Rasbora dorsiocellata
Encyclopedia
Brevibora dorsiocellata is a small fish belonging to the Family Cyprinidae, subfamily Danioninae, which is known by the common names of ocellated rasbora, hi-spot rasbora, and eye-spot rasbora, an allusion to the marking situated upon the dorsal fin. This small fish is a popular aquarium
fish, having been one of the species featured in the landmark textbook Exotic Aquarium Fishes by Dr William T. Innes
(page 180.1 - see References below). Its appearance in this work only occurs in later editions of the book, however, therefore the species is not subject to the same degree of aquarium domestication as the more familiar Harlequin rasbora
.
. It is an inhabitant of streams and other waterbodies with an acidic pH, at least some of these being situated in habitats classified as peat swamp forest
s (more details covered in the Habitat section below).
and the pelvic fins (corresponding roughly to the sac enclosing the alimentary canal). Under conditions of reflectied light, the fish sometimes displays a fine lateral band from the opeculum to the end of the caudal peduncle (Walker, 1971, p. 98) this being an olive-gold hue. The fins, with the exception of the dorsal fin, are hyaline
, the relation of the pectoral and pelvic fins being typical of the ostariophysans
(fishes possessing an auxiliary mechanism for detecting sound consisting of a set of internal bones called the Weberian Ossicles
). In such fishes, the pectoral fins are located immediately behind the operculum, whilst the pelvic fins are located further back upon the ventral side of the body - in the case of Brevibora dorsiocellata, their position is to be found vertically beneath the dorsal fin. The dorsal fin is positioned approximately equidistant between the operculum and the caudal fin, and it is the marking upon this fin that gives rise to the common names of the fish: the base colour is white, with a large rounded black oval overlaid upon the base colour, in appearance fancifully likened to an eye.
A fully mature individual Brevibora dosriocellata attains a standard length of 6 cm. There is a smaller variety, the Emerald Eye Rasbora which attains a standard length of 3.5 cm.
Males are cited as possessing a pinkish or reddish hue to the caudal fin during the breeding season (Walker, p. 98) whilst females lack this colour. Otherwise, visual differences between the sexes are far from obvious, and the principal reliable differentiating characteristic is the notably more rounded and fuller-bodied profile of gravid females.
s. The waterlogged soils of these forests inhibit the complete decay of leaf litter, and result in the formation of peat
, which leaches humic acids and related compounds into the watercourses flowing through these forests.
Because the water chemistry of the fish's natural habitat is similar to that of an entirely different habitat on another continent, namely the blackwater rivers of South America, the species is environmentally compatible in an aquarium with fishes from those habitats (see Aquarium Maintenance below).
"Reproduction" below for more details.
Like other rasbora
s, the eye-spot rasbora is a shoaling fish, and should be maintained in the aquarium as a group consisting of a minimum of 6 individuals, a larger number being preferable if space permits. Innes refers to the visual spectacle that a large shoal of these fishes presents in a spacious and well-furnished aquarium, which with the temperament of the fish is a reason for its popularity.
The species is relatively peaceful, though it is possible that some 'fin nipping' behaviour may occur if the species is kept with slow-moving and long-finned fishes in an aquarium. The incidence of this behaviour is not considered to be particularly marked, however, and is certainly not as visibly manifest as is the case with certain notorious species such as the tiger barb
. However, the lively, fast-moving eye-spot Rasbora is most likely to be compatible with similarly active fishes. Among the species that may be kept in the same aquarium are small characins from South America, assorted small barb
s, danio
s, other small rasbora
s, Corydoras
catfishes, Otocinclus
catfishes, the more peaceful dwarf cichlid
s (and peaceful cichlid
s such as Laetacara curviceps
), and smaller labyrinth fishes. The eye-spot rasbora makes for an interesting 'contrast fish' in company with a shoal of a more brightly coloured species.
Furnishing the aquarium for the eye-spot rasbora should (as should be the case with all aquarium fish species) be guided principally by the features of its natural habitat. Therefore, the aquarium should have open swimming areas, interspersed with planted sections, the plants in question being a mixture of crown-leaved plants such as Aponogeton
and Cryptocoryne
with fine-leaved plants such as Myriophyllum
. Being mainly an open water fish in the wild, using plant thickets for refuge from predation when danger threatens, the eye-spot rasbora is at home in a well-lit aquarium facilitating the growth of more demanding aquarium plants, though the fish is likely to appreciate the thoughtful provision of some floating plants for additional cover. The fish is mainly a middle and upper level swimming species.
Filtration should be of good quality, with a relatively high turnover rate. Moderate currents are appreciated by the species.
The species feeds upon small worms, crustaceans and insects in the wild (details available at FishBase), but in the aquarium individuals readily accept all good-quality aquarium foods. To condition the species for breeding, however, live foods should be provided, with bloodworm and mosquito larvae being the live foods of choice as they correspond closely to the wild diet. However, other live foods such as Daphnia
or brine shrimp
can also be used.
The lifespan of Brevibora dorsiocellata has not been systematically determined, but individuals in the aquarium can be expected, with good care, to live for 4 to 6 years.
with respect to breeding, namely it is a scatterer of non-adhesive eggs, choosing fine-leaved aquatic foliage as the repository for its eggs. However, success at the captive breeding of this species is heavily contingent upon water chemistry - the species is only likely to spawn in soft, acidic water matching that of its natural habitat, and thus particularly scrupulous attention to water chemistry is required if captive breeding is to be attempted. While as an additional measure to control water chemistry, filtration over peat is not vital, it is likely to be a contributory factor in success with this species (or, alternatively, the use of commercially available 'blackwater tonic' type products to condition the water accordingly).
Once the matter of water chemistry has been settled, the breeding aquarium should be furnished with fine-leaved aquatic foliage. Cabomba
and Myriophyllyum are suitable choices, and Java moss
is likely to be a useful addition to the breeding aquarium as well. Synthetic substitutes can also be utilised if live plants are unavailable, or the requisite species are difficult to obtain. Prospective parents should be conditioned using live foods as described above, and introduced with some care to the breeding aquarium. Note that if the water chemistry of the maintenance aquarium is substantially different from that of the breeding aquarium, acclimatisation of the fishes to the breeding aquarium will be a lengthy process, requiring several weeks to accomplish fully, with gradual changes in water chemistry imposed during that period until the target chemistry for breeding is obtained.
Once conditioned and acclimatised parents are residing in the breeding aquarium, the temperature should be slowly increased to 27°C, and additional aeration or filter current provided.
Once suitable conditions are provided (and the water chemistry is the most critical factor in determining success), the eye-spot rasbora proves to be a relatively enthusiastic and prolific spawner. After rapid darting chases through the aquatic foliage, male and female will assume a side-to-side positional relationship, emit a cloud of eggs and sperm, then after a brief rest pause, resume the chase. This can continue for some time - 2 hours or so - after which anything between 100 and 200 eggs may be laid. Parents should be removed from the breeding aquarium once spawning is completed, in order to forestall any 'egg eating' behaviour that the fishes may manifest.
. If infusoria
are unavailable, commercial prepared foods for egglayer fry may also be used.
The eye-spot rasbora takes approximately 10 to 12 weeks for the fry to assume full adult colouration.
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
fish, having been one of the species featured in the landmark textbook Exotic Aquarium Fishes by Dr William T. Innes
William T. Innes
William Thornton Innes III, L.H.D. was an American aquarist, author, photographer, printer and publisher. Innes was the author of numerous influential books and hundreds of articles about aquarium fish, aquatic plants and aquarium maintenance during the formative years of the aquarium hobby in...
(page 180.1 - see References below). Its appearance in this work only occurs in later editions of the book, however, therefore the species is not subject to the same degree of aquarium domestication as the more familiar Harlequin rasbora
Harlequin rasbora
The Harlequin Rasbora a small fish belonging to the Family Cyprinidae, subfamily Rasborinae, which was originally given the scientific name of Rasbora heteromorpha...
.
Distribution
Brevibora dorsiocellata is a native of Malaysia and SumatraSumatra
Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...
. It is an inhabitant of streams and other waterbodies with an acidic pH, at least some of these being situated in habitats classified as peat swamp forest
Peat swamp forest
Peat swamp forests are tropical moist forests where waterlogged soils prevent dead leaves and wood from fully decomposing, which over time creates a thick layer of acidic peat...
s (more details covered in the Habitat section below).
Description
Brevibora dorsiocellata is an elongate fish, with a pointed snout, whose base colour is a reflective, metallic silver, though under some lighting conditions, the fish can take on a yellowish hue, with a slight pink flush present in the ventral area of the body between the operculumOperculum (fish)
The operculum of a bony fish is the hard bony flap covering and protecting the gills. In most fish, the rear edge of the operculum roughly marks the division between the head and the body....
and the pelvic fins (corresponding roughly to the sac enclosing the alimentary canal). Under conditions of reflectied light, the fish sometimes displays a fine lateral band from the opeculum to the end of the caudal peduncle (Walker, 1971, p. 98) this being an olive-gold hue. The fins, with the exception of the dorsal fin, are hyaline
Hyaline
The term hyaline denotes a substance with a glass-like appearance.-Histopathology:In histopathological medical usage, a hyaline substance appears glassy and pink after being stained with haematoxylin and eosin — usually it is an acellular, proteinaceous material...
, the relation of the pectoral and pelvic fins being typical of the ostariophysans
Ostariophysi
Ostariophysi is the second-largest superorder of fish. Members of this superorder are called ostariophysians. This diverse group contains almost 8,000 species, about 28% of known fish species in the world and 68% of freshwater species, and are present on all major continents except Antarctica...
(fishes possessing an auxiliary mechanism for detecting sound consisting of a set of internal bones called the Weberian Ossicles
Weberian apparatus
The Weberian apparatus is an anatomical structure that connects the swim bladder to the auditory system in fishes belonging to the Superorder Ostariophysi. When it is fully developed in adult fish, the elements of the apparatus are sometimes collectively referred to as the Weberian ossicles...
). In such fishes, the pectoral fins are located immediately behind the operculum, whilst the pelvic fins are located further back upon the ventral side of the body - in the case of Brevibora dorsiocellata, their position is to be found vertically beneath the dorsal fin. The dorsal fin is positioned approximately equidistant between the operculum and the caudal fin, and it is the marking upon this fin that gives rise to the common names of the fish: the base colour is white, with a large rounded black oval overlaid upon the base colour, in appearance fancifully likened to an eye.
A fully mature individual Brevibora dosriocellata attains a standard length of 6 cm. There is a smaller variety, the Emerald Eye Rasbora which attains a standard length of 3.5 cm.
Males are cited as possessing a pinkish or reddish hue to the caudal fin during the breeding season (Walker, p. 98) whilst females lack this colour. Otherwise, visual differences between the sexes are far from obvious, and the principal reliable differentiating characteristic is the notably more rounded and fuller-bodied profile of gravid females.
Habitat
Brevibora dorsiocellata inhabits streams and other watercourses characterised by a mineral-deficient and acidic chemistry, featuring dissolved humic acids. Among tropical Asian watercourses, this chemistry typically arises as a consequence of those waters flowing through peat swamp forestPeat swamp forest
Peat swamp forests are tropical moist forests where waterlogged soils prevent dead leaves and wood from fully decomposing, which over time creates a thick layer of acidic peat...
s. The waterlogged soils of these forests inhibit the complete decay of leaf litter, and result in the formation of peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
, which leaches humic acids and related compounds into the watercourses flowing through these forests.
Because the water chemistry of the fish's natural habitat is similar to that of an entirely different habitat on another continent, namely the blackwater rivers of South America, the species is environmentally compatible in an aquarium with fishes from those habitats (see Aquarium Maintenance below).
Aquarium Maintenance
Whilst the water chemistry of the habitat of Brevibora dorsiocellata is relatively uniform, with a pH of 6.0 to 6.5 and a hardness value ranging from 0 to 12°dH, the species is more adaptable with respect to general aquarium maintenance, and will tolerate a wider variation of pH and hardness so long as extremes are avoided. The principal factor to bear in mind is that like many fast-swimming and active species, the eye-spot rasbora has a greater than average need for clean, well-filtered water in order to maintain optimum health. Temperature range is usually cited as 20°C to 25°C for maintenance, rising to 27°C for breeding. Whilst water chemistry is not especially critical for maintenance, it becomes much more so for breeding: see"Reproduction" below for more details.
Like other rasbora
Rasbora
A rasbora is a member of a group of small minnow-type fish in the family Cyprinidae . Fish from genera such as Boraras, Microrasbora, Rasbora and Trigonostigma are commonly referred to as rasboras...
s, the eye-spot rasbora is a shoaling fish, and should be maintained in the aquarium as a group consisting of a minimum of 6 individuals, a larger number being preferable if space permits. Innes refers to the visual spectacle that a large shoal of these fishes presents in a spacious and well-furnished aquarium, which with the temperament of the fish is a reason for its popularity.
The species is relatively peaceful, though it is possible that some 'fin nipping' behaviour may occur if the species is kept with slow-moving and long-finned fishes in an aquarium. The incidence of this behaviour is not considered to be particularly marked, however, and is certainly not as visibly manifest as is the case with certain notorious species such as the tiger barb
Tiger barb
The tiger barb or Sumatra barb, is a species of tropical freshwater fish belonging to the Puntius genus of the minnow family. The natural geographic range reportedly extends throughout the Malay Peninsula, Sumatra and Borneo, with unsubstantiated sightings reported in Cambodia...
. However, the lively, fast-moving eye-spot Rasbora is most likely to be compatible with similarly active fishes. Among the species that may be kept in the same aquarium are small characins from South America, assorted small barb
Barb
Barb may refer to:* A backward-facing point on a fish hook or similar implement, rendering extraction from the victim's flesh more difficult* Wind barbs for each station on a map of reported weather conditions...
s, danio
Danio
The Danio genus comprises many of the species of danionins familiar to aquarists. The common name "danio" is used for members of the genera Danio and Devario.-Taxonomy:...
s, other small rasbora
Rasbora
A rasbora is a member of a group of small minnow-type fish in the family Cyprinidae . Fish from genera such as Boraras, Microrasbora, Rasbora and Trigonostigma are commonly referred to as rasboras...
s, Corydoras
Corydoras
Members of the South American Corydoras genus are freshwater temperate and tropical catfish in the armored catfish family , and are commonly referred to as corydorases, cories, or cory catfish.-Taxonomy:...
catfishes, Otocinclus
Otocinclus
Otocinclus is a genus of catfish of the family Loricariidae commonly called "dwarf suckers" or "otos". Otocinclus originate from tropical, freshwater rivers in South America.-Taxonomy:...
catfishes, the more peaceful dwarf cichlid
Dwarf cichlid
Dwarf cichlid is a term used by fishkeeping hobbyists to describe an arbitrary assemblage of small-sized fish from the family Cichlidae. Although the grouping is widely used in the aquarium industry and hobby, the grouping has no taxonomic or ecological basis and is poorly defined...
s (and peaceful cichlid
Cichlid
Cichlids are fishes from the family Cichlidae in the order Perciformes. Cichlids are members of a group known as the Labroidei along with the wrasses , damselfish , and surfperches . This family is both large and diverse. At least 1,300 species have been scientifically described, making it one of...
s such as Laetacara curviceps
Laetacara
Laetacara is a small genus of five species of fish, endemic to soft, acidic freshwater habitats in South America. Laetacara is part of the family Cichlidae and is included in subfamily Cichlasomatinae. The genus is also collectively known as the smiling acaras. The range of the genus extends from...
), and smaller labyrinth fishes. The eye-spot rasbora makes for an interesting 'contrast fish' in company with a shoal of a more brightly coloured species.
Furnishing the aquarium for the eye-spot rasbora should (as should be the case with all aquarium fish species) be guided principally by the features of its natural habitat. Therefore, the aquarium should have open swimming areas, interspersed with planted sections, the plants in question being a mixture of crown-leaved plants such as Aponogeton
Aponogeton
Aponogeton is a genus of 45 - 50 species of flowering plants, the only genus of the family Aponogetonaceae. The Aponogetonaceae is considered to be allied to the Potamogetonaceae - Najadaceae complex of families....
and Cryptocoryne
Cryptocoryne
Cryptocoryne is a genus of about 50-60 species of aquatic monocot plants from the family Araceae . The genus is naturally distributed in tropical regions of Asia and New Guinea....
with fine-leaved plants such as Myriophyllum
Myriophyllum
Myriophyllum is a genus of about 69 species of freshwater aquatic plants, with a cosmopolitan distribution. The center of diversity for Myriophyllum is Australia with 43 recognized species...
. Being mainly an open water fish in the wild, using plant thickets for refuge from predation when danger threatens, the eye-spot rasbora is at home in a well-lit aquarium facilitating the growth of more demanding aquarium plants, though the fish is likely to appreciate the thoughtful provision of some floating plants for additional cover. The fish is mainly a middle and upper level swimming species.
Filtration should be of good quality, with a relatively high turnover rate. Moderate currents are appreciated by the species.
The species feeds upon small worms, crustaceans and insects in the wild (details available at FishBase), but in the aquarium individuals readily accept all good-quality aquarium foods. To condition the species for breeding, however, live foods should be provided, with bloodworm and mosquito larvae being the live foods of choice as they correspond closely to the wild diet. However, other live foods such as Daphnia
Daphnia
Daphnia are small, planktonic crustaceans, between 0.2 and 5 mm in length. Daphnia are members of the order Cladocera, and are one of the several small aquatic crustaceans commonly called water fleas because of their saltatory swimming style...
or brine shrimp
Brine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...
can also be used.
The lifespan of Brevibora dorsiocellata has not been systematically determined, but individuals in the aquarium can be expected, with good care, to live for 4 to 6 years.
Reproduction
Brevibora dorsiocellata is a typical rasboraRasbora
A rasbora is a member of a group of small minnow-type fish in the family Cyprinidae . Fish from genera such as Boraras, Microrasbora, Rasbora and Trigonostigma are commonly referred to as rasboras...
with respect to breeding, namely it is a scatterer of non-adhesive eggs, choosing fine-leaved aquatic foliage as the repository for its eggs. However, success at the captive breeding of this species is heavily contingent upon water chemistry - the species is only likely to spawn in soft, acidic water matching that of its natural habitat, and thus particularly scrupulous attention to water chemistry is required if captive breeding is to be attempted. While as an additional measure to control water chemistry, filtration over peat is not vital, it is likely to be a contributory factor in success with this species (or, alternatively, the use of commercially available 'blackwater tonic' type products to condition the water accordingly).
Once the matter of water chemistry has been settled, the breeding aquarium should be furnished with fine-leaved aquatic foliage. Cabomba
Cabomba
Cabomba is an aquatic plant genus, one of two belonging to the family Cabombaceae. It has divided submerged leaves in the shape of a fan and is much favoured by aquarists as an ornamental and oxygenating plant for fishtanks...
and Myriophyllyum are suitable choices, and Java moss
Java moss
Java Moss is a moss belonging to the Hypnaceae family. Native to Southeast Asia, it is commonly used in freshwater aquariums. It attaches to rocks, roots, and driftwood...
is likely to be a useful addition to the breeding aquarium as well. Synthetic substitutes can also be utilised if live plants are unavailable, or the requisite species are difficult to obtain. Prospective parents should be conditioned using live foods as described above, and introduced with some care to the breeding aquarium. Note that if the water chemistry of the maintenance aquarium is substantially different from that of the breeding aquarium, acclimatisation of the fishes to the breeding aquarium will be a lengthy process, requiring several weeks to accomplish fully, with gradual changes in water chemistry imposed during that period until the target chemistry for breeding is obtained.
Once conditioned and acclimatised parents are residing in the breeding aquarium, the temperature should be slowly increased to 27°C, and additional aeration or filter current provided.
Once suitable conditions are provided (and the water chemistry is the most critical factor in determining success), the eye-spot rasbora proves to be a relatively enthusiastic and prolific spawner. After rapid darting chases through the aquatic foliage, male and female will assume a side-to-side positional relationship, emit a cloud of eggs and sperm, then after a brief rest pause, resume the chase. This can continue for some time - 2 hours or so - after which anything between 100 and 200 eggs may be laid. Parents should be removed from the breeding aquarium once spawning is completed, in order to forestall any 'egg eating' behaviour that the fishes may manifest.
Development
Fertile eggs of Brevibora dorsiocellata require approximately 24 to 36 hours to hatch at a temperature of 27°C. Upon hatching, the fry are translucent, around 3 to 4 millimetres long, but a peculiarity of the species is that the fry require an additional 3 to 5 days to absorb the yolk sac before becoming free-swimming (Innes, 1966, p. 180.1). Once this process is completed, the fishes become free-swimming, and at this stage, require very fine sizes of food such as live infusoria for a period of up to 14 days, after which the fry are able to feed upon newly hatched brine shrimpBrine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...
. If infusoria
Infusoria
Infusoria is a collective term for minute aquatic creatures like ciliates, euglenoids, protozoa, and unicellular algae that exist in freshwater ponds...
are unavailable, commercial prepared foods for egglayer fry may also be used.
The eye-spot rasbora takes approximately 10 to 12 weeks for the fry to assume full adult colouration.