Microcotyle brevis

Microcotyle brevis
Scientific classification
Kingdom:	Animalia
Phylum:	Platyhelminthes
Class:	Monogenea
Order:	Mazocraeidea
Family:	Microcotylidae
Genus:	Microcotyle
Species:	M. brevis
Binomial name
	Microcotyle brevis; Dillon & Hargis, 1965

Last updated November 09, 2019

Microcotyle brevis is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae.^[1]

In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. 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. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined.

Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods. Because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces is considered a typological, but not a phylogenetic classification.

Microcotylidae is a family of polyopisthocotylean monogeneans. All the species in this family are parasitic on fish.

Taxonomy

Microcotyle brevis was first described by Dillon & Hargis in 1965, based on one specimen from the gills of striped triplefin, Forsterygion varium . Dillon & Hargis (1965) noted the need for a study of this species based on more adequate material due to the contracted nature of the single specimen used for the description and thus the limitations of the given measurement. The type and only specimen of Microcotyle brevis was inadvertently destroyed during shipment to the U. S. National Museum.^[1]

Morphology

Microcotyle brevis has the general morphology of all species of Microcotyle , with a body comprising an anterior part which contains most organs and a posterior part called the haptor. The haptor is symmetrical, extending nearly to the level of the genital atrium and bears 60 clamps similar in structure and dissimilar in size, arranged as two rows, one on each side. The clamps of the haptor attach the animal to the gill of the fish. There are also two buccal suckers at the anterior extremity, provided with minute sclerotized tooth-like papillae. The digestive organs include an anterior, terminal mouth, a pharynx, a relatively short oesophagus and a posterior intestine bifurcating at the level of the genital atrium in two lateral branches provided with numerous secondary branches. Each adult contains male and female reproductive organs. The reproductive organs include an anterior genital atrium, armed with numerous very spines, a medio-dorsal vagina, a single ovary and 2-3 postovarian testes which are posterior to the ovary. The egg is provided with filaments at both ends.^[1]

Microcotyle is a genus which belongs to the phylum Platyhelminthes and class Monogenea. Species of Microcotyle are ectoparasites that affect their host by attaching themselves as larvae on the gills of the fish and grow into adult stage. This larval stage is called oncomiracidium, and is characterized as free swimming and ciliated.

The haptor is the attachment organ of the monogeneans, a group of parasitic Platyhelminthes. The haptor is sometimes called opisthaptor to emphasize that it is located in the posterior part of the body, and to differentiate it from the prohaptor, a structure including glands located at the anterior part of the body. According to Yamaguti (1963), the chief adhesive organ of the monogeneans, the haptor, is posterior, more or less discoid, muscular, may be divided into alveoli or loculi, is usually provided with anchors, has nearly always marginal larval hooklets, or is in a reduced form with anchors. The haptor may consist of symmetrical or asymmetrical, sessile or pedunculate, muscular suckers or clamps with or without supporting sclerites; accessory adhesive organs may be present in form of armed plaques, lappets or appendices.

Clamps are the main attachment structure of the Polyopisthocotylean monogeneans.
These ectoparasitic worms have a variable number of clamps on their haptor ; each clamp is attached to the host fish, generally to its gill. Clamps include sclerotised elements, called the sclerites, and muscles. The structure of clamps varies according to the groups within the Polyopisthocotylean monogeneans; microcotylids have relatively simple clamps, whereas gastrocotylids have more complex clamps.

Diagnosis

Microcotyle brevis differs from other congeners by body size, the haptor coinciding with the greater part of the body proper, and by the number of testes.^[1]

Hosts and localities

The type-host is the striped triplefin, Forsterygion varium (Tripterygiidae). The type-locality is Akaroa off New Zealand.^[1]

Akaroa is a small town on Banks Peninsula in the Canterbury region of the South Island of New Zealand, situated within a harbour of the same name. The name Akaroa is Kāi Tahu Māori for "Long Harbour", which would be spelled "Whangaroa" in standard Māori.

New Zealand is a sovereign island country in the southwestern Pacific Ocean. The country has two main landmasses—the North Island, and the South Island —and around 600 smaller islands. It has a total land area of 268,000 square kilometres (103,500 sq mi). New Zealand is about 2,000 kilometres (1,200 mi) east of Australia across the Tasman Sea and 1,000 kilometres (600 mi) south of the Pacific island areas of New Caledonia, Fiji, and Tonga. Because of its remoteness, it was one of the last lands to be settled by humans. During its long period of isolation, New Zealand developed a distinct biodiversity of animal, fungal, and plant life. The country's varied topography and its sharp mountain peaks, such as the Southern Alps, owe much to the tectonic uplift of land and volcanic eruptions. New Zealand's capital city is Wellington, and its most populous city is Auckland.

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References

1 2 3 4 5 Dillon, W. A., & Hargis, W. J. (1965). Monogenetic trematodes from the southern Pacific Ocean. 2. Polyopisthocotyleids from New Zealand fishes: the families Discocotylidae, Microcotylidae, Axinidae and Gastrocotylidae. Antarctic Research Series, 5, 251-280.

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[Dillon&Hargis1965-1] 1 2 3 4 5 Dillon, W. A., & Hargis, W. J. (1965). Monogenetic trematodes from the southern Pacific Ocean. 2. Polyopisthocotyleids from New Zealand fishes: the families Discocotylidae, Microcotylidae, Axinidae and Gastrocotylidae. Antarctic Research Series, 5, 251-280.