How many shrimp species are there?
Fransen & De Grave (2009) working from a preliminary version of the present catalogue estimated the species/subspecies richness of shrimps as follows: Dendrobranchiata (505), Stenopodidea (58) and Caridea (circa 3108), with those figures slightly adjusted in De Grave et al. (2009). Since then numerous descriptions have appeared, synonymies corrected and species placed in synonymy. The current tally stands as follows: Dendrobranchiata (68 genera, 533 species), Procarididea (2 genera, 6 species), Stenopodidea (12 genera, 71 species) and Caridea (389 genera, 3438 species). Although the figures listed in De Grave et al. (2009) for the other decapod taxa have clearly been adjusted by now, the Caridea remain the second most species-rich group within the Decapoda, with approximately half as many species as Brachyura, the dominant taxon within Decapoda.
On a more inclusive level, the Caridea are dominated by Palaemonidae (981 species), followed by Alpheidae (663), Atyidae (469), Hippolytidae (338) and Crangonidae (219). Under the traditional classification employed here, Palaemonidae comprises two subfamilies, with Pontoniinae being considerably richer in species (602) than Palaemoninae (379). In contrast to those species-rich families, are those 12 families which are monogeneric, some only consisting of a single species, e.g. Physetocarididae.
On a generic level, the most speciose genera are Caridina (Atyidae, 290 species), Alpheus (Alpheidae, 286), Macrobrachium (Palaemoninae, 243), Synalpheus (Alpheidae, 159) and Periclimenes (Pontoniinae, 152). As doubt has been cast on the monophyletic status of these mega-genera in recent years, this ranking may substantially alter when phylogenetic studies progress.