sexing bristlenose

[d3n2]

Ok, I've had these fish for 7+ months, and I am totally confused. I always thought sexing BNs was a straight forward thing. I guess as a beginner, it's no surprise that I am in this situation.. Well, here goes..

So I've been told (read somewhere) that getting 6 fish gives a fairly high chance that you will get fish of both sexes, so thats what I did. I got 6 common BNs when they were 1-2 inches TL. After a month or so, some started growing bristles, so I thought, yay, some male and some female? But in another month all of them had little bristles around 1 mm in length. So I thought, too bad, all male. BUT, until recently, none of their bristles grew to more than 1-2 mm. At the same time, the growth was isolated to the edges of the snouts. So, again I changed my assessment; all female. Finally, just in the past week, I've noticed that some of the fish, the bigger ones, have developed a sort of ridge down the snout. No visible bristles yet, but i see tiny bumps down the ridge. They are now around 5 inches TL.

I do have a pair of younger albino BNs around 3 inches TL. One is slightly larger and clearly male, because he has a bristle or two down the snout and the edge of his snout is full of bristles. The other one is, so far, female; she has no bristles at all.

This is why I am so confused . I even bought 5 more common BN juvies a month ago just in case I ended up with only one sex. So, what do people think? Do I have both sexes in my original group of 6? All male? All female?

Thanks in advance for the replies!!

[MatsP]

If you have a look at the FAQ section (under the Help! menu above), there is a list of several "keys" to sexing bristlenoses.

I find that if the fish are reasonably mature and well fed, the females body shape will be a good key - mature females are "fat" between the pectoral and ventral fins, where the male is "straight" from the head all the way to the tail.

--
Mats

[d3n2]

Thanks for the reply.

Yes I've seen that FAQ. I've always had trouble sexing by looking at the body shape, I guess I'll give it another try.

[andywoolloo]

the boys have bristlies up their snout and on the front of their mouth and the girls either none or some around the front of their mouth.

my males got bristles at around 4 mos maybe? cannot really remember when.

the adults are far easier to tell.

and definitely easy on the body shape, look at them from above.

[MatsP]

If the fish are 5 inches, and

Ancistrus cf_cirrhosus

, they should show quite clearly if they are male or female. It is possible that they are a different, larger, species, where the bristles are bigger on females [there are several species of bristlenose that are larger, and where both males and females have bristles].

As Andy says, look at it from above (or below when it's sitting on the glass, perhaps), and the belly shape should be quite clear indication.

It is, for obvious reasons, much easier to tell if you actually have a group with both males and females! We don't know well what factors affect the male/female distribution in a batch of fry - it's possible that temperature is a factor, and if we assume that "warmer -> more males", perhaps that chances of getting all males is much more likely in the Philippines than, say, in a more moderate temperature country. This is pure speculation on my part, so don't take this as evidence that "we only get males in this country".

I'm also pretty sure that if the fry/juveniles are kept in a small tank, the males will dominate at feeding times, and more males than females will survive to mature size. To prevent this, the largest fish should be split from the group - the smaller fish is often the females.

--
Mats

[d3n2]

The fish are around 4-4.5 inches TL. I don't think they'd grow anymore than half an inch as I would assume they are around 9-10 months old. I will definitely try to sex them by looking at the body shape, although as mentioned, this would be hard if I have a group of only one sex.

As for bristles, they all have the same amount of 1-2 mm bristles at the edges of their snouts. This is what led me to believe that they are all female. Although, some of them are a little more robust and belligerent than others.

BNs are not very widespread here in the Philippines, and I actually have not encountered them here, or any other type of pleco (besides the common pleco), until the past year. This has led me to believe that the ones I have are imported, so I hope the temperature is not a factor of the sex of my BNs. It IS a hassle though knowing that some of my fish (cories) need cooler temperatures when my tanks all fluctuate between 28-29 Celsius, and I can't do anything about it.

Again, thanks for the input everyone! I really appreciate it.

[d3n2]

I need a little more help guys.. Just want to clarify, if the BNs are around 9 months old, males should have bristles on the ridge of their snouts already, right?

I tried sexing them by looking at the body type, and it just confused me more. I guess I still don't really know what to look for (the ones that have the widest heads have a slight bump at the belly, some narrower headed ones don't have it, etc). Or I have all of one sex, and I'm looking too much into the slight differences within a sex. I know this must be getting annoying since I am worrying about one of the most common and easily bred plecs out there..

Did manage to sex some of my other plecs though, and I now know I have a male Baryancistrus beggini, female Hemiancistrus subviridis, a pair of Hypancistrus inspector, female Peckoltia braueri, 1 male and 2 female P. compta..

[MatsP]

At 9 months, they are not OLD. Fish grow their entire life, and the male bristlenose will look more male when they are two-three years old than they will when they are 9 months. Remember, these fish live a lot longer than for example guppies - there are known populations of corys that are well on their way to 20 years old, and Hypancistrus zebra that are over 15 years old (and still spawning). Ancistrus may not live that long, but I have ones that I have had for 6 years or so, and show no signs of being "old".

--
Mats

[d3n2]

Alright, I guess I'll just have to wait it out.

Thanks again for the replies Mats.

[gaballench]

Hi there,

In addition to the useful observations already posted, there are two good ways to decide between sexes in Ancistrus (Once reaching maturity, of course). One of them is SL, as males are notably larger than females at maturity (I can post images later), and degree of development of snout odontodes. As you already noted, even juveniles of Ancistrus do develop tentacles (as do females), so presence-absence of such structures is not an indicative of sexual condition. However, males in all the Ancistrus species I know of (mostly Colombian, Panamian, Venezuelan and Brazilian species) show more developed tentacles, and with high-order ramifications (vs. females showing more restricted unplated areas, with less ramified tentacles).

I think it's hard to decide whether your specimens are adult and even less to guess a standard for a genus actually showing a considerable variation in SL, so I would suggest to try to ID the fish before guessing it should or shouldn't be mature yet.

Cheers,

Gustavo.

[MatsP]

Gustavo, nice to see you here on Planet Catfish. It is very much appreciated to see scientists that take an interest and help us hobbyists in keeping the fish.

Your suggestions are very good of looking at the reative size and formation of the bristles/tentacles. I think most of what you are describing is already covered by the FAQ entry I suggested earlier:
http://www.planetcatfish.com/general/ge ... d=441#a357

Identifying the species is definitely a very good idea, as that will determine whether the fish are mature or still juvenile. Of course, if they are captive bred species, it can be quite difficult to pin it down to a particular species, as there are often similar looking species from several parts of South America - they are different species, but the only (non-lethal) key to differentiate them is by knowing which river/country they came from - and even that is often difficult.

Also, I have a pair of

Ancistrus cf_cirrhosus

where the male is smaller than the female... So size isn't a reliable measure, either.

--
Mats

[d3n2]

Yes, I think my BNs are the standard, common

Ancistrus cf_cirrhosus

. I have no idea where they came from, I assume the store just ordered them from some distributer. I think in this case, knowing their true identity would be rather difficult.

Though after reading 'The identity of the common bristlenose' article, if I were forced to pick from the most commonly imported brown bristlenose catfish, I'd say my BNs look the most like

Ancistrus punctatus

. They have the same rusty edges around their fins, pretty dark as juvies, and turning a bit browner as they grew. Only thing is that their spots are not as bright as the ones pictured, and I don't think they will grow to 9.8 inches (hope not ). But that doesn't say much as there are probably tons of other species out there that have similar traits.

I'm curious though, Mats. For the pairs where the males are smaller than the females, are both sexes from the same 'source'? And do they consistently produce offspring where males are smaller than females?

*EDIT: Just realized that A. punctatus is NOT one of the commonly imported brown bristlenose catfish. I probably looked up the wrong fish when I searched to compare..

[MatsP]

The pair where the male is smaller is just a single male. The offspring of this pair have produced much larger males. They did not come from the same tank at once - I bought the female a long time before I got the male. It is quite possible that the male is a "runt" or that it's stunted in early development. The female is also older than the male, but the sons of this pair have exceeded the size of the female and male - so it's either a genetic effect, or an early deficency in the diet that stunted the male.

--
Mats

[d3n2]

Ah, yes. That makes sense.