Genus Epsilonretrovirus

Type Species	Walleye dermal sarcoma virus	(WDSV)

Distinguishing Features

All members of the genus are exogenous retroviruses. They are complex retroviruses in that their genomes range in size from 11.7  kb to 12.8  kb and contain from one to three ORF’s, presumably encoding accessory proteins, in addition to those encoding the structural proteins and enzymes of the virion (Fig. 6). ORFa, present in all three walleye retroviruses appears to be a viral homologue of cyclin D. The function of the two additional ORFs in walleye or the single ORF in the snakehead retrovirus has not been determined. The LTR’s of the fish retroviruses range from about 500 to 650  nts in length, of which the U3 region is about 450  nts, the R sequence about 80  nts and the U5 region about 75  nts in size. The primer used by the walleye retroviruses is tRNA^His while the snakehead retrovirus uses a tRNA^Arg. Phylogenetic analysis comparing the polymerase region shows that the walleye and perch retroviruses cluster and diverge significantly from the snakehead retrovirus. Nevertheless all piscine retroviruses to date appear to group with the mammalian type-C retroviruses.

List of Species Demarcation Criteria in the Genus

The list of species demarcation criteria is:

	Differences in genome sequence and viral oncogenes,
	Differences in gene product sequence,
	Differences in natural host range.

The genus Epsilonretrovirus is comprised of three species of fish retroviruses, Walleye dermal sarcoma virus (WDSV), Walleye epidermal hyperplasia virus type 1 (WEHV-1), and Walleye epidermal hyperplasia virus type 2 (WEHV-2). These species are distinguished from one another on the basis of phylogenetic diversity. In addition, two tentative species, Snakehead retrovirus (SnRV) and Perch hyperplasia virus (PHV) are listed. As additional fish retroviruses are identified and characterized the Snakehead retrovirus may provide a basis for an additional genus. The Perch hyperplasia virus has only been sequenced within the polymerase gene and remains tentative until further sequence information becomes available.

List of Species in the Genus

Official virus species names are in italics. Tentative virus species names, alternative names ( ), strains or serotypes are not italicized. Virus names, genome sequence accession numbers [ ], and assigned abbreviations ( ) are:

Species in the Genus

Walleye dermal sarcoma virus	[AF033822]	(WDSV)
Walleye epidermal hyperplasia virus 1	[AF014792]	(WEHV-1)
Walleye epidermal hyperplasia virus 2	[AF014793]	(WEHV-2)

Tentative Species in the Genus

Perch hyperplasia virus		(PHV)
Snakehead retrovirus	[U26458]	(SnRV)