''Synalpheus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of snapping shrimp of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Alpheidae Alpheidae (also known as the snapping shrimp, pistol shrimp or alpheid shrimp) is a family (biology), family within the shrimp infraorder Caridea characterized by having asymmetrical claws, the larger of which is typically capable of producing a ...

, presently containing more than 160

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

; new ones are described on a regular basis, and the exact number even of described species is disputed.

Taxonomy

Although the genus ''Zuzalpheus'' was proposed for ''S. gambarelloides'', ''S. brooksi'', and their closest relatives, this has not been adopted and is not considered a monophyletic clade within the genus ''Synalpheus''. Over 160 species are recognised in the genus ''Synalpheus''. For a complete listing, see List of ''Synalpheus'' species.

Distribution

In the narrower sense, ''Synalpheus'' occur in the eastern Pacific where they are most plentiful and probably originated, and to a lesser extent in the Atlantic and the Indian Ocean; the species placed in ''Zuzalpheus'' occur mainly in the western Atlantic where their lineage probably originated, and to a lesser extent in the eastern Atlantic and Indian Ocean, and the eastern Pacific. It may thus be that the closure of the

Isthmus of Panama The Isthmus of Panama, historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific Ocean, linking North America, North and South America. The country of Panama is located on the i ...

in the

Piacenzian The Piacenzian is in the international geologic time scale the upper stage (stratigraphy), stage or latest age (geology), age of the Pliocene. It spans the time between 3.6 ± 0.005 year#SI prefix multipliers, Ma and 2.58 Ma (million years ago). T ...

(about 3 million years ago) was a key factor in separating the two lineages, as species referred to ''Synalpheus sensu stricto'' are most plentiful in the western Pacific.

Behaviour and ecology

Snapping

The snapping behaviour of ''Synalpheus'' is rather well studied. In ''Synalpheus parneomeris'',

peak to peak The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...

source levels of 185–190 dB re 1 μPa at 1 m were measured, depending on the size of the claw.

Eusociality

The only known

eusocial Eusociality ( Greek 'good' and social) is the highest level of organization of sociality. It is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations wit ...

aquatic species occur within the genus ''Synalpheus''. The species known to be eusocial are ''S. brooksi'', ''S. chacei'', ''S. elizabethae'', ''S. filidigitus'', ''S. rathbunae'', ''S. regalis'', ''S. microneptunus'', and ''S. duffyi'' as well as potentially ''S. riosi''. Eusociality has evolved at least three times within ''Synalpheus''. It appears that there were multiple rapid radiations between 3 and 9 mya from which the ancestors of these eusocial species appeared. Eusociality is thought to have arisen due to competition for space, because among the species that host ''Synalpheus'', empty sponges are rarely found. It also appears that

kin selection Kin selection is a process whereby natural selection favours a trait due to its positive effects on the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin selection can lead ...

was necessary for this evolution to occur because the only species in which eusociality has appeared are non-dispersing shrimp that hatch directly into crawling individuals. Until recently, eusocial species of ''Synalpheus'' have appeared in far greater abundance than, and appear to outcompete, less social species for space in sponges.

References

External links

{{Authority control Alpheidae Decapod genera Taxa named by Charles Spence Bate