a ) SalmoThe majority of Salmo species: gairdneri (rainbow trout), clarki (cutthroat trout), aguabonita (golden trout), apache (apache trout), gilae (gila trout), mykiss (Kamchatkan trout) and the redband trout belong in category B, i.e. they possess karyotypes containing around 60 chromosomes, approximately 104 chromosome arms, and more metacentric than acrocentric chromosomes (Table I ) . In most species both metacentric . A new subgenus and species of trout, Salmo (Platysalmo) platycephalus, from south central Turkey, with comments on the classification of the subfamily Salmoninae. Mitteilungen aus den Hamburgischen zoologischen Museum und Institut 66, 1-1 5 . 6. BEHNKE, R. J. (1970). The application of cytogenetic and biochemical systematics to phylogenetic problems in the family Salmonidae. Transactions of the American Fisheries Society 99, 237-248. 7. BOOKE, H. E. (1968). Cytotaxonomic studies of the coregonine fishes of the Great Lakes, U . S . A . : DNA and karyotype analysis.

Stock-specific variation in the number and chromosome locations of the nucleolar organizer regions (NORs) was found in North American and European stocks of arctic char (Salvelinus alpinus) using chromomycin A₃ staining and silver staining. The number of NORs varied from two to eight per diploid genome. An unusual pattern of one NOR consistently present on both members of the largest submetacentric chromosome pair and additional NORs with variable locations was found. These findings suggest that NORs are being transposed to new chromosome sites in this species and this is discussed in relation to similar findings in other Salvelinus species and in amphibians.

The fluorescent banding patterns of the chromosomes of Salmo gairdneri (rainbow trout), Salmo trutta (brown trout), and Salmo salar (Atlantic salmon) from North America and Great Britain are described. Quinacrine stained a subset of C bands in S. gairdneri and S. salar from North America. No bright quinacrine (Q) bands were found on the chromosomes of S. salar from Great Britain or the chromosomes from any of the three stocks of S. trutta that were examined. Q bands were found at the centromeres of three to seven different chromosome pairs in S. gairdneri, including the pair that has been identified as the sex chromosome pair in some populations. In S. salar from North America the Q bands were found at the teleomeres of three to four chromosome pairs and at interstitial locations in the 10–13 large acrocentric chromosome pairs. Chromomycin A3 stained either the nucleolar organizer region or the adjacent heterochromatin or both in all three species. In S. trutta the entire short arm of the acrocentric chromosome containing the nucleolar organizer region always stained with chromomycin A3 while in S. gairdneri and S. salar the staining properties of the NOR and adjacent heterochromatin were polymorphic.Key words: banding, C-, Q-; Salmo; trout.

Chromosome numbers and polymorphisms in rainbow trout, Atlantic salmon, and brown trout are described. The karyotypes of these three species are compared with each other and with those of other salmonid fish from the genera Salmo, Salvelinus, and Oncorhynchus. Karyotype evolution from a postulated ancestral tetraploid is discussed.

Two morphologically and ecologically distinct forms of Arctic charr, Sulvelinus alpinus, are found in Loch Rannoch, Scotland. The differences in morphology are adaptations to different modes of life, one being pelagic, the other benthic. Both forms have been the subjects ofextensive genetic studies including cytogenetics, nuclear and mitochondria1 DNA analysis, and protein electrophoresis. Significant differences between the two forms are revealed by some techniques but not others and provide evidence for the reproductive isolation of these two morphs. The findings are discussed in relation to the derivation of sympatry and the phylogenetics of Arctic charr.