Smallest organisms with mature females measuring as little as in standard length. This fish, a member of the carp family, has a translucent body and a head unprotected by a skeleton. The one of world's smallest fish based on the minimum size at maturity is "Schindleria brevipinguis" from Australia,their females reach it at 7 mm (0.28 in) and males at 6.5 mm (0.26 in), Males of "S. brevipinguis" have an average standard length of , a gravid female was . This fish, a member of the goby family,its first anal-fin ray further forward, under dorsal-fin 4. Male individuals of the anglerfish species
Smallest organisms 3.5 kilo base pairs (kb) and particle diameters of 80 nanometres (nm). The smallest double stranded DNA viruses are the hepadnaviruses such as Hepatitis B, at 3.2 kb and 42 nm; parvoviruses have smaller capsids, at 18-26 nm, but larger genomes, at 5 kb. It is important to consider other self replicating genetic elements, such as satelliviruses, viroids and ribozymes. The genome of "Nasuia deltocephalinicola", a symbiont of the European pest leafhopper, Macrosteles quadripunctulatus consists of a circular chromosome of 112,031 base pairs. "Nanoarchaeum equitans"'s genome is 490,885 nucleotides long. "Pelagibacter ubique" is one of the smallest known free-living bacterium