Megastoma and Barlowi how to tell the difference?

[Tim_Smith]

Hi guys,

Ok so Megastoma and Barlowi are super similar. How do we tell the difference and what makes them different species? I thought it was Barlowi that has the half orange cudal but this seems like it comes and goes. I have also see. people say their fish is Megastoma but the cudal fin is half orange. I was going off this for ID as I supposedly have a megastoma . It is quite a large individual at nearly over 3 inches. Anyway would love to see some discussion about this with those that know more than me. I’ve included the male I have.

Tim

 

[Frank Hättich]

It can in fact be very difficult to distinguish A. barlowi and A. megastoma. Usually barlowi males show a pattern of rows of dots only in the upper half of the caudal fin with the lower half being yellow/orange. In megastoma males the completle caudal fin shows rows of dots and merely the tips of the fins are yellow/orange (as in your fish). Moreover, megastoma males usually show red spots and "worm-like" markings on the lower head whereas in barlowi males this area is more or less orange colored or colorless (as in your fish). So your fish shows features of both species. I have seen quite some males showing a mix of features of both species. What makes things even more complicated is that there are more species which are very similar to barlowi and megastoma (see here) but of which we don't know very much.
The best way to distinguish barlowi and megastoma is by looking at the females: barlowi females usually show a large breast band that reaches to or above the pectoral fin base whereas in megastoma females merely the area between the pectoral fins is black (sometimes reaching a bit higher). Moreover in their brooding dress barlowi females regularly show a pronounced lateral spot whereas megastoma females don't. And large megastome females can develop a two tipped caudal fin which I haven't seen in barlowi females so far.
Do you have any information on the catch location of your fish and can you show us photos of your female?

 

[Tim_Smith]

Thanks for your reply Frank. The female I gots separately. The first female I was sold to was in fact a different species. They must have mixed them up. You let me know this Frank. The second female I sourced was from the same supplier. I think they get them
out of Malaysia. So no locality. They keep their fish in tanks without lids and I had seen what looked to be a Barlowi in the megastoma tank it had presumably jumped across as they were kept next to each other. I did tell them. Anyway in Al likely hood they could cross which would make it even harder.
I’ll try and get a good photo of the new female and see how we go.

 

[Frank Hättich]

I found a typo in my post that might lead to confusion. Instead of "pectoral" it must read "ventral" here: "whereas in megastoma females merely the area between the ventral fins is black".