Dr. Dean W. Blinn
A NIGHT IN THE WELL
A number of similar events also occur in the water. First, the
resident muskrats leave their mud burrows along the shore of the
Well and swim into the aquatic plants to feed. Also, many of the
amphipods swim to the surface of the open water and gorge
themselves on algae by trapping these tiny plants in specialized
feeding hairs near their mouth (see illustration below). The
amphipods can no longer be fed upon by ducks and turtles because
they can't be seen, but they must escape from a new predator....
Once the amphipods have collected the algae on their feeding hairs and have filled their guts, they disperse into deeper water and also into the aquatic plants located around the margin of the Well. This movement usually occurs several hours after sunset; the leeches follow in pursuit! Hungry leeches may track down additional amphipods in the vegetation, while leeches that are full probably return to their soft mud tunnels at the bottom to conserve energy and digest their evening meal. A typical evening meal for each leech consists of about 14-20 amphipods.
Not only do the amphipods need to be aware of leeches sneaking up from below, but they also need to be concerned about the water scorpions that swim out from the vegetation. These water scorpions swim near the surface and feed on the amphipods with their piercing beaks. This cat-and-mouse game between prey and predator is most active around twilight but continues until sunrise after which all is calm in the surface waters of Montezuma Well.