Argulidae

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Argulidae
Temporal range: Carboniferous–Recent
Argulus.jpg
Argulus sp. on a stickleback
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Ichthyostraca
Subclass: Branchiura
Thorell, 1864
Order: Arguloida
Yamaguti, 1963
Family: Argulidae
Leach, 1819
Genera

The family Argulidae, whose members are commonly known as carp lice or fish lice, are parasitic crustaceans in the class Ichthyostraca. It is the only family in the monotypic subclass Branchiura and the order Arguloida, although a second family, Dipteropeltidae, has been proposed. [1] [2] Although they are thought to be primitive forms, they have no fossil record.[ citation needed ]

Contents

Taxonomy

Branchiurans were once thought to be copepods but are now recognised as a separate subclass in the superclass Oligostraca due to their distinct morphological characteristics. [3] There are approximately 170 species in four genera recognised in the family Branchiura. [4] The centres of diversity are the Afrotropical and Neotropical realms. [5]

Description

Branchiurans have a flattened, oval body, which is almost entirely covered by a broad, oval carapace, four thoracic segments each with a pair of swimming legs, a pair of anterior compound eyes, and an unsegmented abdomen without appendages which ends in paired abdominal lobes separated by the medial anal cleft. [6] [7] [8] They are compressed dorsoventrally and can vary in size from just a few millimetres to over 30 mm (1.2 in) long, with females usually somewhat larger than the males. [5]

The mandibles are generally toothed hooks in Branchiurans. The maxillules provide sucking capability, and in the genera Argulus, Chonopeltis, and Dipteropeltis, the adults have a pair of suction cups that are from modified first maxillae. [6] The genus Dolops, keeps the larval stages claw-like appendages into adulthood. [6] It is still unknown whether the ancestral state of these organisms had suction discs or the hooked condition seen in Dolops, although it is thought that the specialized suctions discs are a later product of evolution. [9] Also, females tend to be larger than the males. [6] Between the genera there are multiple distinction between the sexes. [6] For example, males in Argulus and Chonopeltis possess secondary sexual modifications on legs 2-4. [6] The sexes both have their own sexual reproductive organs on their abdomens. [6] The females have a spermathecae, while the males have a pair of testes. [6]

Their compound eyes are prominent, and the mouthparts and the first pair of antennae are modified to form a hooked, spiny proboscis armed with suckers, as an adaptation to parasitic life. They have four pairs of thoracic appendages, which are used to swim when not attached to the host. [5]

Not much research has been done on the respiratory system, which lack gills, but respiratory areas on the carapace and gas exchange through the fleshy abdomen has been suggested. [10] [11]

Distribution and habitat

Branchiurans are widely distributed throughout the world. Most species are found in Africa and South America, and none are found in Antarctica. [12] In North America, the genus Argulus is the only one known to be found in freshwater ecosystems.

Behaviour and ecology

Parasitism

Branchiurans are obligate ectoparasites that are found primarily on marine and freshwater fish (only the genus Argulus occurs in marine environments), [13] but can also be found on other aquatic organisms such as invertebrates, salamanders, tadpoles and alligators. [6] [14] [3] Some species feed on the blood of their host, while others feed on mucus and extracellular material. [3] Feeding is facilitated by distinct morphological adaptations (see Anatomy). Branchiura are able to attach to hosts through two mechanisms, hooked maxillae (as seen in Dolops) or suction disks. [9] After engorging themselves, the parasites typically wait two to three weeks before feeding again. [3] Mitigation of these parasites has been studied through the use of a treatment containing plant parts. [15] From this study, it is thought that Tobacco leaf dust (containing nicotine) can safely and effectively eliminate adult Branchiurans from fish, although this may be specific to only Argulus bengalensis. [15]

Reproduction

Only the life cycle of freshwater forms of the genus Argulus is well known. [16] Branchiurans are not permanently attached to their hosts, and leave them for up to three weeks to mate and lay eggs, and reattach behind the fish's operculum, where they feed on mucus and sloughed-off scales, or pierce the skin and feed on the internal fluids. [17] The eggs hatch into parasitic postnauplius larvae. While on their host, Branchiurans mate. [6] The female holds the eggs in the thorax and in some species the eggs can be found inside the lobes of the carapace. [6] The spermathecae on the female stores the sperm. [6] In the genus Dolops, the males deposit a spermatophore onto the females. [6] Once the eggs are fertilized the females leave the host organism to lay their eggs in rows on surfaces of plants, rocks, etc. [6] Like the adults, the larvae are parasites on fish. They are opportunistic in selecting host species of fish, and females are motile in their pursuit of locality of egg-laying. Chonopeltis larvae appears to be less developed than the other genera. One group of Argulus hatch as metanauplius-larvae, followed by a juvenile stage. Another Argulus group, and all known species of Dolops, hatch as juveniles. [18]

Impact

Fish lice occasionally reach high enough densities to cause fish kills in aquaculture operations, or more rarely in wild populations of fish. They can also become abundant in aquaria, sometimes resulting in the death of ornamental fish. [5]

Related Research Articles

<span class="mw-page-title-main">Copepod</span> Subclass of crustaceans

Copepods are a group of small crustaceans found in nearly every freshwater and saltwater habitat. Some species are planktonic, some are benthic, a number of species have parasitic phases, and some continental species may live in limnoterrestrial habitats and other wet terrestrial places, such as swamps, under leaf fall in wet forests, bogs, springs, ephemeral ponds, puddles, damp moss, or water-filled recesses of plants (phytotelmata) such as bromeliads and pitcher plants. Many live underground in marine and freshwater caves, sinkholes, or stream beds. Copepods are sometimes used as biodiversity indicators.

<span class="mw-page-title-main">Mysida</span> Small, shrimp-like crustacean

Mysida is an order of small, shrimp-like crustaceans in the malacostracan superorder Peracarida. Their common name opossum shrimps stems from the presence of a brood pouch or "marsupium" in females. The fact that the larvae are reared in this pouch and are not free-swimming characterises the order. The mysid's head bears a pair of stalked eyes and two pairs of antennae. The thorax consists of eight segments each bearing branching limbs, the whole concealed beneath a protective carapace and the abdomen has six segments and usually further small limbs.

<span class="mw-page-title-main">Ostracod</span> Class of crustaceans

Ostracods, or ostracodes, are a class of the Crustacea, sometimes known as seed shrimp. Some 33,000 species have been identified, grouped into 7 valid orders. They are small crustaceans, typically around 1 mm (0.04 in) in size, but varying from 0.2 to 30 mm in the case of the marine Gigantocypris. The largest known freshwater species is Megalocypris princeps, which reach 8mm in length. In most cases, their bodies are flattened from side to side and protected by a bivalve-like valve or "shell" made of chitin, and often calcium carbonate. The family Entocytheridae and many planktonic forms do not have calcium carbonate. The hinge of the two valves is in the upper (dorsal) region of the body. Ostracods are grouped together based on shell and soft part morphology. While early work indicated the group may not be monophyletic and early molecular phylogeny was ambiguous on this front, recent combined analyses of molecular and morphological data suggested monophyly in analyses with broadest taxon sampling, but this monophyly had no or very little support. They have a wide range of diets, and the class includes carnivores, herbivores, scavengers and filter feeders, but most ostracods are deposit feeders.

<span class="mw-page-title-main">Isopoda</span> Order of arthropods

Isopoda is an order of crustacean, which includes woodlice and their relatives. Members of this group are called Isopods and include both terrestrial and aquatic species. All have rigid, segmented exoskeletons, two pairs of antennae, seven pairs of jointed limbs on the thorax, and five pairs of branching appendages on the abdomen that are used in respiration. Females brood their young in a pouch under their thorax.

<span class="mw-page-title-main">Rhizocephala</span> Superorder of barnacles

Rhizocephala are derived barnacles that parasitise mostly decapod crustaceans, but can also infest Peracarida, mantis shrimps and thoracican barnacles, and are found from the deep ocean to freshwater. Together with their sister groups Thoracica and Acrothoracica, they make up the subclass Cirripedia. Their body plan is uniquely reduced in an extreme adaptation to their parasitic lifestyle, and makes their relationship to other barnacles unrecognisable in the adult form. The name Rhizocephala derives from the Ancient Greek roots ῥίζα and κεφαλή, describing the adult female, which mostly consists of a network of thread-like extensions penetrating the body of the host.

<span class="mw-page-title-main">Pentastomida</span> Subclass of crustaceans

The Pentastomida are an enigmatic group of parasitic arthropods commonly known as tongue worms due to the resemblance of the species of the genus Linguatula to a vertebrate tongue; molecular studies point to them being highly-derived crustaceans.

<span class="mw-page-title-main">Sea louse</span> Family of copepods

Sea lice are copepods of the family Caligidae within the order Siphonostomatoida. They are marine ectoparasites that feed on the mucus, epidermal tissue, and blood of host fish. The roughly 559 species in 37 genera include around 162 Lepeophtheirus and 268 Caligus species.

<span class="mw-page-title-main">Ascothoracida</span> Group of crustaceans

Ascothoracida is a small group of parasitic marine crustaceans, comprising around 100 species and divided into Dendrogastrida and Laurida. They are found throughout the world on cnidarians and echinoderms. Dendrogastrida are parasites on echinoderms, and Laurida are parasites on cnidarians, except from the species Waginella Grygier, which is also a parasite on echinoderms (crinoids). Piercing and sucking mouthparts are used for feeding, and more advanced forms also absorbs nutrients through a modified integument of the carapace. More basal forms are ectoparasitic, but most genera are meso- and endoparasitic. The sexes are separate, except from secondary hermaphroditic species of the Petrarcidae. In many species the larger female often have smaller males living inside her mantle cavity.

Dipteropeltis hirundo is a little-known species of fish louse. It is an ectoparasite of fish found in South America, including piranhas and barred sorubim.

<span class="mw-page-title-main">Crustacean larva</span> Crustacean larval and immature stages between hatching and adult form

Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult, and there are still cases where it is not known what larvae will grow into what adults. This is especially true of crustaceans which live as benthic adults, more-so than where the larvae are planktonic, and thereby easily caught.

Argulus ambystoma is a species of branchiuran parasitic on Lake Patzcuaro salamanders, sharing that species' very limited range in Lago de Pátzcuaro, Mexico.

<i>Argulus</i> Genus of crustaceans

Argulus is a genus of fish lice in the family Argulidae. There are about 140 accepted species in the genus Argulus. They occur in marine, brackish, and freshwater environments. They sit tightly against the host body, this minimises risk of detachment. As juveniles, these species feed on mucous and skin cells of their host. With age they become blood feeders because the parasite moves from feeding on the fins to feeding on the body of the fish, causing the feeding change. At least some species can have severe impacts on their host populations.

<span class="mw-page-title-main">Crustacean</span> Subphylum of arthropods

Crustaceans are invertebrate animals of the subphylum Crustacea, a large, diverse group of mainly aquatic arthropods including decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, opossum shrimps, amphipods and mantis shrimp. The crustacean group can be treated as a subphylum under the clade Mandibulata. It is now well accepted that the hexapods emerged deep in the Crustacean group, with the completed group referred to as Pancrustacea. The three classes Cephalocarida, Branchiopoda and Remipedia are more closely related to the hexapods than they are to any of the other crustaceans.

<i>Argulus foliaceus</i> Species of crustacean

Argulus foliaceus, also known as the common fish louse, is a species of fish lice in the family Argulidae. It is "the most common and widespread native argulid in the Palaearctic" and "one of the most widespread crustacean ectoparasites of freshwater fish in the world", considering its distribution and range of hosts. It can cause the severe disease state argulosis in a wide variety of fish species. It is responsible for epizootic outbreaks that have led to the collapse of aquaculture operations. Fish lice are not related to lice, which are insects.

<i>Argulus japonicus</i> Species of crustacean

Argulus japonicus, also known as the Japanese fish louse, is a species of crustacean in the family Argulidae. This species is light brown in colour and may be between 4 and 9 mm long and 3 to 6 mm wide. It has a stumpy tail, and is shaped somewhat like a round shield. The female and male are phenotypically distinct, categorizing them as a dioecious species. Although they are not drastically different, their transparent skin highlights the minor differences such as the different copulatory accessories.

<span class="mw-page-title-main">Oligostraca</span> Superclass of crustaceans

Oligostraca is a superclass of crustaceans. It consist of the following three classes:

<i>Anilocra capensis</i> Species of crustacean

Anilocra capensis is a species of parasitic isopod in the family Cymothoidae. It is endemic to southern Africa. The species preferentially attaches itself to the hottentot seabream.

Chonopeltis is a genus of fish lice in the subclass Branchiura. These crustaceans are ectoparasitic freshwater fish host. Species of this genus are exclusively found in rivers in Africa.

<i>Argulus coregoni</i> Parasitic of crustacean

The carp louse Argulus coregoni is an obligate ectoparasitic branciuran species on fish. It occurs in China and Japan, and Scandinavia. Argulus coregoni can pose a threat to fish kept in fish farms.

References

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