Redescriptions of species of Ancyrocephaloides Yamaguti, 1938 (Monogenea: Ancyrocephalidae) from triacanthid fishes caught off Peninsular Malaysia and a report of their haptoral secretions
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Abstract
Numerous specimens of Ancyrocephaloides triacanthi Yamaguti, 1938 and A. chauhani Bychowsky & Nagibina, 1975 were collected from two triacanthid fishes, Triacanthus biaculeatus and Tripodichthys blochii, off Peninsular Malaysia. The two monogenean species are redescribed and considered to be the only valid species of Ancyrocephaloides Yamaguti, 1938. Examinations of these worms revealed new features, e.g. the presence of exudates (both net-like and bundle-like) and superficial grooves in the anchors in both species, which necessitated re-descriptions of the two species and amendments to the generic diagnosis. Both species have relatively small anchors with two lateral superficial grooves along the shaft and point, peduncular glands and four large, pyriform secretory reservoirs in the peduncular-haptoral region, each with a single tubular extension to an associated anchor, and net-like structures (exudate) attached to the anchors. The net-like structures are one of the external manifestations of the secretion produced in the peduncular glands and stored in the pyriform secretory reservoirs. When released within the gill-tissue of the host, the exudate is in the form of bundles which extend within the gill-filament. The small anchors convey secretions from the secretory reservoirs via lateral superficial grooves into the gills as the anchors pierce the host tissue for attachment. The secretion coagulates as left and right thread-like bundles of exudate within the gill tissues and is only apparent as nets when it is released into the surrounding water. The recurved point of the anchor and position of the point of exudation allow the nets to remain attached to the anchor point, even after the detachment of the anchors from the gill tissue. This exudate possibly acts somewhat like a ‘belay device’ or ‘safety belt’, preventing the parasite from being washed away by the respiratory current during the onset of its leech-like locomotion, as well as assist the relatively small anchors in attachment.
Keywords
Gill Tissue Copulatory Organ Seminal Receptacle Intestinal Caecum Accessory PieceNotes
Acknowledgements
We would like to thank Mr Liew K.S. for preparing the specimens and for helping with the fieldwork and Mr Wong W.L. for assistance with the histology. We are also grateful to two reviewers whose comments greatly improved the manuscript. This work is made possible by an R&D grant from the Malaysian Government to the senior author.
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