Calydiscoides

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Calydiscoides
Calydiscoides euzeti.jpg
Calydiscoides euzeti
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Platyhelminthes
Class: Monogenea
Order: Dactylogyridea
Family: Diplectanidae
Genus: Calydiscoides
Young, 1969
Species

See text

Calydiscoides is a genus of monopisthocotylean monogeneans, included in the family Diplectanidae. [1]

The genus currently includes 16 species, which are all parasitic on the gills of marine fish of the family Lethrinidae and Nemipteridae. [1] [2] All species are from the Indo-Pacific Ocean. The type-species of the genus is Calydiscoides australis Young, 1969. [3]

Morphology

Lamellodisc of Calydiscoides euzeti Lamellodisc of Calydiscoides euzeti (Monogenea, Diplectanidae).png
Lamellodisc of Calydiscoides euzeti

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 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. [2] Generally, central lamellae are circles, but peripheral lamellae may be circles or semicircles.

Adults are hermaphroditic. The reproductive organ include a single ovary and a single testis. As in all diplectanids, the ovary (or germarium) is anterior to the testis and loops around the right intestinal caecum. Species of Calydiscoides are characterized by a sclerotized male copulatory organ, which is used in systematics to differentiate species.

Systematics

The characteristics of the lamellodisc, without paired elements, is the main character which differentiate Calydiscoides from other genera of the family Diplectanidae. Relationships of CalydiscoidesYoung, 1969 with Protolamellodiscus Oliver, 1969 are not clear; the two genera were described almost simultaneously, and it might be that they are synonym. [2] [4]

Hosts

Nemipterus furcosus JNC1121.JPG
Lethrinus ravus JNC1761 - MNHN 2006-1637.JPG
Threadfin breams (Nemipteridae) (up) and emperors (Lethrinidae) (bottom) are hosts of species of Calydiscoides in the Indo-Pacific Ocean

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 Ocean. Lethrinids known to harbour Calydiscoides species include Lethrinus miniatus , Lethrinus nebulosus and Lethrinus atkinsoni ; [2] nemipterids include Nemipterus japonicus , Scolopsis temporalis , Scolopsis monogramma , Scolopsis margaritifera and Pentapodus aureofasciatus . [5] [6] In all cases, species of Calydiscoides were only found on the gills of the fish.

List of species

List according to the World Register of Marine Species [7]

Related Research Articles

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<span class="mw-page-title-main">Diplectanidae</span> Family of flatworms

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<span class="mw-page-title-main">Squamodisc</span>

Squamodiscs are epidermal structures, which are typical of and found only in certain monogeneans of the family Diplectanidae. There are, typically, two squamodiscs, one ventral and one dorsal, located on the haptor of the monogenean. Squamodiscs are usually made up of scales embedded in the epidermis, which appear from the outside as rodlets arranged in rows.

<span class="mw-page-title-main">Lamellodisc</span> An organ of diplectanid Monogeneans

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. Lamellodiscs are made up of concentric lamellae embedded in the epidermis. Lamellodiscs are considered as special type of squamodiscs, which are homologous structure found in many diplectanid monogeneans but formed of rows of rodlets instead of lamellae.

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Pseudorhabdosynochus caledonicus is a diplectanid monogenean parasitic on the gills of the Blacktip grouper, Epinephelus fasciatus. It has been described in 2005.

<i>Lamellodiscus</i> Genus of flatworms

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<i>Pseudorhabdosynochus oliveri</i> Species of flatworm

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Pseudorhabdosynochus justinei is a species of diplectanid monogenean that is parasitic on the gills of the longfin grouper Epinephelus quoyanus. It was described in 2007 by Binjian Zeng and Tingbao Yang from material from the South China Sea, and redescribed in 2009 by Justine, Dupoux & Cribb from material from off Queensland, Australia.

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Rhabdosynochus is a genus of monopisthocotylean monogeneans, belonging to the family Diplectanidae.

References

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  7. WoRMS: Calydiscoides Young, 1969
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