Tetraonchidae is a small and relatively monomorphic family of dactylogyroid monogeneans. Since the morphology of sclerites of the attachment organ (haptor) is one of the primary criteria in tetraonchid taxonomy, the confocal study of sclerites and associated musculature may provide valuable taxonomic information.
The aim of this study was to examine the haptoral sclerites and musculature in Tetraonchus monenteron (Wagener, 1857), a common parasite of pike.
Haptoral musculature of T. monenteron was studied using phalloidin staining and confocal microscopy, with sclerites visualized in the reflection confocal mode.
Haptoral armature of T. monenteron consists of ventral and dorsal pairs of anchors, a ventral bar, eight pairs of marginal hooks and at least three pairs of accessory sclerites. Anchors are operated by 14 muscles, of which the most prominent are extrinsic muscles, the transverse muscle interconnecting the ventral anchors, three muscles connecting the ventral anchor to the ventral bar, and four muscles of the dorsal and ventral anchors inserting on the haptoral wall. The extrinsic muscles are attached to the braceshaped sclerites, which in turn are connected to the dorsal anchors via muscle bundles.
The gaffing action of the dorsal anchors is likely to be achieved by the extrinsic muscles and the transverse muscle that clamps the extrinsic muscles against the body wall. The ventral anchors are probably held in attached position by the transverse muscle and four muscles inserting on the ventral bar and haptoral wall. The haptoral musculature may have potential utility for tetraonchid taxonomy.
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Anterior ridge of the ventral bar
Blade of the dorsal anchor
Muscle bundles of the brace-shaped sclerites
Blade of the ventral anchor
Central bridge of the ventral bar
Muscles connecting the dorsal anchor to flabellate sclerite
Muscles connecting the dorsal anchor to the body wall
Dorsal branch of the extrinsic muscles
Muscles connecting the ipsilateral dorsal and ventral anchors
Muscle connecting the opposite dorsal and ventral anchors
Muscle of the filament loop
Inner root of the dorsal anchor
Fibrous loop of the dorsal anchor
Lateral branches of the extrinsic muscles
Fibrous loop of the ventral anchor
Blade of the marginal hook
Protractor muscle of the marginal hook
Shaft of the marginal hook
Outer root of the ventral anchor
Posterior endings of the extrinsic muscles
Ridge on the inner root of the dorsal anchor
Ridge on the inner root of the ventral anchor
Ridge on the outer root of the dorsal anchor
Ridge on the outer root of the ventral anchor
Retractor muscle of the hook-bearing papilla
Thumb of sickle
Tip of the inner root of the dorsal anchor
Tip of the inner root of the ventral anchor
Tip of the outer root of the dorsal anchor
Tip of the outer root of the ventral anchor
Transverse muscle of the ventral anchors
Muscles connecting the ventral anchor and the ventral bar
Muscle connecting the ventral anchor to the body wall
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This work was supported by budget funding of the Russian Academy of Sciences (projects AAAA-A17-117030110029-3 and AAAA-A17-117030310322-3). Confocal microscopy was performed at the “Taxon” Research Resource Centre (Zoological Institute RAS) (http://www.ckp-rf.ru/ckp/3038/).
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Petrov, A.A., Gerasev, P.I. Muscular Arrangement and Sclerite Morphology in the Haptor of Tetraonchus monenteron (Monogenea, Dactylogyridea). Acta Parasit. 64, 138–147 (2019). https://doi.org/10.2478/s11686-018-00015-7
- Confocal microscopy