Fish Diseases and Management

4.1.1 Classification of parasites

Following are the important fish parasites belonging to different groupof invertebrates.

Protozoa

Single celled eukaryoticorganisms. Classification - Levine et al. 1980

Phylum Sarcomastigophora - Flagella / pseudopodia presentand single nucleus.

Subphylum Mastigophora. -

ClassPhytomastigophorea - contain chloroplasts in their cytoplasm -dinoflagellate parasites Oodinium / Piscinoodinium sp. and Amyloodiniumsp.

ClassZoomastigophorea - do not possess chloroplasts and have a varying number offlagella

Order:Kinetoplastida - one or two flagella. Cryptobia and Trypanosoma.

Order:Retortamonodida- two to four flagella, bodinid parasites of Ichthyobodo sp.

Order:Diplomonadida - one to four flagella - Hexamita

Subphylum Sarcodina

Order:Amoebida - amoebae possess pseudopodia - divide by asexual fission.

Phylum Apicomplexa

ClassSporozoea.

Order:Eucoccidiorida. - Haemogregarina,Eimeria, Cryptosporidia and Goussia.

Phylum Microspora - obligatory and intracellular parasites.

ClassMicrosporea -Microsporidium, Pleistophora and Glugea.

Phylum Myxozoa

ClassMyxosporea. Order: Bivalvulida. Spore- 2valves. - Myxidium, Sphaerospora, Ceratomyxa and Myxobolus.

Order:Multivalvulida. Spores with 3 or more valves. Kudoa.

Phylum Ciliophora

ClassKinetofragminophorea. Oral ciliature slightly distinct from body ciliature.

SubclassVestibuliferia. Includes Balantidium.

SubclassHypostomatia. Includes Chilodonella

SubclassSuctoria. Possess suctorial tentacles, adult sessile. Includes Trichophyra.

ClassOligohymenophorea. Oral ciliature distinct from somatic ciliature.

SubclassHymenostomatia. - Ichthyophthirius.

SubclassPeritrichia - Epistylisand Trichodina.

Phylum Platyhelminthes - flatworms.dorso-ventrally flattened, bilaterally symmetrical and acoelomate lack an anusand specialized skeletal, circulatory and respiratory systems. Majoritymonoecious

Class Monogenea. The monogeneans - no intermediate hosts - small worms< 3 cm in length. - haptor, armed with hooks or suckers.

sub-classes Monopisthocotylea and Polyopisthocotylea.

SubclassMonopisthocotylea. Gyrodactylidae (viviparous, parasitic on skin, gill and fins,0.3-1 mm) and Dactylogyridae (gill parasite, oviparous, 2mm).

SubclassPolypisthocotylea.

ClassDigenea. -endoparasitic - metacercarial stages – encysted in fish

ClassCestoidea - endoparasitic - scolex - parasitic in intestine

Phylum Nematoda - bilaterally symmetrical-cylindrical body tapering at both ends. They possess gut and are sexuallydimorphic.

Phylum Acanthocephala - elongate cylindrical worms having retractile proboscis bearing hooks. They have no guts and the sexes areseparate.

Phylum Mollusca The larvae of fresh-water bivalve molluscs are often found attached to the gills and outer surfaces of fish. The larvae have thin bivalve shells often with little hooks on their inner edge.

Phylum Arthropoda

Class Crustacea - Crustaceans are bilaterally symmetrical animals with segmented bodieshaving jointed appendages. The body is covered with a rigid chitinoidexoskeleton.

Subclass Branchiura. Body flattened dorsoventrally -prehensilesuckers, They also have pre-oral proboscis. e.g. Argulus.

Subclass Copepoda. Mainly ectoparasitic in fish. Ergasilu s, Lernaea Cyclopidea, Caligidea andLernaeopodidea.

Phylum Annelida

These are  segmented,coelomate worms with a muscular body wall. Important fish parasite under this group is the leech, which may also act as vectors for other pathogens.

ClassHirudinea - They have asegmented body round or dorsoventrally flattened with anterior and posteriorsuckers. Leeches are ectoparasitic on fish.

Phylum Chordata

The lampreys, or cyclostomes,which are eel-like, mostly fresh-water or anadromous, jawless fishes having around suctorial disc-like mouth with horny teeth attach to other animals andact as parasites.