Ellucidating Differences Between Cryptic Species of Stone Loaches

Ajay Patel

Authors: Ajay Patel, Lawrence Page

Faculty Mentor: Lawrence Page

College: Florida Museum of Natural History


Schistura mahnerti and S. poculi are currently regarded as two species of stone loaches, in the family Nemacheilidae. Schistura poculi is distributed along much of Thailand’s northwestern border, while S. mahnerti is found along the same western border, but farther south. The species have overlapping distributions along the central western border with Myanmar. They are usually distinguished through differences in color pattern and 15 vs. 17 caudal-fin rays. However recent genetic data suggest that these characters may be intraspecifically variable and unreliable in separating species. Individuals morphologically identified as one species were genetically identified as the other. This situation comes as no surprise because coloration and fin-ray counts often show variation in other species of Schistura. To address the taxonomic question of whether the individuals examined represent one variable species or two species, I have gathered morphological data on 50 specimens from throughout the range of the species. These data will be analyzed using a sheared principal component analysis to see if individuals are separated into two groups, as well as to identify morphological characteristics other than caudal-fin rays that may be useful in distinguishing species. I also soon will be phylogenetically analyzing DNA sequence data from specimens throughout the range of the species to assess relationships among individuals as a test of the morphological results.

Poster Pitch

Click the video below to view the student's poster pitch.


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Callie San Antonio
Callie San Antonio (@guest_1192)
1 year ago

Hey Ajay,
Your research is quite interesting! I’ve had coursework on conservation genetics and this question you’ve posed is similar to some of the topics I learned. Do you think, aside from the morphological inquiry, that there is some crossbreeding occurring, possibility along a gradient between the two species? I know you haven’t done the DNA processing yet, but have you considered to any degree that this might be something that could come up? Cool work!

Ajay Patel
Ajay Patel (@guest_3254)
Reply to  Callie San Antonio
1 year ago

Hi Callie,
There may be cross breeding, however our phylogenetic trees do not suggest this. That being said, the phylogenetic data I used was not originally intended for this project and only has 6 specimens of relevance. There may be introgression, but we need to do more tests to find out! Thanks for the question!

Dave Blackburn
Dave Blackburn (@guest_1990)
1 year ago

Hi Ajay
The poster notes that there are two mitochondrial DNA clades. Are these for the same individuals for which you also have measurement data? If so, you might explore using a discriminant analysis to see whether your measurement data can recover the groupings based on your sequence data. Nice job.

Ajay Patel
Ajay Patel (@guest_3424)
Reply to  Dave Blackburn
1 year ago

Unfortunately they are not. My data collection was cut short de to covid-19. I also became aware of the genetic data available after ”evacuating” gainesville. I will read up discriminant analyses for sure! They seem like a useful tool. If I have a question about them, would you mind fielding my email?
Thanks for the advice!

Max Woodbury
Max Woodbury (@guest_2080)
1 year ago

Hi Ajay,
Really cool research. Your use of PCA to look for correlations between the groups in your data was smart. Did you collect these specimen yourself?

Ajay Patel
Ajay Patel (@guest_3736)
Reply to  Max Woodbury
1 year ago

I did not collect these specimens. My initial project involved a catfish from the same region, and I did collect some of those. That project sadly did not work out due to trouble with international collaborators and lack of data.

Mark (@guest_2112)
1 year ago

Very interesting. It might be worthwhile to investigate whether there is a gradient of intraspecific morphological variation according to the distribution of these fish. From what I understand, even if there is no adaptational purpose to this variation, there still might be differences in trait abundance in different populations.

Ajay Patel
Ajay Patel (@guest_3850)
Reply to  Mark
1 year ago

I believe it would be worth while! I have a previous potential project about something similar to what you posed. If you click my name, you can still read my old proposal!

Valerie Prytkova
Valerie Prytkova (@guest_2246)
1 year ago


I am cracking up!!!! Of course your background is a rainforest!! I love this SO much! You are such an awesome and impressive human! Thanks for sharing your project with us! 🙂


Ajay Patel
Ajay Patel (@guest_3926)
Reply to  Valerie Prytkova
1 year ago

:D:D:D , Thanks Val. I thought the fish tank background would be a hit lol. I hope you liked the presentation!

Nirali Pathak
Nirali Pathak (@guest_2912)
1 year ago

Hi Ajay, love the background for your video presentation! Your project is very interesting and I enjoyed your presentation. What do you think will be some future impacts from the study? Also, how did you collect specimen?

Ajay Patel
Ajay Patel (@guest_4210)
Reply to  Nirali Pathak
1 year ago

Future impacts are hard to say. I think if we better understand the relationship between these two species it can help understanding of the impacts of connectivity between basins on species distributions in the region. Fish research in this specific river system is vastly understudied, making any ground work useful. I am just happy to be a part of finding new stuff!

Jennifer McCloskey
Jennifer McCloskey (@guest_2964)
1 year ago

Hi Ajay! As someone who mainly learned about fish from Animal Crossing (specifically a loach) I found your video very informative and easy to understand. Fish are wild. Very interesting stuff, keep up the good work!!


Ajay Patel
Ajay Patel (@guest_4320)
Reply to  Jennifer McCloskey
1 year ago

Fish are super cool! They do some pretty crazy stuff too! Google the pirate perch, they have crazy breeding behavior and associated morphology.

Ajay Patel
Ajay Patel (@guest_4544)
1 year ago


Should have put this earlier lol

Katie Everett
Katie Everett (@guest_4646)
1 year ago

Hi Ajay,

It’s so great to see the results of the research you were telling me about. You’ve done an excellent job!

Ajay Patel
Ajay Patel (@guest_7008)
1 year ago

Thanks for all the comments and suggestions. They were extremely helpful, and will further enhance the conclusions I make when this project is done.
Thanks a billion y’all!!!!

David Malcolm
David Malcolm (@guest_7454)
1 year ago

Great work, Ajay! These sorts of phylogenetic questions are really interesting to me, because for a long time, I struggled with understanding how and why we classify different populations as separate species, subspecies, regional varieties, etc. I could see how those stone loaches could be misidentified morpgologically (I’d probably end up putting them in the same species…). This project is going to be really interesting when it comes back!

Ajay Patel
Ajay Patel (@guest_7656)
Reply to  David Malcolm
1 year ago

I agree! I have wondered the same thing. I especially like the biogeography aspect of taxonomy.

Zach Randall
Zach Randall (@guest_7746)
1 year ago

Great job, Ajay! Presence of head spots are very prominent in some individually. Do you think this could be a potential color character? If the character is present interspecifically, is it correlated to specimen size?