Morphology Data of Otocinclus arnoldi
Identification keys
Abnormalities
Main Ref. Lehmann, A.P., F. Mayer and R.E. Reis, 2010
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors
Remarks

Descriptive characteristics of juvenile and adult

Striking features
Body shape lateral elongated
Cross section
Dorsal head profile
Type of eyes
Type of mouth/snout
Position of mouth
Type of scales
Diagnosis

Distinguished from all congeners species except Otocinclus mimulus, by having five pectoral branched rays (vs. six pectoral branched rays), and except from Otocinclus mimulus and Otocinclus xakriaba by having the prootic involved in the contact with the hyomandibular articular condyle (vs. only compound pterotic contacting the hyomandibular articular condyle). Differs from Otocinclus mimulus by having a not elevated patch of enlarged odontodes on the postero-dorsal parietosupraoccipital tip and 15 caudal vertebrae (vs. having an elevated patch of enlarged odontodes on the parietosupraoccipital and typically having 16-17 caudal vertebrae). Can be further distinguished (except for Otocinclus affinis, Otocinclus hasemani, Otocinclus xakriaba, Otocinclus mimulus and Otocinclus flexilis) by possessing an iris operculum, and from Otocinclus affinis, Otocinclus mimulus and Otocinclus xakriaba by having a not elevated patch of enlarged odontodes on the postero-dorsal parieto-supraoccipital tip. Differs also from all remaining congeners (except for

Otocinclus xakriaba, Otocinclus flexilis, and Otocinclus mimulus) by having a lateral trunk coloration composed of either a row of 3-6 distinct dark blotches or a distinct dark stripe extending from the compound pterotic to the base of the caudal fin, or a diffuse mixture of those two color patterns (Ref. 86395).

Ease of Identification

Meristic characteristics of Otocinclus arnoldi

Lateral Lines 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
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb
total
Vertebrae
preanal
total

Fins

Dorsal fin(s)

Attributes no striking attributes
Fins number 1
Finlets No. Dorsal   
Ventral  
Spines total
Soft-rays total
Adipose fin absent

Caudal fin

Attributes forked

Anal fin(s)

Fins number
Spines total
Soft-rays total

Paired fins

Pectoral Attributes  more or less normal
Spines     
Soft-rays   
Pelvics Attributes  more or less normal
Position    abdominal
Spines     
Soft-rays   
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