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 Vallisneria aethiopica (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