Red claw sexing is easy. If you look at them from above, the females will have a tail that is wider than the males. By tail I mean everything behind the legs. Of course as the males get bigger the dominate one will get the big claws. However, at the moment I have 2 males in the same tank that have big claws. The tank is a 29 gal. They seem to stay at opposite ends. I love these shrimp!
The second one is a female for sure. She has the extended abdomen to accommodate eggs. Can't tell with the other shrimp. Immature males and females can look deceivingly similar.
Yep, the second one has bigger swimerettes (the paddles underneath). All the better for carrying eggs. She won't breed though until she molts. I have actually witnessed it . Just as described on this web site. It happened so quick I wasn't sure if what I saw was it. But it was.
There are, but you need a microscope to tell with most shrimp we are concerned with (except some giant Macros). The first pleopod (swimmerets) of the males is shaped differently for mating purposes.