Morphology Data of Thymallus arcticus
Identification keys
Abnormalities
Main Ref. Scott, W.B. and E.J. Crossman, 1973
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors
Remarks

Descriptive characteristics of juvenile and adult

Striking features none
Body shape lateral fusiform / normal
Cross section compressed
Dorsal head profile more or less straight
Type of eyes more or less normal
Type of mouth/snout more or less normal
Position of mouth terminal
Type of scales
Diagnosis

Distinguished by its greatly enlarged dorsal fin and its small mouth, which has fine teeth on both jaws (Ref. 27547). Dorsal greatly enlarged in adults (especially males), reaching adipose fin when depressed, but is shorter in females; pelvic fins rather long, reach anal fin in adult males, but not in females; lower lobe of caudal often longer than upper (Ref. 27547). A strikingly colored fish, the dorsal surface is dark purple, or blue black to blue gray, the sides gray to dark blue with pinkish iridescence, the ventral surface gray to white (Ref. 1998). Scattered dark spots on sides, these being more numerous on the young; a dark longitudinal stripe along lower sides between pectoral and pelvic fins; dorsal fin dark with narrow purple edge (rows of reddish to orange or purple to green spots on body of fin); pelvic fins dark with irregular diagonal orange-yellow stripes; adipose, dorsal, anal, caudal and pectorals dusky to dark (Ref. 27547).

Ease of Identification easy to distinguish from other species.

Meristic characteristics of Thymallus arcticus

Lateral Lines 1 Interrupted: No
Scales on lateral line
Pored lateral line scales 77 - 103
Scales in lateral series
Scale rows above lateral line
Scale rows below lateral line
Scales around caudal peduncle
Barbels 0
Gill clefts (sharks/rays only)
Gill rakers
on lower limb 11 - 15
on upper limb 5 - 7
total 16 - 23
Vertebrae
preanal
total 58 - 62

Fins

Dorsal fin(s)

Attributes no striking attributes
Fins number 1
Finlets No. Dorsal   0 - 0
Ventral  0 - 0
Spines total 0 - 0
Soft-rays total 17 - 25
Adipose fin present

Caudal fin

Attributes forked; more or less normal

Anal fin(s)

Fins number 1
Spines total 0 - 0
Soft-rays total 11 - 15

Paired fins

Pectoral Attributes  more or less normal
Spines     0
Soft-rays   14 - 16
Pelvics Attributes  more or less normal
Position    abdominal  behind origin of D1
Spines     0
Soft-rays   10 - 11
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