The Phyllonemus catfishes

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Dr Michael Hardman strokes the ego of the Kapondo or spatula-barbeled catfish - a creature with a very liberated lifestyle, and explains how to tell the various members of Phyllonemus apart.

Europe has known about the Phyllonemus catfishes for over a century, thanks to George Boulenger who pioneered the exploration of African fish. Although it was known to local fishermen as kapondo, Boulenger, a master ichthyologist, saw this catfish was special because of its peculiar barbels and teeth.

Coming from Lake Tanganyika, this 10-15cm/ 4-6” siluriform delight has features as elegant as its name: huge anime eyes, leaf-like tips to the maxillary barbels and parenting skills to make Supernanny proud.

In the aquarium, they can add siluriform spice to a run-of-the-mill Tanganyikan set-up. Plenty of rockwork and hard (10-20 GH) and alkaline (pH 7.5-9.5) plus water at 24-26°C/75-79°F should keep these laid-back and tolerant cats happy.

Phyllonemus probably feeds on small invertebrates and young fish in the lake, but readily adapts to the frozen and prepared foods that make up the balanced aquarium menu.

Kapondo is found singly, in pairs or groups up to four under large boulders in water less than 10m/4” deep. Given their fondness for company, larger aquaria could house a small group of three to six, which would promote the chance of a captive spawning.

Therein lies its reproductive behaviour...the real beauty of this fish.

Like many of us, Phyllonemus has adapted to a mobile lifestyle. Instead of the 1970s-style bravado employed by most catfish fathers to protect their nest, both male and female provide shelter to eggs or young in their expanded mouths.

Mouthbrooding behaviour is well known in cichlids, but sea catfish (Ariidae), Lophiobagrus (another small claroteid from Lake Tanganyika) and a few marine families (including cardinals, jawfishes and lumpsuckers) also practice oral incubation. However, in many cases, only one parent provides childcare — and it’s usually dad.

The advantages of a mobile family are obvious. If a predator comes sniffing it’s easy to relocate at a moment’s notice.

Spot the difference

Phyllonemus typus

Phyllonemus filinemus

Phyllonemus brichardi

Breeding behaviour

If you’re small, which Phyllonemus is, you need to choose your fights carefully and this is a strategy that works. In Lake Tanganyika it also works well for Lophiobagrus and lots of cichlids of a similar size.

Males are slightly larger than females, but otherwise the sexes are very similar. In Lake Tanganyika, clutch sizes of 12-70 are shared between both parents and the separated eggs are each 3-4mm in diameter. Fry are free swimming by 12mm/0.5”.

In the lake Phyllonemus breeds during the wet season. Of course, during this time it may be using many changes in the environment as cues to start reproduction, but many fish are triggered by the wet season when temperature increases slightly (+1-2°C) and aquatic habitats experience a flush of freshwater.

These would be a great combination to try if your females look full of eggs and ready to spawn.

Expert Q&A

Dr Michael Hardman answers your most frequently asked questions about Phyllonemus typus.

Why do they have flattened barbels?

Catfish are well known for their heightened ability to taste, touch and sense changes in pressure. Barbels are used for picking up this kind of information and relaying it to the brain.

While Phyllonemus clearly has modified barbels, if they offered an improvement in sensory capabilities I would expect to see them in other catfish, so I don’t think that’s the whole story.

A study of Chrysichthys filamentosus, C. nigrodigitatus and C. walkeri found that these claroteids used their barbels only to sense movement in the substrate and relied on vision to locate prey. For claroteids, these three species have very short, simple barbels and hugely expanded eyes.

Phyllonemus has large eyes but I haven’t seen its brain so can’t say which sensory centres, if any, are most developed.

Chrysichthys ornatus, sometimes seen in the shops, develops pale yellow tips to its maxillary barbels and I’m tempted to think they act as lures. This Congo species is a cryptically coloured ambush predator, so it sort of makes sense. However, I don’t think P. typus uses its barbels as lures.

Because both sexes have these structures on their barbels rarely seen elsewhere in the catfish world, and given that Phyllonemus is a bi-parental mouthbrooder — which is also rare if not unique — I think it would be worth studying their possible role in reproduction.

Maybe they are used to shepherd the juveniles, to call them home, or give a predator something flashy to target instead of the family. Whatever the answer, I’m sure it will be a surprise and aquarists could be the first to see for what P. typus uses its fancy barbels.

How many species of Phyllonemus are there, described and undescribed, and how can fishkeepers tell them apart?

There are three species described and I don’t know of any yet to be given a formal name, although I haven’t been focusing on this genus as part of my work. Two are quite similar — P. typus and P. filinemus — and the third is distinct (P. brichardi).

Phyllonemus typus has a maxillary barbel that ends in a leaf-like expansion and the inner pair of chin barbels originate between or slightly in front of the corners of the mouth. The pectoral fins are also pale compared to P. filinemus.

The latter also has a slightly flattened maxillary barbel and is without the leaf-like flange of P. typus. All chin barbels originate well behind the mouth corners and all the paired fins are dusky.

Phyllonemus brichardi has a toothless palate, the other two have similar toothplates on the roof of the mouth. The outer chin barbels are longer than the maxillary barbels and more than twice as long as the head.

This species also has an adipose fin longer than the space between it and the end of the dorsal fin.

Are they the only catfish with this feature?

The barbels of Chrysichthys have a lure-like structure at the tip.

Phyllonemus filinemus, the likely sister species of P. typus, also has flattened and broad barbels, but these are less pronounced and do not end in leaf-like structures.

Flattened barbels are also seen in other cats such as Goslinia platynema (Pimelodidae), Bagarius spp. (Sisoridae), and Hemisynodontis membranacea (Mochokidae). In Goslinia they likely serve as a sensory function, but in the other two I think they might act as food funnels.

Keeping them

These peaceful catfish from Lake Tanganyika can be mixed with small or medium sized Tanganyikan cichlids to create a biotope-style aquarium based on their natural habitat.

Go for a tank of around 100-200 l/22-45 gal and furnish it with large rocks to provide them with shelter.

If you live in a softwater area you may need to harden your water by adding calcareous rocks or sand, but avoid using marine coral sand and tufa rock.

Give them some love and there’s a good chance they’ll spawn among large rocks with spaces underneath they can access and easily defend.

Excellent water quality of the right chemistry (pH 7.5-9.5, 10-20 GH), a few quiet tank mates and plenty of protein-rich foods should get them in the mood.

This item was first published in the September 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.