Comparative morphology of the pereiopod 1 carpo-propodal (P1-CP) antennal flagellar grooming brush in caridean shrimps (Crustacea, Decapoda)

The carpo-propodal brush on the first pereiopod (P1-CP) is a unique specialisation of natant decapods used to groom the antennal flagellum. Previous studies have documented its occurrence in several families of Caridea, Procarididea, Dendrobranchiata and Stenopodidea. These studies have been updated to include material from 33 out of the 35 currently recognised caridean families. The results demonstrate the majority of families have a P1-CP: species from only 12 of 33 families surveyed lacked the brush. Considerable variation is noted in the structure of the brush and its constituent setae which are principally serrulate. In general, two different patterns of brush structure can be recognised, with extensive minor variation within a pattern; although several families deviate widely from this pattern. As the structure appears conservative within families, it is evident that the P1-CP brush could be a phylogenetically informative character, which should be included in future cladistic analysis at generic level and above.