isalineae: named for Mrs. Isaline Drecq, wife of Mr. Guy van den Bossche, a participant in the expedition on which the species was discovered.
- Order: Characiformes
- Family: Acestrorhynchidae
The specimens that were used to describe the species, known as the type series, were gathered from a specific location in the western Brazilian Amazon, which is a tributary of Rio dos Marmelos in the Rio Madeira basin. This location is situated approximately 110 kilometers east of Humaitá along rodovia Transamazônica, in the state of Amazonas, Brazil. While official records mainly refer to this specific locality, it is possible that the species has a wider distribution within the Madeira river system.
Acestrorhynchus isalineae is a species of fish that is found in the Amazon Basin of South America, specifically in the lower and middle Amazon River and its tributaries. This species is primarily associated with freshwater habitats, such as rivers, streams, and lakes, and it is commonly found in areas with clear or slightly turbid water.
Acestrorhynchus isalineae is a predatory fish and feeds on other fish and invertebrates. It prefers to live in areas with moderate to strong water currents, and it is known to inhabit both shallow and deep water habitats. This species has been observed in areas with sandy or rocky substrates, as well as in areas with submerged vegetation or fallen trees.
Overall, Acestrorhynchus isalineae can be found in a variety of freshwater habitats within the Amazon Basin, but it is most commonly associated with clear or slightly turbid water, moderate to strong water currents, and areas with a variety of substrate types and underwater structures.
Maximum Standard Length
100 – 105 mm.
To provide a suitable environment for Acestrorhynchids, it is recommended to design the aquarium to resemble a flowing stream or river with a substrate consisting of variably-sized rocks, sand, fine gravel, and some larger water-worn boulders. If desired, driftwood roots and branches can also be added, but it is important to leave enough open swimming space. Additionally, plants that can grow in sand or attach to solid surfaces, such as Microsorum pteropus, Taxiphyllum barbieri, or Anubias spp., can be included, and lighting should be tailored to the specific plants being used.
For deeper tanks, it is possible to fill them to 50-70% of their capacity and add emergent branches or plants for a visually appealing effect. However, it is essential to use a tightly-fitting cover for all tanks since Acestrorhynchids are powerful jumpers.
Efficient filtration is crucial when keeping predatory species due to the amount of waste they produce. Therefore, it is recommended to install one or more external canister filters and/or a sump system, organizing the return in a way that creates some surface movement.
Weekly water changes of 30-50% are necessary as Acestrorhynchids can be sensitive to organic pollutants and fluctuations in water chemistry. For this reason, they must never be introduced to biologically immature setups.
- Temperature: 24 – 28 °C
- pH: 6.0 – 7.5
- Hardness: 18 – 215 ppm
Acestrorhynchids are obligate piscivores, capable of consuming relatively large prey in proportion to their body size. Newly-imported specimens may only accept live fish initially, but most can be gradually introduced to dead alternatives once they recognize them as edible. Some individuals may even learn to accept dried foods.
It is important to avoid feeding Acestrorhynchids mammalian or avian meat such as beef heart or chicken, as these can contain lipids that the fish cannot properly metabolize. This may lead to the accumulation of excess fat deposits and organ degeneration.
Feeder fish, such as livebearers or small goldfish, should also be avoided as they carry the risk of introducing parasites or diseases. Additionally, they do not provide high nutritional value unless properly conditioned beforehand.
Behaviour and Compatibility
Acestrorhynchids are relatively peaceful with tankmates that are too large to swallow and can be kept in a community aquarium as long as suitable tankmates are chosen carefully. Aggressively territorial or highly competitive species should be avoided, and the best choices include placid fishes such as Geophagus species, Acarichthys heckelii, medium-sized doradid or loricariid catfish, and characids from genera such as Ctenolucius, Mylossoma, or Myloplus.
Acestrorhynchids are not aggressive towards conspecifics, and juveniles, in particular, exhibit a marked schooling instinct. While older individuals tend to be more solitary, they still group together from time to time, and it is best to maintain them in numbers of four or more.
It is important to note that acestrorhynchids are cannibalistic given the opportunity, so if purchasing a group or adding to an existing school, it is advisable to ensure that all individuals are of comparable size.
Sexually mature females tend to grow a little larger and be deeper-bodied than males.
Research on the closely-related species, A. falcatus, suggests that spawning takes place in midwater with the female staying still while the male swims around her in a ‘figure-of-eight’ pattern. The eggs are scattered in large quantities and there is no parental care.
This species belongs to the proposed “A. nasutus group” of closely-related species within the genus, which includes A. nasutus, A. maculipinna, and A. isalineae. All of these species are identified by their possession of two dark, longitudinal stripes, with one running from the snout tip to the caudal-fin base and the other from the posterior edge of the lower maxilla to the underside of the caudal peduncle. Juvenile specimens of A. falcirostris have similar patterning, but it is distinguishable in adulthood by its larger size compared to the other three species, which tend to grow no larger than 100 mm SL and retain their body stripes into adulthood.
The rest of the genus is currently divided as follows: A. microlepis group, which includes A. britskii, A. grandoculis, A. microlepis, and A. minimus; A. nasutus group, which comprises A. falcirostris, A. nasutus, A. isalineae, and possibly A. maculipinnis; and A. heterolepis, which cannot be assigned to any group.
The Acestrorhynchidae family is most closely related to the Cynodontidae family, which contains the genera Cynodon, Hydrolycus, and Rhaphiodon.
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