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New Information on the Zebra Pleco,
Hypancistrus zebra

By Ingo Seidel (Tropical Fish Hobbyist, Volume 44, Number 5, January 1996)

It was about 1989 that the catfish world was taken by storm when the first photographs of a small black - and - white - striped loricariid catfish were published in aquarium magazines. This little beauty certainly made the hearts of many catfish fanciers beat faster. However, the first imports of the zebra pleco, as it came to be called, were absolutely unaffordable. However, prices continued to drop as supply increased, and before too long even ordinary mortals could afford this catfish. In 1991 the species was described by Isbrucker & Nijssen as Hypancistrus zebra. Again and again, there were reports about the spawning of this catfish, but there were never any details. They had been considered just rumors until eventually two reports appeared in DATZ (10/93) on the spawning of the zebra pleco.

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Fish Fur Feather sm2

Since then some aquarists have definitely been successful in the regular spawning of this species; among others, my friends Karin & Gerd Arndt. Since there were still some questions left unanswered after the two spawning reports by Pahnke (1993) and Walter (1993), we are taking this oppurtunity to give another report on Hypancistrus zebra. I will also give you the Arndt's very detailed information on their detailed experiences. I also made the acquaintance of a Mr. Rickhoff at an aquarium society meeting, and he related his experiences in spawning H. zebra in a densely planted community aquarium. During the writing of this article my own zebra plecos surprised me with fry, so I also can draw on my own experience.

Systematics

Since the species differs strongly from all other known species of loricariids, Isbrucker & Nijssen erected a new genus for it. The genus is monotypic; that is to say, H. zebra is currently the only species in the genus Hypancistrus.

When Stawikowski (1992) introduced the loricariid L98 in DATZ, which possessed a longish irregular spotting instead of the black striping, some speculated that this was a second species of the genus. While not completely certain, this probablyis not the case. To all appearances, L98 is a color variant of H. zebra. It would be interesting to find out whether the color pattern breeds true.

Another variation of H. zebra is L173 (see Stawikowski, 1994). The only speciman of this form known presently deviates from the normal zebra pleco primarily in that it has a different body shape. Perhaps it is a single deformed animal.


Father and Son

Sexual Differences

In H. zebra there is no very strongly marked sexual dimorphism. Males and females are colored about the same. The first pectoral fin ray of the male is somewhat thicker than that of female. In sexually ripe males, the odontodes (small toothlike spines) of this ray are somewhat more strongly developed. In addition, the interopercular odontodes in the males are somewhat longer. If you look closely, you can also detect differences in the body shape. When the fish are observed from above, the males are distintly broader than the females in the head and pectoral region. The stoutness of the body, on the other hand, cannot be cited as a certain distinguishing criterion, since the male can also be quite robust in the belly region. Probably, he stores up a layer of fat to live on during the time that he tends the eggs and cannot eat. When you are trying to determine the sexes it helps if you net out the fish and place them in a small bare bowl so that you can examine them more closely.


An adult female


Although the difference is slight, the male has a slightly broader head than the female

The Natural Habitat

The home of Hypancistrus zebra is the Rio Xingu, one of the larger southern clearwater tributaries of the Amazon, whose source lies in the Brazilian state of Mato Grosso. According to the orginal description, the type locality of this catfish is in the state of Para, about an hour's ride upstream of Altamira by speedboat. It is assumed that the type locality is also the principal collecting area of the species.

The Rio Xingu has, in recent years, been a source of many new loricariid species. In the vicinity of Altamira the river is about 1 kilometer (0.6 mi) wide. The substrate consists of dark rocks and stones of volcanic origin; in many places these are honey combed with holes.

At Altamira in the Rio Xingu, on 25 September, 1998, at about 1400 hours, the following measurements were taken by Schliewen & Stawikowski. The air temperature was 34.5o C (94o F). The water had a temperature of 32.2o C (90o F); near the shore, even 35o C (95o F) was measured. The pH was about 6.5. There was a conductivity of 120 S / cm and a carbonate hardness of around 1odH. The iron content was less than 0.05 mg / l.

Acquisition

A couple of years ago, zebra plecos were problem fish. When we finally got our hands on some, a number of our wild specimens arrived in poor health. Many of these fish had sunken bellies or deeply sunken eyes. Many aquarists, ourselves included, experienced high losses. Fortunately, this has changed today, and most zebras that you can obtain in pet shops are in very good condition. During the principal collecting time, summer to early winter (the dry season), this species is imported in larger quantities. However, they also are imported outside of the season, but in smaller numbers. At this time the collectors, because of the higher water levels, usually can capture the fish only by diving, and for that reason, the prices are somewhat higher. Meanwhile, should you be lucky enough to acquire tank-bred specimens from a breeder, the risks are always smaller. Above all, they are already adapted to aquarium water conditions.


The mouth of H. Zebra is not as large or as heavily toothed as in some other loricariids,
and indicates that the fish is not a good algae-eater

Care

On the basis of its small size (under 4 inches), the zebra pleco is ideally suited to keeping in the aquarium. Like many other South American catfishes, the species is extremely adaptable, so we do not have to imitate in every detail, the conditions of their home waters. Even in somewhat alkaline, hard water, they do well. For day-to-day keeping, temperatures of 79-81o F are fine. Although water chemistry is not critical, water quality is. These fish need very clean water, with plenty of oxygen. Supplemental aeration is strongly recommended.

Although some have reported the opposite, in our experience zebra plecos are not as territorial as many other loricariids and several can be kept in one tank with out any problems. Between the males there often are small skirmishes: however, these always turn out without injuries. You must be careful with aggressive tankmates, though, as very large or rambunctious fishes can quickly oppress the zebras. A tank for zebras need not be huge, but it is of great advantage when the bottom area is as large as possible.

Remember that in their natural habitat zebra plecos inhabit rocky areas where they find many crevices and holes satisfactory for hiding places. Therefore, to duplicate the natural conditions for these catfishes closely, construct some caves for them with slate or some stones. Driftwood can be omitted, since zebra plecos do not favor wood as a hiding place, and apparently do not chew on driftwood like some other plecos.

Zebra plecos, in contrast to many other loricariids, are quite active during the day. However, they are quite shy, and take the smallest movement in front of the tank as an occasion to retreat into their hiding places. If you sit still and completely motionless in front of the aquarium, you can observe how they roam through the tank in search of food.

The plecos become quite hectic when you place brine shrimp nauplii into the tank. Small live or frozen foods, such as small cyclops and daphnia, are also very hapilly eaten. Bloodworms are also a favorite. It appears that these fish have a special liking for anything that is red. Mosquito larve, adult brine shrimp, and krill, are, according to our observations, accepted only with hesitation, if at all. Also, various prepared dry foods, such as food tablets with a vegetable base, are happily taken.

However, it is a fallicy that every suckermouth catfish automatically is a good algal "terminator." Hypancistrus zebra, at any rate, totally refuses it. Because of this, you need have no fear about keping live plants with these fish, since these also are spared. It is also not necessary to offer them any fresh veggies, such as lettuce or zucchini. You should feed as varied a diet as possible and not avoid trying out something new at times. Also, just because our zebras accepted certain foods, this does not mean yours must do likewise. We all have particular foods that we like and dislike, and likewise, our fish are entitled to a certain amount of individuality!

Spawning Preparations

It has been shown that three factors are the most important for successful spawning of H. zebra: higher temperature, good oxygenation of the water, and suitable breeding caves.

Since in the Rio Xingu temperatures of more than 86o F prevail, you should keep these fish at higher temperatures in the aquarium as well. Although we mentioned earlier that 71 - 81o F was fine for day - to - day keeping, it has been shown that at a temperature of 81o F is about the lowest at which these fish will spawn. According to Rickhoff (verbal communication), he spawned his H. zebra for the first time in a discus tank at a temperature of 86o F. As he was then concerned with the discus and the temperatur dropped, the catfish discontinued their spawning activity. Then, when the temperature again was increased, they became sexually active again. The Arndt's zebras spawned at the first time at 84o F. After they had begun spawning regularly, however, a temperature drop to 81o F did not disturb them.

For spawning, other water values appear to be of secondary importance. Even when keeping them in hard alkaline water, zebra plecos are not dissuaded from spawning. Pahnke (1993) carried out daily 10% water changes with fresh reverse osmosis water, but this certainly is not imperative. I do not exclude the possibility, though, that this perhaps can have a favorable effect on the spawning readiness of the adults and the development and growth of the young.

Conspicuous in nearly all previous spawning successes is that the spawning tank was equipped with very strong filtration. Whether the biological filtration or the strong aeration of a powerful filter is more important, I can not judge. Both are certainly very closely connected. I recommend the insertion of diffusers that produce very fine air bubbles, and in that way strongly increase the oxygen content of the water. It is not very simple to give an index as to filter rate vs. tank size; but I used a 150 gal/hr filter on a 25-gallon tank.

Rickhoff and Pahnke had success with oblong "caves" of clay or ceramic, whereas Walter's fish used a hole in a rock. Gerd & Karin Arndt swore by slate caves that they made themselves. These caves were also very well accepted by my fish. The best experience was with caves whose inner space was calculated as follows:

Length = Length of the fish;
Width = Body width + 2/3 of the length of the pectoral fin;
Height = Height of the body + 2/3 of the height of the dorsal fin.

If you want to spare yourself the measurement of your fish, you can use the measurements of 3.5 x 1.0 x 0.6 inches (L x W x H) for a cave to accommodate full-grown fish. For younger fish you should select accordingly smaller caves. Most other loricariids also accept these caves very well.
Eventually, the location of the cave also is of importance. Rickhoff made the observation that his zebras mostly received a strong current from the filter. Perhaps the caves were selected so that the eggs and young get the optimum amount of fresh water and oxygen. This is only a supposition, but one that tallies completely with my observations.


A male in one of the specially constructed breeding caves.

Spawning

As a rule, the caves are accepted by the fish soon after they are placed in the tank. In a broad sense, the spawning of Hypancistrus resembles that of the bristlenose plecos of the genus Ancistrus, but there are differences. Whereas spawning readiness in Ancistrus males is announced by wagging with the paired fins in front of the cave, Hypancistrus males exhibit little activity beforehand. You will simple notice all of a sudden that the fish have paired off.

According to Karin & Gerd Arndt, the egglaying behavior resembles very strongly that of Ancistrus species. The zebras often lay on top of each other in the cave. Finally, the male lays sideways with his caudal fin and half of his body on the head of the female. She produces her eggs in several batches. The male blocks the cave entrance with his head. After each group of eggs is laid, the female makes fidgety forward and backward movements to signal to the male that the eggs can now be fertilized. Since the female often will not leave the cave after spawning is over, she occasionally must be pushed out by the male.

Eggs of H. Zebra soon after being laid.
At one day, the embryo is visible as a whitish line.
Eggs at two days.

The eggs are deposited in the slate cave mostly in the outermost corner, on the bottom. Whether the males mouth the eggs, as in Ancistrus, has not yet been observed. The fanning movements with the pelvic fins are sporadic. When "danger" threatens (for example, when a flashlight is shined into the cave) the male covers the egg mass almost completely, so that at most only one to two eggs can be seen.

The Arndts's zebra plecos spawned on 10 June 1994 for the first time. Unfortunately, they had little luck, since on 13 June the empty eggshells lay in front of the cave. Probably this spawn was not fertilized. There was no basis for worry, however, since in other loricariids there are many cases in which the first spawn in not fertilized.

Eggs at three days, blood vessels are visible.
Four days; eyes are visible as tiny dark spots.
Five days.

The second spawn went better. The eggs were laid on the evening of 13 June. In spite of frequent inspections the next day, the exact number could not be determined. On 18 June, six fry with enormous yolk sacks were sighted outside of the cave and were siphoned out. The fry were transferred to a net-covered breeder box hung inside the tank in the filter current. Unfortunately, three of the young died after a short time. On 23 June the male once more was seen sitting on a spawn, and on 24 June a second male in another hole did the same. Since then the Arndts have had their zebras producing pretty regularly.

As I mentioned earlier, the spawning of my H. zebra happened very unexpectedly. I kept three fish for than two years, but in the end they reached a size of about 3.6 inches and all were obviously males. Therefore, I expanded my H. zebra stock in the late summer of last year with about five additional fish, all of which were smaller. After their quarantine I still did not place them with the full-grown males, since to me they simply appeared much too small to be able to spawn with them. So, I placed them in a 75-gallon tank for grow-out, along with five large Pseudohemiodon laticeps and some Ancistrus sp. Apart from some plants in clay pots and some slate, there were only two of the specially made spawning caves. The zebra plecos hid mostly under the slate or behind the filter. After several months, however, the largest specimen, a male, had reached a size of 2.6 inches and showed interest in the cave. It even selected the larger of the two caves, manageing to chase away the larger Ancistrus. After two days, a somewhat smaller zebra was staying near the male. Obviously this was a female. Soon, she entered the cave with the male. I could not quite believe that the fish were spawning at this small size, and so the next day I turned the cave somewhat in order to be able to light it for photography. The frightened male performed some jerky movements, and to my total shock, 12 eggs were dislodged from the cave.

Six days: The eyes are clearly visible, and hatching is imminent.
Seven days. The fry have hatched and have huge yolk sacs.
Top view of fry. They are as yet incapable of swimming.

Since I had had previous experience with artificial rearing of other loricariids, I had no great concern about the eggs. I transferred them carefully into a small Plexiglas tank that was filled with aged fresh water. In order to maintain the proper temperature, it was simply hung in the adults' tank. An airstone provided the necessary oxygen supply. For prevention of fungus I added acriflavine. After a day, it was apparent that two eggs were bad. I prodded these eggs with a pipette and sucked the contents out completely so that only the shells remained. This measure is necessary because the eggs stick so strongly together that the bad eggs cannot be separated without risking damage to the good ones. Afterward I did a complete water change in the brooder box. After four days it could be seen that another egg showed no development. This egg was also siphoned out. At 86oF, nine fry hatched on the seventh day. In a second spawn, about four weeks later, my artificial rearing was more successful; I managed to get 11 fry out of 12 eggs.

The fry at this stage look like nothing more than eggs with tails.
One day after hatching, the fry are about ½ inch long.
Two days after hatching, very slight pigmentation can be seen.
Three days; the pigmentation is a bit darker, and the fry starts to look a bit like a catfish.
Five days. The color pattern is particularly distinct on the head. The yolk sac is shrinking.
Six days. The zebra pattern is fairly distinct, and the yolk sac begins to flatten out as it is absorbed.

Development of Eggs and Young

In nearly all of the ancistrine loricariids that have been spawned to date, the eggs are yellow in color. When you see the eggs of the zebra pleco for the first time, on the basis of their milky white coloration you would think that they were infertile. The size of the eggs also is a curiosity. The egg diameter, according to the age and feeding condition of the female, can vary between 4 and 5 mm. Interestingly, larger loricariids, such as the Ancistrus species or Lasiancistrus scolymus (see Elsholz & Elsholz, 1992), usually have smaller eggs. Accordingly, however, the number of eggs is small. In past broods the number varied between 7 and 12 eggs. I expect, however, that fully grown females that are well fed might be able to lay up to 20 eggs.

Seven days.
Eight days.
Nine days.

Immediately after they are laid, hardly any structures are recognizably in the interior of these eggs. After one day, however, the body of the embryo is recognizable as a lighter line in the egg. On the third day you can see the small heart distinctly pulsating. Although the outline of the embryo from day to day becomes more distinct, shortly before hatching there is hardly any recognizable pigmentation to be seen. Only the eyes are clearly recognized as dark spots. How quickly the eggs develop is strongly dependent on temperature. At relatively high temperatures it is about six days until hatching. At 81o F it can take one day longer. You have to look closely to recognize that hatching has occurred. The yolk sack is about the same size as the original egg, and the unpigmented body of the fry is hard to see.

Ten days.
Eleven days: feeding begins.
Fourteen days.

 


An apparent mutation:
the "ghost zebra."

The young of Ancistrus species usually use up their yolk sacks after about four days and then begin to eat. In H. zebra it takes considerably longer: 11-13 days until the enormous yolk sac has completely disappeared. After two days you can see the first signs of pigmentation; by the eighth day the young already exhibit the first signs of a zebra pattern. The intensity of the color is not strong, however. Only after two or three weeks do they take on intense black-and-white coloration.

The Arndts have most recently found that in captivity very differently patterned zebra plecos are sometimes produced. One of their pairs suddenly produced four colorless young. The father already had a somewhat unusual caudal fin pattern; instead of a long band, this fish possessed elongate spots there. Three of the young strongly resembled L98 in their coloration at first. Later they colored up, however, and now have light coloration with a few irregular dark bands and some elongate spots. The forth animal is extremely light colored. Instead of the black pattern, it has a light gray one. Therefore, we have (just for fun) given it the name “ghost zebra.” It remains to be seen just how these aberrations arise. Are they genetic or environmental?

 


This fish, with a slightly aberrant pattern, resembles L98.

It is assumed that the young of Hypancistrus zebra stay in the cave with the adult male until their yolk sacs are completely used up. This is the case with the related Ancistrus. I say that this is assumed, because I do not know whether it actually is so. At present, none of the breeders consulted by me swear that this is the case. The young were always already out of their brood cave when first seen. I do not believe, however, that this is normal, since in the wild, young with such a large yolk sac probably would not survive without parental protection.


Juvenile at two months old and a length of about an inch.

It also sometimes happens that the entire spawn or individual eggs get swirled out of the cave. Whether the adhesiveness of the eggs is connected with water chemistry, as is known of some other tropical fish eggs that lose their stickiness in hard water, must one day be clarified. The eggs of Hypancistrus zebra, however, can be raised artificially with a good degree of success, so that this is not quite so bad.

But even when the male looks after the eggs faithfully, some dangers may lurk for the eggs. Small snails can multiply so greatly that the male scarcely can win out against them. Planarians in the tank are far worse. Actually, when you notice the latter it often is already too late, since they hide during the day. Under cover of darkness they can destroy an entire spawn. Using chemicals against planarians often fails, as they can be quite resistant. It is often necessary to remove the fishes from the tank and sterilize everything.


Juvenile at four months.

The Rearing of the Yong Zebras

The rearing of the young presents no real problems. Since they are even larger than the fry of Ancistrus by the time they have absorbed their yolk sacs, the survival rate is high. They immediately take dried foods and fine frozen or live foods. I feed principally with brine shrimp nauplii and a mixture of various chopped dried foods, most of which contain Spirulina algae.


Juvenile at six months.

As with the rearing of all loricariids, cleanliness in the fry tank is vital. Uneaten food must be vacuumed up as quickly as possible, and frequent water changes are important. Their growth rate is quite slow, but continuous. After 2½ months they reach a size of about one inch.

Summary

To summarize in a few words, I can say that Hypancistrus zebra is a good aquarium fish and a very spawnable loricariid when following conditions are met: there are well conditioned breeders of both sexes available; feeding is generous and varied; suitable spawning caves are offered; above-average filtration ensures a good water quality and a high oxygen level; and the water temperature is at least 81o F. (Tropical Fish Hobbyist, Volume 44, Number 5, January 1996).

Literature Cited

Elsholz, K.D. and W. Elsholz. 1992. Erfolgreiche Zucht von Lasiancistrus scolymus. DATZ (Sonderheft "Harnichenwelse").

Insbrucker, I.J.H. and H. Nijssen. 1991. Hypancistrus zebra, a new genus and species of uniquely pigmented ancistrine loricariid fish from the Rio Xingu, Brazil (Pisces: Siluriformes: Loricariidae). Ichthyol. Explor. Freshwaters, 1(4):345-350.

Pahnke, H. 1993. Seit zwei Jahren regelmassig gezuchtet: Hypancistrus zebra. DATZ, 42(4): 227-231.

Schliewen, U. and R. Stawikowski. 1989. Zebras aus Brasilien. DATZ, 42(9):521.

Stawikowski R. 1992. "Kaktusse," "Russelzahn," und ein merkwurdiges "Zebra." DATZ, 45(6):348-349.

Steindachner, F. 1882. Beitrage zur Kenntnis der Flussfische Sudamerika's II. Denkschr. Akad. Wiss. Wein. Math.-naturw. Cl. 43:103-146, 7pls.

Walter, O. 1993. Nachzucht gelungen: Hypancistrus zebra. DATZ, 46(10):633.