Moved from Brine Shrimp and Fairy Shrimp.

I asked Chrisopher Rogers to take a look at these photos. Below are his comments.

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The elongated brood pouch (the egg sac and the lateral ova pouches are within the brood pouch) is not specifically diagnostic for Branchinecta mackini. There are populations of B. mackini on the Carrizo, but there are also many good sites for Branchinecta campestris which also has an elongated brood pouch. B. campestris also has lateral outgrowths/spines at the base of the brood pouch, but they would not be readily visible in that photo. Other species on the Carrizo include Branchinecta lindahli, B. longiantenna, B. lymchi, both of the latter two are federally listed under the Endangered Species Act, so I do not recommend collecting any material from there.

Branchinecta mackini's diagnostic characters are: male second antennal proximal antennomere lacking pulvilli, conical apophyses present, medial surface with a few, small, randomly scattered spines; second antenna distal antennomere apex nearly straight, at most slightly bent laterally, (as opposed to B. campestris, B. potassa, B. lateralis, and B. readingi, which are all bent laterally 70 degrees or more, see figure 1 in Rogers, 2006); female with first antennae at least twice as long as second antennae; brood pouch extending posteriorly to thoracic segment VII . . . I could go on, but the point is, that from that part of the world, I would really need to see it under a microscope to give a proper determination.

That being said, just eye balling this animal, I would say that based on the brood pouch length and shape it is either a female Branchinecta lindahli or a B. longiantenna. The brood pouch does not extend all the way to abdominal segment VII (as it would in B. mackini and B. campestris), and that brood pouch is subcylindrical, rather than fusiform, as it should be for B. mackini.

Please feel free to post this message to the BugGuide. I am happy to be contacted if there are more questions or discussion about crustaceans.

Rogers, D. C. 2006. Three new species of Branchinecta (Crustacea: Branchiopoda: Anostraca) from the Nearctic. Zootaxa (1126):35-51.