The Diplostraca or Cladocera, commonly known as water fleas, are a
superorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
of small
crustacean
Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapoda, decapods, ostracoda, seed shrimp, branchiopoda, branchiopods, argulidae, fish lice, krill, remipedes, isopoda, isopods, barnacles, copepods, ...
s that feed on microscopic chunks of organic matter (excluding some predatory forms).
Over 1000 species have been recognised so far, with many more
undescribed.
The oldest fossils of diplostracans date to the
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
, though their modern morphology suggests that they originated substantially earlier, during the
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ...
. Some have also adapted to a life in the ocean, the only members of Branchiopoda to do so, even if several
anostracans live in
hypersaline lake
A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing that of ocean water (3.5%, i.e. ).
Specific microbial species can thrive in ...
s. Most are long, with a down-turned head with a single median
compound eye
A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...
, and a
carapace
A carapace is a 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 tortoises, the unde ...
covering the apparently unsegmented thorax and abdomen. Most species show cyclical
parthenogenesis
Parthenogenesis (; from the Greek grc, παρθένος, translit=parthénos, lit=virgin, label=none + grc, γένεσις, translit=génesis, lit=creation, label=none) is a natural form of asexual reproduction in which growth and developmen ...
, where
asexual reproduction
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the ...
is occasionally supplemented by
sexual reproduction
Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote th ...
, which produces resting eggs that allow the species to survive harsh conditions and disperse to distant habitats.
Description
They are mostly long, with the exception of ''
Leptodora'', which can be up to long.
The body is not obviously segmented and bears a folded
carapace
A carapace is a 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 tortoises, the unde ...
which covers the
thorax
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the c ...
and
abdomen
The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the to ...
.
The head is angled downwards, and may be separated from the rest of the body by a "cervical sinus" or notch.
It bears a single black compound eye, located on the animal's midline, in all but two genera, and often, a single
ocellus is present.
The head also bears two pairs of
antennae – the first antennae are small, unsegmented appendages, while the second antennae are large, segmented, and branched, with powerful muscles.
The first antennae bear olfactory
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. ...
e, while the second are used for swimming by most species.
The pattern of setae on the second antennae is useful for identification.
The part of the head which projects in front of the first antennae is known as the
rostrum or "beak".
The
mouthparts
Mouthparts may refer to:
* The parts of a mouth
** Arthropod mouthparts
The mouthparts of arthropods have evolved into a number of forms, each adapted to a different style or mode of feeding. Most mouthparts represent modified, paired append ...
are small, and consist of an unpaired labrum, a pair of mandibles, a pair of maxillae, and an unpaired labium.
They are used to eat "organic detritus of all kinds" and
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were am ...
.
The thorax bears five or six pairs of lobed, leaf-like appendages, each with numerous hairs or setae.
Carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is t ...
is lost, and
oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
taken up, through the body surface.
Lifecycle
With the exception of a few purely asexual species, the
lifecycle
Life cycle, life-cycle, or lifecycle may refer to:
Science and academia
*Biological life cycle, the sequence of life stages that an organism undergoes from birth to reproduction ending with the production of the offspring
*Life-cycle hypothesis, ...
of diplostracans is dominated by asexual reproduction, with occasional periods of sexual reproduction; this is known as
cyclical parthenogenesis.
When conditions are favourable, reproduction occurs by parthenogenesis for several generations, producing only female
clones. As the conditions deteriorate, males are produced, and sexual reproduction occurs. This results in the production of long-lasting dormant
eggs. These
ephippial
Ephippia (singular: ephippium) are winter or dry-season eggs of the various species of small crustacean in the order Cladocera (within the Branchiopoda); they are provided with an extra shell layer, which preserves and protects the resting ...
eggs can be transported over land by wind, and hatch when they reach favourable conditions, allowing many species to have very wide – even
cosmopolitan
Cosmopolitan may refer to:
Food and drink
* Cosmopolitan (cocktail), also known as a "Cosmo"
History
* Rootless cosmopolitan, a Soviet derogatory epithet during Joseph Stalin's anti-Semitic campaign of 1949–1953
Hotels and resorts
* Cosmopoli ...
–
distributions.
Except for the genus Leptodora, which has a
metanauplius
Metanauplius is an early larval stage of some crustaceans such as krill. It follows the nauplius stage.
In sac-spawning krill, there is an intermediary phase called pseudometanauplius, a newly hatched form distinguished from older metanauplii b ...
stage, a
nauplius larval stage is absent in Diplostraca.
Evolutionary history
Diplostraca are nested within the
clam shrimp, being most closely related to the order Cyclestherida, the only living genus of which is ''
Cyclestheria''. Though several fossils from the
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ...
have been claimed to represent fossils of diplostracans, none of these records can be confirmed. The oldest confirmed records of diplostracans are from the Early
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
of Asia. Fossils from the Jurassic are assignable to modern as well as extinct groups, indicating that the initial radiation of the group occurred prior to the beginning of the Jurassic, likely during the late
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ...
.
Ecology
Most diplostracan species live in
fresh water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does incl ...
and other inland water bodies, with only eight species being truly
oceanic.
The marine species are all in the family
Podonidae, except for the genus ''
Penilia''.
Some diplostracans inhabit leaf litter.
Taxonomy
According to the World Registry of Marine Species, Cladocera is a synonym of the superorder Diplostraca, which is included in the class
Branchiopoda. Both names are currently in use. The superorder forms a
monophyletic group
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, ...
of 7 orders, about 24 families, and more than 11,000 species. Many more species
remain undescribed.
[ ] The genus ''
Daphnia
''Daphnia'' is a genus of small planktonic crustaceans, in length. ''Daphnia'' are members of the order Anomopoda, and are one of the several small aquatic crustaceans commonly called water fleas because their saltatory swimming style resembl ...
'' alone contains around 150 species.
The following families are recognised:
Superorder Diplostraca
Gerstaecker, 1866 (=Cladocera)
: Order
Anomopoda G.O. Sars, 1865
:: Family
Acantholeberidae Smirnov, 1976
:: Family
Bosminidae Baird, 1845
:: Family
Chydoridae
Chydoridae is a family of water fleas in the order Anomopoda. There are more than 50 genera and 520 described species in Chydoridae.
Genera
These 52 genera belong to the family Chydoridae:
* '' Acroperus'' Baird, 1843
* '' Alona'' Baird, 1850
...
Dybowski & Grochowski, 1894
:: Family
Daphniidae Straus, 1820[
:: Family Dumontiidae Santos-Flores & Dodson, 2003
:: Family Eurycercidae Kurz, 1875
:: Family Gondwanothrichidae Van Damme, Shiel & Dumont, 2007][
:: Family Ilyocryptidae Smirnov, 1976
:: Family Macrothricidae Norman & Brady, 1867
:: Family ]Moinidae
Moinidae is a crustacean family within the order Cladocera. Species within this family are widely occurring, including North America and Africa. In newer classifications, it is sometimes included in the family Daphniidae
Daphniidae is a family ...
Goulden, 1968
:: Family Ophryoxidae Smirnov, 1976
: Order Ctenopoda G.O. Sars, 1865
:: Family Holopediidae G.O. Sars, 1865
:: Family Pseudopenilidae Korovchinsky & Sergeeva, 2008
:: Family Sididae Baird, 1850
: Order Cyclestherida Sars G.O., 1899
:: Family Cyclestheriidae Sars G.O., 1899
: Order Haplopoda G.O. Sars, 1865
:: Family Leptodoridae Lilljeborg, 1861
: Order Laevicaudata Linder, 1945
:: Family Lynceidae Stebbing, 1902
: Order Onychopoda G.O. Sars, 1865
:: Family Cercopagididae Mordukhai-Boltovskoi, 1968
:: Family Podonidae Mordukhai-Boltovskoi, 1968
:: Family Polyphemidae Baird, 1845
: Order Spinicaudata Linder, 1945
:: Family Cyzicidae
Cyzicidae is a family of crustaceans in the order Spinicaudata. They are distinguished from the family Leptestheriidae by the absence of a rostral spine. Some members of Cyzicidae are known to burrow through mud, leading to speculation that they ...
Stebbing, 1910
:: Family Eocyzicidae Schwentner, et al., 2020
:: Family Leptestheriidae Daday, 1913: 44
:: Family Limnadiidae
Limnadiidae is a family of crustaceans in the order Spinicaudata that live in seasonal wetlands, inland saline pools and lakes. They are found on all the world's continents except Antarctica, and are distinguished from other families in the same ...
Burmeister, 1843
Etymology
The word "Cladocera" derives via New Latin
New Latin (also called Neo-Latin or Modern Latin) is the revival of Literary Latin used in original, scholarly, and scientific works since about 1500. Modern scholarly and technical nomenclature, such as in zoological and botanical taxonomy ...
from the Ancient Greek
Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...
(', "branch") and (', "horn").
See also
*'' Bythotrephes longimanus'' (invasive species) ormerly known as ''Bythotrephes cederstroemi''- Spiny Water Flea[(April 16, 2013]
NorthAmericanFishing - "Silent Invaders" Spiny Water Flea PT 1 2013
/ref>
*'' Cercopagis pengoi'' (invasive species)
*'' Daphnia lumholtzi'' (invasive species)
*''Moina
''Moina'' is a genus of crustaceans within the family Moinidae. The genus was first described by W. Baird in 1850. They are referred to as water fleas, but are related to the much larger ''Daphnia magna'' and the larger ''Daphnia pulex''. Thi ...
'' (smallest)
*Zooplankton
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...
References
* Brusca, R.C.; Brusca, G.J. (1990). Invertebrates. Sinauer Associates: Sunderland, MA (USA). ISBN 0-87893-098-1. 922 pp
* Martin, J.W., & Davis, G.E. (2001). An updated classification of the recent Crustacea. Science Series, 39. Natural History Museum of Los Angeles County. Los Angeles, CA (USA). 124 pp.
*Norambuena, J., J. Farías & P. De los Ríos. (2019). he water flea ''Daphnia pulex'' (Cladocera, Daphniidae), a possible model organism to evaluate aspects of freshwater ecosystems. Crustaceana, (11-12): 1415-1426.
External links
Cladocera
– Guide to the Marine Zooplankton of South Eastern Australia
*
*
{{Taxonbar, from1=Q768012, from2=Q391240
Freshwater crustaceans
Crustacean orders