Having several cusps, as teeth.

A section of a phylogeny in which the evolutionary relationships can not be fully resolved to dichotomies.

A division of organisms into two groups, typically based on a characteristic present in one group and absent in the other.

Meaning ‘below distal‘; often used to refer to the position of markings in the fins of fishes.

Genus of unicellular ciliate protozoa with a shape resembling a grain of rice, a number of species of which are cultured as live food for small fishes and fry.

Paramecium aurelia. © Barfooz

Latin term meaning a species of doubtful identity requiring further investigation; a questionable species.

In biology, Darwinian fitness or simply fitness of a biological trait describes how successful an organism has been at passing on its genes.

The more likely that an individual is able to survive and live longer to reproduce, the higher is the fitness of that individual.

In ichthyological and aquarium literature typically refers to habitats containing transparent water with no material in suspension or staining by organic material, thus differing from whitewater or blackwater environments.

A clearwater tributary in the Río Ebro drainage, Spain. © Matt Ford

Type of seasonally-inundated floodplain forest in the Amazon region. The term is normally used for those forests flooded by blackwater rivers.

Typical igapó in the rio Negro basin, Brazil. © Jennifer O. Reynolds

In ichthyological and aquarium literature typically refers to habitats with turbid water containing material in suspension and often rich in nutrients and dissolved ions, thus differing from clearwater or blackwater environments.

Not to be confused with the term ‘white water’ which refers to turbulent water typically formed in rapids.

A typical whitewater river in Brazil. © Leonard G