Top 29 Crustaceans that Live as Parasites

The following points highlight the top twenty-nine crustaceans that live as parasites. Some of the crustaceans are: 1. Monsirilla 2. Notodelphys 3. Asterocheres 4. Nicothoe 5. Lichomolgus 6. Anthosoma 7. Ergasilus 8. Bomolochus 9. Hondrocattthus 10. Philichthys 11. Giardella 12. Caligus 13. Lernaea 14. Lesteira 15. Tracheliastes and Others.

Crustacean # 1. Monsirilla:

The adult of this crustacea is free-swimming. The larva is free-swimming in the beginning but after a short period it pierces the epidermis of a polychaete worm (Salmacina) and clings with the help of man­dibular hooks. Gradually the larva enters within the body of the host worm and finally settles within the ventral blood vessel.

From the beginning of its life the larva does not possess any alimentary canal and at the time of its journey through the body of the host it loses all the structural details and turns into a loose mass of cells. These cells remain within a chitinous covering. Further devel­opment of adult structure occurs from these cells. The second antenna acts as a structure for absorbing nourishment.

When full-grown, the adult breaks the body of the host and becomes free-swimming. The second antenna is left within the body of the host. In the adult the appendages are a pair of antennules and several biramous thoracic legs. The thoracic appendages are used as swimming organs.

No functional mouth parts are seen in the adult and the alimentary canal in­cludes a mouth leading into a blind short stomach. It has been observed that if more than one Monstrilla infect a worm all be­come males. Otherwise in the case of a single infection, it may be either a male or a female.

Crustacean # 2. Notodelphys:

Both the sexes infect the gill chambers of Ascidians (lower chordate), but are capable of coming out to lead a free- swimming life. Thus parasitism encountered here is of temporary nature. First antenna is different in male and female. Second anten­nae are prehensile. In another closely related genus, Dropygus, the females are fixed with the body of the host and thus are unable to swim.

Crustacean # 3. Asterocheres:

It lives as ectoparasite in various animals, i.e., sponges, echinoderms and ascidia. Excepting the presence of a siphon, practically no structural changes have occurred due to parasitic mode of life. Si­phon is formed by the oral appendages and contains three elongated grooves. Styli-form mandibles work in the outer grooves of the siphon.

Crustacean # 4. Nicothoe:

It is a parasite on the gills of the lobster. Body is poorly segmented and deformed. Antennae and mouth parts are modified for suction. First antenna is made up of more than seven joints. Thorax is produced into huge lobes but abdomen is of normal size. Paired egg-sacs are present.

Crustacean # 5. Lichomolgus:

One species (L. agilis) is a temporary parasite on the gills of Doris (mollusc). The anterior end is semi-circular and last five thoracic segments are distinct. Size of the thoracic segments gradually re­duces from anterior to posterior direction. First abdominal segment is the largest. Cau­dal styles are well marked.

Crustacean # 6. Anthosoma:

It lives as parasite in the mouth of Porbeagle shark. The elongated body is to some extent cylindrical. Antennule is many-jointed. Second antenna is chelate- like. Pleopods are reduced and eyes are absent. Body is modified to form overlap­ping lobes and possesses paired egg-sacs.

Crustacean # 7. Ergasilus:

It lives as parasite on the gills of a fish, called Bass (Morone sp.). The body is cylindrical and the segments are distinct. The antennule is five-jointed and the an­tenna is transformed into a hook-like struc­ture for holding the body of the host. The maxillipeds are prehensile and eyes are ab­sent. Paired egg-sacs are present.

Crustacean # 8. Bomolochus:

It is an ectoparasite on certain fishes, either on skin (in Sole) or in the nostrils (in Cod). First antennules are small but joints are distinct. Second antennae are curved. Maxilliped is well-formed. No siphon is present. First thoracic appendage is modified. Abdominal segment rarely con­tains any significant appendages.

Crustacean # 9. Hondrocattthus:

Females are parasites on the gills and mouths of different marine fishes. It has depressed and un-segmented body with crinkled lobes. Antennae are modified into hook-like structures for at­tachment. Mandibles, maxillae and two pairs of thoracic legs are present. Males remain attached to the body of the female and are much smaller.

Crustacean # 10. Philichthys:

These are ectoparasites on the skin of certain teleostean fishes (Sole) and remain fixed near the lateral line of the fish. It exhibits sexual dimorphism—females have long finger-like processes but males are normal. Siphon is absent. They feed on mucus from the slime glands of fishes.

Crustacean # 11. Giardella:

Only the adults are ectopara­sites on the decapod crustaceans. The lips around the mouth form a hollow projection, but it is not the true siphon, which is present in some crustacean parasites.

Crustacean # 12. Caligus:

It is an ectoparasite on fish, infecting the gill-chamber. Antennules are provided with bristles. Antennae are hook-­like. Oral appendages around mouth form a definite siphon, within which the mandible works. Fifth thoracic appendage is long. Females are slightly larger than males and sometimes bear a pair of elongated egg sacs.

Crustacean # 13. Lernaea:

Only female members are para­sites. These parasites with vermiform bodies live in the skin and blood vessels of different fishes. A peculiarly lobed anterior end pos­sesses maxillae for piercing. Minute vestiges of feet are present. Both the sexes remain free-swimming at the beginning. After re­production, the female becomes parasite and undergoes degenerative changes.

Crustacean # 14. Lesteira:

These are parasites on fishes and have un-segmented body. The head is swollen and bears suctorial mouth parts. Appendages are reduced and the egg sacs are filamentous.

Crustacean # 15. Tracheliastes:

These endoparasites of annelids have elongated and segmented body which bears serrated mandibles and uniramous maxillipeds. Second maxillae are enlarged for attachment.

Crustacean # 16. Achtheres:

The male is smaller than the female. First antennulae are short but similar in both the sexes. In the female, the segments are indistinct. Maxillipeds are fused at their free end with a pad which is beset with chitinous hooks. In males, the posterior seg­ments are distinct and the prehensile maxillipeds are not united. Both the sexes cling to the gills of fishes (Perch, Trout) and live as ectoparasites.

Crustacean # 17. Stenochotheres:

It lives as parasite within the marsupium of another group of crusta­ceans belonging to the family Gammaridae. Both sexes reside within the same marsu­pium. Both the sexes have similar appear­ance, only the males possess a median glan­dular thread for its attachment with the female body or with the body of the host. Females are more sluggish than males.

Crustacean # 18. Argulus:

It lives as an ectoparasite within the gill-chamber of fresh-water fishes. It does not remain permanently fixed and ei­ther swims freely or crawls over the surface of the body. The leaf-like body includes a flat and oval cephalothorax and a small bilobed abdomen. Two compound eyes are distinctly visible and near each eye two short antennae are present.

Short first maxillae and styli- form mandibles work inside a siphon which together with a poison spine in front acts as the piercing organ. The second maxillae are transformed as suckers. The maxillipeds are modified for clasping and four pairs of tho­racic legs are swimming appendages. Breed­ing takes place outside the body of the host and fertilization is internal.

Crustacean # 19. Alcippe:

It resides as parasite in the shell of a kind of snail, called Whelk. The thoracic appendages are absent but abdominal appendages are present.

Crustacean # 20. Laura:

These bean-shaped crustaceans are parasites within the cnidarians (Black corals, Gerardia sp.). The body is placed within a soft mantle and consists of eleven segments. The thoracic appendages are modi­fied. It is hermaphrodite.

Crustacean # 21. Proteolepas:

These parasites with mag-got-like segmented bodies infect another cirripedian crustacea (Alepas). It was first collected and described by Charles Darwin but was never found again. The numbers of segments are eleven of which first eight are thoracic segments and the last three are abdominal segments. Antennae are modified for attachment. The mouth and the legs are absent.

Crustacean # 22. Gnathia:

The adults are free-living but do not take any food. The nutrition is provided by the stored food materials which were obtained in the parasitic state of its larval forms.

The larvae live as ectoparasites on different fishes. It absorbs so much fluid that it loses its segmentation and becomes completely round. The adults are 1-8 mm in size and exhibit remarkable sexual dimor­phism. In females, the body is filled with the enormous ovary but in males the liver is enormous.

Crustacean # 23. Cymothoa:

These crustaceans are her­maphrodite. The free-swimming young’s are males. After certain period of growth, Cymothoa becomes ectoparasite on different fishes and behaves as female. The legs are short and clawed and the mouth parts be­come modified for piercing.

Crustacean # 24. Cymodoce:

These are temporary ectopara­sites and often are regarded as scavenger on decomposing parts of fishes and other ani­mals. Body is broad, flat and in females the mouth parts are reduced. But this degenera­tion is compensated by the enormous growth of the maxillipeds.

Crustacean # 25. Danalia:

The larval stages are free-swimming. First free-swimming larva is called Epicaridian larva. It transforms into another free-swimming larval stage, called Cryptoniscus. It contains a pair of promi­nent testes in the thorax and a rudimentary ovary on the tip of each testis. At the free- swimming stage it acts as a male and ferti­lizes the female, which remains parasitic on other parasitic crustaceans like Sacculina.

After reproduction, the male fixes itself on the host (parasitic crustacea) as a parasite and turns into a female. The body of a full- grown female looks like a sac containing only eggs and growing embryos. Two pairs of spermathecae are present on the ventral side to receive sperm cells.

Crustacean # 26. Bopyrus:

Like Danalia, this is also a protandric hermaphrodite, i.e. same indi­vidual first behaves as male and then trans­forms into female. But in this crustacea, after epicaridian and cryptoniscus stages, another larval stage appears which is called Bopyrus larva. It acts as male and bears two pairs of rudimentary antennae and eight pairs of thoracic appendages (first pair is insignifi­cant). Four pairs of abdominal appendages act as gills.

The male after fertilizing the female, fixes within the wall of the gill- chamber of crustaceans like prawn and trans­forms into female. The female body becomes asymmetrical. The maxillipeds grow consider­ably to cover the antennae and mandibles. The bases of the thoracic appendages be­come leaf-like and form a brood pouch.

Crustacean # 27. Portunion:

These are reddish crustaceans and their adult females live as parasites within the thoracic cavity of crabs and re­lated forms. Development passes through epicaridian, cryptoniscus and bopyrus stages. Bopyrus stage after working as male at first fixes on the thoracic wall within the gill- chamber of crab.

It gradually becomes fe­male and slowly penetrates inside the tho­racic cavity of the host. Finally, the body of the parasite contains a rudimentary head and abdomen, but the thoracic appendages form a distinct brood pouch. The brood pouch communicates with the gill-chamber through a minute aperture, which acts as the outlet of fertilized eggs.

Crustacean # 28. Cyamus:

These crustaceans with their biting mouth parts attack the skin of whale. Broad and depressed body is expanded lat­erally and has three pairs of clawed thoracic appendages. Abdomen is vestigial.

Crustacean # 29. Peltogaster:

It is an endoparasite and it infects crab. The body has changed consid­erably due to the parasitic mode of life. The body of the adult remains attached with the body of the host as a bag-like mass. The outer covering of the mass is a muscular mantle which is fixed with the body of the host by a ring-like muscular fold.

Within the mantle there is a mantle cavity, at the inner wall of which lies the visceral mass. The visceral mass primarily contains the repro­ductive organs, testes and ovaries. The testes are two in number and are tubular. Each testis opens within a vas deferens. The ova­ries are also paired and communicate with the exterior through a pair of oviducts.

A slender nerve ganglion is present near the opening of the mantle. This opening of the mantle cavity is present at the anterior end and is provided with a sphincter muscle. Segmentation and appendages are absent in the adult mass. Larva is free-swimming and bears distinct crustacean features.