Question

these questions are about crayfish

9. Compare walking legs and swimmerets. How do their different shapes relate to their functions? 10. Compare the chelipeds with the other walking legs. Are the claws identical? 11. What is the function of the antennae? 12. What is the advantage or having eyes on top of movable stalks? 13. What is the function of the gastric mill? 14. What is the function of the antennal glands?

Answer 1

Answer 9) walking legs (aka pereiopods) in crayfishes are usually used for the function of moving from one place to the other. Usually during the time when they are attacked by other organism, they are known to lose thier walking legs but an interesting fact about crayfishes is that they can grow back their walking legs which arises at the level of their thorax more towards the cephalic part, hence at cephalothorax. Some located on the inside and some outside therefore they majorly differ in size. There are also gills which are attached to the walking legs for getting oxygen in the water.

Swimmrets are similar looking of that of the walking leg but the difference is that they are smaller than the walking legs and are in multiple pairs. The other difference is that as the walking legs arise next to throax, the swimmerts of the crayfish attaches next to the abdomen (usually attached to the abdomen). Their functions are not only for motility (or swimming to be precise)  but are mostly used in the process of reproduction and one can determine the crayfish's gender looking at their swimmrets. if the swimmret is hard and closer to the abdomen it is considered to be a male one.

Answer 10) Chilepeds are another structure present in the crayfish which are two in number and mostly arises ahead of the walking legs therefore is marked to be present in the anterior part of the throax. Unlike walking legs which are used for locomotion the chilepeds are structures like the walking legs but modified with the presence of a claw (they can grow more of these in numbers ) and mainly used for gripping, holding, cutting/processing of the food. therefore they play an essential role in attacking the prey and for their food requirement.

Answer 11) The antenna's of the crayfishes are usually used for sensing different things, for eg they act like receptors for senses like [precepting, taste, smell etc

Answer 12) The movable stalks keeps moving during the locomotion of the crayfish, and having the eyes on topo f those movable stalks helps the crayfishes to see all around in different directions (like an adaptation) . therefore when they move their stalks in water whenever they wish to see something somewhere.

Answer 13) The stomach is also known as the Gastric mills in crayfishes and has similar function as that of the digestive system in processing and digesting of food ( by grinding). they are named so because they have teeth like structures in the stomach and the surfaces present in the inside of the gastric mills helps them breaking off their food.

Answer 14)The function of antennal gland is secretary. they are present in the lower end of the antennae and help in excretion. they are commonly refered to as Green Glands. Therefore here, the urine is produced by sequence of absorption and reabsorption before it passes on finally to the bladder.

i would recommend you to have a detailed look of the diagram in your textbook for a much better understanding,

I hope i was able to help you with the answers ! :)