genus
Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
which belongs to the
phylum
In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...
Platyhelminthes
Platyhelminthes (from the Greek πλατύ, ''platy'', meaning "flat" and ἕλμινς (root: ἑλμινθ-), ''helminth-'', meaning "worm") is a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrates commonly called f ...
and
class
Class, Classes, or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used d ...
Monogenea
Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...
. Species of ''Microcotyle'' are
ectoparasite
Parasitism is a Symbiosis, close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the Host (biology), host, causing it some harm, and is Adaptation, adapted str ...
s that affect their host by attaching themselves as
larva
A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...
e on the
gills
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
of the
fish
A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...
and grow into adult stage. This larval stage is called
oncomiracidium
An oncomiracidium is the ciliated and free-living larva of a monogenean, a type of parasitic flatworm commonly found on fish. It is similar to the miracidium of Trematoda
Trematoda is a class of flatworms known as trematodes, and commonly as ...
, and is characterized as free swimming and
ciliated
The cilium (: cilia; ; in Medieval Latin and in anatomy, ''cilium'') is a short hair-like membrane protrusion from many types of eukaryotic cell. (Cilia are absent in bacteria and archaea.) The cilium has the shape of a slender threadlike pr ...
.
Species of ''Microcotyle'' have only one host in their entire life cycle. Different species of ''Microcotyle'' inhabit marine and freshwater and they can also infect different species of fishes. They are uniquely characterized by their
haptor
The haptor is the attachment organ of the monogeneans, a group of parasitic Platyhelminthes.
The haptor is sometimes called opisthaptor (from ''opistho-'': behind) to emphasize that it is located in the posterior part of the body, and to diffe ...
having a lot of tiny clamps on the lateral margins.
Although not really known to cause that much damage in marine wildlife, some of them are reported to cause agricultural problems like ''Microcotyle sebastis'' as an example. ''Microcotyle sebastis'' commonly affects ''Sebastes schlegeli'', a
mariculture
Mariculture, sometimes called marine farming or marine aquaculture, is a branch of aquaculture involving the cultivation of marine organisms for food and other animal products, in seawater. Subsets of it include ( offshore mariculture), fish fa ...
d fish in Korea.Kim, Ki. H, and Eun. Lee, and Se. Kwon, and Jae. Cho. (2001). Treatment of ''Microcotyle sebastis'' infestation in cultured rockfish ''Sebastes schlegeli'' by oral administration of praziquantel in combination with cimetidine. Diseases of Aquatic Organisms, 44 (2), pp. 133–136
Morphology
Individuals of species of ''Microcotyle'', like any typical
polyopisthocotylea
Polyopisthocotylea is a subclass of parasitic flatworms in the class Monogenea.WoRMS (2023). Polyopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119220 on 2023-12-21Yamaguti, S. (1963). Systema Helminthum Volu ...
n
monogenea
Monogeneans, members of the class Monogenea, are a group of ectoparasitic flatworms commonly found on the skin, gills, or fins of fish. They have a direct lifecycle and do not require an intermediate host. Adults are hermaphrodites, meaning they ...
n, have an anterior organ called prohaptor, which is mainly used for feeding and attachment. Although the prohaptor is not the primary attachment organ, it is used to anchor the body of the parasite while the opisthaptor is being repositioned. The opisthaptor is found in all ''Microcotyle'' species and it is an important attachment organ that allows these
ectoparasites
Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The en ...
to latch onto their hosts.
Located at the anterior part of the worm is the funnel-shaped mouth that is connected to the
pharynx
The pharynx (: pharynges) is the part of the throat behind the human mouth, mouth and nasal cavity, and above the esophagus and trachea (the tubes going down to the stomach and the lungs respectively). It is found in vertebrates and invertebrates ...
, followed by the
esophagus
The esophagus (American English), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...
that is smaller in diameter compared to the pharynx. About one tenth of the entire length of the worm, the esophagus then divides into intestinal crura, which extends further posteriorly. The cruca is divided into pouches, which extend between vitellaria. Vitallaria are glands that secrete yolk around the egg. This digestive pathway is observed to be continuous throughout the entire worm. Food particles were observed to be passing back and forth along these pathways in vivo.Remley, L. W. 1942. Morphology and life history studies of ''Microcotyle spinicirrus'' MacCallum 1918, a Monogenetic Trematode parasitic on the gills of ''Aplodinotus grunniens''. Transactions of the American Microscopical Society, Vol. 61, No. 2 (Apr., 1942), pp141–155
The worms are
hermaphroditic
A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic.
The individuals of many ...
, containing both male and female organs. Each worm has reproductive organs such as vas deferens,
testis
A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is Homology (biology), homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of Androgen, androgens, p ...
,
uterus
The uterus (from Latin ''uterus'', : uteri or uteruses) or womb () is the hollow organ, organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic development, embryonic and prenatal development, f ...
, vitelline duct,
ovary
The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...
, and
vitellaria
''Vitellaria paradoxa'' (formerly ''Butyrospermum parkii''), commonly known as shea tree, shi tree (, also ), or vitellaria, is a tree of the family Sapotaceae. It is the only species in the genus ''Vitellaria'', They also have flame cells that function as a
kidney
In humans, the kidneys are two reddish-brown bean-shaped blood-filtering organ (anatomy), organs that are a multilobar, multipapillary form of mammalian kidneys, usually without signs of external lobulation. They are located on the left and rig ...
and remove waste material. A short duct that opens to the outside on the dorsal surface is composed of four canals on each side, two posterior and two anterior, that come together laterally to the cirrus. During observation on immature specimens, these canals can still be seen. However, on adults, these canals are concealed by vitellaria.
Life cycle
Species of ''Microcotyle'' have a direct life cycle; no intermediate hosts are needed to complete its life cycle. Marine fishes are the definitive host of these parasites. The adults live on the gill of the fishes as ectoparasites. The eggs are released into water, hatch and develop as oncomiracidium. The oncomiracidia, free swimming form larvae, move around and attach to another fish and grow into adult stage. The life cycle of species of ''Microcotyle'' is completed and repeated again and again.
Treatment
Bath treatment using praziquantel is the effective methods of treating ''Microcotyle sebastis'' on rockfish.Kim, Ki. H, and Jae. Cho. (2000). Treatment of ''Microcotyle sebastis'' (Monogenea: Polyopisthocotylea) infestation with praziquantel in an experimental cage simulating commercial rockfish ''Sebastes schlegeli'' culture conditions.. Diseases of Aquatic Organisms, Vol.40: 229-231, pp. 229–231 An experiment was done to indicate that feeding a praziquantel-adsorbed diet significantly reduces the abundance of ''M. sebastis'' infestation, and bathing in 100 ppm praziquantel for 4 minutes is effective for controlling ''M. sebastis'' infestation in a practical rockfish culture system.
Species
According to the World Register of Marine Species,WoRMS (2018). Microcotyle Van Beneden & Hesse, 1863. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119381 on 2018-11-29 there are more than one hundred species in this genus: