Crayfish Dissection questions...subject: gills and rostrum?

Question

I have a few questions from a crayfish dissection worksheet..

1. When the crayfish is NOT walking, how does water move over the gills?

2. The carapace's most anterior point is called the rostrum. Why is it called this?

thanks! :)

Answer 1

1. The swimmerets (appendages under the abdomen) beat to move water over the gills. The maxillae can help in this effort, too.

2. The origin of the word rostrum is a Latin term for a ship's beak -- the pointed part at the front of a ship.

Answer 2

Crayfish Dissection Worksheet

Answer 3

1. Good question. There's a specialized pair of feathery limbs on the "face" which flap incessantly, probably pulling water from the gills. I think these are "maxillipeds." When the water is warm, the crayfish will move its legs back and forth even when not walking. If the water is stagnant, the crayfish will climb to the surface and pull air under its carapace and into the gill area (and when it descends, you can see it slowly release small bubbles from a couple of "holes" near where those feathery appendages are).