Calanus pacificus Landry, and Acartia tonsa Jonsson and Tiselius, The copepod seems to be capable of a very detailed three-dimensional interpretation of the fluid signal, presumably through differences in signal characteristics received by individual setae positioned along the antennules Fields et al.
The duration of the attack lunge is similar to the nerve transmission time through the antennules, both a few milliseconds, so the copepod cannot receive additional information of the position of the prey during the attack. The attack jump is accomplished similarly to an escape jump by sequentially striking the swimming legs backwards.
An essential feature of the attack itself is its rapidity. First, the rapidity allows the copepod to surprise the prey; even if an evasive prey like a ciliate may perceive the fluid disturbance generated by the attacking copepod, typical prey latency times are similar or longer than the duration of the attack lunge 2—10 ms, Machemer and Deitmer, A smaller or slower zooplankter would be surrounded by a thicker viscous boundary layer that would prevent the predator from approaching its prey.
A prey attack in ambush feeding Acartia tonsa. Frozen high-speed video images, 2. The circle shows the position of the ciliate prey. Upon prey detection, the copepod jumps forward by striking the swimming legs backwards, and subsequently flings out the highly setose feeding appendages. This creates a vacuum that sucks in the prey. In the shown sequence, the copepod misses the prey in the first attempt but gets it in the second.
Ambush feeding is mandatory for pelagic cyclopoid copepods and is found also among some calanoids e. Acartia spp. This is accomplished by vibrating the feeding appendages and in some species also the swimming legs in regular but rather complex patterns e.
Van Duren and Videler, Fig. The sticky nature of water at the low Reynolds number of the feeding current essentially prevents the filtering of large quantities of water through a small, fine-meshed filter the maxillae and remote prey detection and individual prey capture circumvents this hydrodynamic constraint.
I am unaware of other zooplankters that use a scanning current in a manner similar to copepods; there are examples of ctenophores that remotely perceive prey in the feeding current, but this seem not to be essential for their feeding Costello et al.
Feeding-current feeding in two species of copepods, Acartia tonsa upper panel and Metridia longa lower panel. Both panels should be read from left to right and the sequence of pictures are frozen high-speed video images selected at intervals 2. This generates a rather fluctuating feeding current, while the animal is almost stationary in the water.
Metridia longa lower panel generates a feeding current mainly by flapping the second antennae and the mandibles at 12 Hz, while the maxillipeds are almost stationary. The feeding current pulls the copepod rapidly through the water. Prey capture mechanism is unknown.
A video of the two species feeding is in the Supplementary data. Detection of prey in the feeding current is probably mainly by chemical cues: the cloud of leaking solutes that surround a phytoplankton cell is drawn out in the accelerating and sheared feeding current, and a chemical signal thus arrives to the copepod prior to the prey itself and allows the copepod to redirect the feeding current and capture the prey particle Andrews, ; More et al. The concentration of solutes around the prey cell and, hence, the strength of the chemical signal is proportional to the leakage rate and thus increases with the size of the prey cell.
Large prey can therefore be detected at a further distance than small ones, and the clearance rate on large prey is therefore larger than on small prey, consistent with observed prey size spectra in copepods e. Frost, Yet, smaller particles are captured, albeit at a lower efficiency, possibly strained by the setae on the maxillae. Such filter? Rosenberg, , but the capture mechanism has never been clearly observed, described, nor quantitatively understood.
For example, A. The maxillae plays an important role in generating the feeding current, but prey seems not to be captured on the maxillae own observation.
Despite the lower feeding efficiency of ambush feeding, this may still be a feasible feeding mode. Thus, a lower feeding efficiency is compensated for by a lower mortality risk, potentially making the two feeding modes equally fit. While the two main feeding modes described above are shared by only very few other plankters and thus are nearly unique to pelagic copepods, I shall briefly mention a final way of acquiring food that is utilized by a great variety of zooplankters but which has received little attention in the past: colonizing and feeding on marine snow aggregates and other large particle.
Some copepods, despite living in the water column, are often found on aggregates and appear to be much better adapted to feed on surfaces, e. Oncaea spp. Many mesozooplankters reproduce mainly parthenogenetically e. Others are hermaphroditic and thus may self-fertilize many ctnophores although cross-fertilization may be the rule rather than the exception in most hermaphroditic species, such as chaetognaths Reeve and Walter, Others again spawn their sexual products in the water and hence need not mate e.
In contrast, copepods require sex with actual mating in each generation, and many species need multiple matings in the course of their reproductive career in order to stay fertile. Frequent mating is not entirely unique to copepods in the plankton, it is found also among chaetognaths, for example, but it is not common.
We now pretty well understand how mates find one another or otherwise cope with potentially low mate encounter rates. Many cyclopoid and harpacticoid copepods have pre-copulatory mate guarding; the male attaches to the female while still immature and is thus in an advantageous position when the female matures.
This leaves the mates a long time to find one another and random encounters may be sufficient to prevent encounter limitation; mate recognition is through contact pheromones Kelly et al.
In most other species, pre-copulatory attachment is short-lasting few minutes and mate detection is remote and either through chemical or hydromechanical cues. Remote mate detection through diffusive pheromones in copepods has been known since at least Parker Parker, and has since then been described in more detail for a number of species e. Katona, ; Griffiths and Frost, ; Doall et al. The general pattern is that the females produce pheromones and the males search and find the pheromone signal that leads him to the female.
To this end, males of species with chemical mate detection typically have many more aestetascs chemosensory structures on the antennules than the females Ohtsuka and Huys, Understanding the lives of marine copepods, and how their populations will respond to climate change, is crucial for predicting the future health of the marine environment and how it helps our planet.
Copepods are tiny crustaceans—distant relatives of crabs and lobsters. They are members of the zooplankton, animals that drift at the mercy of ocean currents.
One of the most important groups of copepods in the Northern Hemisphere is called Calanus Figure 1. A single adult Calanus may only measure a few millimeters in length, but the total existing population of Calanus probably weighs more than all of the 7. The huge abundance of Calanus is what makes them so important for the healthy functioning of marine ecosystems. Just as wildebeest are the main grazers of the Serengeti, so Calanus are the great grazers of the Atlantic and Arctic oceans, feeding on aquatic meadows of phytoplankton, microscopic plant-like algae that bloom in spring.
Calanus filter the chlorophyll-rich phytoplankton out of seawater using rapid movements of their feathery mouthparts and their sense of touch Figure 1. The bodies of Calanus are transparent, which may explain why the famous eighteenth century Norwegian bishop and scientist Johan Ernst Gunnerus named them after the philosopher Kalanos Calanus , who refused to wear clothes!
The cycle begins in spring when adult females release batches of 50 or more eggs into the water. The eggs hatch a day or so later and, being cold-blooded, develop at a rate that is largely controlled by water temperature. Like all crustaceans, Calanus has a rigid external skeleton exoskeleton that it must shed in order to grow and develop. In total, there are 12 development stages to their life cycle. During the first 6 they are known as nauplii. The 6 later stages are known as copepodites, all of which have the cylindrical shape that is characteristic of Calanus Figure 1.
In the laboratory, it takes between 30 and 80 days for an egg to develop into an adult, depending on the water temperature and feeding conditions. In nature, however, this process is often interrupted by spending winter at great depths as an immature adult Figure 2. Facing these challenges helps an animal to live long enough to reproduce. Calanus is so successful because of their response to these two challenges. In order to provide sufficient expert knowledge for maintaining the list, we have formed an editorial committee which will be editing and improving this database.
This database will hopefully promote the stability in copepod nomenclature and act as a tool for higher taxonomic revisions and regional monographs and then provide a base link for other online databases that use copepod nomenclature.
Current number of accepted species: 11, Current number of references: 75, What is a copepod? Editorial board Editors T. Copepod Links for further information about copepods. Scott U. Citation Usage of data from the World of Copepods in scientific publications should be acknowledged by citing as follows: Walter, T. World of Copepods Database. There may be additional data which may prove valuable to such analyses.
Individual pages are individually authored and dated. These can be cited separately: the proper citation is provided at the bottom of each page. Argulus Chonopeltis Dipteropeltis Dolops. As a cyclopoid, Apocyclops panamensis differs from the harpacticoids Tisbe and Tigriopus in that it is neither entirely pelagic nor benthic throughout its entire life cycle.
Due to its adaptations to unstable environments, it is relatively hardy and productive. Under ideal conditions, Apocyclops pods can reach densities as high as 20,, individuals per liter in as little as days. It is rich in important dietary compounds such as proteins, free amino acids and highly unsaturated fatty acids. Its adults also an excellent food for zooplanktivorous fishes such as seahorses small wrasses. Though the Tigriopus californicus may take a bit longer to establish itself due to its pelagic tendancies, it can be exceptionally productive.
Its larvae are similarly useful to filter-feeders. Also, Tigripous has a habit of skipping into the water column where it can be more easily be seen and picked off by planktivores such as small wrasses. Thus, Tigriopus tends not to dominate Tisbe when used together in community aquaria. Tigriopus pods also rich in astaxanthin, which enhances the natural coloration of both fish and invertebrates. Clearly, not all copepods even of the same order are the same. It is therefore ideal especially in a reef aquarium, which contains a wide variety of organisms from all over the world to use a balanced mix of pod species.
This will add enough diversity in terms of size, behavior and nutrition to suit the needs of most aquarium livestock. Luckily, such mixes are available to discerning aquarists everywhere. For example, Pods contains a mix of live Tisbe, Apocyclops and Tigriopus in a single package that may be added directly to your main tank or refugium. These are the only such high-end products that include a mix of species in juvenile to adult sizes, making them immediately of use to a large variety of creatures and all but guaranteeing successfully established in-tank populations.
If very large pod populations are desired for maximum nutritional and tank cleaning benefits, these products can be utilized just as easily for routine replenishment. The regular addition of quality algal mixes such as Ocean Magik will also help to maintain large pod populations as well as enrich their nutritional content. However used, the mere presence of a diverse mix from multiple copepod groups is a fail-proof and low-cost means of promoting the health, beauty and natural ecology of any marine aquarium system.
References [1] Waller, Geoffrey. Washington, D.
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