Branchinecta gaini
Encyclopedia
Branchinecta gaini is a species of fairy shrimp
from Antarctica and Patagonia
. It is the largest freshwater invertebrate in Antarctica, at 16 mm (0.62992125984252 in) long. It lives on bacteria
and other organisms, surviving the winter as resting egg
s.
" northwards, including southernmost South America
and subantarctic islands such as South Georgia and the South Orkney Islands
. It is the only fairy shrimp on mainland Antarctica, where it is "rather widespread on the Antarctic Peninsula"; records of "Branchinecta granulosa" from Antarctica are all misidentifications of B. gaini. In the South Shetland Islands
, B. gaini has been recorded from the lakes on the ice-free Byers Peninsula
of Livingston Island (alongside Boeckella poppei and the benthic cladocera
n Macrothrix ciliata), in Lake Wujka, and in Sombre Lake
on Signy Island
(alongisde Boeckella poppei and the carnivorous Parabroteus sarsi).
The only known fossil
records of the genus Branchinecta
are of B. gaini; its eggs
have been found in mid to late Holocene
(4,200 BP
) lake deposits on James Ross Island
, on the east side of the Antarctic Peninsula. B. gaini no longer occurs on James Ross Island, presumably because the lakes are unfrozen for too short a period for B. gaini to complete its life cycle
. The egg cases were found to be most abundant during the Holocene climatic optimum
, indicating that cyanobacterial mats
must have been present in the lake then. Eggs dating from 5,500 BP have also been found on Signy Island
, where the species persists.
s in bacterial mats, and on the mats themselves. The gut contents of B. gaini are dominated by green algae
, hyphae and remains of other B. gaini individuals. They live for over six months, and produce resting eggs which can survive the winter, when the lakes are frozen. Although B. gaini often coexists with the copepod Boeckella poppei, they are rarely seen in close contact. They may be in competition
for food, or B. gaini may feed on the nauplii of the copepod.
B. gaini can be quite abundant, dominating the crustacean biomass
in freshwater bodies in the South Orkney
and South Shetland
islands.
The dispersal
of B. gaini between lake
s is probably passive, with the most likely dispersal vectors being birds; branchiopod eggs swallowed by seabird
s, even if still being brooded by the mother, can survive passage through the bird's digestive system.
by the Hungarian biologist Eugen von Daday de Deés (also called Jenö Daday or Jenö Daday de Dées) in 1910 based on material collected from Petermann Island
by the aboard the Pourquoi Pas ?, captained by Jean-Baptiste Charcot; the specific epithet commemorates the French algologist Louis Gain, who was responsible for preserving the specimens from that expedition.
Fairy shrimp
Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are also known as fairy shrimp. They are usually long . Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia , and the body lacks a carapace...
from Antarctica and Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
. It is the largest freshwater invertebrate in Antarctica, at 16 mm (0.62992125984252 in) long. It lives on bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and other organisms, surviving the winter as resting egg
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
s.
Distribution
B. gaini is found from "half-way down the Antarctic PeninsulaAntarctic Peninsula
The Antarctic Peninsula is the northernmost part of the mainland of Antarctica. It extends from a line between Cape Adams and a point on the mainland south of Eklund Islands....
" northwards, including southernmost South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
and subantarctic islands such as South Georgia and the South Orkney Islands
South Orkney Islands
The South Orkney Islands are a group of islands in the Southern Ocean, about north-east of the tip of the Antarctic Peninsula. They have a total area of about ....
. It is the only fairy shrimp on mainland Antarctica, where it is "rather widespread on the Antarctic Peninsula"; records of "Branchinecta granulosa" from Antarctica are all misidentifications of B. gaini. In the South Shetland Islands
South Shetland Islands
The South Shetland Islands are a group of Antarctic islands, lying about north of the Antarctic Peninsula, with a total area of . By the Antarctic Treaty of 1959, the Islands' sovereignty is neither recognized nor disputed by the signatories and they are free for use by any signatory for...
, B. gaini has been recorded from the lakes on the ice-free Byers Peninsula
Byers Peninsula
Byers Peninsula is a mainly ice-free peninsula forming the west end of Livingston Island in the South Shetland Islands. It occupies , and includes the small freshwater Basalt Lake. The area was visited by early 19th century American and British sealers who came almost exclusively from New England,...
of Livingston Island (alongside Boeckella poppei and the benthic cladocera
Cladocera
Cladocera is an order of small crustaceans commonly called water fleas. Around 620 species have been recognised so far, with many more undescribed. They are ubiquitous in inland aquatic habitats, but rare in the oceans. Most are long, with a down-turned head, and a carapace covering the apparently...
n Macrothrix ciliata), in Lake Wujka, and in Sombre Lake
Sombre Lake
Sombre Lake is the northernmost lake in Paternoster Valley in northern Signy Island. So named by United Kingdom Antarctic Place-Names Committee because of the sombre setting of the lake and the proximity of Stygian Cove....
on Signy Island
Signy Island
Signy Island is a small sub-antarctic island in the South Orkney Islands group locted at . It is about long and wide and rises to above sea level. Much of the island is permanently covered with ice. The average temperature range is to about in winter...
(alongisde Boeckella poppei and the carnivorous Parabroteus sarsi).
The only known fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
records of the genus Branchinecta
Branchinecta
Branchinecta is a genus of crustacean in family Branchinectidae. It includes around 50 species, found on all continents except Africa and Australia...
are of B. gaini; its eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
have been found in mid to late Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
(4,200 BP
Before Present
Before Present years is a time scale used in archaeology, geology, and other scientific disciplines to specify when events in the past occurred. Because the "present" time changes, standard practice is to use AD 1950 as the origin of the age scale, reflecting the fact that radiocarbon...
) lake deposits on James Ross Island
James Ross Island
James Ross Island is a large island off the southeast side and near the northeastern extremity of Antarctic Peninsula, from which it is separated by Prince Gustav Channel. Rising to , it is irregularly shaped and extends in a north-south direction. It was charted in October 1903 by the Swedish...
, on the east side of the Antarctic Peninsula. B. gaini no longer occurs on James Ross Island, presumably because the lakes are unfrozen for too short a period for B. gaini to complete its life cycle
Biological life cycle
A life cycle is a period involving all different generations of a species succeeding each other through means of reproduction, whether through asexual reproduction or sexual reproduction...
. The egg cases were found to be most abundant during the Holocene climatic optimum
Holocene climatic optimum
The Holocene Climate Optimum was a warm period during roughly the interval 9,000 to 5,000 years B.P.. This event has also been known by many other names, including: Hypsithermal, Altithermal, Climatic Optimum, Holocene Optimum, Holocene Thermal Maximum, and Holocene Megathermal.This warm period...
, indicating that cyanobacterial mats
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
must have been present in the lake then. Eggs dating from 5,500 BP have also been found on Signy Island
Signy Island
Signy Island is a small sub-antarctic island in the South Orkney Islands group locted at . It is about long and wide and rises to above sea level. Much of the island is permanently covered with ice. The average temperature range is to about in winter...
, where the species persists.
Description
Branchinecta gaini can reach a total length of 16 millimetre (0.62992125984252 in), making it the largest freshwater invertebrate in Antarctica. It uses its trunk limbs to scrape food from the substrate.Ecology and life cycle
Branchinecta gaini feeds on epiphyteEpiphyte
An epiphyte is a plant that grows upon another plant non-parasitically or sometimes upon some other object , derives its moisture and nutrients from the air and rain and sometimes from debris accumulating around it, and is found in the temperate zone and in the...
s in bacterial mats, and on the mats themselves. The gut contents of B. gaini are dominated by green algae
Green algae
The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic...
, hyphae and remains of other B. gaini individuals. They live for over six months, and produce resting eggs which can survive the winter, when the lakes are frozen. Although B. gaini often coexists with the copepod Boeckella poppei, they are rarely seen in close contact. They may be in competition
Competition (biology)
Competition is an interaction between organisms or species, in which the fitness of one is lowered by the presence of another. Limited supply of at least one resource used by both is required. Competition both within and between species is an important topic in ecology, especially community ecology...
for food, or B. gaini may feed on the nauplii of the copepod.
B. gaini can be quite abundant, dominating the crustacean biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
in freshwater bodies in the South Orkney
South Orkney Islands
The South Orkney Islands are a group of islands in the Southern Ocean, about north-east of the tip of the Antarctic Peninsula. They have a total area of about ....
and South Shetland
South Shetland Islands
The South Shetland Islands are a group of Antarctic islands, lying about north of the Antarctic Peninsula, with a total area of . By the Antarctic Treaty of 1959, the Islands' sovereignty is neither recognized nor disputed by the signatories and they are free for use by any signatory for...
islands.
The dispersal
Biological dispersal
Biological dispersal refers to species movement away from an existing population or away from the parent organism. Through simply moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but also for population dynamics, population...
of B. gaini between lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
s is probably passive, with the most likely dispersal vectors being birds; branchiopod eggs swallowed by seabird
Seabird
Seabirds are birds that have adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations...
s, even if still being brooded by the mother, can survive passage through the bird's digestive system.
Taxonomic history
Branchinecta gaini was first describedAlpha taxonomy
Alpha taxonomy is the discipline concerned with finding, describing and naming species of living or fossil organisms. This field is supported by institutions holding collections of these organisms, with relevant data, carefully curated: such institutes include natural history museums, herbaria and...
by the Hungarian biologist Eugen von Daday de Deés (also called Jenö Daday or Jenö Daday de Dées) in 1910 based on material collected from Petermann Island
Petermann Island
Petermann Island is a small island just off the west side of the Antarctic Peninsula of Antarctica, located at , just a short distance south of Booth Island and the Lemaire Channel...
by the aboard the Pourquoi Pas ?, captained by Jean-Baptiste Charcot; the specific epithet commemorates the French algologist Louis Gain, who was responsible for preserving the specimens from that expedition.