Welcome to the Part II of “my first blog post!” Part I provided insight into what a Cypriniform is and the distribution of species across families. Part II will focus more on what these fish look like – i.e., what makes a Cobitid a Cobitid and a Cyprinid a Cyprinid. Part III will then focus on the evolutionary history of this group, how the families are related to each other, and what the implications are for the evolution of Cypriniform diversity!
If you remember from my previous post, there are 11 families that contain 4,182 species! There were at least two interesting points about this diversity:
- Cyprinidae is an exceptionally large family. It contains almost five times as many species as the next largest family. It’s fair to wonder if Cyprinidae, ultimately, will be broken down into multiple families at some point in the future, but that is an issue for another post.
- The diversity is distributed a bit funny with Cyprinidae containing the majority of species followed by some families with a large number of species, a few families with a moderate number of species, and a few families with only a few species.
So, with those patterns in mind, let’s take a more in-depth look at each family. When possible, I will post a picture of a representative species for each family. Unfortunately, I don’t have pictures of most of these families right now (and will link to pictures of them). If you have a good picture of species for any of the groups for which I don’t have a picture and you don’t mind them being posted to my blog, I will post them with photo credit to you!
OK, let’s take a look at the major divisions of Cypriniforms (now grouped by suborders):
The majority of families (8 of the 11) are in the suborder Cobitoidei and are commonly known as loaches. Loaches are small, benthic fish that have a very characteristic set of body shapes. Generally speaking, they are vermiform (worm-like) although they usually have a relatively flat ventral side. And their paired fins (the pectoral and pelvic fins) are typically on a somewhat horizontal plane. Why?
HINT: Think about where they live (ahem…Generally, they live in fast flowing rivers and streams across Europe, Asia, and a few species in Africa. …ahem).
By having a flat ventral side, large pectoral and pelvic fins, and a streamlined dorsal side, the fish are well adapted to live in fast flowing streams. They are able to cling to the substrate without “much” effort because their pectoral and pelvic fins can help adhere to rocks and such in the habitat. Wanna see? Check out this photograph:
Despite this generalization, there are some very peculiar looking loaches: check out the look of Tarimichthys bombifrons, pretty wild!
To me, there are some other peculiar things about loaches (relative to other Cypriniforms). A lot of loaches tend to have barbels, which are the sensory organs around the mouth. Most people, at least from where I am from in the southern US, call them whiskers and usually only talk about them when we catch a catfish.They are thought to be involved in foraging (Kasumyan and Sidorov 2010; Kasumyan et al. 2010) although the diversity of barbels across loaches almost certainly warrants a thorough investigation. Theoretically, they could be involved in other functions such as acquiring mates and sexual selection. Anecdotally, loaches frequently tend to have vertical stripes more frequently than horizontal stripes. I assume these are probably involved in camoflauge considering that we see vertical stripes serve as crypsis in several benthic North American fishes (Barlow 1972; Armbruster and Page 1996).
It’s somewhat easier to take a look at loach taxonomy because of the recent publication of a manuscript addressing the state of taxonomy of the loaches (Kottelat 2012). As mentioned in this paper, there are likely hundreds of additional undescribed species that will be described (hopefully) over the next few years. They place the valid species in ten families, the eight below plus Gastromyzontidae and Botiidae (Botiinae is recognized as a subfamily in the Catalog of Fishes).
- Gryinocheilidae (3 species)
- Vaillantellidae (3 species)
- Cobitidae (245 species)
- Ellopostomatidae (2 species)
- Barbuccidae (2 species)
- Balitoridae (230 species)
- Nemacheilidae (627 species)
- Serpenticobitidae (3 species)
- Catostomidae (83 species)***
It is worth taking a look at how species from each of these families look. You can see a lot of excellent pictures in Kottelat 2012 so I would suggest starting there – by using this paper, you also can assure you are looking at the species you think you are looking at.
Within this suborder, Cyprinidae clearly constitutes the majority of species: Psilorhynchidae constitutes less than 1% of the species in this suborder. So, what made the minnows so successful relative to their loach relatives? Well, at this point, I’m not sure anyone knows. Generally speaking, there are quite a few differences that can be seen with the idea. Perhaps the most notable difference is body shape. They tend to have laterally compressed shape relative to their loach counterparts.
Look at the Luxilus pictured above relative to the Homalopterula pictured above. See how the Luxilus has a much deeper body that is somewhat symmetrical along the horizontal plane? Now, that isn’t to say that there aren’t cyprinids that have flattened ventral sides. Some do. Look at Cyprinus carpio. They have flattened ventral sides and barbels, but are cyprinids, not loaches! As a quick side note, Psilorhynchus also exhibit these characteristics and not surprisingly, is probably closely related to these species (He et al. 2008). Why is this cool? Because if this is the case, this suggest that the body plan evolved likely only once in the minnow clade. Anyways, we can talk more about this later.
Barbels also seems to be less frequent in minnows relative to their loach and sucker counterparts. Several minnow genera do have barbels – Macrhybopsis, Cyprinus, etc – and they likely serve a similar function in foraging. Additionally, and again generally, it seems that minnows much more frequently have horizontal stripes rather than vertical stripes. This could be a visual bias for me: I see North American minnows much more frequently than minnows in other portions of the world and I simply could be generalizing the stripe-pattern too broadly. If I’m wrong, someone should let me know.
The taxonomy of these two families is much more difficult to tackle. For example, within Cyprinidae, there at least fourteen – YES, F-O-U-R-T-E-E-N – subfamilies according to the Catalog of Fishes. I suspect that is a minimum number and we are only recently beginning to understand relationships among these subfamilies.
- Cyprinidae (2960 species)
- Psilorhynchidae (24 species)
Given these taxonomic concerns, there hasn’t been a recent publication on the taxonomy of these two families. It makes it difficult to publish such a beast when we understand so little about their diversity. Nonetheless, multiple researchers are working on resolving this problem although it may be several more years before we thoroughly understand Cyprinidae.
As a quick side note, you will note that I use “generally” a lot when referring to morphological characters. This is due to the fact that it is difficult to make a definitive claim about some aspect of morphology when talking about such a diverse group of fishes. This is largely the result of convergent evolution – i.e., evolution should lead to similar morphological traits in species that inhabit similar environments. I will cover this more in a later post, but I just wanted to make a quick note of why I use “generally” so frequently.
In my next post, I will address how loaches and minnows are related, evolutionarily speaking. It should be an interesting post to look at the phylogenetics of this group and try to make heads or tails of the diversification of this group!
Armbruster, J. W., and L. M. Page. 1996. Convergence of a cryptic saddle pattern in benthic freshwater fishes. Environmental Biology of Fishes 45:249-257.
Barlow, G. W. 1972. The attitude of fish eye lines in relation to body shape and to stripes and bars. Copeia 1972(1):4-12.
He, S., Gu, X., Mayden, R. L., Chen, W. J., Conway, K. W., and Y. Chen. 2008. Phylogenetic position of the enigmatic genus Psilorhynchus (Ostariophysi: Cypriniforms): evidence from the mitochondrial genome. Molecular Phylogenetics and Evolution 47(1):419-425.
Kasumyan, A. O., Sidorov, S. S., and E. A. Marusov. 2010. Taste preferences and behavior of testing gustatory qualities of food in stone loach Barbatula barbatula (Balitoridae, Cypriniforms). Journal of Ichthyology 50(8):682-693.
Kasumyan, A. O., and S. S. Sidorov. 2010. Taste preferences and feeding behavior of the stone loach Barbatula barbatula (Balitoridae, Cypriniforms) after partial deprivation of circum-mouth external gustatory and tactile receptors. Journal of Ichthyology 50(11):1021-1029.
Kottelat, M. 2012. Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cyprniforms: Cobitoidei). The Raffles Bulletin of Zoology 26:1-199.