Highly aggressive male of Apistogramma sp. “Cuiari”.  (Photo: Frank Hättich)

     Apistogramma sp. "Cuiari" was discovered and exported to Japan as early as 2011. Later that year, some specimens also reached Taiwan (WISE, pers. comm. to FH). Outside Asia, however, the species has remained largely unknown. Through the collaboration of two of the authors (TC and DM), some specimens of the "Cuiari"-Apistogramma finally reached Europe for the first time in spring 2018.
With this paper we would like to provide insights into the nature of the natural habitat, present their most important phenotypic characteristics, inform about the aquarium biology of these dwarf cichlids which have never been presented in any publication so far, as well as discuss some considerations about their systematic position within the genus Apistogramma.

Female two days after oviposition.
(Photo: Frank Hättich)

Apistogramma sp. "Cuiari", aggressively tempered male with sooty belly blotch and abdominal stripes. (Photo: Frank Hättich)

History of discovery

     The locality of A. sp. "Cuiari" is situated in a very remote area in the extreme east of Colombia, which can only be reached by charter planes, and is therefore hardly ever visited by foreigners.

The region around the site where Apistogramma sp. "Cuiari" was found is characterised by tepuís. These monadnocks towering over the surrounding lowland rainforest not only offer a fantastic view, but are often home of endemic animal and plant species.
(Photo: Uwe Römer)

The Cuiari is a fast flowing blackwater river.
(Photo: Tom Christoffersen)

     The province of Guainía, in which the Departamento del Guainía is located, covers about 72,200 km2 and is inhabited by just over 35,000 people, more than half of whom live in Puerto Inirida. The area covered by lowland rainforests, in which the collecting site of the species presented herein is located, belongs to the southwestern foothills of the Guayana Shield and is characterised by numerous granite hills and individual small table mountains, so-called Tepuis.

     In spring 2011, a Japanese, who worked for the company Japan Pet Communications, visited the Rio Cuiari. The largest area of this river's basin nowadays belongs to the Puinawai National Reserve, established in 1989, representing the second largest national park in Colombia, covering an area of almost 11,000 km2. Under partly adventurous circumstances, the Japanese discovered a hitherto unknown species of Apistogramma in the vicinity of a small village at this river. In order not to be kidnapped by FARC guerrillas who were still active at the time and who presumably expected a high ransom for him, he had to hide in the village school for several days until he luckily managed to escape with the help of a charter plane that happened to arrive. Despite the adverse circumstances, he managed to take a few living individuals of the Apistogramma species he had discovered with him back to Japan (OHNOTA, pers. comm. to FH).

Location and habitat

     Not least due to the easing of the political situation in Colombia, two of the authors (DM & TC) were able to eventually rediscover the species again on 14th and 15th of December 2018, despite the remoteness of the site, and as well to collect some information on its ecology.

     In the vicinity of the village already visited by the Japanese, A. sp. "Cuiari" can be found – in varying population densities – almost everywhere, from the smallest streams to the main course of the Río Cuiari itself. Here smaller species of fish such as Apistogramma seem to benefit from the fact that larger, predatory species are rather rare. The Curripaco Indians living in the region tell the following legend:

Dugout canoes like this one are the common means of transport to the sites of Apistogramma sp. "Cuiari". (Photo: Tom Christoffersen)

     "All the fish derive from a large tree that originally stood in the Río Içana area. When this tree was felled, each of its leaves, branches and twigs turned into a species of fish. Near its location, in the area of the Río Içana itself, its main branches transformed into the largest species, such as predatory tetras and catfish. Towards the periphery, smaller branches accordingly transformed into smaller species, and finally, in the most remote areas, such as that of the Río Cuiari, no branches or twigs fell into the water, but only leaves – the smallest fishes."

     The story, the core of which is now also reflected to some extent in scientific studies (e.g. ARBOUR & LÓPEZ-FERNÁNDEZ, 2014), impressively refers to what can also be seen when snorkelling in the Río Cuiari itself. Even at first glance, low biodiversity among fish is revealed. Large predatory catfish, tetras or cichlids such as Cichla BLOCH & SCHNEIDER, 1801 are completely absent. The largest cichlids found were Heros HECKEL, 1840 (only smaller specimens could be caught as the larger ones were hiding between rock crevices), Satanoperca GÜNTHER, 1862 and some unidentified Crenicichla HECKEL, 1840.

     The reasons for the low number of species and low density of larger predators in this region are unclear. Apart from various natural causes, antropogenic influence may also play a role. Field biological studies referring to this would certainly also be of great general scientific interest.

Apistogramma sp. "Cuiari" shortly after capture. They mainly inhabit the leaf layer. (Photos: Tom Christoffersen)

     In the Rio Cuiari itself, TC and DM observed A. sp. "Cuiari" foraging mainly in shallower shore areas. However, DM also observed them there occasionally at a depth of more than two metres. In smaller streams they got the impression that the population density is largely dependent on food availability, light conditions and habitat structure. In very small streams, the species was represented only in very small numbers and mainly by juveniles. But in the Rio Cuiari itself no juveniles were sighted. It is possible, however, that other parameters (chemical and physical, which unfortunately could not be recorded due to defective measuring instruments) influence the local population structure to a greater extent (cf. BENINDE et al., 2020; CHIPPARI-GOMES et al., 2005; ECKERT-HETZEL et al., 2001; KOCHHANN & VAL 2015, 2017; KOCHHANN et al., 2015; RÖMER, 1998a,b, 2001; ROZE et al., 2013; STEELE & LÓPEZ-FERNÁNDEZ, 2014).

     In any case, according to these observations, the lower, sunlit sections of streams overgrown with aquatic and riparian plants seem to be the preferred breeding territories of the species. Females in brood care colouration were only found here, but not in the main river or in the upper reaches of the streams.
In addition to various structural habitat factors, such as the risk of drying out during the low water season (cf. WILLIS et al., 2005), the productivity of these areas could also influence the distribution of the small fish (cf. e.g. VIEIRA et al., 2020).
The fact that the well-lit areas of the streams are preferred by the Apistogramma could be partly because more algae and small invertebrates thrive there, which serve as food for them, and partly because predators such as Hoplias GILL, 1903 and Erythrinus SCOPOLI, 1777 are rarely found in these areas. Various observations (BENINDE et al., 2020; KULLANDER & PRADA-PEDREROS, 1993) suggest that in such areas, the particular extremely low oxygen levels, which are easily tolerated by most dwarf cichlid species, could be responsible for the absence of the usually more oxygen-demanding larger predators.

Apistogramma sp. "Cuiari" were also found at sites strongly influenced by humans.
(Photo: Tom Christoffersen)

     That food sources specifically exert a great attraction could also be observed in streams used by humans. In some areas of the stream, the natives store root tubers of Cassava (Manihot esculenta CRANTZ, 1766). Cassava is a nutty-flavored, starchy root vegetable or tuber, and a major source of calories and carbs for people in developing countries. However, it contains large quantities of poisons (especially Acteoncyanhydrine, which – when consumed – decomposes to Acetone and the suffocation poison Hydrogen Cyanide in the body). The storage in the stream helps to ferment it and wash out the poison. These areas of the stream were teemed with "Cuiari"-Apistogramma¹⁾. Endnote 1 ¹⁾ It is possible that many species of the genus Apistogramma have an advantage compared to other species in such habitats in that they are adapted to much lower oxygen levels in their body tissues than their competitors or aquatic predators.
This would be even more pronounced with increased tolerance to high carbon dioxide levels and high temperatures of inhabited waters. Observations from Peru and recent laboratory studies by Brazilian scientists indicate extreme adaptations in this regard in several species that are still reproductively active even at oxygen levels below 1 mg/l (e.g., BENINDE et al. 2020, KOCHHANN et al., 2015; RÖMER, 1998b).
Once the storage of the cassava roots is complete, they are peeled and the shells thrown into the water. More A. sp. "Cuiari" were present here than anywhere else in the rest of the stream. Possibly the fish are attracted by micro-organisms and small animals living en masse on and from the cassava remains. UR and his travelling companions were able to observe something similar in 1992 in the outskirts of the Brazilian jungle town of Barcelos (RÖMER, 1996, 1998b), where in the Rio Salgado (as shown by nocturnal trap catches) masses of shrimp lived on cassava waste, attracting numerous predatory small fish, including Apistogramma mendezi RÖMER, 1994.

     Towards the upper reaches of the streams, the "Cuiari"-Apistogramma is found rarer and rarer and is eventually replaced by the only other dwarf cichlid species recorded by our team in the region, Ivanacara adoketa (KULLANDER & PRADA-PEDREROS, 1993). These can survive in surprisingly shallow areas of the headwaters, where otherwise only species of Rivulus POEY, 1858 and Copella MYERS, 1956 thrive. In these shallow waters they seem to completely abandon their otherwise known high aggressiveness towards conspecifics, and can even be found in larger groups. Further detailed information on the ecology of this species was provided by RÖMER (1993, 1998a).

Appearance and sexual dimorphism

     Apistogramma sp. "Cuiari" has a slightly high-backed, laterally clearly compressed, highly oval head and body (about twice as high as wide). Nevertheless their body appears noticeably elongated, not least due to the rather long caudal peduncle.

Apistogramma sp. "Cuiari", male (dominant) with "chequerboard" pattern of lateral and dorsal spots. The reddish-brown seam along the base of the pectoral fin is also clearly visible. (Photo: Frank Hättich)

Female in neutral mood. (Photo: Frank Hättich)

With a total length of up to 10 cm in males and 6 cm in females, the species belongs to the large representatives of the genus. Their body colour can vary from a very light, sometimes almost white, to a yellowish or strong brownish beige, with the lower half of the body often noticeably lighter than the upper. On the lower half of the head, adult males usually have quite variable dark red spots or worm lines in addition to bluish glossy stripes. In some males, some red spots or blotches may also continue on the upper abdomen. Pre-, sub-, post- and a narrow interorbital-stripe are shown depending on mood, while supraorbital stripes are usually only rudimentarily present as dark spots immediately above the eyes. The number of dental pores seems to be reduced in A. sp. "Cuiari". Three of the four specimens we examined had four (instead of five) dental pores only on each side of the head, one specimen had four pores on one side of the head and only three on the other. The infraorbital pores also showed a less than clear picture. One animal had a complete set of four pores on each side of the head. One specimen had only three and two specimens had three pores on one side of the head and four on the other. Although these results are not statistically reliable, due to the small number of animals examined, they at least indicate a tendency towards a reduction of dental pores.

     The dorsal fin of the males, which reaches about two thirds, rarely even three quarters of the body height, is clearly serrated, especially in the frontal half, and usually also has clearly elongated membranes in this section.

Male of Apistogramma sp. "Cuiari" in lateral threat display. (Photo: Frank Hättich)

In large dominant males, it may also be distinctly serrated over the entire hard ray area of the dorsal, with the anterior half then often also having strongly elongated membranes. In females, the anterior part of the dorsal is usually serrated and slightly pointed also, and the membranes may be slightly elongated. From the sixth membrane onwards, however, in females they are usually truncated and also do not extend beyond the hard rays. The first two dorsal membranes and the upper half of the third are often blackened, which is far less common in males.

     In males, the lower sometimes bluish or more rarely milky greenish iridescent part of the dorsal is separated from the bright orange-red tips of the membranes by a black seam running obliquely backwards and upwards and reaching to the end of the hard ray area. This makes the dorsal fin of male "Cuiari"-Apistogramma one of the most impressive within the genus.
A similar colouration of the dorsal can also occur in females, but with much less intensity. The soft part areas of the dorsal and anal fins are usually rounded in females – depending on age – but often slightly pointed. In males they are clearly extended and may even extend beyond the posterior edge of the caudal fin.

The tips of the dorsals of females of the "Cuiari"-Apistogramma may also be orange.
Male in the background. (Photo: Frank Hättich)

The ventral fins of males may be extended to the middle of the anal fin, rarely even beyond. In females, on the other hand, they are barely elongated, but often have a black seam on their front, which is less often seen in males.
The rounded caudal, transparent in both sexes, shows a striking pattern of eight to ten thin bluish iridescent stripes or rows of dots running along its entire height in dominant males. In many subdominant animals, however, it covers only the posterior half of the fin. Females may rarely have a few pale whitish translucent dots or, exceptionally, even a hint of a row of dots.

     If vertical bars are shown on the body, they are usually limited to its upper half. Only in the caudal third of the body they may reach below the lateral band or even extend over the entire height of the body sometimes. Distinct dorsal spots are present, extending slightly into the dorsal, often merging into a distinct dorsal band, which may extend anteriorly to above the centre of the eye.
The lateral band, which is up to slightly more than one scale wide, merges with the narrow postorbital-stripe without interruption. It extends over three interlocking scale rows, covering the upper half of the middle scale row, the complete adjacent row above, and the lower half of the scale row above.

Female (dominant) with pattern of lateral and dorsal spots merging over remnants of vertical bars. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari" possess a distinctly high-oval narrow body structure. (Photo: Uwe Römer)

In adults, it only exceptionally shows a completely or partially zigzag shape. Usually, the lateral band consists of a series of laterally rounded hexagons or diamonds formed by the dark scale edges, to each of which an additional short vertical line at the top and bottom is attached. With this lattice- or chain-shape, it resembles the lateral band typically seen in species of the A.-macmasteri-group as well as in A. sp. "Rautenband/Diamond-band" (HÄTTICH & RÖMER 2018). Occasionally this pattern is extended to the entire body by accentuating the dark scale edges, creating an impressive net-like body pattern. Depending on mood, the hexagons or diamonds forming the lateral band can also be darkly coloured in their interior, which is predominantly the case in the area of the vertical bars. In the sections between the vertical bars, on the other hand, they are usually light-coloured on the inside. Here the lateral band may often even disappear more or less completely. Thus broken up into segments or side spots, a pronounced checkerboard-like pattern is often formed together with the dorsal spots. A lateral spot at the intersection of the third vertical bar and the lateral band is missing. The lateral band usually extends beyond the seventh vertical bar and slightly touches the very variably shaped caudal spot. Sometimes the shape of the latter is vertically-rectangular with rounded corners and has a notch in the middle on its rear. Often, however, its shape has most accurately to be described as "irregular".

Apistogramma sp. "Cuiari", about half-grown male, not territorial, subdominant, neutrally tempered. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", almost adult male, non-territorial, dominant, slightly aggressive mood. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", almost fully grown male, territorial, dominant, slightly aggressive mood.
(Photo: Uwe Römer)

Apistogramma sp. "Cuiari", almost adult female(?), non-territorial, subdominant, aggressively tempered.
(Photo: Uwe Römer)

There is a dark spot on the upper and lower edge of the caudal peduncle. Depending on mood these spots may be invisible, but are usually more or less extended and can even merge with the caudal spot, giving the impression of a caudal spot occupying the entire height of the caudal peduncle.

     Up to four rows of – more or less wide – abdominal streaks or stripes may occure, usually starting at the level of the pectoral-fin base, the upper two rows of them may be extended to the end of the seventh vertical bar. Reddish-brown or blackish spots on the upper and lower edges of the usually orange pectoral-fin base are present in both sexes.

Apistogramma sp. "Cuiari", male with chain-like lateral band. The pattern is distantly similar to that of species of the Apistogramma-macmasteri-group and A. sp. "Rautenband". (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", "yawning" male. The pattern of markings is typical for relaxed dominant individuals.
(Photo: Uwe Römer)

Apistogramma sp. "Cuiari", dominant male presenting itself tail-slapping to a female. Note the milky area in the dorsal fin.
(Photo: Uwe Römer)

Apistogramma sp. "Cuiari", dominant male presenting itself in the group in front of a female (lower right).
(Photo: Uwe Römer)

While the upper of these pectoral spots is usually distinct, the lower one is smaller and often less intensely coloured, frequently not visible at all. Especially in males, the upper pectoral spot is often extended a little further along the back of the pectoral fin base. Sometimes it may even be extended as a reddish-brown seam along the entire posterior margin of the fin base up to its lower end.

Females do generally not have black markings on their ventral side.
(Photo: Uwe Römer)

In females, however, such a margin seems to occur only exceptionally.

     Aggressive or displaying males often show a mid-ventral stripe that can extend from the base of the anal fin to near the base of the ventral fins, and sometimes also a dark stripe in the area of chin and throat. Likewise, a large sooty-dark spot, sometimes overlaid with a bluish-metallic sheen, may then appear below the lateral band on their bellies, as is known particularly from species of the A- macmasteri-group, but also occurs in species of other species-groups (cf. HÄTTICH & KIPPER 2017; HÄTTICH & RÖMER 2018; RÖMER 2018).
In contrast to the males, even highly aggressive or brood-caring females of A. sp. "Cuiari" usually do not present a sooty belly blotch or markings on the chin or throat. A distinct lacquer-black underbelly stripe does not occur in all females, but – if present – extends in a slight zigzag pattern about the middle third over the area between the base of the ventral fin and the anal opening. A black anal spot is not present in all females. However, it seems that it is more frequently presented during brood care, especially in younger (smaller) females while it is practically not seen in older ones.

     As in most Apistogramma species, spawning females have a yellowish body and fin colouration and more distinct black markings. Between egg-laying and the first free-swimming of the fry, this typical yellow-black colouration becomes even more intense and contrasting. The cheek stripe, lateral band, caudal spot, dorsal spots or band, the anterior seams of the ventral fins as well as the first 2-3 dorsal membranes then usually stand out in deep black against the strong yellow colouration of the body and fins. Often the lateral band, which is usually divided into six side spots, together with the dorsal spots forms a conspicuous, chessboard-like pattern, similar to that known mainly from breeding females of the A.-macmasteri-group. Unlike these, however, females of the "Cuiari"-Apistogramma do not show any markings on the chest, throat or chin and also only rarely show a distinct black seam on the front of the anal fin.

Apistogramma sp. "Cuiari", courting, highly aggressive males show the sooty belly blotch and a violet-tinted body.
(Photo: Uwe Römer)

Apistogramma sp. "Cuiari", highly aggressive male in S-posture shortly before attack. The highlighted abdominal streaks on the belly blotch are typical. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", aggressive dominant male in front of a newly occupied breeding cave. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", typical colouration of courting pairs in front of the breeding cave. (Photo: Uwe Römer)

     A. sp. "Cuiari" show a distinct sexual dimorphism, which, however, develops relatively late in almost fully grown individuals: Males grow considerably larger and tend to be more high-backed than females, have a considerably longer and more intensely coloured dorsal fin, more elongated pelvic and anal fins, and a strongly patterned caudal fin. In addition, females rarely show red facial markings, no dark stripes in the chin and throat area, no sooty belly spot and (usually) no red-brown seam at the back of the pectoral fin base. On the other hand, the anterior dorsal membranes and the anterior edge of the ventral fins are more frequently and intensively blackened than in males. In stressful situations, however, the colouration unfortunately fades and then only the morphological features and – to a limited extent – the pattern of markings in the caudal fin allow the sex to be determined.

Notes on the systematic position

     A. sp. "Cuiari" shows a combination of traits that makes a safe assignment to a certain species group – or even to one of the four known lineages – almost impossible! A classification in the A.-regani-lineage, which is characterised by a complete set of dental and infraorbital pores, seems obsolete due to the reduced number of dental pores²⁾. Endnote 2 ²⁾ In fact, the characterisations of various hitherto "defined" lineages and species groups appear at least worthy of revision due to the current development of genetic studies. And even "classical" findings from reproductive biology cast doubt on some systematic classifications. For example, a female of the "Cuiari"-Apistogramma successfully spawned with a male of a species (A. sp. "D25") that is currently assigned to the A.-macmasteri-group (KIPPER in lit. to UR)!.
An assignment to the A.-pertensis- or A.-trifasciata-lineage, for which a lateral spot is characteristic, is out of question due to the absence of this very spot (cf. WISE, 2020).

     If we disregard the reduction in the number of dental pores, which stands in the way of an assignment to the A.-regani-lineage, A. sp. "Cuiari" is reminiscent, not least because of its lattice- or chain-like lateral band consisting of rows of rhombuses or hexagons, of some species of the A.-macmasteri-group (within the A.-regani-lineage) as well as to A. sp. "Rautenband", which is probably close to the A.-macmasteri-group (HÄTTICH & RÖMER, 2018). For an unambiguous clarification of the systematic position of A. sp. "Cuiari" within the genus Apistogramma surpassing beyond these purely speculative considerations, a comparative study of its genome seems absolutely indispensable.

Biology in the aquarium

     In the aquarium, Apistogramma sp. "Cuiari" proves to be a partly demanding species depending on the conditions of maintenance. The temperature may well be in a lower range (22 to 30°C) than the measured field data (24 to 34°C) from other streams in the region suggest (cf. RÖMER, 1998a, b). However, maintenance at about 25 to 27°C has been shown to be favourable for a balanced sex ratio among the offspring, because in this species too the determination of sex seems to depend on environmental factors (cf. BAROILLER, 1999; RÖMER, 2000, 2006; RÖMER & BEISENHERZ, 1995). For this species, however, detailed studies are still lacking due to the initial limitation of material. In principle, "Cuiari"-Apistogramma should be kept in water similar to field conditions. Since the species lives in low-mineral black water in the upper Rio Negro, the pH-value should be kept well below 6 via an enrichment by humic acids and the water hardness should not be significantly above 100 µS/cm.

Apistogramma sp. "Cuiari", semi-adult slightly aggressive suppressed male. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", non-territorial subdominant individuals show the vertical bars when harassed. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", laterally threatening males. In comparison to subdominant individuals, dominant ones show a lighter colouration. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", highlighted lateral band and band-like caudal spot signal an aggressive change of mood.
(Photo: Uwe Römer)

For attempts in productive breeding, the pH-value of the water, which is then even lower in minerals, should even be pushed into the range between 4.5 and 5.5, as otherwise, according to our experience, only relatively low hatching rates are achieved – if clutches are produced at all. For the enrichment of the reverse osmosis water with humic acids and their degradation products, UR found that the use of briefly pre-watered beech leaves is optimal. The leaves should be introduced into the tank in a thick layer.

Apistogramma sp. "Cuiari", encounter of two non-territorial subdominant males. The dorsal spots indicate subdominance. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", yellow coloured female fending off a subdominant male in the larval phase in front of the cave.
(Photo: Uwe Römer)

Apistogramma sp. "Cuiari", young female, subdominant, non-territorial. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", female, subdominant, beginning territorial mood. (Photo: Uwe Römer)

Apart from the effects of water treatment, it offers these fish hiding places similar to the conditions in the wild. A behavioural-biological effect that can be achieved in this way is particularly striking with this species: the fish stand relaxed above the layer of leaves, calmly searching for food in it or interact with conspecifics or other aquarium co-inhabitants. If the layer of leaves is missing, they are usually quite shy and also jumpy in comparison.

     Various other observations have shown that Apistogramma sp. "Cuiari" seem to be dominant over other species kept with them in the long term. It has been repeatedly observed that other cichlids, tetras and livebearers kept together with these relatively robust dwarf cichlids no longer reproduced as before, they became weak, emaciated and gradually disappeared (KIPPER in lit. an UR, & UR). Although direct aggressive interactions could only be observed in exceptional cases, "Cuiari"-Apistogramma show an unusual persistence compared to other dwarf cichlids.

Apistogramma sp. "Cuiari", adult female, dominant, neutrally tempered in the larval care phase. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", female, dominant, aggressively inclined against foreign male. (Photo: Uwe Römer)

Apistogramma sp. "Cuiari", female with a few days old fry.
(Photo: Frank Hättich)

For example, they do not allow themselves to be driven away from their food by the approach of larger species and sometimes stubbornly hold their position or at most move away minimally. This may reflect an adaptive evolutionary reaction to low food availability and high competition from larger species in the natural habitat.

     "Cuiarí"-Apistogramma do not have any special dietary requirements. Like most small fish, they seem to be omnivorous, but favour small animal food. They prefer (as typical for all species of the genus) live food of all kinds, as long as it is not too big. The animals greedily consume microworms, nauplius larvae of Artemia, Cyclops and water fleas, but also like to prey on fruit flies from the water surface. Fine food granules from various manufacturers are also readily accepted, but flake food is usually ignored. When feeding granulated food, low-fat types should be chosen as far as possible, as otherwise the animals quickly tend to become obese, which noticeably limits their vitality and willingness to breed.

     For keeping small groups of this large Apistogramma species, aquariums with a base area of about 100x40 cm are suitable. Surprisingly, harmonious pairs can also be kept in relatively small aquariums of about 60x40 cm if there are enough hiding places for both individuals. In addition to dense planting and the use of bog-wood, the introduction of a thick layer of leaves, as already mentioned, has proven to be particularly beneficial. In the layer of leaves, the fish not only find hiding places and search for food, but they also like to spawn on the undersides of the leaves. The humic substances contained in the leaves can also suppress the development of bacteria and thus ensure a higher hatching rate of the laid eggs.

Apistogramma sp. "Cuiari", "yawning" female with young.
(Photo: Frank Hättich)

Apistogramma sp. "Cuiari", frontally threatening female defending its territory. (Photo: Frank Hättich)

Pair of the "Cuiari"-Apistogramma. (Photo: Frank Hättich)

Apistogramma sp. "Cuiari", adult male, dominant, neutrally tempered. The fish tirelessly shovel the substrate into their surprisingly spacious mouths in search of food. (Photo: Uwe Römer)

     If Apistogramma sp. "Cuiari" are kept in groups, their complex social behaviour can be observed. One of the authors (UR) was able to study the species in groups of up to 30 individuals over a longer period of time. The observations revealed that within a few hours to days a more or less stable hierarchical structure is established within a group. Large adult animals dominate the group and divide the available aquarium space (150 × 50 cm) among themselves into territories of about equal size. At the boundaries of the territories regular mock attacks occur, in which the fish use the instruments known from other cichlids: Presenting the spread fins, threatening with lowered throat membrane, tail flapping and parallel swimming. Only exceptionally do they actually attack for damage, and hence mostly breeding females, which react much more aggressively than territory-owning males. Actual biting attacks, however, are extremely brutal and usually result in considerable damage to the caudal and dorsal fin. Occasionally, scales on the caudal peduncle and side of the body also fall victim to such attacks. If specimens attacked in this way cannot hide in time, they may be pursued and repeatedly attacked to the point of their death. Younger, subadult individuals repeatedly engage in mock fights, which may also involve several individuals. The mock fights of these groups, often consisting of several males and one or two females, can sometimes last for hours. Previous observations indicate that pairs do form from these groups and spawn together some time later. The mock fights of the males, in which they present their physical characteristics (colouration, body and fin structure, fighting strength, perseverance), may thus be regarded as a decisive element in the females mate choice.

     If the maintenance conditions largely correspond to the requirements given by the field conditions, courtship behaviour can often be observed abruptly, which is usually initiated by the dominant male of a group. Females not yet ready to spawn usually flee at the approach of the displaying male. The male first approaches the female in an impersonation posture with his fins spread wide and begins to flap his tail fin in the direction of the female. When ready to spawn, the female then turns onto her side and presents her belly to the male, while curving her body in an S-shape. The male now performs the typical cichlid jerking movements of head and body with clinging fins, in order to lure the female into a nearby cave. To do this, it usually swims quickly away from the courted female towards the potential egg-laying site. From the wide range of breeding sites, mainly those structurally similar to the underside of leaves are selected. Larger cave-like hiding places are usually avoided by the females for spawning, but later they like to use them for depositing larvae. Some females are reluctant to follow the courting male, while others immediately swim after him and inspect the spawning site. This behavioural pattern, in which some females select their mate particularly critically, is also called "brittleness" (Sprödigkeit) in science (SAUERMOST & FREUDIG, 2020). "Brittle" Apistogramma sp. "Cuiari" females almost always chose a spawning site other than the one originally offered by the male (data UR). The reason for their brittle behaviour was initially unclear, but according to available observations it could have a biological cause, which will be discussed later.

     Once the female has accepted the male as a reproductive partner, she swims into the chosen breeding cave and begins to clean its interior. This process can take several hours. In contrast, the laying of the eggs, usually on the ceiling of the cave, takes only about one to one and a half hours. The male usually only stays in the cave for a short time to deliver the sperm, as he is often aggressively harassed immediately by the female when swimming into the cave. Given it’s size, the species is merely moderately productive, as usually only between about 70 and 120 eggs are laid even by adult females. The care of the eggs, larvae and later also the young is taken over by the mother alone. The larvae hatch about 48-60 hours (27 or 23 °C) after spawning, depending on the temperature. The total development time until free swimming is between eight and eleven days. The female usually cares for the brood over a period of about 4-6 weeks, exceptionally also well over two months. It is not yet clear which factors are responsible for a particularly long brood care. From the first day after leaving the breeding cave, the fry greedily feed on nauplius larvae of Artemia or vinegar eel. After a few days they will also cope with somewhat larger replacement food such as fine-grained granulate. With good feeding and regular water changes with soft water rich of humic substances, the fry will grow up quickly. Severe fluctuations in pH and temperature should, however, be avoided when changing the water, as from our experience so far, they can have an inhibiting effect on the growth of the fry. If these conditions are met, they can reach a total length of about 5 cm already after four months. At this time, the first of them also start to become territorial.

     Males of the species have not yet been observed directly caring for the brood, but intensively defending the common territory. The male's contribution to brood care is thus indirect. Repeatedly, males were observed to steal (and eat) eggs from the brooding caves during egg laying. Occasionally, they also entered the brooding cave during the larval phase and ate some of the larvae, usually under heavy resistance from the female. That Apistogramma species can be potent larval and juvenile predators has been known in the literature for some time from studies of the stomach contents (KNÖPPEL, 1970; GOULDING, 1980; GOULDING et al., 1980). This may also be the reason for the brittle behaviour of some females. Since cannibalistic behaviour is possibly widespread among males of the "Cuiari"-Apistogramma, the females should have developed effective counter-strategies to this. One of these could be to accept only those breeding sites that can be defended by the female as easily as possible. This selection criterion could lead females to quite frequently not accept the caves chosen by males. However, systematic studies on this aspect of the breeding biology of the dwarf cichlid presented here are still lacking. However, the now regular successful breeding of the species opens up the possibility for such studies, and also the chance of a further spreading of this attractive species in aquaristics.

Acknowledgements

     We would like to thank Yukitoshi Ohnota, Ivan Law and Roland Kipper for their support with numerous information and the additional photo material provided. We would also like to thank Roland Kipper for critically reviewing an earlier version of this article.

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