Thoughts on T. pustulatus/T. lineatus hybridization

[maryhm]

I've been doing a little research on this topic, as I am determined to find a T. pustulatus that is either 100% spotted or only lined on the top. I figured there were three explanations for the "mottling" phenomenon- actual hybridization, subspeciation, or morphological differences within each species based on location of the specimens (there's a term for that that starts with an "A", but I can't remember it!). Here is some information I'd like to share.

http://www.genoscope.cns.fr/spip/A-phyl ... study.html
This study shows that hybridization is possible between Tetraodon species.

http://www.fishbase.org/trophiceco/Ecos ... pustulatus
This shows the ecosystem information for T. pustulatus. The range is much smaller, only showing two rivers. The smaller distribution would explain why this species is harder to find within the trade. The Sanaga River is the largest in Cameroon, and by looking at a map of the Sanaga River basin (http://www.internationalrivers.org/file ... Sanaga.pdf, we can see where the Cross River branches off, and it's probably safe to say that T. pustulatus could occur anywhere in this area.

http://fishbase.org/trophiceco/EcosysLi ... e=lineatus
This shows the ecosystem information for T. lineatus. As you can see, there are several rivers and two lakes the fish is endemic too, which would explain why they are so easily found within the aquarium trade. However, from looking at maps of the areas, these ecosystems are primarily far to the north of T. pustulatus territory. I really don't see where habitat overlap is occurring that would allow for hybridization.

I've heard some people say that both species look alike. That is absolutely not the case. This http://www.youtube.com/watch?v=lJe8tysOVc8 does not look like this http://www.youtube.com/watch?v=zJqqL5oDLhM. Obviously, the only way to know for sure what's going on is to do DNA studies. However, just based on the natural habitats of these two species, and seeing just how separated they are, I'm more inclined to believe that the color morphs we've seen in T. pustulatus are due to one of the following:
1. A batch of T. lineatus arrive at an exporter's facility. He sees a couple of them exhibiting a few spots instead of lines, and to make a fast buck calls them T. pustulatus.
2. There are actual subspecies of T. lineatus and/or T. pustulatus that exhibit both lined and spotted morphology.
3. There are color morphs of T. pustulatus based on separate geographical locations.

Anyone else have any thoughts about this, or am I the only weirdo that finds this stuff interesting?

[Hierony]

The article on genoscope.cns.fr was very interesting. Thanks for sharing that!

[Hilly]

On visual appearance alone there are a few standout points, what I consider a true Pustulatus has a totally different base colour to Lineatus, also the Pustulatus tail is shorter than a Lineatus. Where the confusion arises is that there are some specimens that have characteristics of the 2, so you would get some that have a base colour of a Lineatus with some lines and some spots. That is what I consider a hybrid of the 2. If i was going to put money down on a PustulatusI would want it to have the base colour that I expect and all spots.

Then what you also have to be prepared for is that the spots as the fish ages will join together, not to make the defined lines you get on some Lineatus but the spots bleed into each other. This has been discussed on another thread.

The confusion of the 2 looking similr is as juveniles. I cannot recall ever seeing a pic of what is proved to be a juvenile Pustulatus. Some juvenile Lineatus have several spots which is where the confusion originates from.

There could be sub-species of them like there seem to be in the Fluviatilis family but a scientific study would need to be carried out to determine that.

Corvus has the most knowledge on this subject IMO.

[maryhm]

Hilly,

Concerning the ones that you think are hybrids, how do you account for the fairly separate geographical range of each species?

[Hilly]

Lineatus has an extremely wide distribution if the information on fishbase is accurate so you can go from Egypt on one side all the way over to Senegal. So if that is the case there is a potential that these species have cross bred.

[maryhm]

There is some information on T. pustulatus in this document, Page 42 of the PDF, page 44 of the actual document:
http://www.repository.naturalis.nl/document/148966

I'm going to seek out as much scientific information as I can about it, and I'll post it all in this thread.

Concerning distribution- yes, T. lineatus has a wide distribution as noted, but I haven't found anything that shows its range is in that of T. pustulatus, which is very limited.

[Hilly]

Just had a quick look at that document and it seems to be relating to fish of the Niger Delta, if that is the case and I have read it correctly. I believe Lineatus have been found there, obviously were not talking about a small body of water so it could be a possibility. Lineatus seems to have been found in rivers across the width of Africa so you could hypothesise that it is more of a nomad and will just keep on moving looking for food, where as the Pustulatus seems to be more localised.

[maryhm]

Finally! I've been searching for an ID key to distinguish between the two, and lo and behold it was on Fish Base the whole time.

http://fishbase.org/keys/description.php?keycode=1511
Hit the open key button.

It clearly states right there that juvenile T. lineatus can have the red spots as juveniles. Maybe some have more spots than others, and those are being passed off as T. pustulatus, which would easily explain why they go from spots to lines as adults!

Looks like the main difference is in the caudal fin length and shape. I wish it were something like caudal ray count- that would make it soooooooo much easier! I'm still looking in to this, but I'm still not convinced we are seeing hybrids, and there is no scientific literature I can find to support hybridization. I'm more convinced we're seeing juvenile T. lineatus with lots of red spots passed off as T. pustulatus that magically turn into lined Fahakas as adults, and then we're seeing morphological pattern/color differences in true T. pustulatus. Jury is still out though!

[maryhm]

Distribution map here on page 3. Anyone speak French?
http://horizon.documentation.ird.fr/exl ... /36602.pdf

Is it possible that they cross each others path on occasion? Sure. But from that map, I wouldn't say it was likely or very frequent. At least not enough to create a hybrid species.

[Pufferpunk]

So maybe it would be best to purchase an adult, with the spots fully formed & no chance of lines developing?

[maryhm]

Aside from the general interesting nature of the topic of hybridization vs. morphological differences, I think if someone were wanting to make for absolute certain that they were getting a T. pustulatus, that purchasing a 2" juvenile could end up a huge and expensive disappointment! The question now would be- at what size do adult colors dominate? Maybe some of you guys who have raised Fahakas from babies could answer that one. Of course, using the caudal fin characteristics on a juvenile, one might be able to determine the species.

[pufferpuggirl]

My point has always been, if there is such a hybrid, then there's got to be lots of them, and as you've pointed out maryhm, the areas they tend to inhabit don't really overlap. It seems to me that there must be loads of hybrids out there if what's being sold as a true pustulatus are only hybrids and I really just don't think that a lineatus and a pustulatus are breeding, over and over again, to produce that many hybrids to be sold with any regularity. And not to sound like a broken record, but if there is such a hybrid, personally I'd be happy to own one!

I'd love to hear Corvus's take on all of this.

If you use Google as a search engine/browser, it will translate any web pages that are in a foreign language. I use it all the time when I visit other websites that aren't in English, and find it quite useful.

[Pufferpunk]

I'd love to hear Corvus's take on all of this.

Already sent him a PM on this.

[purplecandle]

Is it possible that they cross each others path on occasion? Sure. But from that map, I wouldn't say it was likely or very frequent. At least not enough to create a hybrid species.

You are forgetting a few things here.

1. Human intervention/trade routes
Numerous people in these regions depend on fish from these rivers and lakes to eat and to trade over vast distances.

Example- Fisherman goes fishing and ends up with a couple of puffers. He thinks they are cool. So he puts them in a bucket of water and brings them over to his favorite spot to sell fish in a popular fish market in a larger city. Once he get there, people at the market refuse to buy them because they are poisonous. So the fisherman walks over to the nearest river and dumps them into the water. If this happens only once a year for the past 100 years or so...you can do the math...

2. Life expectancy of puffers

Puffers can live for quite a long time, meaning that they can reproduce for longer. Few species present may seem like too few to get a population going, but the life expectancy of a puffer should even that out.

Just my thoughts

[maryhm]

Purplecandle:

You make an interesting point, but I would counter that any real fisherman in those waters that is from an area inhabited by T. lineatus would already know that puffers aren't edible. Indigenous fishermen are extremely savvy to what is edible and what is not, and if a similar looking species in their area is known to be poisonous, I can't come up with a scenario where a fishermen would carry a T. pustulatus potentially hundreds of miles, keeping it alive the entire time, only to discard it back into the river. Believe me, having dealt with collectors for about 2 decades, they are not apt to carry a worthless live animal back to the river so it can live. They'll throw it in the bushes or trash and be done with it. Also, as territorial and aggressive as these puffers are to their own species, mortality rates would probably be in excess of 35% at a minimum for "newcomers".

Life expectancy doesn't have as much to do with reproductive rates as fecundity does. Admittedly, I don't know anything about puffer reproduction or survival rates of fry. Some animals live decades, but only produce a couple of offspring per year or less. Some animals live months, and can produce thousands of offspring in that time.

I'm really loving the responses from you guys! THIS is the stuff that I love about this hobby. I'm not a "put a pretty fish in a tank and feed it twice a day" kind of hobbyist. I like to really think about things, plan things out, and delve a bit deeper into my chosen species. Nice to see that many of you share that passion!