Synalpheus regalis Duffy, 1996
Synalpheus regalis is a unique species of sponge-dwelling snapping shrimp, and the first described example of eusociality in the sea (Duffy 1996a). Like social insects such as ants and honeybees, Synalpheus regalis lives in large colonies consisting of one breeding female "queen" and typically 100 or more non-breeding workers that jointly defend the sponge against intruders (Duffy 1996b, 2007). Allozyme work has confirmed that most colonies consist of full-sibs produced by the queen and possibly a single male "king."
S. regalis belong to the gambarelloides species group in the genus Synalpheus, and molecular work suggests that eusociality evolved independently at least three times in this group.
Ecology and Behavior
Synalpheus regalis lives in coral reefs, most commonly in the sponge species Xestospongia spp. and Hyattella intestinalis.
Habitat and Host Associations
Lives in coral reefs; associate of sponges (phylum Porifera), specifically the sponges Xestospongia spp. and Hyattella intestinalis.
Reproduction and Life History
Like several other species in the genus Synalpheus, S. regalis exhibits eusocial population structure (defined here as living in large colonies with a single breeding female). This species undergoes direct development, with embryos hatching into crawling larvae.
Western Atlantic: Belize (Duffy 1996a,c, Macdonald et al. 2006; Ríos and Duffy 2007); Jamaica (Macdonald et al. 2009)
Evolution and Phylogenetics
Synalpheus regalis is one of at least six described eusocial Synalpheus species in the gambarelloides species complex, making this group a model system for examining the evolution of eusociality in the sea (Duffy et al. 2000, Morrison et al. 2004).
Sequenced in Morrison et al. 2004 (as regaBE02, regaBE01); sequences available in GenBank for 16S mtDNA (AF230271 ) and COI mtDNA (AF230794).
Identification and Taxonomy
Systematics and Identification
Synalpheus regalis belongs to the gambarelloides species complex (Duffy, 1996) within the genus Synalpheus. The species name is derived from the Latin "regalis," meaning royal, referring to the social structure of this species in which large colonies are headed by a single "queen".
Like most members of the Synalpheus gambarelloides species group, Synalpheus regalis has a streamlined body adapted to living in sponge canals and a thick brush of setae on the minor chela (claw). Maximum body size (carapace length, or CL) of males is 3.2 mm; females, 4.14 mm (Macdonald et al. 2009). Color: Body translucent to faint translucent-orange; distal tips of major chela brighter orange, ovaries and embryos pale green (Duffy 1996b, Rios and Duffy 2007).
Synalpheus "rathbunae C" (Duffy 1996c, BJLS); Zuzalpheus regalis (Rios and Duffy 2007).
Type locality: Carrie Bow Cay, Belize (Duffy, 1996), types stored at the National Museum of Natural History, Smithsonian Institution (USNM). Holotype: USNM 280092, allotype: none.