Male vs. female
I e-mailed a similar question to Pros. Scott Santos of
Auburn University. He and his people have researched this species quite extensively. Here is our e-mail chat:
> Hello Scott Santos,
> While I was researching halocaridina rubra on the internet I came across pictures that you took in Hawaii. Very nice. I have one question at this time. Are there noticable differences between males and females? ie. color, size Does the female have a noticable saddle when she is producing eggs?
> Thank you in advance,
> Ken P
Nice to meet you and thanks for the email.
In my experience, there is no easy way to visually identify males vs females based on gross overall appearance like size and/or color. We have had some luck sexing individuals via microscopy, but it is labor intensive and not always easy.
Hope this helps,
Here is a thread from David Weese a doctorate student under Pros Santos.
As far as sexing the shrimp, I haven't had any luck. When the females go reproductive its easy when they are carrying 12-24 eggs, but other then that I don't know. A couple of people have told me that when they go into reproductive mode you should be able to see the developing ovaries forming right behind the eyes in females or developing testes in males. However I have not been able to reliably sex them with any confidence yet.
Yet another question and answer:
Another question. Do you think this is a female?
> I suspect that the dark area on the shrimp's back are developing eggs.
> Ken P
I'm sorry to say, but I don't think you have a female there. What you are seeing is the hepatopancreas, which is part of the digestive system of arthropods like crustaceans and insects. Most people know it as the green spongy material that is encountered when they get up into the head area of their lobster dinner. I see it among individuals animals in my tanks at various intensities, some being more apparent (like your example) than others.