What is Daphnia
Common daphnia is a small crustacean. Thanks to its movement in sharp jerks, it received a second name - water flea.
Depending on the type, sizes can range from 0.2 mm to 6 mm. Large species reach the size of a small pea and can be seen without a microscope.
When magnified, the structure of the crustacean is clearly visible. The body of daphnia is slightly flattened on the sides and has an oval shape. On top it is dressed in a bicuspid leathery shell - the carapace, which ends in a tail needle and protects the internal organs.
Head
The head is covered with a hard chitinous covering. On it there is a beak-like outgrowth - the rostrum, under which there are short anterior antennae - antennules, which perform an olfactory function thanks to the short outgrowths with olfactory setae located on them. The posterior antennae are longer and covered with projections. They help daphnia move through the water column by making leaps.
Crustaceans have five pairs of legs of a complex structure. The thoracic legs of daphnia perform the main functions of respiration and nutrition. They are located on the head. Within one minute, the crustacean makes up to 500 strokes, passing through itself unicellular algae and bacteria suspended in the water. On the limbs there are gill sacs, which are filled with oxygen when they move.
Organ of vision
Daphnia have a paired organ of vision, which is double in mature individuals. Large compound eye, consists of 22 facets. In some species the number of facets can reach three hundred. Below the compound eye is the nauplial ocellus.
When magnifying the daphnia, the internal organs are clearly visible in the photo. The intestinal canal extends from the mouth opening. On the back side there is a pulsating heart. In females, between the body and the dorsal shell there is a brood chamber in which the eggs are located.
Parasites[edit]
Life cycle of Pasteuria ramosa,
bacterial parasite of the cladoceran
Daphnia magna
.
The diagram on the left shows the life cycle of Pasteuria ramosa,
bacterial parasite
of Daphnia
. Susceptible hosts become infected from spores in sediment or suspension. The parasite develops primarily in the body cavity and muscle tissue of the host, increasing in density and eventually expanding to occupy the entire host. Typical consequences for the owner are infertility and gigantism. The spores are released mainly after the host dies and sinks to the ground, and sometimes directly into the water by a lumbering predator.
Daphnia magna
infected with
Pasteuria ramosa
Places and living conditions
These cladocerans can be found in all ponds and lakes in different parts of the world.
Character and lifestyle
Large accumulations of crustaceans are observed in temporary reservoirs - ditches, puddles, small lakes with stagnant water. Getting into water even with a weak current, daphnia filter suspended particles of soil and clog the intestines. This makes it difficult for them to move and causes their death.
Crayfish spend most of their lives in the water column. Some species, filtering water, feed on microscopic algae, while others live near the bottom and eat dead particles of plants and invertebrates. Some varieties, halophiles, easily tolerate drought by hibernating.
These creatures are very voracious. The daily volume of food consumed can reach 600% of their own weight. Daphnia's main diet consists of bacteria, yeast and blue-green algae. The largest concentrations of crustaceans are observed in reservoirs with “blooming” water, where they reproduce especially intensively.
Daphnia reacts sharply to lighting. In bright light, it tries to stay closer to the bottom of the reservoir.
Systematics and evolution[edit]
Main article: List of Daphnia species
Daphnia
are a large genus—including more than 200 species—belonging to the Cladoceran family of Daphnia.
[1] It is divided into several subgenera ( Daphnia
,
Australodaphnia
,
Ctenodaphnia
), but this division has been controversial and is still under development. Each subgenus has been further divided into a number of species complexes. Understanding species boundaries is hampered by phenotypic plasticity, hybridization, intercontinental introductions, and poor taxonomic descriptions. [6] [7] [8]
Appearance
Sex differences
Under favorable conditions, daphnia do not have males. Females give birth to their own kind. When conditions change, some females give birth to males.
Female and male individuals have some differences in external and internal structure:
- females are larger in size;
- on the head shield and outer cover of females there is a pattern of rhombuses and polygons, which is clearly visible when magnified;
- The first and second pairs of legs in males have hook-shaped projections that allow them to cling to females during mating.
Subspecies
About 150 species of these crustaceans live in natural conditions . Very often, several dozen species of crustaceans live in one body of water.
Daphnia magna
This variety is used as live food for aquarium fish due to its high nutritional value. The body length of the female is 3-5 mm, the male – no more than 2 mm. Newborns are microscopic in size. The main color of the outer cover is yellow or pinkish-orange. This species easily tolerates low temperatures. It is quite rare in nature, but in permanent habitats it is found in abundance. The lifespan of adult specimens is 3 months.
Daphnia pulex
The length of an adult female does not exceed 4 mm, a male – 1.5 mm. The color of the outer covers varies from light yellow to red. Externally, the crustaceans resemble Daphnia magna. The difference lies in their smaller size and life expectancy, which does not exceed one and a half months. The variety is characterized by incredible fertility. Females lay eggs every five days. Each clutch consists of 15 eggs.
Links[edit]
- ^ ab A. Kotov; L. Forro; N.M. Korovchinsky; A. Petrusek (March 2, 2012). "Checklist of Crustaceans-Cladocera" (PDF). World List of Freshwater Species of Cladocera
. Belgian Biodiversity Platform. Retrieved October 29, 2012. - NNSmirnov (2014). Physiology of Cladocera
. Amsterdam: Academic Press. - ^ B s d e g Dieter Ebert (2005). "Introduction to the biology of Daphnia
". Ecology, epidemiology and evolution of parasitism in Daphnia. Bethesda, MD: National Center for Biotechnology Information. ISBN 978-1-932811-06-3. - ^ abcdef "Daphnia". Oneida Lake Education Initiative
. Stony Brook University. Retrieved October 9, 2013. - van Bergen, Ifke (2004). “DAPHNIA BREATHES EASILY.” biology.org
. Retrieved April 11, 2022. - Niles Lehman; Michael E. Pfrender; Philip A. Morin; Teresa J. Crisis; Michael Lynch (1995). "Hierarchical molecular phylogeny within the genus Daphnia
".
Molecular phylogenetics and evolution
.
4
(4): 395–407. DOI: 10.1006/mpev.1995.1037. PMID 8747296. - Derek J. Taylor; Paul D. N. Hebert; John C. Colborne (1996). "Phylogenetics and evolution of the Daphnia longispina group (Crustacea) based on 12S rDNA sequence and allozyme variation" (PDF). Molecular phylogenetics and evolution
.
5
(3): 495–510. DOI: 10.1006/mpev.1996.0045. PMID 8744763. Archived from the original (PDF) on April 18, 2007. - Sarah J. Adamowicz; Paul D. N. Hebert; Maria Cristina Marinone (2004). "Species diversity and endemism of Daphnia of Argentina: a genetic study". Zoological Journal of the Linnean Society
.
140
(2):171–205. DOI: 10.1111/j.1096-3642.2003.00089.x. - ^ ab Barbara Pietrzak; Anna Bednarskaya; Magdalena Markovska; Maciej Rojek; Ewa Szymanska; Miroslav Slusarchik (2013). "Behavioral and physiological mechanisms underlying extreme longevity in Daphnia". Hydrobiology
.
715
(1):125–134. DOI: 10.1007/s10750-012-1420-6. - ^ a b c Z. Maciej Gliwicz (2008). "Zooplankton". In Patrick O'Sullivan; C. S. Reynolds (ed.). Handbook of Lakes: Limnology and Limnetic Ecology
. John Wiley and Sons. pp. 461–516. ISBN 978-0-470-99926-4. - ^ a b Stanley L. Dodson; Carla E. Caceres; D. Christopher Rogers (2009). "Cladocera and other Branchiopoda". In James H. Thorpe; Alan P. Kovic (ed.). Ecology and classification of freshwater invertebrates of North America
(3rd ed.). Academic Press. pp. 773–828. ISBN 978-0-08-088981-8. - Kristjani, Mark (2016). "Phenotypic plasticity of three Daphnia genotypes in response to a predatory kairomone: evidence for the involvement of chitin deacetylases". Journal of Experimental Biology
.
219
(Pt 11): 1697–704. DOI: 10.1242/jeb.133504. PMID 26994174. S2CID 36557263. - S. Michael Hogan (2008). "Makgadikgadi". Megalithic portal
. - Fernandez, Carla Heloise; Reyas, Danny (2017-04-05). "Effects of UV-B radiation on grazing by two cladocerans from high Andean lakes". PLOS ONE
.
12
(4):e0174334. DOI: 10.1371/journal.pone.0174334. ISSN 1932-6203. PMC 5381789. PMID 28379975. - USGS: Non-indigenous aquatic species: Daphnia lumholtzi
- Center for Freshwater Biology - University of New Hampshire: Daphnia lumholtzi
- ISSG: Global Invasive Species Database: Daphnia lumholtzi (crustaceans)
- James A. Stokell, Illinois Natural History Review: Daphnia lumholtzi: The Next Great Lakes Exotic? Archived December 20, 2016, at the Wayback Machine.
- Elizabeth A. Colburn (2004), Vernal Pools: Natural History and Conservation
, page 118 of the 2008 paperback second edition. - Patrick Lavens and Patrick Sorgeloos, Guide to the Production and Use of Live
Food
for Aquaculture: Daphnia and Moina
Benefits and harms for the aquarium
These are useful creatures that filter water and regulate the microflora of the aquarium. They serve as live food for many inhabitants of the home pond.
The water flea is not capable of biting a person or harming aquarium fish, since crustaceans do not have a piercing-sucking oral cavity. Allegations regarding bites are fictional.
The main harm of copepods is associated with their high allergenicity. An allergic reaction is caused by the dusty suspension obtained when they are dried for use as dry food.
When dust particles enter a person, an allergic reaction may begin, accompanied by a dry cough, redness of the eyes, excessive lacrimation, runny nose, and exacerbation of bronchial asthma. After some time, a skin rash, itching, and burning appears.
To treat allergies, you should immediately seek medical help or take an antihistamine.
Value as fish food
The water flea is very often used as food for aquarium inhabitants. Crayfish contain up to 70% protein. It is given to fish in dry, fresh or frozen form. Crustaceans are caught in reservoirs or bred at home.
How to catch it from reservoirs yourself
Daphnia is caught from the end of spring until the end of autumn, until the reservoirs are covered with ice. It is recommended to catch in the morning or evening in cloudy, windless weather. In such conditions they rise closer to the surface of the water. For fishing, you can use a regular fabric net.
Caught specimens should be placed in a tin container and shaken periodically. It should be remembered that at high densities they may die during transportation. At home, the crustaceans are washed and passed through a sieve to sort by size.
Breeding at home
Breeding crustaceans is not difficult. To do this, it is enough to create suitable conditions.
Containers for growing
To grow crustaceans at home, you can use containers with a volume of up to 20 liters, made of glass, propylene or stainless steel. If they are raised in a regular aquarium, the surface area must be large to allow for gas exchange.
Environment Settings
Daphnia can be grown in almost any conditions.
Crawfish feel most comfortable in water with the following parameters:
- Temperature. The water flea thrives in a body of water with a wide temperature range. The optimal water temperature is 18-24 degrees.
- Salinity. Daphnia is a freshwater crustacean, so the water in the container must be fresh.
- Oxygen. Under natural conditions, daphnia can live in ponds with dirty water, so oxygen levels can fluctuate from zero to very saturated. This endurance of organisms is associated with their ability to produce hemoglobin. Crayfish do not tolerate intense aeration with a large number of small bubbles. When the container is slowly saturated with oxygen, a layer of foam forms on the surface, which can be destructive.
- Ammonia. Even a small amount of ammonia has a negative effect on the body of daphnia and can affect the intensity of their reproduction.
- Minerals. Crawfish react sharply to changes in the chemical composition of water. A slight increase in the amount of zinc, magnesium or potassium in the aquatic environment can be detrimental to them. Thus, a slight increase in the amount of copper reduces the activity of daphnia, and phosphorus can cause the death of young individuals.
Aeration
Additional enrichment of water with oxygen is desirable when growing certain species. Aeration promotes the development of phytoplankton and prevents the formation of a film on the surface of the water. The air flow should be of medium intensity so as not to cause inconvenience.
What to feed
Under natural conditions, daphnia feeds on microplankton, bacteria and yeast.
To obtain bacteria, soak banana peels in warm water and leave for 6-7 days. When the water becomes cloudy, the nutrient medium can be added to the aquarium at the rate of 0.5 liters per 20 liters of water.
For feeding, you can use dry or wet baker's yeast, which is rich in nutrients. Feed is added at the rate of 28 grams per 20 liters of water daily.
Chlorella is used as microscopic algae, which inhabits almost all bodies of water. To breed such algae, it is enough to place a small amount of water from the aquarium in a warm, well-lit place. In such conditions, algae begin to actively reproduce.
To diversify the diet of crustaceans, it is recommended to add a small amount of beet, cabbage or carrot juice to the water, which will serve as an additional source of vitamins.
How to increase cultivation productivity
Growing daphnia at home is not difficult even for beginners.
To increase productivity, you should use the following recommendations:
- to aerate the container when breeding crustaceans, you should use an airlift filter used in cages with fry;
- water changes are carried out taking into account the feed used and the volume of the container; if the aquarium is large, then replace up to 30% of the water once every 7-10 days;
- regularly collect daphnia; this will help maintain constant reproduction and growth of crustaceans;
- the duration of daylight should be at least 18 hours; 24-hour lighting is ideal.
Reproduction
Water fleas are prolific. Sexually mature females are capable of laying 15 to 30 eggs up to once a week. Population renewal occurs at a rapid pace. The lifestyle of larvae does not differ from that of adults. After birth, they stay together. In winter, the egg laying process slows down. Females lay two eggs once a week.
Peculiarities
Daphnia is characterized by cyclic parthenogenesis , that is, the ability to reproduce offspring without fertilization. Under favorable conditions, the female gives birth to a population consisting of female individuals.
Embryos develop under the outer covering in the brood chamber and are accompanied by several molts. Young individuals become capable of reproduction 4 days after birth. During her life, one female produces offspring up to 25 times.
When external conditions worsen, the crustaceans give birth to males, and the next generation lays eggs that will need to be fertilized. From such eggs, embryos are formed, covered with a protective shell. They hibernate and in this state survive drought or low temperatures. After external conditions normalize, they continue to grow and develop into adults. The next generation again gives birth to females capable of parthenogenesis.
A feature of the reproduction of daphnia is cyclomorphosis, in which specimens with different body shapes are born in the same population at different periods of time. Crustaceans born in the warm season have a long tail spine and a growth on the head helmet.
Individuals born in spring or autumn have a short tail spine, and the helmet may be absent altogether. This is due to the fact that energy expenditure on growing shoots reduces fertility.
The necessary conditions
Daphnia live and reproduce only in their familiar aquatic environment. Attempts to breed crustaceans in tap water will end in failure.
A favorable place is an aquarium with a water temperature of up to 25 degrees, good lighting and the presence of food in the form of dry yeast or single-celled algae.
Daphnia do not tolerate large colonies well and can die from lack of oxygen. As the population grows, crustaceans should be transplanted into another container.
Lifespan
The lifespan depends on the species and ranges from 22 days to 6 months. Large species live somewhat longer than small ones.
Life expectancy is influenced by water temperature. In warm bodies of water, metabolic processes proceed faster, which leads to rapid development of the organism and rapid death.
Spreading
Genus Daphnia
Daphnia studeri
, previously assigned to the genus
Daphniopsis
, was discovered in the relict salt lakes of the
Vestfold Hills ).
At the beginning of the 20th century, the prevailing opinion was that most species had a cosmopolitan distribution, but it later became clear that the faunas of different continents differ greatly. Some species, however, have very wide ranges and are distributed on several continents. The smallest number of species is typical for equatorial regions, where daphnia are rare. The most diverse fauna is in the subtropics and temperate latitudes. In recent decades, the ranges of many species have changed due to human dispersal. Daphniaambigua,
was introduced into Europe (England) .
In many reservoirs of the southern United States, D. lumholtzi
, which was previously found only in the Old World, has become common.
In ponds and puddles in central Russia, the following crustaceans of the genus Daphnia are often found (and most popular among aquarists):
Daphnia magna
(
Daphnia magna
), female - up to 6 mm, male - up to 2 mm, newborns - 0.7 mm. They ripen within 10-14 days. Litters in 12-14 days. There are up to 80 eggs in a clutch (usually 20-30). Life expectancy is up to 3 months.
Daphnia pulex
(
Daphnia pulex
), female - up to 3-4 mm, male - 1-2 mm. Litters in 3-5 days. There are up to 25 eggs in a clutch (usually 10-12). They live 26-47 days.
Daphnia cucullata is often found in lakes of the temperate zone of Eurasia
,
Daphnia galeata
,
Daphnia cristata
and several other species.
Price of daphnia in the form of food
Daphnia contains a large amount of protein, so in any form it serves as good food for aquarium fish.
Moreover, it is affordable. A package of dried daphnia weighing 100 grams costs 30-50 rubles, frozen - up to 100 rubles. You can often find live food in pet stores. They have a short shelf life and are not inferior in nutritional value to frozen ones.
Source: Daphnia in the aquarium: description, maintenance and reproduction
