Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


J. E. Duffy


Snapping shrimp in the family Alpheidae are remarkably abundant in coral reef ecosystems worldwide. The second most speciose genus, Synalpheus , includes species usually small and reclusive, and their general morphology is notably uniform, yet the number of species is staggeringly high, as is the intraspecific variability. These features have contributed to a poorly resolved taxonomic status, as evidenced both by recurring lumping and splitting of species and by lack of proper definition of several common species. I examined western Atlantic species of Synalpheus in the large and regionally dominant "Gambarelloides group of species", an informal but widely used guild within the genus. Analysis of external anatomical features of preserved and live specimens enabled a reassessment of morphological characters traditionally used in taxonomy, and incorporation of novel characters. Identity and validity of every species described from the western Atlantic has been reevaluated. Detailed ecological records and observations on live specimens under laboratory conditions yielded ancillary data useful in distinguishing the species. Seven new species are preliminarily described. Recognition of the Gambarelloides group as a distinct subgenus within Synalpheus is recommended. A systematic account of 17 species with selected illustrations and color photographs is included, together with a dichotomous identification key. The evolution of morphological characters was traced onto the current best reconstruction of the phylogenetic relationships among the species of the Gambarelloides group. The phylogenetic tree was obtained by analyzing molecular data from segments of two mitochondrial genes (COI and 16S) from 39 species of Synalpheus, with Alpheus cylindricus as the outgroup. Most of the morphological characters studied bore weak phylogenetic signal and homoplasies were frequent. Nevertheless, two characters provided consistent synapomorphies defining the Gambarelloides group: the dorsal brush of setae (used in feeding) on the dactyl of the minor first chela, and the coxal lamella on the third pereiopods. Evolution studies of Synalpheus are particularly interesting because of the high number of closely related species, similar general ecological preferences with microhabitat specificity, and variation in social organization. This reassessment of western Atlantic species provides a solid taxonomy and an important frame of reference for future studies of Synalpheus.



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