Cell that fuses with another during fertilization in organisms employing sexual reproduction, e.g., an egg or sperm cell.

Large genus of amphipod crustacean in the family Gammaridae of which members occur in both fresh and salt water. An important source of food for many fishes.

Plastic or metal, adjustable valve used to split a length of air line, and allowing two or more air-driven devices to be operated at once. Also known as an air-control valve.

Hard, shiny, enamel-like scale. Found in gars, bichirs and reedfishes, for example.

The width of the space between the jaws when open to their maximum extent.

Straight-line measurement from the snout tip to the angle of the mouth.

Gas-filled sac with 1-3 chambers, situated just below the vertebral column in most ray-finned fishes. Its primary function is to aid in buoyancy by offsetting the weight of heavier structures such as bone, but is also used for respiration or sound production in some species. Often reduced in benthic fishes and sometimes absent altogether. Also […]

Any member of the mollusc class Gastropoda.

Class of molluscs of which the majority of members possess a flattened, muscular foot for locomotion and a head bearing specialised sensory tentacles, with some also having a univalve, coiled shell. Includes all snails, whelks, limpets, conches, and slugs.

The condition of being male or female; sex.

Basic hereditary unit comprising a sequence of nuceleotides within a strand of DNA or RNA and occupying a fixed position on a chromosome. Generally determines  a particular character or trait present in an organism by directing  production and activity of RNA.

An account of the direct descent of an individual or group from an ancestor; study or investigation of the evolutionary development of an organism(s) from older, related forms; a record, chart, or table depicting a pattern of descent.

Plural of genus.

Measure of the overall concentration of calcium, magnesium and other ions in a water sample with values usually quoted in units of degrees (dGH), of which 1 dGH corresponds to 17.848 ppm. Also referred to as total or permanent hardness.

The scientific name of a taxon with the rank of genus; the first part of a binomen or trinomen.

Branch of biology concerned with the study of heredity and variation of organisms; the genetic constitution of a single organism, species, or other taxonomic group.

Of or relating to the genitals or the process of biological reproduction.

Small tube arising from the urogenital opening in some fishes through which male or female gametes are expelled. May only be visible during the reproductive period depending on taxon. Its shape can sometimes used as a feature to identify the gender of an individual.

The reproductive organs, especially used in reference to external sex organs.

The genitalia.