Dana, 1849
When identifying halocyprids the first task is to determine whether the specimen is adult. The novice will not find this a simple task without resorting to dissection, especially when dealing with species which are opaque (e.g., Halocypris inflata).
a) Any specimen with clear male secondary sexual characters is adult: i.e., first antenna with armature (male frontal organ /1st antenna ),
b) well developed hook appendages on the endopodites of the second antennae (male endopodite of 2nd antenna ),
c) sixth limb with a strongly developed basal segment visible through the side of the carapace (male, sixt limb ),
d) and a fully-developed copulatory organ (male,caudal furca/cop.appendage ).
Many adult females have well-developed ovaries, which show up as white opaque patches on either side of the abdomen, and an iridescent patch of stored sperm at the base of the caudal furca. A character that is definitive for most species is the caudal furca carrying eight pairs of hook setae, however, some adults of some Archiconchoecia species have fewer pairs. Juvenile characteristics include: a lack of development of the fifth and sixth limbs, and small but distinct swellings on the tips of the sensory setae of the first and second antennae, and in most species the occurrence of fewer than 8 pairs of hook setae on the caudal furca. Specific identification of immature stages is difficult because they lack many of the diagnostic characters and some species undergo large allometric changes in carapace.
Although the majority of species can be identified without resorting to dissection, there are several complexes of sibling species, including some of the more abundant taxa, for which accurate identification requires some dissection. Before attempting any dissections measure the carapace length, height and breadth, and sketch the outline. Note any special characteristics of the carapace, and most importantly try to locate whether the carapace glands are asymmetrical and where exactly they open. Identification of some species requires recognition of whether there are accessory glands at various positions around the carapace valves, but in most species these can only be seen under high power. Dissection is simple. Lay the specimen on its back and, with a fine needle, slice through the body wall and adductor muscles down each side. The main part of the body with all the limbs can then be hooked out. The carapace can be mounted either permanently or temporarily, with or without staining, for closer examination of where the carapace glands are situated. The limbs can then be picked off in order, but for most purposes only the first antennae together with the frontal organ and the left-hand second antenna will be needed.