Marine Viruses 130 are circular or linear, and whether they are mono or multipartite If multipartite, the segments may be packaged together in a single virion or they may be individually encapsidated Monopartite genomes range from 1775 nucleotides (nt) of ssDNA for a member of the family Circoviridae to 1,259,197 base pairs (bp) of dsDNA for a member of the family Mimiviridae The total genome length for multipartite viruses (sum of the length of all segments) ranges from 3100 bp dsRNA (in the family Partitiviridae) to Z600,000 bp dsDNA (in the family Polydnaviridae) The smallest individual segment of a multipartite genome in which the segments are packaged together is reported to be only 200 bp dsRNA (family Reoviridae), but is more typically 4600 nt or bp For multipartite genomes in which the segments are packaged individually, the segments range from 923 nt ssDNA to 9800 nt ssRNA Describing all of the known viral morphologies in detail is beyond the scope of this article, but some examples are provided to illustrate the range of morphological types one may encounter (Figure 3) These include the familiar polyhedral (often icosahedral) capsids, which may be isometric or elongated, and may be enveloped or not A number of viruses appear to be spherical, but have polyhedral symmetry in their construction from subunits Among the viruses infecting Bacteria and Archaea, are those that have a polyhedral capsid (a) (b) (c) (e) (f) (d) (h) (i) (m) (g) (j) (l) 100 nm (k) Figure Examples of some the morphological diversity among viruses (a)–(f) Show virions with capsids having icosahedral symmetry (a)–(c) Illustrate the types of tails that are observed among virions in the order Caudovirales and (c) also illustrates a prolate icosahedron (d) and (e) Illustrate the range in size observed among virions with isometric capsids and represent the largest and smallest viruses recorded (f)–(h) and (j)–(m) represent viruses in which the capsid is enclosed in a membrane (g) Shown in cut away to reveal the rod-shaped capsid within and (h) illustrates a pleomorphic virion (h) Illustrates a filamentous virus with helical symmetry (j)–(m) Illustrate some of the other unusual morphologies of virions The taxa in which virions with these morphologies may be found are: (a) Podoviridae, (b) Siphoviridae, (c) Myoviridae, (d) Mimiviridae, (e) Parvoviridae, (f) Herpesvirales, (g) Nimoviridae, (h) Paramyxoviridae (also Bunyaviridae, Arenaviridae, and Coronaviridae), (i) Inoviridae (also Closteroviridae, Alphaflexiviridae, and Betaflexiviridae), (j) Rhabdoviridae, (k) Ampullaviridae, (l) Poxviridae, and (m) Fuselloviridae