Squawfoot, Strophitus undulatus

This species utilizes the "leghold trap" strategy to catch its host fish.   Squawfoot conglutinates are adhesive and stick to the substratum.  Each conglutinate consists of roughly 1-15 eggs, usually arranged in single-file.  The glochidia "hatch" shortly after release of the conglutinate, but remain tethered to it by short larval threads (similar to a leg-hold trap).  The glochidia are large and have prominent hooks, and they attach readily to the fins of benthic fishes.  The larval thread is quite strong, and the whole conglutinate may be pulled along if even one glochidium attaches to a fin.  At that point, it becomes the "tar baby" strategy as more glochidia may attach to the fin.

Click on the thumbnails for full-size images

 
stro-1.jpg (101689 bytes) 22'.jpg (67408 bytes) stro-6.jpg (43263 bytes)
This female has released a large number of conglutinates that adhere to the dish These glochidia have emerged from the eggs but remain tethered.   The number of eggs in a conglutinate varies from one to more than a dozen.
stro-3.jpg (83301 bytes) stro-4.jpg (78188 bytes) stro-5.jpg (104806 bytes)
There are two colors of glochidia! Note the cavities from which the glochidia have emerged. The larval thread forms a strong attachment.

Unio Gallery— Home Page http://unionid.missouristate.edu.  Copyright 1998-2006 by M. C. Barnhart.  Please see Usage Policy for conditions of use of images and video.