Dicrossus sp. "Rio Negro"

[Quixotic]

Well, we got a shipment of them recently and was wondering if anyone keeping them could exchange some pointers on their behavior and husbandry.

There don't seem to be a lot of information on these fish from the Internet, aside from citation of some published literature (Datz, Linke & Staeck, Mergus Cichlid Atlas II). Unfortunately, I do not have any of the literature either, so I am having some difficulties in identifying their sexes.

I posted the same thing in some other cichlid specific forums, but don't seem to get any response either. So perhaps they are really rather rare in the aquaria, or not many are interested in this fish.

Based on my observations so far, they aren't difficult to keep (spawning them is altogether a different matter). I am keeping them in a 3 feet community tank, pH reading is about 5.5, feeding them assorted food and they eat all of them, not fussy at all; very active, grazing all the time, extremely brave fish too (they don't flinch even when you press your face up on the glass of the tank); occasional territorial display (i.e. chasing away the other fish), but in my view, not overly aggressive.

One initial problem I had was on sexing them as there is very little information offered on the Internet. However, I managed to track down a Spanish language website with some information. The following information was done over translation tools from the Internet and (mis)interpreted to my limited knowledge.

So, to anyone keeping them, do you see the following with regards to their sexual dimorphism? Please kindly share your views and thoughts.

1. Adult males - round or lanceolate caudal fins. Females - round caudal fins.

2. Males - caudal fins with purple and green flashes(?). Females - transparent caudal fins.

3. Males - red outer edge, black markings/spots in dorsal fins. Females - red outer edge, lacking black spots in dorsal fins.

4. Males - anterior(?) and posterior dorsal fin tips are pointed. Females - rounded fin tips.

5. Males - pointed anal fins. Females - rounded anal fins.

I will post my views later, hopefully with pictures to follow. Any thoughts?

[leeruisheng]

Too bad my batch of Dicrossus sp. were all wiped out otherwise would have contributed. Had no luck in keeping them.

What about those sexual dimorphism information from the publications?

[doppelbanddwarf]

I would really like to know how to differentiate males from females too. I got 2 from the recent shipment, but are unable to tell whether they're male or females even when settled down in my tank. Thinking of getting 2 more but holding back till I can differentiate.

[jacian]

Quixotic,
I am waiting for your picture so that I can see if they are the same as what I saw at Taipei.

[Heiko Bleher]

Hi,

this is Heiko Bleher and if you tell me which variants of Dicrossus sp. yopu have, I am sure I can help. I collected all those published so far and a few more. Please let me know with a pictures of the one you have and surely i can tell you,

best regards

Heiko Bleher
www.aquapress-bleher.com
PS on my website, under Expeditions Rio Aracá, you can find some Dicrossus I collected recently (last november and again next month)

[Quixotic]

Okay, took some quick pictures of them. Pardon the quality, they are always moving (in jerking motions) and my skills are not up to par yet.

From what I can observe, the sexual dimorphism isn't very strong. I had initially bought 4 by random, hoping to have a mix of male and female fish.

After a week in the tank, they are not showing much colour, except for the red/whitish edge on the dorsal fin. Anal fin is also showing a spot or two of black markings. No fish stood out, so I suspected that all could be female (what luck!).

Female?




Therefore, I went back to Biotope again and took time to observe the fish. This time, I see some subtle differences and took the chance. I obtained 2 more to be added to my colony.

After a few days, the newest additions are showing some differences. The anal and caudal fins are showing some visible patterns (albeit a little faint). The dorsal fin is also showing some slight patterns, in addition to the red/whitish edge. I suspect these are the males.

Male?






So based on the differences that I can see, I have 2 males and 4 females. If my suspicion above is true, then the keys that I got from the website don't quite match. My comments in [] brackets.

1. Adult males - round or lanceolate caudal fins. Females - round caudal fins. [no difference that I can see, the males have the same round caudal fins as the females, but... these may be young fish]

2. Males - caudal fins with purple and green flashes(?). Females - transparent caudal fins. [this is probably the key difference, there are obvious patterns on the caudal fins of the males]

3. Males - red outer edge, black markings/spots in dorsal fins. Females - red outer edge, lacking black spots in dorsal fins. [not that obvious, one of the males show this markings, while the other doesn't]

4. Males - anterior(?) and posterior dorsal fin tips are pointed. Females - rounded fin tips. [not obvious either, but posterior dorsal fin tips on one of the males is elongated, not exactly pointed]

5. Males - pointed anal fins. Females - rounded anal fins. [again not obvious, the males show slightly longer anal fins but not exactly pointed]

Any views or thoughts?

I am thinking that, perhaps these fish may still be young, so sexing them may not be so obvious. The suspected males are around 4.5 to 5 cm SL while the suspected females (could even be younger males) are around 3.5 to 4 cm SL.

P.S. Thanks Heiko! From the pictures, are they D. sp. "Rio Negro", same as what they also call D. sp. "Rotflossen" / "Red-finned" / "Twin spot"?

[leeruisheng]

Probably you could try making them flare at a mirror. That's what I did and it reveals much reddness. When colours are out, maybe it'll be easier for you to notice the differences.

Your Dicrossus are adapting very well.

[illumnae]

i'm thinking that the "red ventral fins (with no blue edging) in females that bred before" feature found in Dicrossus filamentosus might hold true in this species as well.

I was looking intently in the tank the last time I was at Biotope, and another difference I noticed was the shape of the belly. Females tend to look fuller behind the stomach than males as that's where the egg sac/ovaries/whateveryoucallit is. This is harder in this species than in D. filamentosus though, as this has a broader body than D. filamentosus.

Then of course there's the difference in intensity of colour, which isn't very accurate due to the tendency of dwarf cichlids to have "sneaker males", but anyhow females seem to have alot less red intensity in the dorsal fins than males do, though both exhibit the electric-blue edging. The tails in both males and females look red to me though.

Just some observations on my part. I spotted what I thought were 2 females at Biotope last week. Couldn't tell for sure with the others.

[Quixotic]

I'll see if I can drop in a mirror.

illumnae, thanks for your input. I will observe them some more.

jacian, understood that there is a batch of D. sp. "Rio Negro" in Taiwan now. Googled and found some pictures from Basil Aquarium.

This picture didn't state the sex, but looking at them, I think they are males.
http://www.u2u.idv.tw/stone/htm/APIS...0Dicrossus.htm

This is a picture of a female, the belly looks much fuller, so that could be a key in sexing them. Difference colour wise is difficult to tell.
http://www.u2u.idv.tw/stone/htm/APIS...gro-female.htm

[illumnae]

the basil photos seem to corrobrate my findings a little:

1. clear/red ventrals in female vs blue in male
2. rounder ovaries section in female (area behind stomach, not at the stomach itself)
3. intensity of colour in fins/tail

hopefully heiko is able to come shed some light, i'm feeling my way around in the dark as well

[jacian]

jacian, understood that there is a batch of D. sp. "Rio Negro" in Taiwan now. Googled and found some pictures from Basil Aquarium.

Yes Quixotic, those are the Dicrossus sp. "Rio Negro" I saw at Basil, looks similar to what is available at Biotope except that they are bigger in size and more intense in colour. Do continue to share with us more information on this fish.

Now I am very tempted to get myself a pair.

[Heiko Bleher]

Hi,

this is Heiko and thanks for the photos.

This Dicrossus is from the Rio Demini (left-hand-affluent of the middle Rio Negro), I found it many years ago and introduced it. Ones in a while exporters form Manaus are shipping them, but seldom.

The species is still undrescribed. I called it Dicrossus sp. "Demini" according to its location.

Unfortunately I can see no male on your photos, it seems that you have only females. The males are much brighter in colour. But one female seems to be with eggs.

All the very best,

always

Heiko Bleher
www-aquapress-bleher.com

[Quixotic]

Thanks Heiko for the information. Rio Demini makes sense, these are imported as "Rio Negro - Barcelos".

You mentioned that the males are much more colourful. So I suppose the colours on the fins are much much more intense and distinctive than this?



Urgh, it is possible then that the fishes I have are all female. Kind of anti-climatic.

[Heiko Bleher]

Hi,

yes, see if you can get any males (or at least one). I will actiallu be in the Demini, Araca and elsewhere in the Rio negro system collecting begin of Auguts. If you cannot gte them I will collect (hopefully) some, although the area I colelcted it is under water in August...


All the best

Heiko

[Quixotic]

Interesting that they have now learned how to feed like tetras. They now swim to the water surface to feed on the flakes during feeding times.

[Savant]

Hi,

yes, see if you can get any males (or at least one). I will actiallu be in the Demini, Araca and elsewhere in the Rio negro system collecting begin of Auguts. If you cannot gte them I will collect (hopefully) some, although the area I colelcted it is under water in August...


All the best

Heiko

Do you mean you will collect some fishes and bring to us?

Wow! Would look forward to that...

[Heiko Bleher]

Hi,

yes I collect in Amazonia every year (and usually several times in uncollected places). I will be in the Demini next month and I will see. The problem might be, that the water is still very high. I will see.

All the best, from a collector (you can see a little of my work at www.aquapress-bleher.com)

always

Heiko Bleher

[leeruisheng]

Hey Quixotic,

Any updates and photos? Manage to identify their sex?

[Quixotic]

Well, they have grown in size but not showing too much sexual dimorphism. Most of them have shown some additional subtle colours and patterns, not dissimilar to the one in the picture above.

Plus, there don't seem to be any coupling activities, only territorial displays, so the assumption remains the same that, unfortunately, they are of the same sex (females).

I have also noticed that they seem to have a liking for vegetable matters, constantly picking on rotting leaves or those that are not doing well. Will see if I can get some updated pictures.

Am I the only one keeping them?!? Don't see inputs from other keepers.

[doppelbanddwarf]

My 2 D.sp "Rio Negro" look the same as yours too. Also no sign of sexual dimorphism. And they munched holes in my frogbits.