Table 1: Relationship between the genetic code variations and modified nucleosides in the anticodon of the corresponding tRNAs in the animal phlyla.
(a) UGA codon.

Animal phylaUGA specificityAnticodon

VertebrataTrpτm5UCA(a)
Tunicata (Urochordata)Trpτm5UCA(b)
CephalochordataTrp(TCA)
EchinodermataTrp(TCA)
ArthropodaTrpU*CA(c)
Most invertebrate phylaTrpcmnm5(s2)UCA(d)
PlatyhelminthesTrp(TCA)
Cnidaria, Placozoa, PoriferaTrp(TCA)

(b) AUA codon.

Animal phylaAUA specificityAnticodon

VertebrataMetf5CAU(e)
Tunicata (Urochordata)Metτm5UAU(f)
CephalochordataMet(CAT)
EchinodermataIle(GAT)
ArthropodaMetf5CAU(g)
Most invertebrate phylaMetf5CAU(h, i)
Platyhelminthes
  Most (Echinostomida, Trematoda)Met(CAT)
  Rhabditiophora, PlanariaIle(GAT)
CnidariaIle(j)
PlacozoaIle(GAT)
PoriferaIle(CAT)(k)

(c) AAA codon.

Animal phylaAAA specificityAnticodon

VertebrataLys(CTT)
Tunicata (Urochordata)Lys(TTT)
CephalochordataLys(TTT)
EchinodermataAsnGΨU(l)
ArthropodaLysCUU(m)/(TTT)
Most invertebrate phylaLys(CTT/TTT)
PlatyhelminthesAsn(GTT)
CnidariaLys(j)
PlacozoaLys(TTT)
PoriferaLys(TTT)

(d) AGA/AGG codons.

Animal phylaAGA/AGG specificityAnticodon

VertebrataTerm.None
Tunicata (Urochordata)Glyτm5UCU(n)
CephalochordataSer(GCT)
EchinodermataSerm7GCU(o)
Arthropoda
  Most ArthropodsSer(GCT/TCT)
  Drosophila melanogaster Ser(p)GCU(q)
Most invertebrate phylaSerm7GCU(r)
PlatyhelminthesSer(GCT/TCT)
CnidariaArg(j)
PlacozoaArg(TCT)
PoriferaArg(TCT)

In case that only the tRNA gene sequences are known, the anticodon sequences at DNA level are shown in parentheses. (a)Homo sapiens (Suzuki et al. [39]) (b)Halocynthia roretzi (Suzuki et al. [23]) (c)Drosophila melanogaster (Tomita et al. [12]). U* is an unkown modified uridine. (d)Ascaris suum (Sakurai et al. [15]) (e)Bos taurus (Moriya et al. [9]) (f)Halocynthia roretzi (Suzuki et al. [23]) (g)Drosophila melanogaster (Tomita et al. [12]) (h)Loligo bleekeri (Tomita et al. [30]) (i)Ascaris suum (Watanabe al. [31]) (j)Corresponding tRNA gene is not encoded in the mitochondrial genome. The tRNA decoding this codon is presumed to be imported from cytoplasm [40]. (k)Poriferan mt genomes encode three tRNA genes with anticodon CAT at DNA level. One of these tRNA is thought to be gene (L is the modified C (lysidine) found at the anticodon first position of most bacterial decoding AUA codon) [41]. (l)Asterias amurensis (Tomita et al. [42]) (m)Drosohila melanogaster (Tomita et al. [12]) (n)Halocynthia roretzi (Kondow et al. [29], Suzuki et al. [23]) (o)Asterias amurensis (Matsuyama et al. [10]) (p)No AGG codon appears in the D. melanogaster mitochondrial genome. (q)Drosophila melanogaster (Tomita et al. [12]) (r)Loligo bleekeri (Tomita et al. [11]).