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Fish Profile: The Striped Raphael Catfish (Platydoras armatulus)

Updated: Mar 25, 2022



Catfish are some of the most interesting aquarium inhabitants. Observing their biology, anatomy, and behavior can be a fascinating pastime. Few catfish are more interesting than the 78 species of talking catfish in the family Doradidae (door-ad-id-ee).


One of my favorites, and a prolific specimen in the aquarium hobby, is Platydoras armatulus (plat-ee-door-us) (arm-at-u-lus). This species has several common names, such as the striped Raphael catfish, the humbug catfish, and the striped talking catfish.


What’s In a Name.

P. armatulus was originally described to western science in 1840 by Achille Valenciennes, a renowned French zoologist. Valenciennes studied under Georges Cuvier, who is considered the father of modern paleontology (the study of fossils).


Valenciennes originally classified the fish in 1840 under the name Doras armatulus. The genus Platydoras wasn’t named until 1862, by Dutch ichthyologist Pieter Bleeker. From 1840 to 1862, P. armatulus was known as Doras armatulus.


In the aquarium hobby, P. armatulus was sold as Platydoras costatus, a similar species of Doradidae catfish known as the Raphael catfish. Piorski et al (2008) corrected the hobby by showing that the "true” striped Raphael catfish sold in the hobby was not P. costatus, but in fact P. armatulus. The main physical difference between the two species is the white stripe does not extend to the front of the head on P. costatus.


Distribution

P. armatulus is quite abundant in the wild, and can be found all over the Amazon, Parana, and Orinoco River basins of Brazil, Paraguay, Bolivia, and Argentina.


P. armatulus finds its home amongst the sandy, muddy, soft bottoms of whitewater rivers. As opposed to blackwater, whitewater rivers have high nutrient and turbidity levels. P. armatulus is nocturnal, hiding amongst vegetation and cover during the day, then coming out at night to feed.


The water parameters in different areas of the Amazon River Basin vary widely. The Parana river basin for example ranges as follows: pH (6.5 - 8.2), Alkalinity (24-326 mg/l), calcium/magnesium (0.9 - 170 mg/l), sodium (3.3 - 1100 mg/l), nitrates (0.05 - 2.8 mg/l), temperature (73 - 86 degrees F) (Ronco et. al. 2016). Where P. armatulus is most commonly found, within the whitewaters of the Paraguay-Parana basin, these values tend to be at the lower end of these ranges. (Ronco et. al. 2016).


Description

As their common name would suggest, P. armatulus sport a white to yellowish stripe from the dorsal (top) portion of the head to the caudal (tail) fin rays. They have a yellowish underbelly with dark brown on the sides and top and beige along the primary spines of each fin and along their back. This species also has a series of barbs along the flank, starting above the pectoral fin. Their maximum standard length (nose to base of tail) is 178 mm (7 inches) (Graça, Pavanelli 2007).


P. armatulus are omnivorous. In the wild, they will consume available matter as they search along the river bottoms. Their diet normally ranges from insects, crustaceans, and smaller fish, to carrion, and plant matter.


P. armatulus is reported to be sexually dimorphic. Typically, females are wider from side to side.


Breeding

Wide scale breeding of this species has yet to be accomplished in captivity. This is most likely due to the fact that it is difficult to replicate the spawning conditions of their wild habitats. In the wild, P. armatulus has been observed spawning in fast-moving rivers.


There have been some reports of this species breeding in captivity. However, it did not occur under controlled conditions, so this result was not able to be replicated.


Any specimens which have been bred in captivity are produced using hormone injections in the parents, which forcibly initiates spawning. Most specimens available for sale are wild-caught. Neither of these scenarios are ideal.


I believe, due to known incidences of accidental breeding, that this species can be readily captive bred. The wild conditions would need to be replicated; all we need are some devoted aquarists to accomplish this.


Talking Catfish

Some species of fish, especially many catfish, have the ability to communicate through auditory signaling. P. armatulus, along with the other species of the family Doradidae, has evolved two unique methods of auditory communication.


The first method is by way of an elastic spring mechanism located in the back of its head, next to the swim bladder. When triggered by muscle spasms, this mechanism hits against the air-filled swim bladder, causing it to resonate and produce sound, much like a drum.



The second method is by locking and rotating the primary spine of the pectoral fin within its socket producing a “clicking” sound.


These auditory signals are used to communicate in combative and reproductive behaviors, as well as contexts of general disturbance (Kaatz & Stewart 2012).


You can sometimes hear the clicking or drumming sound these fish make at night, when they are most active. Sound waves travel better through water than through air, so turn off any extra noise and listen carefully for a few minutes after the lights go out. They will also make this noise when disturbed, for example, after being netted.


It's also worth noting, you should be very careful when netting this species. Along its flank, on both sides, P. armatulus has a line of boney barbs. It also has barbs along the primary pectoral fin spine. All of these spines can easily become entangled in nets.


You can try using passive traps to capture the catfish when necessary. Alternatively, I have found a fine mesh net to be less likely to catch the fish’s spines than a coarse net.


Water parameters

pH

6.0 to 7.0

General Hardness

2 to 10 dGH

Alkalinity

2 to 6 dKH

Temperature

74 to 79 degrees F.

Preferred Lighting

Low

Maximum Length

7 inches

Tank Size

50+ US gallons

Disposition

Shy, non-aggressive. Predatory towards smaller fish.


P. armatulus evolved in the softer whitewater rivers of the Amazon. Keeping your aquarium parameters stable is most important in terms of this fish’s health, but I recommend you stay within the above ranges as well.


Tank Size and Habitat

The larger the tank the better, but 50 gallons is a good starting point. With this fish relegating most of its time to the bottom of the tank (benthic zone), I would recommend a shallow tank with sprawling width and depth, as opposed to height.


Within the aquarium, you will want plenty of cover. PVC tunnels (decorated or otherwise), driftwood, rock caves, and vegetation are all crucial sources of cover. Without proper cover, some catfish keepers will see their fish experience heater burn. This occurs when the specimen hides behind the aquarium heater. When the heater turns on, it can severely burn, or even kill your catfish. This is easy to avoid by supplying plenty of cover for your fish to hide in during the day. You’ll want at least one cave that is well hidden enough that even you can’t see them. The idea being, when they're within this refuge, they are not exposed to any movement outside of the tank. This effectively reduces that source of stress to zero.


Next, surround that cave and the neighboring areas with dense cover in the form of driftwood, rocks, and plants. When you observe your fish swim about, you’ll want to see them go from one point of cover, safely to another, without being exposed for too long. This is their ideal environment in which to comfortably move about.


It may seem counterintuitive at first, but the more cover you provide, the safer they feel, and the more normal activity and sightings you’ll get from them.


Tank Mates

P. armatulus is a shy, peaceful fish. They won’t show territorial aggression toward conspecifics (inhabitants of the same species), or other species. However, they are nocturnal omnivores. They are not above munching on sleeping snails, shrimp, and even small fish. Make sure whatever fish you add are fast moving, or are larger than the catfish's head. Otherwise, you may expect to lose a few here and there.


Behavior in the Aquarium

As I mentioned, P. armatulus are nocturnal. In my experience, to get the most out of this fish, and be able to observe them, you should get a dimmer for your aquarium light. After I added one to a tank with a P. armatulus in it, the aquarium’s owners reported observing their P. armatulus frequently after the light reached below 50% intensity. They went from seeing him streak across the tank only once in a while, to being able to observe him for several minutes at a time.


A red light can also be used in place of a dimmer, as fish don’t see well in that light spectrum. You will be able to observe your catfish, but they will think the lights are off. Just turn the red light on for an hour or so while you observe the tank after the main light is off.


P. armatulus will scavenge for food throughout the day, but mostly at night. There is most likely leftover food available for them to consume at night; if you're worried that there isn't, you can feed your tank later in the day or just before lights out. If you use a dimmer, don’t feed too late, as your diurnal fish won’t be active enough to consume much.


Even though P. armatulus is nocturnal, you can still train them to eat during the day. By placing food in the same spot, outside their favorite cave, at the same time everyday, you can train them to eventually come out and expect food, or even come near the surface of the tank when they see you approaching.


Prehistoric

Despite the catfish order Siluriformes only being 100 million years old, P. armatulus has a rather cool prehistoric look to it. This fish does best with heavy cover and low lighting. Make sure they are well fed with a balanced, protein heavy diet. If you have a male and female in the tank together, be sure to record your aquarium parameters and conditions. If they breed, any data on their environment can go a long way to helping the effort to breed this fish in captivity and end the need to collect wild caught specimens.


Literature Cited

Graça, W.J.D. and C.S. Pavanelli, (2007) "Peixes da planíce de inundação do alto do rio Paraná e áreas adjacentes." EDUEM, Maringá, 241 p.


Kaatz, I.M., Stewart, D.J. (2012) “Bioacoustic variation of swimbladder disturbance sounds in Neotropial doradid catfishes (Siluriformes: Doradiade, Auchenipteridae): Potential morphological correlates”. Current Zoology 58(1): 171-188.


Ronco, A.E., et. al. (2016) “Water quality of the main tributaries of the Parana Basin: glyphosate and AMPA in surface water and bottom sediments.” Environmental Monitor Assessment. 188:458.


Photos
  • https://commons.wikimedia.org/wiki/File:Platydoras_costatus_5_(Piotr_Kuczynski).jpg https://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License


  • https://www.researchgate.net/figure/Head-and-anterior-portion-of-body-in-Platydoras-armatulus-MZUSP-91686-1517-mm-SL-in_fig20_278091001 https://commons.wikimedia.org/wiki/Commons:GNU_Free_Documentation_License



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