Lamellodisc of Calydiscoides euzeti (Monogenea, Diplectanidae)

Squamodiscs are epidermal structures, which are typical of and found only in certain

monogenea Monogeneans 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 have both male and female reprod ...

ns of 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 numerou ...

. There are, typically, two squamodiscs, one ventral and one dorsal, located on 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 differ ...

of the monogenean. Squamodiscs are usually made up of scales embedded in the epidermis, which appear from the outside as rodlets arranged in rows. According to the classical book of Bychowsky (1967), Bychowsky, B. E. (1957) Monogenetic Trematodes. Their systematic and phylogeny. Akad. Nauka. USSR. English translation by the American Institute of Biological Science, Washington. 509 pp. “the Diplectanidae] have special paired attaching formations lying above the disc and also partially on it, on the dorsal and ventral sides in the shape of small rounded convexities equipped with numerous ..thorn-shaped little hooks or thin thread-like plates located more or less in concentric rows ("squamodisc")". Ultrastructural studies of squamodiscs have shown that they include epidermally-embedded spines which are covered by the outer epidermal membrane. The spines are composed of a moderately electron-dense material with denser fibrils embedded within it. A diplectanid genus ''Squamodiscus'' Yamaguti, 1934 was created but is now considered Yamaguti, S.(1963). Systema Helminthum Volume IV Monogenea and Aspidocotylea: John Wiley & Sons. a synonym of '' Diplectanum'' Diesing, 1858. Some diplectanids, such as members of the

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial ...

'' Lamellodiscus'' or ''

Calydiscoides ''Calydiscoides'' is a genus of monopisthocotylean monogeneans, included in the family Diplectanidae. The genus currently includes 16 species, which are all parasitic on the gills of marine fish of the family Lethrinidae and Nemipteridae. A ...

'', have a similar structure which is composed of lamellae, not rodlets; in this case the structure is called a lamellodisc.

References

{{reflist Platyhelminth anatomy Animal morphology Parasitic protostomes Monogenea Monopisthocotylea Diplectanidae