''Synalpheus microneptunus'' is a

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 ...

of small

snapping shrimp 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 ...

native to the waters off the island of

Barbados Barbados is an island country in the Lesser Antilles of the West Indies, in the Caribbean region of the Americas, and the most easterly of the Caribbean Islands. It occupies an area of and has a population of about 287,000 (2019 estimate). ...

. It is one of at least seven known species of

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 ...

shrimp. They are cryptofauna, living exclusively within the network of tunnels in the

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s '' Neopetrosia proxima'' and '' Neopetrosia subtriangularis''. They form small colonies of six to fifteen individuals, usually with only a single breeding female.

Taxonomy

''Synalpheus microneptunus'' belongs to the

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 ...

Synalpheus ''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 ...

'' of the snapping shrimp family,

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 ...

. It was first described by Kristin M. Hultgren, Kenneth S. MacDonald III, and J. Emmett Duffy in 2011, from specimens collected from the Cement Factory Reef off the northwest coast of the island of

. It is one of five closely related and morpholologically very similar species in the '' Synalpheus paraneptunus''

species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

. ''Synalpheus microneptunus'' can readily be distinguished from other members of the complex by the presence of four carpal segments on each of the second pair of walking legs (

pereopod 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) on both adult and juveniles. This is in contrast to the five segments present in other species of the ''S. paraneptunus'' complex. Their specific name is derived from their affinity to the ''Synalpheus paraneptunus'' complex and the fact that they are the smallest member of the group in terms of body size.

Description

''Synalpheus microneptunus'' are small shrimp, with a

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

length of only . The carapace is smooth with sparsely distributed bristles (setae). The posterior end of which has a distinct cardiac notch. The anterior spine of the carapace (

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ships * Ros ...

) is flanked by two slightly shorter and stouter blunt spines (the ocular hoods) directly covering the eyestalks. The body is more or less cylindrical in shape. The major first pereopod (the snapping claw) is very large, with the palm (carpus) more than twice as long as the fingers. The carpus has a small triangular spine on the outer and upper end, curving towards the movable finger (dactyl). The fixed finger is slightly shorter than the dactyl. The palm of the minor first pereopod (the feeding claw) is less than twice as long as it is wide, with the fingers shorter than the carpus. The dactyl is blade-like in shape with three teeth near the tip. The fixed finger is trowel-like in shape with a single tooth near the tip. The second to fifth pair of pereopods (the walking legs) are slender, progressively growing weaker towards the fifth pair. The second pair is distinctive for having four segments on the carpus. The

telson The telson () is the posterior-most division of the body of an arthropod. Depending on the definition, the telson is either considered to be the final segment of the arthropod body, or an additional division that is not a true segment on accou ...

has two groups of two spines on the outer edges of the posterior end. In between them are six bristles (setae). On the dorsal surface of the telson are two pairs of large spines situated far from the lateral edges, and separated from each other by 35% to 50% of the width of the telson. The

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 ...

s of 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 ...

s each have three teeth on the outer posterior margins, with a movable spine in between them, roughly in line with the central tooth. In life, ''Synalpheus microneptunus'' have pale nondescript coloration, with their extremities tipped by dull yellow-orange. The ovaries and embryos in breeding females are green.

Ecology

Like most members of the genus ''Synalpheus'' found in the western

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 ...

, ''Synalpheus microneptunus'' are exclusively associated with

sponges Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through ...

. They are cryptofaunal, being rarely seen by humans despite their relative abundance because they spend almost their entire lives within the complex network of tunnels of their

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

sponges, feeding on sponge tissue. ''Synalpheus microneptunus'' is one of at least seven known species of

shrimp. The only known marine animals to exhibit eusociality. ''Synalpheus microneptunus'' are only found in the sponges '' Neopetrosia proxima'' and '' Neopetrosia subtriangularis'', forming small colonies averaging at six individuals, with a maximum of fifteen individuals. The colonies usually have a single breeding female (the queen). The rest of the individuals in the colony (all of them close kin) are non-ovigerous "defenders", who cooperatively defend the queen and their nest from invaders (usually

conspecifics Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organis ...

or congeners). Like other

alpheid 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 ...

shrimps, they use specialized enlarged claws that when snapped can produce jets of water capable of stunning small animals.

Distribution

''Synalpheus microneptunus'' is only known from the waters off the island of

. In addition to the type locality, the Cement Factory Reef, additional individuals were also recovered from Brandon's beach, Breach Reef, and Spawnee Reef (all of which are off the western coast of the island).

References

{{Taxonbar, from=Q14432883 Alpheidae Crustaceans of the Atlantic Ocean Crustaceans described in 2011