''Synalpheus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of snapping shrimp of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Alpheidae Alpheidae is a family of caridean snapping shrimp, characterized by having asymmetrical claws, the larger of which is typically capable of producing a loud snapping sound. Other common names for animals in the group are pistol shrimp or alpheid s ...

, presently containing more than 100

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

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

''Zuzalpheus''

The genus ''Zuzalpheus'' was established for ''S. gambarelloides'', ''S. brooksi'', and their closest relatives, which contain several notably

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

species. While these do seem to form a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

, it is not fully resolved whether or not they are indeed the

sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

of all the remaining ''Synalpheus''. However, a detailed

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups (" clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

study of morphological characters found well marked differences between the proposed two genera and concluded that the supposed species groups around ''S. biunguiculatus''/''S. coutierei'', ''S. brevicarpus'' and ''S. neomeris'' are neither clearly defined nor, as it seems,

monophyletic In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...

, while the group separated in ''Zuzalpheus'' was clearly distinct in characters of the minor first walking legs (

pereiopod The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). Each segment may possess one pair of appendages, although in various g ...

s), and usually distinct in some others; in all ''Synalpheus sensu stricto'' checked to date, the transverse

seta In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. Th ...

l comb on the back of the minor first pereopod

dactyl Dactyl may refer to: * Dactyl (mythology), a legendary being * Dactyl (poetry), a metrical unit of verse * Dactyl Foundation, an arts organization * Finger, a part of the hand * Dactylus, part of a decapod crustacean * "-dactyl", a suffix used ...

is missing, and the

carpus In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...

is plump (about as wide as it is long or slightly wider) and small (not longer than half the length of the palm). Moreover, their stylocerite clearly extends beyond the whole first segment of the first

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

e, their scaphocerite blade is never missing, the fixed finger of the major first pereopod is about the same length as the dactyl and the

uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

exopod The arthropod leg is a form of jointed appendage of arthropods, usually used for walking. Many of the terms used for arthropod leg segments (called podomeres) are of Latin origin, and may be confused with terms for bones: ''coxa'' (meaning hip, plur ...

always has one tooth only; these traits however may be also present in some of the species separated in ''Zuzalpheus'' though as far as can be told, most of these differ. While the authors of the 2008 analysis made no explicit comment on the status of the newly proposed genus, they thus found the ''S. gambarelloides'' species group to be well-marked, and their results certainly harden the case for recognition of ''Zuzalpheus'' at least as a subgenus. However, this analysis only included 2 species from the ''S. gambarelloides'' species group, and none from the Caribbean, where the vast majority of the group resides. Opinion is still divided, however, and recently ''Zuzalpheus'' was synonymised with ''Synalpheus''.

Distribution

In the narrower sense, ''Synalpheus'' occur in the

East Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

where they are most plentiful and probably originated, and to a lesser extent in the

Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...

and the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by th ...

; the species placed in ''Zuzalpheus'' occur mainly in the western

where their lineage probably originated, and to a lesser extent in the eastern Atlantic and

, and the

. It may thus be that the closure of the

Isthmus of Panama The Isthmus of Panama ( es, Istmo de Panamá), also 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 and South America. It contains the country ...

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 2.588 ± 0.005 Ma (million yea ...

(about 3

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (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.

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

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 the evolutionary strategy that favours the reproductive success of an organism's relatives, even when at a cost to the organism's own survival and reproduction. Kin altruism can look like Altruism in animals, altruistic behavio ...

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.

Species

''Synalpheus'' contains the following species: *'' Synalpheus agelas'' Pequegnat & Heard, 1979 *'' Synalpheus albatrossi'' Coutière, 1909 *'' Synalpheus amabilis'' De Man, 1910 *'' Synalpheus anasimus'' Chace, 1972 *'' Synalpheus anceps'' Banner, 1956 *'' Synalpheus ancistrorhynchus'' De Man, 1909 *'' Synalpheus androsi'' Coutière, 1909 *'' Synalpheus antenor'' De Man, 1910 *'' Synalpheus arostris'' Wicksten, 1989 *'' Synalpheus bannerorum'' Abele, 1975 *'' Synalpheus barahonensis'' Armstrong, 1949 *'' Synalpheus belizensis'' Anker & Tóth, 2008 *'' Synalpheus bispinosus'' De Man, 1910 *'' Synalpheus bituberculatus'' De Man, 1910 *'' Synalpheus biunguiculatus'' (Stimpson, 1860) *'' Synalpheus bocas'' Anker & Tóth, 2008 *'' Synalpheus bousfieldi'' Chace, 1972 *'' Synalpheus bradleyi'' Verrill, 1922 *'' Synalpheus brevicarpus'' (Herrick, 1891) *'' Synalpheus brevidactylus'' Anker & Tóth, 2008 *'' Synalpheus brevifrons'' Chace, 1972 *'' Synalpheus brevispinis'' Coutière, 1909 *'' Synalpheus brooksi'' Coutière, 1909 *'' Synalpheus carinatus'' (De Man, 1888) *'' Synalpheus carpenteri'' MacDonald & Duffy, 2006 *'' Synalpheus chacei'' Duffy, 1998 *'' Synalpheus charon'' (Heller, 1861) *'' Synalpheus comatularum'' (Haswell, 1882) *'' Synalpheus corallinus'' MacDonald, Hultgren & Duffy, 2009 *'' Synalpheus coutierei'' Banner, 1953 *'' Synalpheus cretoculatus'' Banner & Banner, 1979 *'' Synalpheus crosnieri'' Banner & Banner, 1983 *'' Synalpheus curacaoensis'' Schmitt, 1924 *'' Synalpheus dardeaui'' (Ríos & Duffy, 2007) *'' Synalpheus demani'' Borradaile, 1900 *'' Synalpheus digueti'' Coutière, 1909 *'' Synalpheus disparodigitus'' Armstrong, 1949 *'' Synalpheus dominicensis'' Armstrong, 1949 *'' Synalpheus dorae'' Bruce, 1988 *''

Synalpheus duffyi ''Synalpheus'' is a genus of snapping shrimp of the family Alpheidae, presently containing more than 100 species; new ones are described on a regular basis, and the exact number even of described species is disputed. ''Zuzalpheus'' The genus ''Z ...

'' Anker & Tóth, 2008 *'' Synalpheus echinus'' Banner & Banner, 1975 *''

Synalpheus elizabethae ''Synalpheus'' is a genus of snapping shrimp of the family Alpheidae, presently containing more than 100 species; new ones are described on a regular basis, and the exact number even of described species is disputed. ''Zuzalpheus'' The genus ''Z ...

'' (Ríos & Duffy, 2007) *''

Synalpheus filidigitus ''Synalpheus'' is a genus of snapping shrimp of the family Alpheidae, presently containing more than 100 species; new ones are described on a regular basis, and the exact number even of described species is disputed. ''Zuzalpheus'' The genus ''Z ...

'' Armstrong, 1949 *'' Synalpheus fossor'' (Paul'son, 1875) *''

Synalpheus fritzmuelleri ''Synalpheus'' is a genus of snapping shrimp of the family Alpheidae, presently containing more than 100 species; new ones are described on a regular basis, and the exact number even of described species is disputed. ''Zuzalpheus'' The genus ''Z ...

'' Coutière, 1909 *'' Synalpheus gambarelloides'' (Nardo, 1847) *'' Synalpheus goodei'' Coutière, 1909 *'' Synalpheus gracilirostris'' De Man, 1910 *'' Synalpheus haddoni'' Coutière, 1900 *'' Synalpheus harpagatrus'' Banner & Banner, 1975 *'' Synalpheus hastilicrassus'' Coutière, 1905 *'' Synalpheus heardi'' Dardeau, 1984 *'' Synalpheus hemphilli'' Coutière, 1909 *'' Synalpheus herdmaniae'' Lebour, 1938 *'' Synalpheus heroni'' Coutière, 1909 *'' Synalpheus herricki'' Coutière, 1909 *'' Synalpheus hilarulus'' De Man, 1910 *'' Synalpheus hoetjesi'' Hultgren, MacDonald & Duffy, 2010 *'' Synalpheus idios'' (Ríos & Duffy, 2007) *'' Synalpheus iocasta'' De Man, 1909 *'' Synalpheus iphinoe'' De Man, 1909 *'' Synalpheus irie'' MacDonald, Hultgren & Duffy, 2009 *'' Synalpheus jedanensis'' De Man, 1909 *'' Synalpheus kensleyi'' (Ríos & Duffy, 2007) *'' Synalpheus kuadramanus'' Hultgren, MacDonald & Duffy, 2010 *'' Synalpheus kusaiensis'' Kubo, 1940 *'' Synalpheus laevimanus'' *'' Synalpheus lani'' Hermoso & Alvarez, 2005 *'' Synalpheus laticeps'' Coutière, 1905 *'' Synalpheus lockingtoni'' Coutière, 1909 *'' Synalpheus longicarpus'' (Herrick, 1891) *'' Synalpheus lophodactylus'' Coutière, 1908 *'' Synalpheus macromanus'' Edmondson, 1925 *'' Synalpheus mcclendoni'' Coutière, 1910 *'' Synalpheus merospiniger'' Coutière, 1908 *'' Synalpheus mexicanus'' Coutière, 1909 *'' Synalpheus microneptunus'' Hultgren, MacDonald & Duffy, 2011 *'' Synalpheus minus'' (Say, 1818) *'' Synalpheus modestus'' De Man, 1909 *'' Synalpheus mortenseni'' Banner & Banner, 1985 *'' Synalpheus mulegensis'' Ríos, 1992 *'' Synalpheus mushaensis'' Coutière, 1908 *'' Synalpheus neomeris'' (De Man, 1897) *'' Synalpheus nilandensis'' Coutière, 1905 *'' Synalpheus nobilii'' Coutière, 1909 *'' Synalpheus obtusifrons'' Chace, 1972 *'' Synalpheus occidentalis'' Coutière, 1909 *'' Synalpheus odontophorus'' De Man, 1909 *'' Synalpheus orapilosus'' Hultgren, MacDonald & Duffy, 2010 *'' Synalpheus osburni'' Schmitt, 1933 *'' Synalpheus otiosus'' Coutière, 1908 *'' Synalpheus pachymeris'' Coutière, 1905 *'' Synalpheus pandionis'' Coutière, 1909 *'' Synalpheus paradoxus'' Banner & Banner, 1981 *'' Synalpheus paralaticeps'' Banner & Banner, 1982 *'' Synalpheus paraneomeris'' Coutière, 1905 *'' Synalpheus paraneptunus'' Coutière, 1909 *'' Synalpheus parfaiti'' (Coutière, 1898) *'' Synalpheus paulsonoides'' Coutière, 1909 *'' Synalpheus pectiniger'' Coutière, 1907 *'' Synalpheus peruvianus'' Rathbun, 1910 *'' Synalpheus pescadorensis'' Coutière, 1905 *'' Synalpheus pinkfloydi'' De Grave, 2017 *'' Synalpheus plumosetosus'' MacDonald, Hultgren & Duffy, 2009 *'' Synalpheus pococki'' Coutière, 1898 *'' Synalpheus quadriarticulatus'' Banner & Banner, 1975 *'' Synalpheus quadrispinosus'' De Man, 1910 *'' Synalpheus quinquedens'' Tattersall, 1921 *'' Synalpheus rathbunae'' Coutière, 1909 *'' Synalpheus readi'' Banner & Banner, 1972 *'' Synalpheus recessus'' Abele & W. Kim, 1989 *'' Synalpheus redactocarpus'' Banner, 1953 *''

Synalpheus regalis ''Synalpheus regalis'' is a species of snapping shrimp that commonly live in sponges in the coral reefs along the tropical West Atlantic. They form a prominent component of the diverse marine cryptofauna of the region. For the span of their en ...

'' Duffy, 1996 *'' Synalpheus riosi'' Anker & Tóth, 2008 *'' Synalpheus ruetzleri'' MacDonald & Duffy, 2006 *'' Synalpheus sanctithomae'' Coutière, 1909 *'' Synalpheus sanjosei'' Coutière, 1909 *'' Synalpheus sanlucasi'' Coutière, 1909 *'' Synalpheus scaphoceris'' Coutière, 1910 *''Synalpheus sciro'' Banner & Banner, 1975 *''Synalpheus senegambiensis'' Coutière, 1908 *''Synalpheus septemspinosus'' De Man, 1910 *''Synalpheus sladeni'' Coutière, 1908 *''Synalpheus somalia'' Banner & Banner, 1979 *''Synalpheus spinifrons'' (H. Milne-Edwards, 1837) *''Synalpheus spiniger'' (Stimpson, 1860) *''Synalpheus spongicola'' Banner & Banner, 1981 *''Synalpheus stimpsonii'' (De Man, 1888) *''Synalpheus streptodactylus'' Coutière, 1905 *''Synalpheus stylopleuron'' Hermoso Salazar & Hendrickx, 2006 *''Synalpheus superus'' Abele & W. Kim, 1989 *''Synalpheus tenuispina'' Coutière, 1909 *''Synalpheus thai'' Banner & Banner, 1966 *''Synalpheus theano'' De Man, 1910 *''Synalpheus thele'' MacDonald, Hultgren & Duffy, 2009 *''Synalpheus tijou'' Banner & Banner, 1982 *''Synalpheus townsendi'' Coutière, 1909 *''Synalpheus triacanthus'' De Man, 1910 *''Synalpheus tricuspidatus'' (Heller, 1861) *''Synalpheus tridentulatus'' (Dana, 1852) *''Synalpheus trispinosus'' De Man, 1910 *''Synalpheus triunguiculatus'' (Paul'son, 1875) *''Synalpheus tropidodactylus'' Banner & Banner, 1975 *''Synalpheus tuthilli'' Banner, 1959 *''Synalpheus ul'' (Ríos & Duffy, 2007) *''Synalpheus wickstenae'' Hermoso Salazar & Hendrickx, 2006 *''Synalpheus williamsi'' Ríos & Duffy, 1999 *''Synalpheus yano'' (Ríos & Duffy, 2007)

References

External links

{{Taxonbar, from=Q3934246 Alpheidae Decapod genera Taxa named by Charles Spence Bate