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Nematodes in Fisheries

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It shows the body plan,morphology, Taxonomy of nematodes with their parasitism in tropical fishes,temperate fishes,elasmobranch etc

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Nematodes in Fisheries

  1. 1. Abisha.S.J FC&RI, Tuticorin
  2. 2. Lecture topics Introduction General information Morphology Each system Important fish parasite- capillaria, camallanus Sys classification Host pathogen Relation(pathology) Diagnosis Prevention control
  3. 3. Nematodes are the most numerous multicellular animals on earth. A handful of soil will contain thousands of the microscopic worms, many of them parasites of insects, plants or animals. There are nearly 20,000 described species classified in the phylum Nematoda. In size they range from 0.3mm to over 8 metres.
  4. 4. Common parasite of both Marine and Fresh water fishes.  Although parasitic nematodes can infect almost all organs in a fish, the majority of the currently known species have been described from the intestine. Adult worm in the ovary . Liverwith encysted, anisakid, nematode larvae.
  5. 5. A typical nematode is elongate and cylindrical in cross-section.  Both the larval and adult stages of nematodes parasitise fish, and numerous species have been reported from native fish species, including Spinitectus from Murray cod (Figure).  Nematodes will infest all types of tissues and organs. Nematodes are not often reported as being a serious problem in farmed fish. Head region of the nematode Spinitectus from Murray cod
  6. 6. Taxonomy Phylum – Nematoda Class - Adenophorea Secernentea. Families- Dioctophymatidae, Camallanidae Capillariidae Cystiopsidae i. Adenophorea consist mostly of free-living marine and freshwater species, as well as terrestrial soil nematodes with only a small number of parasitic organisms ii. Secernentea also have free-living taxa, but the vast majority of this class are parasitic organisms.
  7. 7. Classification of the Nematoda PhylumNematoda Class Order Adenophorea EnoplidaI solaimida Mononchida Dorylaimida Trichocephalida Mermithida Muspiceida Araeolaimida Chromadorida Desmoscolecida Desmodorida Monhysterida Secernentea Rhabdita Camallanida Diplogasterida Strongylida Ascaridida Spirurida Tylenchida Aphelenchida
  8. 8. Shape •Elongated, cylindrical; unsegmented Sexes Separate (diecious Head space •No suckers ,no hooks. Well developed buccal capsule in some species Alimentary canal •Present and complete; Anus Present Body cavity present
  9. 9. Generally elongated worm with cylindrical body tapering at the both ends - fusiform shape Most fish nematodes are a whitish to tan color Some are Reddish due the color of Pseudocoelomic fluid •Pseudoterronova larvae – own heamoglobin •Camallanus sp – from feeding on host blood Swim bladder worms ( Anguillicola ). Dark color is due to feeding on blood
  10. 10. The cuticle of nematodes  is elastic, and it is thick in gut-dwelling species (Hysterothylacium, Eustrongylides) and relatively delicate in histozoic specimens (Philometra rischta, Daniconema anguillae) External surface • smooth • some have row of spines on their cuticle (eg;Spintetctus, Gnathosoma) Body wall lacks Circular muscle Body covered by Collagenous Cuticle shed periodically in life of nematodes by Ecdysis The cuticle are without cilia.
  11. 11. •Mouth have lips may prominent in later larval stages and reach their full expressions in adult The structure of the mouth shows great variations. It may be a simple slit-like opening at the anterior end surrounded by distinct or indistinct papillae (Capillaria, Philometra), but it can form large labia or cuticular outgrowths (Fig) called Interlabia (Hysterothylacium, Anisakis, Raphidascaris)
  12. 12. The mouth leads into the buccal capsule (Figs12.7and12.8),which can be sclerotized and furnished with large denticles, ridges, plates or tridents (Camallanus, Cucullanus, Skrjabillanus, Anguillicola).
  13. 13. Some have teeth guarding the rim of mouth ( Anguillicola) Most of them posses sensory structures such as papillae that surround the mouth and the anterior end which serve as chemoreceptors
  14. 14. The male reproductive organ usually consists of testis, vas deferens, seminal vesicle and ductus ejaculatorius. The ejaculary duct, opening into the cloaca, has some accessory copulatory organs. The most common accessory organs are the sclerotized spicules. Mostly 2 Spicules Angullicola-nil Capillaridae-1
  15. 15. The female reproductive organs are composed of ovaries, oviducts, uteri, vagina and vulva.  In Capillaria and Raphidascaris spp - the vulva is found in the first part of the body length,  but in Camallanus and Rhabdochona spp -posteriorally. The Capillospirura -at mid-length. In adult Philometra spp -the vulva and vagina are absent They do not have protonephridia, respiratory organs or blood systems Female nematodes are usually larger than males Life cycle Most fish nematodes are Oviparous
  16. 16. Nematodes have been characterized as a tube within a tube; referring to the alimentary canal which extends from the mouth on the anterior end, to the anus located near the tail. Nematodes possess Digestive system,  nervous system,  excretory system, and reproductive systems, but lack a discrete circulatory or respiratory system
  17. 17. The Nematode Body Plan The phrase tube-within-a-tube is a convenient way to think of nematode body structure, and also a term used to refer to a major trend in the evolution of triploblastic metazoa . It refers to the development of a fluid-filled cavity between the outer body wall and the digestive tube.
  18. 18. Nematodes have 3 cell layers Ectoderm-Outer tissue layer(epidermis) Mesoderm- middle muscle tissue layer(muscle) Endoderm- innermost tissue layer(body cavity) They are  bilaterally symmetrical vermiform. Body covered in a complex cuticle.
  19. 19. (A)acoelomate, (B) pseudocoelomate, and (C)eucoelomate The nature of this body cavity has led to the grouping of metazoa into three grades, acoelomate, pseudocoelomate, and eucoelomate . Nematodes are traditionally grouped together as pseudocoelomates. Because they have internal cavity that is not lined with peritoneum. Therefore it is not a “true” coelom
  20. 20. Male nematodes are usually smaller than their female counterparts. Basic male reproductive structures include: one testis, a seminal vesicle and a vas deferens opening into a cloaca. One testis is most common, but two testis are found in some species, while in others one testis is reduced. Spermatogonia are produced in the testis and stored in the seminal vesicle until the nematode mates. Reproductive system
  21. 21. The presence of one or two copulatory spicules helpdialate the vulva and can also serve as a canal for the spermatozoa.  The spicules are made from hardened cuticle, terminating in sensory dendrites near the tip.  Often the body wall around the cloaca is modified into a bursa, which helps orient the male nematode and then helps hold the two nematodes together.
  22. 22. Spermatozoa Spermatozoa are amoeboid, and can have many different modifications. Some spermatozoa are round to ovoid in shape while others bear a resemblance to flagellated sperm. Different types of spermatozoa characterize different taxonomic groups of nematodes
  23. 23. The basic female structure includes: one or two ovaries, seminal receptacles, uteri, ovijector and a vuvla. The ovary produces oogonia, which later develop into oocytes. The seminal receptacles, sometimes developed into a spermathecea, stores the spermatozoa until they are needed to fertilize an ooctye.
  24. 24. The fertilized oocyte then develops into an egg in the uterus. The uteri often ends in an ovejector. The ovijector is very muscular and uses body movement combined with the high internal body pressure of the nematode to expel the egg through the vagina.
  25. 25. All nematodes lay eggs. Syngamy, or cross fertilization, is common in most nematodes. Hermaphroditism also occurs, with the nematode gonads producing spermatozoa first and storing them until the eggs are produced. Parthenogenesis is also a normal means of reproduction in some nematodes Nematodes laying eggs
  26. 26. The Digestive System The nematode digestive system is generally divided into three parts, the stomodeum, intestine, and proctodeum. The stomodeum consists of the mouth and lips buccal cavity, and  the pharynx (esophagus). Each of these regions are used extensively in taxonomy and classification of nematodes, as well as providing as indication of feeding habit or trophic group.
  27. 27. For example, the buccal cavity of plant parasitic nematodes (and some insect parasites ) is modified in the form of a hollow spear, adapted to penetrate and withdraw the contents of host cells. Predaceous nematodes often have a buccal cavity characterized by teeth or hook-like projections. The buccal cavity of bacterial feeding nematodes is relatively unadorned.
  28. 28. The oesophagus and buccal cavity is lined with cuticle The proctodeum (back ectodermal part of an alimentary canal)also lined with cuticle. The intestine streches from the oesophagus to proctaodeum and is simple tube like structure. The digestive system works when food is secreted by different enzymes found in the glands in the esophagus. Afterwards, it is then sent through the oesophagus to the intestine
  29. 29. Like many living things, nematodes exchange gases with the atmosphere. However, unlike many living things nematodes lack a formal respiratory system. The respiratory system is responsible for performing gas exchange. • In mammals and reptiles, this system consists of trachea, lungs and bronchial tubes. •In the respiratory system of fish the dominant feature is gills. Nematodes do not possess any of these organs, instead, nematode respiration works in a much more simplistic manner. We will examine this in the next slide.
  30. 30. Nematode Respiration Nematode respiration relies on a process calleddiffusion. Diffusion is when molecules, in this case gas molecules, move from an area of higher concentration into an area of lower concentration. Diffusion For example, what would happen if you placed a drop of blue food coloring into a glass of water? Think about it..
  31. 31. The answer is that the drop would slowly spread throughout the glass until all the water was tinted blue. This simple example demonstrates diffusion in that the drop initially had a high concentration of blue dye and the water had a low concentration. The blue dye then moved from the area of greater concentration (the drop) into an area of lower concentration (the water), thus precisely modeling our definition of diffusion
  32. 32. Here you'll notice a picture of the body layout of a nematode. Now, with respiration we're primarily concerned with two gases, oxygen and carbon dioxide. Oxygen is the primary gas animals inhale for use in respiration. Carbon dioxide is a waste product of respiration, and is the primary gas animals exhale. Now notice where the greater concentrations of each gas reside within the image.
  33. 33. The circulatory system is obviously not present in the organisms in this phylum, therefore, the species in this phylum obtain a pseudocoelom, which is basically the body cavity of any multicellular organism filled with superfluous amount of fluids, and also transports the specific nutrients, oxygen, etc. The circulatory system So, because there is an absent of the circulatory system, the metabolic waste is excreted by two ducts that the species have.
  34. 34. The Excretory system The nematode have a network of excretory tubes, which transfer the much of the solid waste to an anus of the worms. The nematode is one of the simplest creature to have two openings for excretion, rather than one in similarly developed organisms.
  35. 35. The secreted / excreted material from the canal and gland cell passes through a cuticle lined excretory duct located just below the terminal bulb of pharynx and is deposited outside via the pore at the ventral midline Four distinctive cell types make up the excretory system One pore cell One duct cell One canal cell(excretory cell) Fused pair of gland cell
  36. 36. The worms also release salt through the body. There are two ways to release this based of the nature of the worm. Parasitic worms tend to have a glandular process to excrete, while nonparasitic worms tend to have a much more tubular method of releasing their salty waste
  37. 37. Life cycles differ depending upon the species of nematode. Organisms that contain the reproductive adult stages of nematodes are known as final or definitive hosts. Organisms that are required for the completion of a nematode life cycle but do not contain the final reproductive adult stage are known as intermediate hosts.
  38. 38. Indirect life cycle where the fish is the final (definitive) host. The nematode eggs/larvae (a) enter an aquatic invertebrate intermediate host (b), such as a copepod, tubifex worm, or insect larva, prior to being eaten by or entering the final host fish (c).
  39. 39. In direct life cycle it does not need an intermediate host and infection can spread directly from one fish to another by ingestion of eggs or larvae.
  40. 40. Some nematodes have the ability to survive in "alternative" organisms, known as "paratenic" hosts. These hosts are not required for completion of the life cycle but they can contain infective nematode life stages and be a source of infection . They can be fish, worms or other aquatic organisms that eat the nematode eggs or larvae
  41. 41. Eustrongylides Camallanus Capillariaa
  42. 42. Capillaria spp Large round worm Commonly found in the gut of angel fish Often recognised by its double operculated eggs in the female worm
  43. 43. Capillaria Species The Capillarids as a group can infect a wide variety of fish hosts. Capillaria pterophylli is a relatively common nematode seen in the intestines of cichlids (including angelfish and discus). Capillaria species are also seen in cyprinids, gouramis, tetras and other species of fish. Capillaria females are easily identified when they are carrying the brown, barrel-shaped eggs with a plug-like structure on each end
  44. 44. Capillaria species have direct life cycles, and can spread from one fish to another by ingestion of infective larvae. It may take Capillaria pterophylli eggs up to three weeks at 68- 73°F (less time at warmer temperatures) before they contain embryos developed enough to be infective when ingested by a fish. The length of time required from infection until the mature adult parasites are producing eggs or larvae is approximately three months at these temperatures.
  45. 45. Even though Capillaria species have direct life cycles, a tubifex worm may act as a paratenic (alternative) host and "carry" infective stages of Capillaria to the fish that consumes them
  46. 46. Diagnosis Capillaria species are relatively transparent , if only immature or male nematodes are present, they may be easily missed during necropsy. However, Capillarid infection is relatively easy to diagnose when females containing the typical barrel-shaped eggs with a polar plug on each end (opercula) or eggs alone are present in the intestinal tract. Capillaria philippinensis
  47. 47. Treatment Capillarid infections can be treated with dewormers such as levamisole or fenbendazole . To avoid reinfection, organic debris and feces should be removed as often as possible, especially following deworming treatment.
  48. 48. Prevention Brood stock should be evaluated for the presence of nematodes prior to use and periodically throughout the breeding period. Proper sanitation will help prevent the spread of nematodes and reduce infection loads. Live foods, such as oligochaete worms (e.g., tubifex worms), may act as carriers, and their use should be avoided if possible tubifex worms – live fish food
  49. 49. Capillaria philippinensis Scientific classification Kingdom: Animalia Phylum: Nematoda Class: Adenophorea Subclass: Enoplia Order: Trichocephalida Family: Capillariidae Genus: Capillaria Species: C. philippinensis
  50. 50. Capillaria philippinensis is a parasitic nematode which causes intestinal capillariasis The natural life cycle of C. philippinensis is believed to involve fish as intermediate hosts, and fish-eating birds as definitive hosts. Humans acquire C. philippinensis by eating small species of infested fish whole and raw Longitudinal section of an adult C.philippinensis from an intestinal Biopsy specimen stained with H&E
  51. 51. Pathology Although C. philippinensis infections are rare, it can serve as an indicator that one is being exposed to raw or undercooked fish. Worms create infection by penetrating the mucosa of the small intestine and reentering the lumen. As they progress into the body, they cause the mucosa and submucosa to degenerate. Infected people can have abdominal pains, diarrhea, weight loss, weakness, malaise, anorexia, and emaciation. They also experience loss of proteins and electrolytes and malabsorption of fats and sugars. If symptoms and the number of worms increase, it can eventually lead to death
  52. 52. Camallanus Species Camallanus species infect the gastrointestinal tract of cichlids, live- bearers (including guppies and swordtails), and other species of freshwater fish. Usually, the first evidence of infection is a red, worm-like animal protruding from the anus of a fish
  53. 53. Camallanus species have indirect life cycles and are live-bearing nematodes. They are considered "ovoviviparous" ("ovo" is the scientific term for "egg" and "viviparous" means live-bearing), as females incubate the eggs which hatch into larvae within their bodies . Close up of a Camallanus sp. female showing larvae inside.
  54. 54. These larvae are excreted into the water with the fish's feces and are ingested by a copepod or other crustacean. Within the copepod, the larvae develop further into a third-stage larvae. After the copepod, containing the third-stage larvae, is eaten by the appropriate fish host, the larvae migrate out into the fish, develop into reproductive adults, and the life cycle is complete
  55. 55. Diagnosis Camallanus species can be identified by their red color. Their location further toward the posterior of the intestinal tract than other worm-like parasites (typically very near, and often protruding from, the anus of the fish). The presence of a buccal capsule (mouth structure) that is divided into two lateral valves, giving the mouth a slit like appearance; and, if gravid females are present, the presence of both eggs and larvae within their bodies.
  56. 56. Treatment Because Camallanus nematodes are located within the intestinal tract, common dewormers should be effective. Prevention As a copepod or other crustacean host is required to complete the life cycle, avoiding the use of copepods or related crustaceans as food items will help reduce potential for infection. Evaluation of brood stock for the presence of parasites prior to use will also aid in identifying carriers.
  57. 57. Camallanus cotti The pathology induced by the nematode Camallanus cotti in the aquarium fishes Beta splendens (beta fish) and Poecilia reticulata (guppy) consisted of gross and microscopic lesions, In beta fish it is characterized by  abdominal swelling with reddish parasites  protruding from the anus in both fish hosts similar in the beta fishes and guppies,  by hemorrhage,  congestion, edema, a few glandular elements, and extensive erosion areas in the rectum mucosa, with a marked thickening of the wall and absence of inflammatory infiltrate.
  58. 58. Eustrongylides Eustrongylides is a nematode that uses fish as its intermediate host. The definitive host is a wading bird, a common visitor to ponds. The worm encysts in the peritoneum or muscle of the fish and appears to cause little damage. Because of the large size of the worms ( Figure ), infected fish may appear unsuitable for retail sales.
  59. 59. Target Tissues: Internal tissues Appearance: Grossly visible; coiled, reddish worm (encysted) Size: Larvae (found in fish) 11-83 mm in length Movement: Movement usually not seen in fish Eustrongylides species can be found in muscle, “free” within the body cavity, or encapsulated on the liver and other organs, but they are found outside the intestinal tract of fish.
  60. 60. Eustrongylid nematodes can affect a number of different species, including  yellow perch, pumpkinseed, mummichug, guppies,  gar, danios, and angelfish. Affected fish typically have bloated abdomens (dropsy), as the nematodes frequently migrate into the body cavity from the gut and can be quite large.
  61. 61. Eustrongylides species have complex, indirect life cycles. Adult Eustrongylides tubifex and other Eustrongylid nematodes are found in fish-eating birds. The eggs are shed by the birds into ponds, where they develop into a life stage that is consumed by an oligochaete worm, such as the tubifex worm. Within these tubifex worms, the nematodes develop still further into a third larval stage, known as an "L3", which is the life stage of the Eustrongylides group that can infect fish when eaten. Once the tubifex worm containing the L3 stages is eaten by a fish and digested, the nematodes migrate (within the fish) into the body cavity and, frequently, over the external surface of internal organs such as the liver.
  62. 62. The eggs of all Eustrongylides species are very tough and can easily survive for some time in fish ponds. At about 77°F, it can take anywhere from three months to four and one- half months from the time the bird infects the pond with Eustrongylides eggs until the time fish become infected After this 3-4 month period, fish raised in ponds with a population of fish-eating birds have an even greater chance of becoming infected as the number of nematodes increases over time.
  63. 63. Diagnosis As Eustrongylides species infect areas outside the gastrointestinal tracts of fish, necropsy of a small group of affected fish is the only sure method to identify them. During necropsy Eustrongylides species, such as E. tubifex, are easily identified from their location in the fish (encysted in mesenteries of the body cavity or in muscle), their red coloration, and their relatively long bodies (11-83 mm); however, there are other nematodes that may appear similar so positive identification will require examination by a veterinarian, other fish health specialist, or parasitologist.
  64. 64. Treatment Other than mechanical removal, there is no effective treatment for these nematodes due to the location of the larvae within the coelomic cavity or in the muscle. Culling affected fish is recommended.
  65. 65. Prevention Removal of the final host (fish- eating birds) or any intermediate hosts (tubificid worms or other oligochaetes) will help reduce the infection rate. Sanitation of ponds or tanks will help remove any intermediate hosts. Sanitation of ponds at the very minimum of once or twice a year is recommended.
  66. 66. Parasites of freshwater tropical fishes No genera associated with freshwater tropical fishes. Eustrongyloides- encysted in muscles Capillaria- frequently found in FW Camallanus- Guppies and swordtails seem to be most frequent Adult & larval forms – in lumen of intestine Free migratory forms – peritonieal Cavity Encysted forms – in musculature Heavy and moderate infections with Anguillicola crassus in opened swim bladders of European eels
  67. 67. Parasites of marine tropical fishes Crustaceans – 1st intermediate host Ascaridoidae- Anisakis, Contracaecum, Terranova Spiruroidae – Ascarophis, metabronema Camallonoidae- Aslanus, Camallanus Dracunuloidae- Philometra, philonema Common pathology visceral adhesion Edema Granuloma Philometra oviata in gudgeon Heavy infestation reported in White spotted puffer fish from Hawaiian waters
  68. 68. Parasites of Elasmobranch •Very small no •Only 68 sp Most belongs to 2 families 1. Heterocheilidae of order Ascanididae 2. Cucullanidae of the order of Spiruridae Primarily in digestive tract  visible nodules on the exterior of the intestion Nematodes of shark require atleast one intermediate host usually Crustaceans Second intermediate host – fish (Pleuronectidae, Gadidae)
  69. 69.  Fish disease and Disorders Volume 2 by P.T.K. Woo  Fish pathology – 4 th edition By Roberts  Introductrion to Freshwater Fish Parasites by RuthEllen Klinger and Ruth Francis Floyd  Fish Disease- Volume 2 By Jorge C.Eiras , Helmut Segner, Thomas Wahli, B.G. Kapoor  Fish Disease diagnosis and treatment by Edward.J.Noga  Marine parasitology Edited by Klaus Rhode  http://edis.ifas.ufl.edu

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