Dear colleagues,
Here attached caudal fin X-ray image of Ameiurus nebulosus (Pisces: Siluriformes).The number of caudal fin rays in descriptions is among 18-20, but nobody tells how he count it. I see 8+8 principal rays (on hypurals+parhypural) + 35 procurrent. Or I can count 6 segmented unbranched, 15 segmented branched and 30 unsegmented rays. O'k, I have 6, 15 and 30. What I must do with these numbers to get in range 18-20? It is not the only one, I have dozens of such tails.
Second image is with how I see the structure of caudal fin of other A. nebulosus.
I'm far from expert in fish biology, but both of these attached illustrations give roughly 18-20, so maybe this is what the description refers to?
Dear Mikhail,
Lundberg & Baskin 1969 say something about the principal rays in catfishes on p. 34. Maybe of some use.
They state 8 + 9 (17) principal rays for the Ictaluridae.
Dear Carl Alexander Frisk,
Thanks for your opinion! But I think it is wrong to count in one pack procurrent small rays on epuralia and uroneuralia and long well-developed principals (first image). In this case one must also count lower procurrent rays on the last two haemal spines, it will be 25 rays. Much more than in the descriptions.
Also I think that it doesn't right to count only neural and haemal spines in caudal fin area (second image). Because some of them support several rays, e.g. first hypuralia (H1) which is modified haemal spine supports even four rays. So the question remains.
Dear Richard Van der Laan,
I am really very grateful to you for sharing that interesting article. It appears that I really need it. But it is still less than 18 :)
Hi Carl:
There is a method of counting caudal-fin rays (Fricke 1983); see the attached paper.
With best wishes,
Ron
Just published, check Figs. 26B, 26C and 26F, text on page 704.
Good luck.
Dear Richard Van der Laan ,
This is a great article. Thank you very much for sharing it. It cleared up a few dark places.
Respectfully,
Mikhail.
Dear Mikhail,
It may be a little late but thought I would answer anyway just in case. You were almost right in your count of 8+8 principle fin rays; however, instead of counting principle fin-rays based on attachment to the hypurals and parhypural, the principle caudal fin rays are counted from the last unbranched fin ray (upper and lower) to the middle of the fin. There are indeed 8 on the upper lobe of the caudal fin but there are 9 on the lower lobe so the count would be 8+9. The description you have of 18-20 fin-rays is likely including some of the procurrent fin rays as the plesiomorphic and most common condition in ictalurids is 8+9.
Cheers,
Kole
Dear Kole,
I assure you, it's never too late to write your opinion! Someone will always find it interesting. The question about the caudal fin of the catfishes did not arise from scratch. I have long been not entirely satisfied with the established methods for counting fin rays. But often this is a diagnostic sign ... which can be seen in different ways, depending on the observer. To unify the method of counting rays for all Teleostei is a thankless task, but necessary. And here even the essence is not in the "truth", it is possible to unify the "untruth" - the main thing is uniformity. I have in mind, for example, the double last rays in the anal and dorsal fins on the stay of many fish, including, for example, siluriformes or perciformes. Now they are considered as one “branched to base”, although in ontogenetical fact they are two “slightly merged”. The point is not the truth, but the unequivocal choice. Let everyone think that there is one ray, but everyone should count so (or additionally indicate in the article) in order to ability to compare the results.
You operate with the value “middle of the fin” to solve the question - is the procurrent ray or the principal one? And if the ray is somewhere right in the middle? What if the ray is broken? What if the fin is snapped off? A whole field of possibilities for different options to count a different number of rays on the same fin. And if the researchers are also different, then the result is multiplied. There are similar questions in counting the first rays of any fin, which are often less developed. I read a lot about ways of counting. Unfortunately, it often happens that the researcher writes the number of rays, but forgets to write how he count. And his data, albeit “correct”, can no longer be used for comparison. Absolutely. The way out is the unification of methods. And we must somehow get away from the subjective assessments of “middle”, “much less”, etc. Otherwise, we will come to anarchy in the style of “I am an artist, that’s how I see it.” How to do this, I don't know yet.
Best wishes,
Mikhail.
- Badges
- Science topic
- Similar topics
- Biological Science
- Zoology
- Ornithology