Taxonomy
Order: Siluriformes
Suborder: Loricarioidei
Family: Loricariidae
Subfamily: Hypostominae
Genus: Hypancistrus
Species: Hypancistrus seideli, Sousa, Sousa, Oliveira, Sabaj Pérez, Zuanon, & Rapp Py-Daniel, 2025
Description
Hypancistrus seideli is a species described in February 2025 that includes numerous L-numbers such as L66, L333, L287, L399, L400, and L236 (and possibly some other L-numbers). It is distinguished from all its congeners by its color pattern: the head, body, and fins feature alternating dark and light patterns of worm-like lines. The shape and number of these lines on the body change as the animals age and also depend on their habitat. In young animals, these lines are relatively thick and less wavy. Sometimes, the lines are interrupted, creating spots.
In large, adult specimens, the lines are generally much thinner and more numerous. Furthermore, the base color can vary from white to yellowish and sometimes even pink. It is also important to note that individuals within the same group (population) can exhibit highly variable patterns of these sinuous lines. This diversity of patterns and body shapes likely stems from different habitats and is therefore not a true species characteristic.
It grows to a medium sized fish of about 12 to 15 cm.
The species is named after German expert Ingo Seidel. He became world-famous for breeding Hypancistrus (and other species) for many years and sharing his extensive knowledge about these fish in books and during his lectures.
Distinguishing features of the L236:
The populations known as L236 are distinguished by a number of characteristics compared to other variants of H. seideli:
- • Shape: Although the overall build is robust, the L236 is often described in the hobby as a pleco with a slightly more elongated and less blunt body shape than, for example, the H. seideli L333.
- • Origin: One important point is that it's not 100% certain where the first L236 was actually caught. The available information that it originated from the Rio Irirí turned out to be a hoax. This lack of a proven, specific capture location contributes to the complex status of this L-number.
- • Color and pattern: The base color of the L236 is typically extremely light; bright white to light cream, with a very fine and variable pattern of thin, black, worm-like lines. The black lines are often thinner, making the white area more prominent than in variants like the L333. The pattern on the head can be very dense, but is often more interrupted and less wavy over the body and tail than in other variants.
- • Breeding forms in the hobby: Over the years, the term L236 has increasingly become a label for a Hypancistrus with a more white than black body color. Other L-numbers, such as L400, can produce young with an identical pattern to the L236 and are therefore sometimes sold as L236. Hybridization (crosses between different Hypancistrus species) is possible and has occurred several times.
This leads to the conclusion that L236 describes a color form or commercial label rather than a specific pleco, subspecies, or local form from a particular catch location. Numerous breeding lines have now emerged within the hobby, some based on years of experience and selection, some are the result of hybridization, and some were simply combined because the fish looked similar. Some of these breeding lines or domesticated forms include:
- Basic: specimens with broader stripes and therefore a darker appearance.
- RB: the famous breeding line of Robert Budrovcan.
- Super White (SW): specimens with an extremely white base color.
- Super Yellow (SY): specimens with a yellowish base color.
Distribution and habitat
Hypancistrus seideli occurs throughout the lower Xingu River, from the extreme downstream of the Volta Grande do Xingu to its confluence with the Rio Amazonas River. Its range, or distribution, is larger than that of any other known species in this genus.
The species inhabits both strong currents downstream of the Volta Grande do Xingu (Middle Xingu) and slow-flowing sections of the Lower Xingu estuary. Their habitat ranges from a few centimeters to over 40 - 50 meters.
The rocks they inhabit vary in size and shape, from granitic boulders to sedimentary rocks (e.g., sandstone).
For now, it appears the species is unlikely to suffer any negative consequences from the Belo Monte Dam. This species' adaptability is evident in an introduced population near Altamira. This population emerged after aquarium fish dealers released specimens captured there a few years ago.
Other populations of Hypancistrus similar to H. seideli are also found downstream in other tributaries of the Rio Amazonas. Their taxonomic status is still under investigation.
Diet
Hypancistrus is often described as carnivores (meat eaters). Although little specific research has been conducted on the diet of Hypancistrus, gut analyses of four species suggest they are not purely carnivorous. For example, in scientific literature (including Zuanon 1999), a gut analysis was included with the description of four Hypancistrus species. Their guts primarily contained various algae and detritus (organic waste).
Numerous processed seeds were found in the gut of the Hypancistrus inspector (Armbruster, 2002). Bryophytes (mosses) were found in Hypancistrus lunaorum, and in Hypancistrus contradens, in addition to primarily algae and detritus, some aquatic invertebrates were also found (Armbruster et al., 2007). This means that Hypancistrus is a generalist, but likely more herbivorous, tending towards a plant-based diet.
What do I feed my Hypancistrus seideli L236?
Based on research in their natural habitat, the captive diet should be very varied. In short: Combine a plant-based diet (algae, vegetables, detritus) with a protein supplement.
I feed them mainly with Dr. Bassleer Biofish Food Chlorella, EBO Spirulina soft granulate, EBO Veggie sticks and sometimes alternate this with Futterdose Krill soft granulate and EBO Artemia soft granulate.
Aquarium
Aquariums from 80 cm in length can be used to house a small group of H. seideli L236.
The substrate can vary from fine sand to coarse gravel. A slate structure with built-in small stones and breeding caves is a good way to give these fish hiding places and breeding opportunities. There should always be more breeding caves or hiding places available than there are fish in the aquarium. This prevents fighting over breeding and hiding places. They dislike bright light and are generally shy fish, rarely seen outside their hiding places during the day.
It's important to provide the fish with good water conditions. Water should be 28 - 30 °C warm, with a strong current, plenty of oxygen via an air stone, and weekly water changes. This species prefers slightly acidic water with an electrical conductivity below 200 microsiemens.
Because Hypancistrus seideli L236 is a very peaceful species, community aquariums can work well if the necessary conditions are met. Dominant fish, which are quicker to eat than L236s, should not be kept together to prevent the L236 from becoming deficient.
Sex difference
Determining the sex of Hypancistrus spp. follows largely the same rules, and this also applies to L236. Generally, it's not too difficult if you examine the specimens carefully and/or if good photos are available.
Like many other Hypancistrus species, L236 can exhibit a highly variable color pattern that varies from specimen to specimen. This is also clearly visible in the two fish in the photos. The color pattern is not a sex characteristic.
How to identify the sex of Hypancistrus seideli L236 by looking at them from the side?
A side view reveals the male's more robust and substantial body. The female has a more pointed silhouette.
What differences between the sexes are visible in the head?
While the male has a rather short, round head, the female has a more pointed snout.
What differences between the sexes are visible in the snout?
Furthermore, the odontodes on the gills in the male are longer and more numerous.
How can you determine sex at the gills?
Other than that, the odontodes on the gills are longer and more numerous with the male.
How can you determine sex at the pectoral fins?
The same applies to the odontodes on the pectoral fins. Females exhibit fewer of them. The hard ray of the pectoral fin itself is also thicker in males.
How can you determine sex by the tail?
When odontodes are visible on the tails, males display them more often, while females are more likely to have a smooth tail.
How do you determine sex based on body shape of Hypancistrus (top view)?
The top-down view of these photos can be a bit confusing at first glance. This is because the male is in quite good shape, while the female appears to be egg-free and therefore shows almost no curves. Upon closer inspection, however, we can still see that the male is broadest around the shoulders. Pregnant females exhibit their thickest part in the abdominal region (hips). Also visible in this photo are the small odontodes on the male's tail.
What gender differences are visible in the head from above?
The male's head is broader and rounder, and the gill flaps protrude more prominently. The female's head is more pointed.
How can I determine the sex of the Hypancistrus seideli based on the papilla?
From below, the sex of these fish is also easy to determine. The male's papilla is quite large but still shows the narrower male shape. The females have a rounder papilla, and upon closer inspection, a few yellow spots are also visible. Probably due to selection for white coloration, the female appears to have less yellow pigment in these spots than other plecos.
Reproduction and breeding
Breeding this species is quite common these days and relatively easy to achieve within the hobby. Like other species in the Hypancistrus genus, this one is a cavity breeder, with the male taking full charge of brooding.
To breed Hypancistrus seideli, a good ratio of adult males to females is first required. It is always good to have slightly more males than females in the aquarium. This allows females to choose which male they want to breed with. The aquarium should not be overcrowded. An ideal group consists of 6 - 8 specimens in a 100 - 200 liter aquarium. The setup should include plenty of hiding places, in the form of stone and slate structures. Breeding caves should be added between the openings and on the bottom. I have had the best results with round breeding caves that are 15 - 19 cm long and about 3,5 - 4 cm in diameter.
The ideal water parameters are 30 °C and an EC of 100 - 150 microSiemens, although captive-bred fish sometimes also breed on regular tap water. It's best to regularly change the water with reverse osmosis water. To get the highly oxygenated water where it's needed, it's best to install a current pump directed towards the entrances of the breeding caves.
The plecos should now be fed a good, high-protein diet. This can be achieved with frozen or processed foods. I've had the best breeding experiences with this species using Futterdose Krill soft granulate and EBO Artemia soft granulate. The females will start producing eggs, and the males will become spiny and sit in their breeding burrows, flapping their fins.
The breeding process and brood care
Once a female is interested in a potential mate, she usually sits next to the male's breeding cave for a few days. If all goes well, the pair will begin tunneling in the breeding cave, and the male will trap the female inside. This usually lasts no longer than two days.
After one or two days, only the male remains in the breeding cave. It's usually slightly elevated because he rests his mouth on the eggs. This species lays up to 10 - 30 eggs at a time. These eggs are then protected and cleaned by the male until the larvae hatch. This usually takes about 6 - 7 days, depending on the temperature.
Literature
Sousa, L. M. de, Sousa, E. B. de, Oliveira, R. R. de, Sabaj Pérez, M. H., Zuanon, J., & Rapp Py-Daniel, L. H. (2025)
Two new species of Hypancistrus (Siluriformes: Loricariidae) from the rio Xingu, Amazon, Brazil.
Neotropical Ichthyology, 23 (1): e240080
