This species is not endangered under the IUCN Red List, CITES appendices, nor the United States Endangered Species Act list. It is a ubiquitous, cosmopolitan copepod that can be found inhabiting almost every ocean.
US Federal List: no special status
CITES: no special status
State of Michigan List: special concern
These copepods are a food source for many species including birds, corals, crustaceans, fishes, jellyfishes, poplychaete worms, seahorses and whales.
This species exhibits a startle behavior to light and water vibrations, consisting of a short burst of swimming speed when an individual is stimulated. This photophobic behavior may be an adaptation to avoid predators such as cnidarian medusae and ctenophores, which cast shadows from above during the day.
Known Predators:
These copepods are small crustaceans ranging from 0.5 mm to 1.5 mm in length. They have translucent, bilaterally symmetrical bodies, and can be differentiated from closely related species by their long first antennae (at least half the length of their bodies) and biramous (branched) second antennae, as well as the presence of a joint between their fifth and sixth body segments. Their bodies lack a protective carapace and have three segments: prosome (head and sensory organs), metasome (housing their legs and swimmerets), and urosome (where their sexual organs are located). These copepods use a pair of maxillipeds to chew food. Females are typically slightly larger than males and their antennae are longer and straighter; males' antennae are curved at the tips and are used for grasping the female during reproduction. Males and females can also be differentiated based on the morphology of their urosomes and swimmerets (pleopods). Male urosomes have five somites (four in females), and female swimmerets are modified for egg brooding and tend to be thicker and more filamentous than those of males.
Range length: 0.5 to 1.5 mm.
Average basal metabolic rate: 0.00057 cm3.O2/g/hr.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: female larger; sexes shaped differently
Females survive longer than males, 70-80 days versus 15 days. Longevity is influenced by food availability, predation, salinity, and temperature.
Range lifespan
Status: wild: 14 to 80 days.
Typical lifespan
Status: wild: 14 to 80 days.
These copepods are free-swimming, planktonic crustaceans that can tolerate a wide range of temperatures (-1 to 32ºC) and salinities (1 ppt to 38 ppt), and can survive sudden changes in these conditions. They are most commonly found in depths from 0-50 meters and temperatures of 17-25ºC, though they have been found as deep as 600 meters. They are commonly found in coastal waters, including brackish estuaries, and often inhabit environmental niches that avoid overlap with closely related species. For example, it is the dominant species of copepod in the lagoons of the North Adriatic Sea, while Acartia clausi is the dominant copepod species in adjacent coastal waters.
Range depth: 1 to 60 m.
Habitat Regions: temperate ; tropical ; polar ; saltwater or marine
Aquatic Biomes: pelagic ; coastal ; brackish water
Other Habitat Features: estuarine
These calenoid copepods were originally observed in the Indo-Pacific region. This species is now regarded as cosmopolitan and is found in the Atlantic, Indian and Pacific Oceans, the Sea of Azov, the Baltic, Black, Capsian, Mediterranean, and North Seas, and also the Gulf of Mexico and other marine environments, as well as estuaries. Its wide geographical range may be the result of transportation in the ballast water of ships.
Biogeographic Regions: nearctic (Introduced ); palearctic (Introduced ); oriental (Native ); ethiopian (Native ); neotropical (Introduced ); australian (Native ); antarctica (Introduced ); arctic ocean (Introduced ); indian ocean (Native ); atlantic ocean (Introduced ); pacific ocean (Native ); mediterranean sea (Introduced )
Other Geographic Terms: cosmopolitan
This species is omnivorous. Individuals feed on nauplii of other copepods (such as Canuella perplexa), dinoflagellates, cilliates (such as Strombidium sulcatum), protozoans, phytoplankton, bacterioplankton, algae, and diatoms (such as Thalassiosira weissflog). They feed in two different ways, depending on what type of prey is available in the greatest numbers. To feed on immotile prey (plankton, diatoms, etc), they produce a feeding current using their feeding appendages and thoracopods to draw in food. They then filter the cells by using their second maxillae to squeeze water out. To feed on motile prey (ciliates, etc), these copepods sink in the water without moving their feeding appendages and sense prey using mechanoreceptors on their antennae, then reorienting themselves and "jumping" to catch their prey when they are 0.1-0.7 mm away. Each method is specialized for its prey type; mechanoreceptors will not help to sense immotile prey and motile prey can escape feeding currents.
Animal Foods: other marine invertebrates; zooplankton
Plant Foods: algae; phytoplankton
Other Foods: microbes
Foraging Behavior: filter-feeding
Primary Diet: carnivore (Eats non-insect arthropods); herbivore (Algivore); omnivore ; planktivore
This species is integral to the oceanic food chain. It feeds on algae and phytoplankton, and is a food source for fish and large mammals. These pelagic copepods can represent 55-95% of the copepod populations in some areas. They also play an important role in the mixing and cycling of nutrients and energy in marine ecosystems, forming a trophodynamic link connecting primary (phytoplankton) and tertiary (e.g., planktivorous fish) production, and are considered a keystone species. They are also important regulators of the marine nitrogen cycle, excreting both inorganic nitrogen (as ammonium) and organic nitrogen (urea).
These copepods can act as hosts for ciliate protazoa (Epistylus sp.). These parasites attach to the cuticle using their stalked-suckers, causing lesions in the cuticle that lead to subsequent bacterial infection, as well as infections by an epibiont, Zoothamnium intermedium. They serve as intermediate hosts for an ectoparasitic bopyrid isopod, Probopyrus pandalicola, whose definitive host is freshwater shrimp. Resarchers have also isolated a virus from this species, "Acartia tonsa copepod circo-like virus" (AtCopCV), which may significantly impact population sizes.
Ecosystem Impact: keystone species
Commensal/Parasitic Species:
These copepods are food for many fish species that account for a tremendous portion of many countries' economies (food, tourism, etc). They are also grown in mass aquaculture tanks to provide food for commercial fish hatcheries. Additionally, they have been used as a control species for Pfiesteria piscicida, an estuarine dinoflagellate that has been responsible for many coastal fish kills. These copepods can also limit the growth of coastal harmful algal blooms, including red tides, which not only affect coastal ecosystems but can present a health threat to humans.
Positive Impacts: research and education; controls pest population
If these copepods overfeed on algae, they may adversely affect the feeding and growth of many species of marine fish and mollusks that seafood industries rely on.
Life cycle and development for this copepod is typical of most copepods. Fertilized eggs, which are spherical, approximately 70-80 µm in diameter, and covered in short spines, slowly sink. Eggs develop and hatch into nauplii within approximately 48 hours (at 25°C, an average water temperature for this species). If water temperatures are too cold, eggs will usually sink to the bottom and enter diapause, hatching when water temperatures rise above 10°C. Nauplii have a maxillopodan eye, which is a simple, median eye with several photoreceptors. These copepods go through six nauplius stages before becoming copepodites, losing their maxillopodan eyes. Copepodites then metamorphose through six additional stages, finally becoming sexually mature adults. Development from newly fertilized egg to adult takes less than 3 days, on average.
Development - Life Cycle: metamorphosis ; diapause
This species uses a set of sensory antennae to detect the surrounding environment. These antennae detect abnormal vibrational patterns, food particulates, chemicals, and nearby mates. In their naupliar larval stages, antennae are used for swimming, becoming modified for sensory purposes in adulthood. These copepods have simple eyes that are unable to form complete images, but are highly photosensitive.
Communication Channels: tactile ; chemical
Perception Channels: visual ; tactile ; vibrations ; chemical
Limiting factors of this species' breeding season can include the amount of light, temperature, salinity, and oxygen concentration. In northern parts of its range, breeding tends to occur during the late summer and early fall, and in southern areas there is often a breeding peak in the early spring; if conditions are optimal, this species may breed year-round. Multiple generations are produced per breeding season. These copepods are polygynandrous, and rely on hydromechanical signals to find mates rather than pheromones. A male and female encounter each other spontaneously and, when a female comes within range, a male detects her movements, and responds in kind. The pair perform a series of synchronized "hops" until the male is close enough to catch the female, followed by mating.
Mating System: polygynandrous (promiscuous)
These copepods are dioecious and both sexes may be reproductively active throughout the year; breeding season depends largely on environmental factors such as water temperature. Females produce eggs for 3-4 weeks at a time and can release a brood of 20-53 eggs every 5-6 days. During mating, males clasp females with their claw-like antennae and deposit spermatophores onto their urosomes, where the eggs are fertilized. After fertilization, eggs are released. Males may mate consecutively with multiple females.
Breeding interval: During breeding season, females produce egg clutches every 5-6 days.
Breeding season: This species may breed year round under optimal conditions; most typically, they breed during warmer months.
Range number of offspring: 20 to 50.
Average gestation period: 48 hours.
Average age at sexual or reproductive maturity (female): 3 days.
Average age at sexual or reproductive maturity (male): 3 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
These copepods exhibit no parental care to their young once fertilized eggs have been released.
Parental Investment: female parental care ; pre-fertilization (Provisioning)
Acartia tonsa is a species of marine copepod in the family Acartiidae.[1]
Acartia tonsa is a species of calanoid copepod that can be found in a large portion of the world's estuaries and areas of upwelling where food concentrations are high.[2][3]
Like many plankton common to estuarine ecosystems, they can live in a wide range of temperatures and salinities.[2] The wide distribution of Acartia tonsa may be a result of these copepods being transported as ballast in ships. Their tolerance to changes in salinity has likely contributed to their success as an invasive species in some regions.[4]
Acartia tonsa is translucent,[5] and is usually between about .8 and 1.5 millimetres (0.031 and 0.059 in) in length in females, and from about .8 to 1.3 millimetres (0.031 to 0.051 in) in males.[6] It "[c]an be differentiated from closely related species by their long first antennae (at least half the length of their bodies) and biramous (branched) second antennae, as well as the presence of a joint between their fifth and sixth body segments".[5]
In estuaries and coastal waters which are warm throughout the year, A. tonsa is found year-round. In cooler climates including the North Atlantic, it is frequently the dominant zooplankton in the spring and summer. Acartia tonsa produces eggs in the winter in colder geographic regions. The eggs hatch when temperatures exceed 15 °C (59 °F).[7][8]
They are an important food source for many commercial fish species.[8] Several studies indicate they aggregate near the ocean floor during the day and rise closer to the surface at night. This behavior likely helps A. tonsa avoid predators who rely on vision to locate and capture prey.[9]
A. tonsa nauplii and adults feed on phytoplankton as well as planktonic ciliates and rotifers.[10] It acts as a suspension feeder when feeding on phytoplankton. When feeding on motile prey it acts as an ambush feeder; it stays nearly motionless in the water, detects movement of its prey, and then jumps toward the prey. Moderate amounts of turbulence improve rates of ambush feedings.[11]
Acartia tonsa is a species of marine copepod in the family Acartiidae.
