Morphology Data of Acanthurus tractus
Identification keys
Main Ref. Bernal, M.A. and L.A. Rocha, 2011
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs no special organs
Different appearance males alike females
Different colors males alike females

Descriptive characteristics of juvenile and adult

Striking features none
Body shape lateral short and / or deep
Cross section compressed
Dorsal head profile clearly convex
Type of eyes more or less normal
Type of mouth/snout more or less normal
Position of mouth terminal
Type of scales

This species is distinguished by the following set of characters: D IX, 23-26; A III, 21-23; pectoral rays 15-17; gill rakers 18-24; covered with very small ctenoid scales; spatulate teeth have denticulate edges, upper jaw with 14, lower jaw 16; body depth about 2.0 in standard length; caudal fin lunate, concavity of caudal fin 5.0-12.0 in SL, more concave in adults; length of caudal spine 3.0-3.5 in SL; eye diameter 3.0-3.5 in head length; colour of body yellowish to grayish brown, without dark vertical bars; yellow lines radiating from the posterior margin of eye; translucent pectoral fin with yellow tints; white or pale spot at the base of caudal fin; posterior margin of caudal, anal and dorsal fins have light blue or white margin (Ref. 87362)..

Ease of Identification

Meristic characteristics of Acanthurus tractus

Lateral Lines 1 Interrupted: No
Scales on lateral line
Pored lateral line scales
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) absent
Gill rakers
on lower limb
on upper limb
total 18 - 24


Dorsal fin(s)

Attributes extending over most of the back length
Fins number 1
Finlets No. Dorsal   0 - 0
Ventral  0 - 0
Spines total 9 - 9
Soft-rays total 23 - 26
Adipose fin absent

Caudal fin

Attributes other (see remark)

Anal fin(s)

Fins number 1
Spines total 3 - 3
Soft-rays total 21 - 23

Paired fins

Pectoral Attributes  more or less normal
Spines     0
Soft-rays   15 - 17
Pelvics Attributes  more or less normal
Position    thoracic  beneath origin of D1
Spines     1
Soft-rays   5 - 5
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
Entered by Luna, Susan M.
Modified by Capuli, Estelita Emily
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