2
Substantial revisions to the species names and higher taxonomy of many fishes in the intervenfi
ing years also make an updated compendium necessary. In this book, synonymies are circumvented by providing both the name reported in the original karyotype papers and currently
recognized names. In particular, the classification of taxa above the species level follows Nelson
fi
(2006: N-68), and species names conform to the up-to-date list in the Catalogue of Fishes by
Eschmeyer (http://research.calacademy.org/redirect?url=http://researcharchive.calacademy.org/
research/ichthyology/catalog/fishcatmain.asp, E-13). The classifi
fi
cation of chromosomes followed
fi
Levan et al. (1964: L-25): chromosomes were classifi ed to metacentrics (M), submetacentrics (SM),
fi
subtelocentrics (ST), and acrocentrics (A). As shown in Table 1 (Levan et al. 1964), M, m, sm, st, t,
and T do not denote chromosomes but rather centromeric position; e.g., acrocentrics is characterized by t. Levan et al. (1964) do not propose abbreviations for chromosomes. Two kinds of abbreviations for chromosomes, M-SM-ST-A and m-sm-st-t(-T), have been adopted in karyotypes. I
adopt M-SM-ST-A because chromosome classification can be differentiated from centromeric
fi
position by these abbreviations and thus the problematic treatment of T in the other system can
be avoided. In addition to providing data for extant fishes, ancestral chromosome numbers (ACN
fi
= NAN sensu Arai and Nagaiwa 1976: A-64) are proposed in this book.
To date, karyotype data have been made available for 53 orders (84% of the known total) and
269 families (52% of total). In addition, genome size has been reported in 52 orders (83%) and
264 families (51%), which are available in standardized form as part of the Animal Genome Size
Database (http://www.genomesize.com, G-85). As a result, it is possible to compare these two
characters, at least at the family level (Tables 2, 3).
In some cases, a given karyotype consists of chromosomes that cannot easily be distinguished
as either SM or ST, such that different authors may report different information. For example, the
arm number (NF 1 ) of Oncorhynchus keta (2n = 74) is reported as 100 in Sasaki et al. (1968: S-14)
versus 102 in Ueda (1985: U-72), and the NF 2 of Alburnus alburnus (2n = 50) is given as 92 in
Cataudella et al. (1977: C-34) versus 86 in Hafez et al. (1978: H-3). These different reports on
karyotypes between conspecific populations were included in the database (Tables 4–7) without
fi
comment, although it should be noted that these differences may derive from artifacts of preparation technique or taxonomic problems, rather than representing real polymorphisms. If so, then
it will be important to resolve these discrepancies before meaningful comparisons can be made.
Similarly, there may be issues relating to differences in reported karyotypes resulting from different degrees of chromosome condensation, to the lack of a uniform terminology among authors,
or even to some miscalculations (number of arms, NOR position, etc.). Some examples of these
sources of error were detected when examining the literature; e.g., the same researcher(s) have at
times defi ned M/SM as two-arm chromosomes in some taxa, but M/SM/ST as two-arm chromofi
somes in other taxa. To prevent such confusion, these two-arm definitions were differentiated in
fi
the present book; i.e., NF 1 means M/SM as two-arm chromosomes and NF 2 means M/SM/ST as
two-arm chromosomes.
There are several fundamental questions that remain to be answered with regard to phylogenetic karyology in fishes. For example: (1) Why is polyploidy in teleost fi
fi
shes only observed in
fi
freshwater species and not in marine species? (2) What is the phylogenetic significance of differfi
ences in the number and location of NORs as shown by different banding methods (especially by
the FISH method with 18S rDNA and 5S rDNA probes)? (3) In cases in which both large and small
B chromosomes have been reported, are both, neither, or only the large B chromosomes to be
counted in the diploid chromosome number? Or should this be considered on a case-by-case
basis? (4) What is the biological significance of microchromosomes, and what is their relationship
fi
(if any) with B chromosomes? (5) Can sex chromosomes be differentiated in more species by using
FISH methods with probes of genes specific to sex chromosomes?
fi
Many individuals helped me in various ways with the preparation of this book. For papers on
karyotypes, I would like to thank Ana Lucia Dias, Eliana Feldberg, Pedro Manoel Galetti, Jr., John
R. Gold, Anisur Rahman Khuda-Bukhsh, Naresh Sahebrao Nagpure, Claudio de Oliveira, Gento
Shinohara, Akihiko Shinomiya, Akinori Takai, Toru Taniuchi, Takayoshi Ueda, Han-lin Wu, and
Substantial revisions to the species names and higher taxonomy of many fishes in the intervenfi
ing years also make an updated compendium necessary. In this book, synonymies are circumvented by providing both the name reported in the original karyotype papers and currently
recognized names. In particular, the classification of taxa above the species level follows Nelson
fi
(2006: N-68), and species names conform to the up-to-date list in the Catalogue of Fishes by
Eschmeyer (http://research.calacademy.org/redirect?url=http://researcharchive.calacademy.org/
research/ichthyology/catalog/fishcatmain.asp, E-13). The classifi
fi
cation of chromosomes followed
fi
Levan et al. (1964: L-25): chromosomes were classifi ed to metacentrics (M), submetacentrics (SM),
fi
subtelocentrics (ST), and acrocentrics (A). As shown in Table 1 (Levan et al. 1964), M, m, sm, st, t,
and T do not denote chromosomes but rather centromeric position; e.g., acrocentrics is characterized by t. Levan et al. (1964) do not propose abbreviations for chromosomes. Two kinds of abbreviations for chromosomes, M-SM-ST-A and m-sm-st-t(-T), have been adopted in karyotypes. I
adopt M-SM-ST-A because chromosome classification can be differentiated from centromeric
fi
position by these abbreviations and thus the problematic treatment of T in the other system can
be avoided. In addition to providing data for extant fishes, ancestral chromosome numbers (ACN
fi
= NAN sensu Arai and Nagaiwa 1976: A-64) are proposed in this book.
To date, karyotype data have been made available for 53 orders (84% of the known total) and
269 families (52% of total). In addition, genome size has been reported in 52 orders (83%) and
264 families (51%), which are available in standardized form as part of the Animal Genome Size
Database (http://www.genomesize.com, G-85). As a result, it is possible to compare these two
characters, at least at the family level (Tables 2, 3).
In some cases, a given karyotype consists of chromosomes that cannot easily be distinguished
as either SM or ST, such that different authors may report different information. For example, the
arm number (NF 1 ) of Oncorhynchus keta (2n = 74) is reported as 100 in Sasaki et al. (1968: S-14)
versus 102 in Ueda (1985: U-72), and the NF 2 of Alburnus alburnus (2n = 50) is given as 92 in
Cataudella et al. (1977: C-34) versus 86 in Hafez et al. (1978: H-3). These different reports on
karyotypes between conspecific populations were included in the database (Tables 4–7) without
fi
comment, although it should be noted that these differences may derive from artifacts of preparation technique or taxonomic problems, rather than representing real polymorphisms. If so, then
it will be important to resolve these discrepancies before meaningful comparisons can be made.
Similarly, there may be issues relating to differences in reported karyotypes resulting from different degrees of chromosome condensation, to the lack of a uniform terminology among authors,
or even to some miscalculations (number of arms, NOR position, etc.). Some examples of these
sources of error were detected when examining the literature; e.g., the same researcher(s) have at
times defi ned M/SM as two-arm chromosomes in some taxa, but M/SM/ST as two-arm chromofi
somes in other taxa. To prevent such confusion, these two-arm definitions were differentiated in
fi
the present book; i.e., NF 1 means M/SM as two-arm chromosomes and NF 2 means M/SM/ST as
two-arm chromosomes.
There are several fundamental questions that remain to be answered with regard to phylogenetic karyology in fishes. For example: (1) Why is polyploidy in teleost fi
fi
shes only observed in
fi
freshwater species and not in marine species? (2) What is the phylogenetic significance of differfi
ences in the number and location of NORs as shown by different banding methods (especially by
the FISH method with 18S rDNA and 5S rDNA probes)? (3) In cases in which both large and small
B chromosomes have been reported, are both, neither, or only the large B chromosomes to be
counted in the diploid chromosome number? Or should this be considered on a case-by-case
basis? (4) What is the biological significance of microchromosomes, and what is their relationship
fi
(if any) with B chromosomes? (5) Can sex chromosomes be differentiated in more species by using
FISH methods with probes of genes specific to sex chromosomes?
fi
Many individuals helped me in various ways with the preparation of this book. For papers on
karyotypes, I would like to thank Ana Lucia Dias, Eliana Feldberg, Pedro Manoel Galetti, Jr., John
R. Gold, Anisur Rahman Khuda-Bukhsh, Naresh Sahebrao Nagpure, Claudio de Oliveira, Gento
Shinohara, Akihiko Shinomiya, Akinori Takai, Toru Taniuchi, Takayoshi Ueda, Han-lin Wu, and