The Difference between Neocaridina and Caridina Shrimp

Difference Caridina vs Neocaridina shrimp

The question of the visual difference between Neocaridina and Caridina shrimp arises all of the time. I have seen countless posts on forums where people have had problems with distinguishing Neocaridina from Caridina shrimp. This may, at first sight, appear as a simple question but it is not. The problem is much more complex and I will tell you why. However, before I start ranting I can tell you the differences between Neocaridina and Caridina, these are:

Endopodite of first maxilliped without protuberance on its distal outer margin.  Endopodite of first pleopod greatly enlarged and pear-shaped in male, subtriangularly elongated in female. Appendix masculina of second abdominal appendage much enlarged, thickened and densely covered with setae.

I bet that most of you did not expect this answer, like what is this?! Frankly saying, me too… at first. 🙂 Do not worry I will explain it with pictures. Nonetheless, this is the only scientific explanation which you can find. Believe me, I have done my research, just keep reading and you will see it yourself.

When I first got into this hobby, I also tried to find the difference between Neocaridina and Caridina. Like many others I wanted to hear the simple answer, like – the rostrum has another shape, the carapace is thicker/thinner, color etc. All in all, is it possible to differentiate between these 2 genera by visual appearance?

Unfortunately, nobody could really answer the question. The situation is pretty hilarious, we have shrimp in our tanks, but in reality we have no idea about their genus! Are they Neocaridina or Caridina? We have to trust to… and who actually can we trust?

I dropped this subject for some time. However, this question kept bothering me again and again. So, eventually, I decided to look at this problem more meticulously.

History of Search between Neocaridina and Caridina

Here is my rant so bear with me. I already knew that forums, YouTube and Facebook groups cannot help me because people did not have any real data about this matter. Of course, from time to time there were some links and references to German sites, which supposedly described the difference between Neocaridina and Caridina but these links were dead as well.

Note: There is only ONE very short article in the English segment of the Internet about this problem (I have not found a single one in German, Russian and Spanish segments at all!). Unfortunately, that article did not provide any links to the sources. So, of course, I thought that maybe I would be able to find something else myself (and, actually, I did).

I started from scratch by finding the very first and then the modern studies about Neocaridina and Caridina. Some of these studies can be found online, while to get other I sent requests. I even tried to look into studies of DNA sequences of Neocaridina denticulata vs Caridina leucosticte, as examples. Frankly saying, I did not understand much about DNA besides that “Recent molecular phylogenetic analyses have shown that the genus Neocaridina and the genus Caridina are very closely related within the family Atyidae”. That is why I returned to standard studies of these species.

Family dwarf shrimp tree

First Studies of Neocaridina and Caridina

Bouvier, Kemp, Haan, Kubo, De Man and Holthuis had been the pioneers to study on Atyids.

In 1904, Bouvier E.L wrote the fundamental work “Crevettes de la famile des Atyidés: espèces qui font partie des collections du Muséum d’Histoire Naturelle”. This work gave an incredible boost to studies about the shrimp in Europe. At that time, the current Neocaridina species were attributed to Caridina.

In 1918, Kemp (“Zoological results of a tour in the Far East”) did not see any difference between these two genuses, as well. Even more, he wrote “Classified according to the scheme outlined by Bouvier in 1913, C. denticulate would find a place alongside with Chinese C. davidi, Bonvier. Balss regards the latter species as synonymous with the former, but in this he is certainly in error. C. davidi, co-types of which are in the Indian Museum, differs in many respects from C.denticulata and may be distinguished at a glance by the depressed rostrum and by the strong curvature of the propodi of the last three pairs of legs”

Note: However, according to the modern Taxonomy, modern biologists consider them as the same species.

Separation Neocaridina from Caridina

In 1938, Prof. Ituo Kubo finished his work “On the Japanese atyid shrimps”. He noticed that “The Japanese atyid shrimps have been studied by many investigators, namely, de HAAN (1849), STIMPSON (1860), ORTMANN, (1890-91), DOFLBIN (1902), RATHBUN (1902), BOUVIER (1906), Deman (1908), BALSS (1914), KEMP (1918), U£NO (1935), and others. But inasmuch as they are variable in several characters, their taxonomy is of no easy task”.

Note: Well, one hundred years later, he is still right! Unfortunately, I cannot give any link to this book. Nonetheless, if you are interested, feel free to ask me, and I will send it to you in pdf format.

However, it did not stop Kubo to propose that the difference in the structure of the genitals can be the sign of different genus. In his work he had prepared a new genus – Neocaridina – separated from Caridina by three characteristics, and reported about the Neocaridina denticulata study of the material with special reference to the features of pleopods. Thus, it allowed him to make emendations and additions in regard to atyid taxonomy. This was the day when Neocaridina was “born” from Caridina.

Kubo wrote “The present genus is closely allied to the genus Caridina but differs from it by the following important characters:

  1. Endopodite of first maxilliped without protuberance on its distal outer margin;
  2. Endopodite of first pleopod greatly enlarged and pear-shaped in male, subtriangularly elongated in female;
  3. Appendix masculina of second abdominal appendage much enlarged, thickened and densely covered with setae”.

About Differences between Neocaridina and Caridina in Details

What do they mean? In order to have a slight understanding let’s take a look at the pictures. Dwarf Shrimp external anatomy

(1) Endopodite of first maxilliped without protuberance on its distal outer margin

Maxilliped of dwarf shrimpMaxilliped – One of the mouth appendages on the heads of the shrimp, used for feeding. Called also jawfoot, and foot jaw Origin: [Maxilla + L. pes, pedis, foot.]

Endopodite – the inner branch of the biramous limb or appendage of a crustacean.

Endopodite of first maxilliped without protuberanceA, N. denticulata;
B, N. dent, sinensis;
С, N. dent, koreana;
D, N. denticulate;
E, N. denticulata;
F, C. japonica sikohuensis;
G, C. japonica;
H, C. serratirostris;
K, G. leucosticta;
L, C. grandirostris;
M, Ctypus.

dwarg shrimp Endopodite of first pleopod(2) Endopodite of first pleopod greatly enlarged and pear-shaped in male, subtriangularly elongated in female

Neocaridina differs from Caridina in shape of the endopod of male first pleopod.
In Neocaridina the endopod is pear-shaped and the appendix interna (if present) is located near the base of the endopod. (female’s endopodite is smaller and more slender).

In Caridina the endopod is more “leave” shaped and in almost all species this appendage is tapering towards the distal end. The appendix interna (if present) is located near the distal end of the endopod. 

(3) Appendix masculina of second abdominal appendage much enlarged, thickened and densely covered with setae Appendix masculina of second abdominal 

As we can see on the picture, neocardina’s second pleopod has a “clubbed” (thick) endopod. However, caridina’s second pleopod has a ciliated endopod (inner arm).

Dwarf shrimp Appendix masculina

Modern Studies of Neocaridina and Caridina

Since then (1938), Kubo’s revision has long been the subject of debate, but in 1966 the species was finally separated by Cai Yixiong  in “A revision of the genus Neocaridina”.

Note: Unfortunately, the most part of that study is written in Chinese. However, according to different translations, the reasons for differentiation Neocaridina from Caridina were the same as mentioned above (more or less).

Biologists noticed that in his revision of the genus Neocaridina, Cai (1996) transferred C. davidi to the genus Neocaridina, and considered it a subspecies of Neocaridina denticulata (Neocaridina denticulata davidi). The differences to the nominate form (carpus of first cheliped strongly excavated vs. slightly excavated in N. d. denticulata, third chelipeds with distinct sexual dimorphism vs. no noticeable sexual dimorphism in N. d. denticulata, rostrum not overreaching antennular peduncle in N. denticulata davidi vs. reaching beyond in N. denticulata denticulata) are however so distinct that species status appears justified, and N. davidi is regarded as distinct species here.

The Taxonomy of Neocaridina and Caridina shrimp

After all these searches I was disappointed a little bit. I tried hard but the results did not satisfy me so I decided to look at the problem from another angle. Thus, I asked myself – what criteria do biologist use for genus classification? What else do they use in general? Therefore, I started looking in this direction.

John Lindley provided an early definition of systematics in 1830. In 1970, Michener defined “systematic biology” and “taxonomy“. The composition of a genus is determined by a taxonomist.

Once again I was in for an unpleasant surprise. The point is that the standards for genus classification are not strictly codified, so different authorities often produce different classifications for genera.

In 2012 Nicholson, K. E.; Crother, B. I.; Guyer, C.; Savage, J.M. in their work “It is time for a new classification of anoles (Squamata: Dactyloidae)” wrote “Which species are assigned to a genus is somewhat arbitrary. Although all species within a genus are supposed to be “similar” there are no objective criteria for grouping species into genera”.

The very same problem we have with Neocaridina vs Caridina taxonomyFor example, even now days, the biologists complain about Neocaridina and Caridina taxonomy, I quote:

That is why in some studies, biologists “adopt the simple binomial nomenclature to treat all subspecies to specific level for convenience, because some taxa have been inconsistently ranked as species or subspecies, whilst some subspecies were ranked under different species in Cai (1996) and Liang (2004).

Conclusion

It is absolutely not possible for you to see the differences between Neocaridina and Caridina with your bare eyes. The morphological differences are too small and you would need the help of special literature and a microscope to see them.

As a result, if you see that somebody says that Neocaridina and Caridina are different because they have different rostrum shape, color, antennae, body size etc., this is just a pure guess. Therefore it is not trustable and reliable.

Another problem is that Taxonomy classification is also changing all the time. Today it can be Caridina and tomorrow it is already Neocaridina.

13 thoughts on “The Difference between Neocaridina and Caridina Shrimp

  1. Hello Michael,

    First of all, very interesting article!

    Can you please send me the article of seperation of neocaridna and Caridina? The pdf format of the book.

    Greetings,

    Sjoerd

    1. Hi, Sjoerd!
      Kubo wrote a fundamental book for shrimp taxomony. It is not just an ordinary article about Neocaridina and Caridina. You will see it yourself.
      I have sent it to you.

      I am glad that you liked the article.
      Best regards,
      Michael

  2. I’m so glad I found you, this early on in my own beginners search. Thanks so much for your article.

  3. Hello Michael,
    Thanks for the info, it is very useful. I have some questions, though – does Caridina and Neocaridina have the same water preferences? What kind of shrimp is the Tiger shrimp – Caridina or Neocaridina? Which one are best to keep together?

    1. Hi Edit,
      Of course, not! In general, ideally, Caridina shrimp prefer PH less than 7.
      However, there are also exceptions. For example, Amano shrimp (Caridina multidentata), Blue tiger shrimp (Caridina mariae) and some others prefer >7pH.
      It is very important to understand that most shrimp (Caridina and Neocaridina) can live within 6.0-8.0 pH (Actually pH fluctuates all the time in our tanks as well. It is almost never the same.) but, as I have just said, they can have different preferences for optimal pH.
      I have a guide about Blue tiger shrimp. It is Caridina.
      It is quite hard to answer your last question because there are so many types of shrimp! If you have something on your mind, tell me and I will be able to say if it is a good combination or not.
      Basically, if they can share the same optimal water parameters, in this case, they can coexist easily.
      On this blog, I have big articles about some popular shrimp species and water parameters (PH, GH, KH, and TDS). Take a look at them. They will clarify lots of your questions.

      Best regards,
      Michael

  4. Hello Michael,

    one thing am a little confused about is why the way shrimps reproduce is not taken into account when defining the genus. For example, the reproduction cycle of caridina cantonensis and neocaridina davidi is quite similar while the one from caridina multidentata is distinctly different. So my first guess would be that a common ancestor evolved to a specialized reproduction type and that caridina cantonensis and neocaridina davidi emerged from this ancestor while the split with caridina multidentata happened earlier. I hope you can shed some light on this.

    Best Regards,
    Tobias

    1. Hi Tobias,

      This is a very good question actually!
      I remember that when I was writing the guide about Amano shrimp, I wanted to find the first description of this species. Well, I hoped that it could help me to understand better the taxonomy of this species.
      According to my notes, Amano shrimp (at that time it was called Caridina japonica) was described by De Man, J. G. in 1892. (Decapoden des Indischen Archipels. Pages 380).
      Unfortunately, I could not find this work online for free.
      Although, it is possible to buy this work on Amazon. Now, I believe, that it won’t help, because:
      1. The main problem is that bioogists do not have strict standards for genus classification!
      2. They all judge by fisical apperance.

      Frankly saying, I do not undestand why Caridina multidentata is in Caridina Genus at all as well.

      Best regards,
      Michael

      1. Hello Michael,

        so I guess the genus is kind of arbitrary 🙁

        Anyway, thanks a lot for the very informative articles on this page and for your quick and detailed answer!

        Bye
        Tobias

  5. Hello Michael! I have a question about Caridina & Neocaridina living together. I currently have a tank with cherry, blue velvet, & some yellow Neocaridina shrimp. I recently purchased some Blue bolts when I saw a good deal pop up. Which those are of course Caridina. I then panicked and got another tank up & running while my new Caridina’s are making their way to me. I am seeing many conflicting articles about them coexisting. I have articles that say “no way” these can not coexist & I have seen articles stating that they are fine to live together if one maintains a ph of 6.5-7.
    Can you please shed some light on this for me? I enjoy your articles and trust and appreciate your input. Thank you!

    1. Hi Juliann,
      They will be fine as long as you do not have extreme water parameters.
      If your pH is less than 7, it will benefit more Blue bolts. If your pH is more than 7 it will be better for Neocaridinas.
      In any case, they can adapt and live together.
      Benefit means that they will breed better.
      Best regards,
      Michael

      1. Hi Michael,

        It was nice to know a lot about shrimps through your writing and appreciate the work you put on. I would like to read the book that you are taking about. Kindly send me the pdf.

        Thank you

        1. Hi JOHN BINO,
          I have sent it to you. Check your email.
          Best regards,
          Michael

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