Sewellia lineolata, coloration patterns
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Hi all
I am sure that many of lovers of hillstream loaches noticed in the trade Sewellia lineolata of different color pattern. For example here https://www.seriouslyfish.com/forums/freshwater-and-brackish-water-fishes/sewellia-ids/#p44422 . I can distinguish two main types of Sewellia colour pattern. These types don’t usually met together in shipments. Thus sewellias of these two types are likely to be different populations from distant areas of their natural habitat of this species. Unfortunately I know nothing about exact places of their collection.
Type 1. Males and females are similar in color pattern and both have dense reticulated pattern with thin wavy black lines on the back and head and as a rule have straight three lines on the sides along the body from head to tail.
Type1 Male N1
type1 male N1 and female N1 (behind)
type1 female N1 (above) and male N1
type1 female N2
type1 male N2
Type 2. Males and females have thick wavy black lines. Three lines on their sides are thick and may be straight or some of them may be wavy. Females and only minor part of males have dense reticulated pattern on the back and head and look like Type1. The other part of males have rare reticulated pattern and so they look significantly lighter than females and sewellias of type1. Males of type2 look to me more square, powerful and thickset than males of type1 (this sign is very subjective and it may prove to be not exact for differences). Variations is likely occur though. Type 2 group is more variable.
type2 male N1
type2 male N2
the same male. No straight lines, but sinusoid on the left side of the body
type2 female
pattern on the head of type2 female
pattern on the head of type2 male
type2 male (above) and female
type2 young male with interesting pattern
And pictures with both types (sorry for bad quality, only for illustration)
type2 male (in great stress, his first day in a tank) and type1 male
type2 young male and type1 male
Here are only pictures of my sewellias. In shops I saw more interesting and rare patterns of type2 males. I can’t buy all of them 🙁
For several years I tried to see in different shipments in LFSs at least one ADULT female of type2 with rare reticulated pattern. I failed in it. If females with rare reticulated pattern are not exist, it may be suggested that gene of rare reticulated pattern is sex-linked, and only males are born with the gene (genes) responsible for rare reticulated pattern. Thus, the rare reticulated pattern of males may be used as additional characteristic for sexing of sewellia lineolata of type2.
It is well-known that sex determination of fishes is due to not only genetic factors but also is temperature-dependent. So I will not wonder if males of type 2 with female-like dense reticulated pattern prove to be genetic females.
This topic is for discussion. Here are my guesses and no approvals. I will be appreciated if anyone will show the photo of type2 adult female with rare reticulated pattern. In this case my findings may prove to be wrong.
Please share your observations and your ideas. Thanks.
Hi Olly
Interesting question.
Type 2 is present in the northern distribution aerea – south of Hue. Provinces going north: Bin Dinh, Quang Ngai, Quang Nam, Thua thien Hue. Other finds are not documented (“some rivers in between”)
As the shipments come from Ho Chi Minh City (Saigon) the aerea of collection of “type” 2 is far in the North. That may be the reason, that this “type” is rare in the hobby. Another point: the collected specimen are a mixed in large cement tubs. So you are lucky to find a batch with only “type” 2. I wasn’t yet and I have seen some thousends the last eight years.
I can’t answer the question if there are females of “type” 2 with that clearly “reduced” pattern.
Freyhof/Sverov (2000) show a male of “type” 2 with striking pattern. The specimen is not preserved, pic obviously taken in a tank.
Same pic in DATZ 2005 by Freyhof
I have some hundreds of pics of my wild caught and bred S. lineolata with largely different patterns, some coming close to “type” 2.
If you have a chance to get fry from a “type” 2 pair: go for it
Cheers Charles
Hi Charles
Thank you very much for your great additions and interesting comments. I very hoped this topic would prove of interest to you.
I would say type2 sewellias occur periodically and rarer in our trade in compare with type1. I saw them in LFSs for periods 0.5 year. Then type2 was rotated with type1 for about a year. I think that locality of collection are changed. Just my guess. My observation time of sewellias in stores is about 5+ years.
However, it is difficult sometimes to ID the type in young sewellias with size smaller than 4,5 – 5 sm with developing pattern. And one more difficulty. I saw the pattern looking like intermediate. I consider them type1. I thought, the place of their collection between habitats of type1 and type2. Or I am mistaken and it is a mix as you said.
Wonderful individual pattern in sewellia male (type1?) in a store: orderly precise cells, and lines on the sides disappear far from the head. Size about 7 sm TL. Bad pics without flash in LFS.
Hi Charles
I think, the different patterns are due to the different localities. The mix is done at the exporters place.
Yes, I think so too.
As the catching is done with electric fishing (car battery) they may stop, when the number required is reached. Next time they move to the next river(s), as this way of fishing is very effective and can empty a river completely.
That is awful 🙁
What you call “intermediate” patttern could this way be just the pattern characteristic for a certain river. As Freyhof collected 99 specimen and shows two very different types of pattern, he certainly knew about these variations but didn’t mention it.
It would be interesting to see how the different patterns look like in bred specimen over the years.Yes, one more relatively isolated population or even subspecies. For example, here is a pic taken in a LFS. Strange pattern (“intermediate”) . However, they are young sewellias with a size about 4 sm and it may change further. (Three sewellias of other two species.)
It would be interesting to see how the different patterns look like in bred specimen over the years.
It is very nice idea. I think cases with breeding of S.lineolata type2 occured in someone’s tank.
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