Morphology Data of Marcusenius pongolensis
Identification keys
Abnormalities
Main Ref. Maake, P.A., O. Gon and E.R. Swartz, 2014
Appearance refers to
Bones in OsteoBase

Sex attributes

Specialized organs
Different appearance
Different colors
Remarks Males approaching sexual maturity develop a striking kink in the base of the anal fin, with several of its first rays longer, stronger and often curved backwards compared to females and juveniles, where the anal fin base is straight and its rays are similar amongst each other (Ref. 75962).

Descriptive characteristics of juvenile and adult

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

Diagnosis: Marcusenius pongolensis can be distinguished from its congeners by the following characters: a more slender body, elongated, smaller body depth, 19.1-26.0% of standard length; distance from dorsal fin origin to end of caudal peduncle 37.1-39.8% of standard length; distance from anal fin origin to end of caudal peduncle 40.8-42.2% of standard length; and length of anal fin 19.5-21.9% of standard length; all shorter and non-overlapping with Marcusenius krameri, M. caudisquamatus and M. lucombesi (Ref. 95448). Total vertebrae ranges between 42-43 vs. 44 in other species; posterior total gill rakers 13-14 vs. 15 and 17 in M. caudisquamatus and M. krameri, respectively; lateral line scales 70-73; scales around caudal peduncle 16-17; dorsal fin rays 20-23; anal fin rays 26-28 (Ref. 95448). Electric organ discharge (EOD) lacking a weak head-negative pre-potential, in females and juveniles Ndur of short duration, no striking sexual dimorphism in EOD waveform present, but longer EOD duration and statistically significant increase with standard length in males (Ref. 75962).

Description: Head with terminal mouth well in front of eye, mental lobe on lower jaw protruding beyond upper jaw; head and body dorsolaterally compressed (Ref. 75962). Dorsal fin situated about three fourths of standard length from snout, obliquely orientated, anteriorly higher and posteriorly lower, distal margin sometimes only slightly crescentic with anterior two or three rays longer than posterior rays, number of rays 20-23; anal fin opposite dorsal fin with distinctly more anterior origin, obliquely orientated, anteriorly lower and posteriorly higher, anterior rays longer than posterior ones, especially in males where they also appear stronger and often darkened, distal margin crescentic, number of rays 26-28 (Ref. 75962, 95448). Scales cycloid with reticulate striae, scales extending anteriorly to operculum and pectoral fins; scales on caudal peduncle circumference, 16-17 (Ref. 75962, 95448). Caudal peduncle subcylindrical entire length, 18-22% of standard length (Ref. 75962). Electric organ discharge biphasic lacking a weak pre-potential, in females and juveniles Ndur of short duration; in large males, statistically longer EOD duration and significant tendency for increase of both Pdur and Ndur with standard length, however, no sexual dimorphism when compared to upper Zambezi males (Ref. 75962).

Colouration: Colour in life ranging from an almost homogeneous medium brown to grey-brown with yellow-golden shimmer, sometimes going into purple, underside lighter, a few strongly faded, darker blotches on sides detectable, fins yellowish (Ref. 75962, 95448). Colour in preservation light to medium brown, fins whitish; irregular fair spots on body sides (Ref. 75962).

Ease of Identification

Meristic characteristics of Marcusenius pongolensis

Lateral Lines Interrupted: No
Scales on lateral line 70 - 73
Pored lateral line scales
Scales in lateral series
Scale rows above lateral line
Scale rows below lateral line
Scales around caudal peduncle 16 - 17
Barbels
Gill clefts (sharks/rays only)
Gill rakers
on lower limb
on upper limb
total
Vertebrae
preanal
total 42 - 43

Fins

Dorsal fin(s)

Attributes no striking attributes
Fins number 1
Finlets No. Dorsal   
Ventral  
Spines total 0 - 0
Soft-rays total 20 - 23
Adipose fin absent

Caudal fin

Attributes forked; more or less normal

Anal fin(s)

Fins number 1
Spines total 0 - 0
Soft-rays total 26 - 28

Paired fins

Pectoral Attributes  more or less normal
Spines     
Soft-rays   
Pelvics Attributes  more or less normal
Position    abdominal  before origin of D1
Spines     
Soft-rays   
Main Ref. (e.g. 9948)
Glossary ( e.g. cephalopods )
Entered by Torres, Armi G.
Modified by Bailly, Nicolas
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