University

1998-2003

Assistant Professor, Department of Biological Sciences
Arkansas Tech University
1998
Adjunct Assistant Professor, Department of Biology
Northeast Louisiana University
1994-1998
Assistant Professor (Graduate Faculty), Department of Biology
Northeast Louisiana University
1992-1994
Post-doctorate, Division of Hematology
Vanderbilt University Medical School
1986-1991
Teaching Assistant
Vanderbilt University

Publications:
C Gagen, T Yamashita, IR MacLeod, KL Schanke. 2013. Radio Frequency Identification And Microsatellite Analysis To Characterize Fish Passage Associated With Road Crossings In Ouachita Mountain Streams. Final Project Report Funded as Part of the Aquatic Organism Passage Project. Submitted to the USDA: Ouachita National Forest.

T Yamashita, DR Rhoads. 2013. Species delimitation and morphological divergence in the scorpion Centruroides vittatus (Say, 1821): Insights from phylogeography. PLoS ONE 8(7): e68282. doi:10.1371/journal.pone.0068282

Yamashita, T. 2004. Surface activity, biomass, and phenology of the striped scorpion, Centruroides vittatus in Arkansas. Euscorpius -Occasional Publications in Scorpiology 17: 25-33.

J Lewter, T Yamashita, and AL Szalanski. 2003. DNA sequence analysis of the freshwater mussel, Lampsilis hydiana (Bivalvia: Unionidae), in select Ozark and Ouachita mountain streams of Arkansas. J. of the Arkansas Academy of Science 57: 216-220.

Yamashita, T. and V. Fet. 2000. Molecular approaches to Biogeography. In G. Polis and P. Brownell (Eds) Scorpion Biology. Oxford University Press.

Bondurant, M.C., T. Yamashita, K. Muta, S.B. Krantz, and M.J. Koury. 1996. c-myc expression affects proliferation but not terminal differentiation or survival of explanted erythoid progenitor cells. Journal of Cellular Physiology 168: 255-263.

Yamashita, T and G.A. Polis. 1995. A Geographic Analysis of Scorpion Populations on Habitat Islands. Heredity 75 (5): 495-505.

Yamashita, T. and G.A. Polis. 1995. A test of the central-marginal model using sand scorpion populations (Paruroctonus mesaensis, Vaejovidae). Journal of Arachnology 23: 60-64.

Polis, G.A. and T. Yamashita 1990. The ecological importance of predaceous arthropods in desert communities. In G. Polis (Ed) The Ecology of Desert Communities. Univ. of Arizona Press, Tucson, AZ





Community Activities:
Arkansas Canoe Club Rendezvous Chair 1999/2000
Assistant Scoutmaster Boy Scout Troop 214 (Russellville, AR) 2012-
Cubmaster Cub Scout Pack 214 (Russellville, AR) 2008-2011
Assistant Scoutmaster Boy Scout Troop 400 (Russellville, AR) 1999-2000
Assistant Scoutmaster Boy Scout Troop 28 (Monroe, LA) 1995-1998
First Assistant Scoutmaster BSA Jamboree Troop 1823 (Monroe, LA) July-August 1998
Ouachita Valley Council Advancement Committee Chair (Monroe, LA) 1998
Instructor for Arkansas Canoe Club's canoe school: 1997-2014
President- Piney Creeks Chapter, Arkansas Canoe Club 1999-2001

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Tsunemi Yamashita
Professor of Biological Sciences
Arkansas Tech University
Russellville, AR 72802

E-Mail: tyamashita@atu.edu
Last Modified: 9/10/2014

 

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