Calydiscoides
| Calydiscoides | |
|---|---|
 |
|
| Calydiscoides euzeti | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Platyhelminthes |
| Class: | Monogenea |
| Subclass: | Monopisthocotylea |
| Family: | Diplectanidae |
| Genus: |
Calydiscoides Young, 1969 |
| Species | |
|
Many, see text |
|
Many, see text
Calydiscoides is a genus of monopisthocotylean Monogenean, 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. All species are from the Indo-Pacific Ocean. The type-species of the genus is Calydiscoides australis Young, 1969.
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 main elongate body and a posterior haptor. The digestive system includes an anterior muscular pharynx, and two lateral intestinal branches (or caeca); as in all Platyhelminthes, there is no anus. The haptor, in the posterior part of the body, is a specialized organ used to attach to the host. 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 lamellodiscs, which are made up of cencentric 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. Generally, central lamellae are circles, but peripheral lamellae may be circles or semicirles.
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