Morphology Data of Oreochromis rukwaensis
Identification keys
Abnormalities
Main Ref. Trewavas, E., 1983
Appearance refers to Male; Female
Bones in OsteoBase

Sex attributes

Specialized organs genital papilla with tassels (m)
Different appearance different morphology during breeding season only
Different colors different colors during breeding season only
Remarks

Descriptive characteristics of juvenile and adult

Striking features none
Body shape lateral short and / or deep
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 cycloid scales
Diagnosis

Diagnosis: Typical tilapiine cichlid, relatively deep bodied, with rather a small head (Ref. 118638). Other distinguishing characters are: caudal fin free of scales except basally; vertebrae 30; scales in lateral line series 30-32; dorsal spines XV-XVII; soft rays usually 11-13; outer teeth bicuspid, in mature fishes occasionally with a few tricuspids; lower gill-rakers 20-22; interorbital region in adults 34.5-40.0% length of head (Ref. 2). Ripe males have a dark body and fins, almost black, with bright red/orange margins on the dorsal and caudal fins; vertical barring can be noticeable in freshly caught specimens; head region in ripe males has a bluish sheen; ripe males have yellow-orange tassels; females and subadult males plain silver/grey with 6-7 post-opercular vertical stripes and bluish snout present in freshly caught specimens (Ref. 118638).

Description: The teeth are in 4-6 series in specimens over 100 mm standard length, 3-4 below this size; with slender shafts and broader, curved crowns; those of outermost row bicuspid except that three mature fishes have a few tricuspids among them; inner rows tricuspid (Ref. 2). Scales on cheek in 2 rows, rarely 2 or 3 scales of a third row present; 4 or 4.5 between origin of dorsal and lateral line (Ref. 2). Caudal fin very slightly emarginate in young, truncate in adults (Ref. 2).

Colouration: Preserved adults are uniformly pale, without markings on the body; the vertical fins and the pelvics are either likewise pale or may be dusky between the rays; the young are also pale, but some show 6-8 grey vertical bands on the flanks and the soft dorsal may be marked with dark oblique bands or with clear ovals on a grey ground; in this pattern the tilapia-mark may be indicated by a darker grey, but most are without even this vestige of a tilapia-mark (Ref. 2).

Ease of Identification

Meristic characteristics of Oreochromis rukwaensis

Lateral Lines 2 Interrupted: No
Scales on lateral line 30 - 32
Pored lateral line scales
Scales in lateral series
Scale rows above lateral line 4 - 4.5
Scale rows below lateral line
Scales around caudal peduncle
Barbels 0
Gill clefts (sharks/rays only) absent
Gill rakers
on lower limb 20 - 22
on upper limb
total
Vertebrae
preanal
total 30 - 30

Fins

Dorsal fin(s)

Attributes extending over most of the back length
Fins number 1
Finlets No. Dorsal   
Ventral  
Spines total 15 - 17
Soft-rays total 11 - 13
Adipose fin absent

Caudal fin

Attributes more or less truncate; more or less normal

Anal fin(s)

Fins number 1
Spines total 3 - 3
Soft-rays total 10 - 11

Paired fins

Pectoral Attributes  more or less normal
Spines     
Soft-rays   
Pelvics Attributes  more or less normal
Position    thoracic  behind origin of D1
Spines     
Soft-rays   
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
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