''Calydiscoides'' is a
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 ...
of
monopisthocotylea
The Monopisthocotylea are an inferior class of parasitic flatworms in the class Monogenea.WoRMS (2019). Monopisthocotylea. Accessed at: http://www.marinespecies.org/aphia.php?p=taxdetails&id=119219 on 2019-02-08
Yamaguti, S. (1963). Systema Helmi ...
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 ...
ns, included in the family
Diplectanidae
The Diplectanidae are a family of monopisthocotylean monogeneans. They are all parasitic on the gills of fish (marine or freshwater). Diplectanids are small animals, generally around 1 mm in length. As parasites, they can be extremely numero ...
.
The genus currently includes 16
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, which are all parasitic on the
gill
A gill () is a respiration organ, respiratory organ that many aquatic ecosystem, 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 r ...
s of marine fish of the family
Lethrinidae and
Nemipteridae.
Indo-Pacific
The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
Ocean.
The type-species of the genus is '' Calydiscoides australis'' Young, 1969.
Morphology
All species of ''Calydiscoides'' are small animals, ranging 0.5–1 mm in length.
As with most monogeneans, they are flat, with an anterior head bearing four oculi and head glands
A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...
, a main elongate body and a posterior 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 ...
. The digestive system includes an anterior muscular 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 ...
, and two lateral intestinal branches (or caeca); as in all 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 ...
, there is no anus. The 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 ...
, in the posterior part of the body, is a specialized organ used to attach to the host
A host is a person responsible for guests at an event or for providing hospitality during it.
Host may also refer to:
Places
* Host, Pennsylvania, a village in Berks County
* Host Island, in the Wilhelm Archipelago, Antarctica
People
* ...
. The haptor includes sclerotized elements, namely a ventral bar, two lateral (dorsal) bars, two ventral hooks, and two dorsal hooks, and fourteen hooklets. As in most diplectanids, the haptor bears characteristic, structures called squamodiscs (one ventral and one dorsal).
The squamodiscs of species of ''Calydiscoides'' are special: they are lamellodisc
Lamellodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two lamellodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Lamellodis ...
s, which are made up of concentric lamellae, not separate rodlets as in regular squamodiscs. The diameter of the lamellodiscs range 25–60 μm. When observed from its concentric axis (ventral or dorsal observation of the specimen, 'polar' view of the lamellodisc), the lamellodisc appears as concentric circles.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 a single 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 ...
. As in all diplectanids, the 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 ...
(or germarium) is anterior to the 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 ...
and loops around the right intestinal caecum.
Species of ''Calydiscoides'' are characterized by a sclerotized male copulatory organ, which is used in systematics
Systematics is the study of the diversification of living forms, both past and present, and the relationships among living things through time. Relationships are visualized as evolutionary trees (synonyms: phylogenetic trees, phylogenies). Phy ...
to differentiate species.
Systematics
The characteristics of the lamellodisc, without paired elements, is the main character which differentiate ''Calydiscoides'' from other genera
Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...
of the family Diplectanidae. Relationships of ''Calydiscoides'' Young, 1969 with '' Protolamellodiscus'' Oliver, 1969 are not clear; the two genera were described almost simultaneously, and it might be that they are synonym.
Hosts
Hosts of species of ''Calydiscoides'' are only members of the families Nemipteridae (threadfin breams) and Lethrinidae (emperors). These families are restricted to the Indo-Pacific
The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
Ocean. Lethrinids known to harbour ''Calydiscoides'' species include '' Lethrinus miniatus'', '' Lethrinus nebulosus'' and '' Lethrinus atkinsoni'';
List of species
List according to the World Register of Marine Species
*'' Calydiscoides australis'' Young, 1969[ Yamaguti, S. 1953: Parasitic worms mainly from Celebes. Part 2. Monogenetic trematodes of fishes. Acta Medicinae Okayama, 8, 203-256 + 209 Pl]
ArticlePDF
*'' Calydiscoides duplicostatus'' ( Yamaguti, 1953) Young, 1969[ ]
References
External links
{{Taxonbar, from=Q18579589
Diplectanidae
Monogenea genera