Above: A subadult individual of
Hemitilapia oxyrhynchus. When a little larger, this fish would have shown
the full adult melanic (black) markings characteristic of the genus Hemitilapia
and its relatives. The two dark spots on the flanks, which do not yet extend to
the top of the fish's back, will "fill in" above, forming specialized spots that
I call saddles. The elongate, straight or (in adults) slightly concave snout is a
distinctive anatomical feature of H. oxyrhynchus.
This common denizen of Vallisneria weed beds on sandy shores has an unusual
feeding method. It grasps a long, straplike
(tape grass) leaf between its jaws (often turning its body nearly horizontally to do so),
and then nibbles repeatedly along the leaf blade toward the tip of the
leaf, scraping off the periphyton the algae or Aufwuchs that grows on the
leaf surface, leaving the leaf itself unharmed. I spent hours hovering in SCUBA gear
near feeding Hemitilapia, recording detailed counts and other notes
on the many hundreds of nibbles each fish makes on the leaves of many
plants per hour.
|Last Update: 18 July 2005
Web Author: M. K. Oliver, Ph.D.
Copyright © 1997-2021 by M. K. Oliver, Ph.D. - ALL RIGHTS RESERVED