Alpheus arenensis (Chace, 1937)

Alpheus arenensis
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Original DescriptionCrangon arenensis Chace, 1937: 119, fig. 4. 
ClassificationArthropoda: Crustacea: Malacostraca: Decapoda: Alpheidae. 
SynonymyAlpheus websteri sensu Wicksten, 1983 and Kim and Abele, 1988. 
Type LocalityArena Bank, S Baja California, Mexico (symbol on the map). 
Type MaterialUSNM 0000000, in ethanol, in fairly good condition. 
Common NameArena snapping shrimp. 
Taxonomic StatusValid. Wicksten (1983) and Kim and Abele (1988) treated A. arenensis as a junior synonym of A. websteri. Taxonomic status revision by Anker, Hurt and Knowlton, 2008a
Geographic DistributionTropical and subtropical eastern Pacific [EP]: from S Gulf of California to Colombia and Galapagos (see map). 
FrequencyRelatively uncommon throughout its range. 
HabitatHard and mixed soft-hard bottoms with sand, corals, coral rubble and rocks; in crevices of coral rocks or coral bases. 
Depth RangeIntertidal and shallow subtidal, probably to about 20 m. 
Life History and BehaviorLives in pairs in rock or coral crevices. 
Related SpeciesAlpheus websteri Kingsley, 1880 [WA]; A. fagei Crosnier and Forest, 1965 [EA]; more distantly: A. rugimanus A. Milne Edwards, 1878 [EA]; more distantly: A. thomasi Hendrix and Gore, 1973 [WA]. Alpheus arenensis differs only slightly from A. websteri and A. fagei, e.g., from A. websteri by the much smaller tooth on the merus of the major cheliped (see Kim and Abele, 1988); from A. fagei by the relatively longer ventrolateral tooth of the antennal basicerite (see Crosnier and Forest, 1966); and from both species by its color pattern (see comparison photos). Alpheus arenensis can be easily separated from A. rugimanus by the much shorter ventrolateral tooth of the antennal basicerite; from A. thomasi by the shorter rostrum and more robust minor cheliped; and from both A. rugimanus and A. thomasi by a clearly different color pattern (see comparison photos). 
SizeBody length to about 22 mm. 
Color PatternSee photo
Molecular BarcodeGenBank number EU339466
Major ReferencesChace, 1937 [original description, as Crangon arenensis]; Wicksten, 1983 [premature synonymy conclusions, records in Gulf of Mexico, as A. websteri]; Kim and Abele, 1988 [description of E Pacific material, illustrations, as A. websteri]; Villalobos, 2000 [records in Gulf of California, as A. websteri]; Williams et al., 2001 [confirmation of validity of two transisthmian species, position within Alpheus based on molecular data, as A. websteri]; Anker, Hurt and Knowlton, 2008a [precision of status, color photos, revision of A. websteri species complex]. 

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