An international team of ichthyologists led by Dr Ralf Britz of Natural History Museum in London, UK, has described a new fish species from the Rio Negro in the Amazon region of Brazil.
Priocharax nanus. Image credit: Ralf Britz.
The Rio Negro contains an abundance of miniature fish species, defined as those that do not grow beyond 26 mm.
The water of the river looks like dark tea and is more acidic than rainwater, with a pH of 4.5-5. It’s a similar habitat to the peat swamps of Indonesia, where the world’s smallest fish, Paedocypris progenetica, was discovered in 2006.
The new fish has been named Priocharax nanus. The species name is derived from the Latin, nanus, meaning a dwarf and alludes to the tiny size of adult specimens.
It is only the third species in its genus, Priocharax.
Priocharax nanus and two other species – Priocharax ariel and Priocharax pygmaeus – are unique in that the skeleton of one set of their fins – paired pectoral fins – is made entirely out of cartilage.
The new species, measuring only 1.5 cm long, is also semi-transparent, a trait shared by many miniature fish. This can make it hard to spot for predators and collectors alike.
“It’s approaching the lower limit of how small a vertebrate can be. You have to fit into that tiny body eyes, muscles, internal organs, and the females have to produce eggs,” said Dr Britz, who is the senior author of a paper published in the journal Neotropical Ichthyology (full paper in .pdf).
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Monica Toledo-Piza et al. Priocharax nanus, a new miniature characid from the rio Negro, Amazon basin (Ostariophysi: Characiformes), with an updated list of miniature Neotropical freshwater fishes. Neotropical Ichthyology, 12 (2): 229-246; doi: 10.1590/1982-0224-20130171
