| Branchinecta gaini | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Branchiopoda |
| Order: | Anostraca |
| Family: | Branchinectidae |
| Genus: | Branchinecta |
| Species: | B. gaini |
| Binomial name | |
| Branchinecta gaini | |
Branchinecta gaini is a species offairy shrimp fromAntarctica andPatagonia. It is the largest freshwater invertebrate in Antarctica, at 16 mm (0.63 in) long. It lives onbacteria and other organisms, surviving the winter as restingeggs.
Branchinecta gaini is found from "half-way down theAntarctic Peninsula" northwards, including southernmostSouth America andsubantarctic islands such asSouth Georgia and theSouth Orkney Islands.[2] It is the only fairy shrimp on mainland Antarctica, where it is "rather widespread on the Antarctic Peninsula";[3] records of "Branchinecta granulosa" from Antarctica are all misidentifications ofB. gaini.[4] In theSouth Shetland Islands,B. gaini has been recorded from the lakes on the ice-freeByers Peninsula ofLivingston Island (alongsideBoeckella poppei and the benthiccladoceranMacrothrix ciliata),[5] inLake Wujka, and inSombre Lake onSigny Island (alongsideBoeckella poppei and the carnivorousParabroteus sarsi).[6]
The only knownfossil records of the genusBranchinecta are ofB. gaini; itseggs have been found in mid to lateHolocene (4,200BP)[7] lake deposits onJames Ross Island, on the east side of the Antarctic Peninsula.[8]B. gaini no longer occurs on James Ross Island, presumably because the lakes are unfrozen for too short a period forB. gaini to complete itslife cycle.[8] The egg cases were found to be most abundant during theHolocene climatic optimum, indicating thatcyanobacterialmats must have been present in the lake then.[9] Eggs dating from 5,500 BP have also been found onSigny Island, where the species persists.[7]
Branchinecta gaini can reach a total length of 16 millimetres (0.63 in), making it the largest freshwater invertebrate inAntarctica.[10] It uses its trunk limbs to scrape food from the substrate.[11]
Branchinecta gaini feeds onepiphytes in bacterial mats, and on the mats themselves.[9] The gut contents ofB. gaini are dominated bygreen algae,hyphae and remains of otherB. gaini individuals.[11] They live for over six months, and produce resting eggs which can survive the winter, when the lakes are frozen.[12] AlthoughB. gaini often coexists with the copepodBoeckella poppei, they are rarely seen in close contact. They may be incompetition for food, orB. gaini may feed on thenauplii of the copepod.[12]
Branchinecta gaini can be quite abundant, dominating the crustaceanbiomass in freshwater bodies in theSouth Orkney andSouth Shetland islands.[11]
Thedispersal ofB. gaini betweenlakes is probably passive, with the most likelydispersal vectors being birds; branchiopod eggs swallowed byseabirds, even if still being brooded by the mother, can survive passage through the bird's digestive system.[2]
Branchinecta gaini wasfirst described by the Hungarian biologistEugen von Daday de Deés (also called Jenö Daday or Jenö Daday de Dées) in 1910 based on material collected fromPetermann Island by theDeuxième Expédition Antarctique Française aboard thePourquoi Pas ?, captained byJean-Baptiste Charcot;[1] thespecific epithet commemorates the French algologistLouis Gain, who was responsible for preserving the specimens from that expedition.[13]