Alpheus normanni Kingsley, 1878
Alpheus normanni is an Western Atlantic and eastern Pacific snapping shrimp that belongs to the Sulcatus species group within the genus Alpheus (Kim and Abele 1988). Alpheus normanni, like other snapping shrimp in the genera Alpheus and Synalpheus, have a powerful major "snapping" claw used primarily for agonistic interactions; A. normanni also uses their major snapping claw to crush and consume juvenile clams (Mercenaria mercenaria). In the laboratory, this species tends to seek shelter (hiding alongside or under hard objects), and digs shelters or burrows with their legs and pleopods. Individuals tend to fight over available shelters (lunging forward, fanning, cocking their claw, touching head appendages, chasing, or snapping); in interspecific interactions, larger individuals tend to dominate.
Alpheus normanni belongs to the Sulcatus species group within the genus Alpheus (Kim and Abele 1988). Originally described as Alpheus affinis by Kingsley (1878a), this species is named after the Rev. A.M. Norman, who pointed out to Kingsley that the original name for the species (affinis) was already occupied. Type locality: Pacific coast of Panama (Chace 1972, Kim and Abele 1988). Kim and Abele (1988) suggested restricting A. normanni to the eastern Pacific based on morphological differences between the Pacific and Atlantic forms, in which case western Atlantic species would be known as A. packardii (Kingsley 1880). Anker (2001) also suggested the eastern Pacific and Western Atlantic forms will be distinct species once a formal taxonomic revision of the A. normanni complex is done; this is supported by molecular data suggesting at least three species in the complex (Williams et al. 2001). For additional descriptions, see Christoffersen 1979, Williams 1984, Kim and Abele 1988.
Alpheus normanni, like other snapping shrimp in the genera Alpheus and Synalpheus, have powerful major "snapping" claws. Although these claws are primarily used in interspecific or intraspecific agonistic interactions, Beal (1983) demonstrated that A. normanni and the related species A. heterochaelis also use their major snapping claw for predation-- specifically, to crush and consume juvenile clams (Mercenaria mercenaria). Female shrimp of both species exhibited a higher predation rate than males, despite (in A. heterochaelis) having a smaller major chela relative to body size than males. Nolan and Salmon (1970) conducted an extensive study of the behavior of both A. normanni and A. heterochaelis. They noted that shrimp in the laboratory tended to seek shelter (hiding alongside or under hard objects), and dug shelters or burrows with their legs and pleopods. Individuals tended to fight over available shelters (lunging forward, fanning, cocking their claw, touching head appendages, chasing, or snapping); in interspecific interactions (A. heterochaelis paired with A. normanni), the larger individual tended to dominate.
This species is quite common in some areas and has been described from many habitats, from shelly or rocky bottoms (in sand burrows or on pilings in shallow water); in eelgrass beds or rubble, occasionally in oyster trays; among blades and rhizomes of seagrass (Thalassia sp.), among Porites sp., on mats of Halimeda sp., intertidal to 73 m depth (summarized in Williams 1984, Kim and Abele 1988).
Knowlton (1973) studied larval development of this species and noted that it had "extended" larval development lasting several weeks, with small eggs and five larval stages. Fecundity of this species has also been studied by Corey and Reid (1991).
Maximum body size is 10 mm carapace length (A. normanni Atlantic, Williams 1984), 7.9 mm carapace length (A. normanni Pacific, Kim and Abele 1988). Color likely varies among localities; Williams (1984) compiled several color descriptions (following): body gray or dullish green, sometimes with median lateral whitish stripe, often mottled with dark green or brown; pale spot behind each eyes; major chela darker green and usually banded with yellow or yellowish brown on inner surface, occasionally with 2 pale bands and blackish fixed finger.
Alpheus affinis (Kingsley 1878a); Alpheus normanni (Kingsley 1878b, in part, specimens from eastern Pacific); Alpheus normanii (Kingsley 1883); Alpheus Normanni (Coutiere 1899); Crangon normanni (Chace 1937); Alpheus packardii (Kingsley 1880); Alpheus bermudensis (Bate, 1888); Alpheus avarus (sensu Heilprin 1888); Alpheus minor (sensu Brooks and Herrick 1891, Herrick 1891); Alpheus or Crangon beanii (Verrill 1922); for more details see Christoffersen (1979), Williams (1984), Kim and Abele (1988).
Snapping shrimp in the genus Alpheus have been a model system for studying molecular divergence in "transisthmian" taxa that diverged following the closure of the Isthmus of Panama. Alpheus normanni is currently known from the eastern Pacific, the Western Atlantic, and Brazil, although molecular work suggests there are at least three distinct species in this complex (Williams et al. 2001).
Sequenced in Knowlton and Weight 1998 (as Alpheus normanni Pacific isolate, Alpheus normanni Atlantic isolate). Also sequenced in Williams et al. 2001, as Alpheus normanni (east Pacific specimens), Alpheus normanni A (Caribbean), Alpheus normanni B (Brazil), Alpheus normanni C (Caribbean). Sequences available for COI G/G4 (AF097872-3, AF309916-20, AF308982), GPI (AF310756-59), EF1-alpha (AF310810-12, AF310836).
Eastern Pacific and Western Atlantic: Kim and Abele (1988) restricted A. normanni to the eastern Pacific, in which case western Atlantic species would revert to the name A. packardii. Specific localities: Gulf of California, Isla Clarion, Panama, Panama, Galapagos Islands, and Costa Rica (Kim and Abele 1988); southern Virginia to Bermuda and Gulf of Mexico, West Indies south to Brazil (Chace 1972, Christoffersen 1979, Williams 1984). For specific localities, see Christoffersen (1979). Williams (1984) points out that this is likely the species listed as Alpheus minor in earlier records (see synonomies).