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A sexually dimorphic basal anal‐fin ray expansion in the weakly discharging electric fish Gnathonemus petersii
Author(s) -
Pezzanite B.,
Moller P.
Publication year - 1998
Publication title -
journal of fish biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.672
H-Index - 115
eISSN - 1095-8649
pISSN - 0022-1112
DOI - 10.1111/j.1095-8649.1998.tb01007.x
Subject(s) - biology , sexual dimorphism , anatomy , fish fin , fish <actinopterygii> , zoology , fishery
Male Gnathonemus petersii (Mormyridae) exhibit two structural, sexually dimorphic characters: anal‐fin ray bone expansion and an indentation of the posterior ventral body wall (formerly described as anal‐fin indentation). Females lack this bone expansion, but may show a slight indentation. Morphometric data on both characters were obtained from radiographs of 414 fish (males and females) ranging in size from 60 to 276 mm L s . Both body wall indentation and bone expansion began to develop in males of about 120 mm L s . At 160–180 mm, the sex ratio of fish with expansion to fish without expansion was 50 : 50. Androgens seem to affect the expression of both these sexual dimorphisms. Bone expansion may provide increased bone surface for muscle attachment and thus facilitate the anal‐fin reflex during courtship behaviour.