An ultrastructural study of the cercarial excretory system in Bucephaloides gracilescens and Prosorhynchus squamatus

Abstract

The ultrastructure of the flame cells, capillaries, collecting tubes, excretory bladder, excretory atrium, caudal vesicle, lateral caudal ducts and excretory pores of cercariae of Bucephaloides gracilescens (Rudolphi, 1819) Hopkins, 1954 and Prosorhynchus squamatus Odhner, 1905 (Digenea: Bucephalidae) is described. Both species are essentially similar except for some details. The terminal parts of the protonephridia have all the structural features that are typical of trematodes. The collecting tubes in the cercarial body are composed of cells that are wrapped around the lumen. The main collecting tubes are joined to the excretory bladder syncytium by septate junctions. Features of P. squamatus excretory bladder epithelium indicate that it is involved in secretory activity, but this is not the case in B. gracilescens. In both species the luminal surface of the excretory bladder epithelium is increased by lamellae, and the basal plasma membrane forms invaginations. In the bladder syncytium of P. squamatus both apical lamellae and basal invaginations are more developed and mitochondria are also more numerous. The excretory atrium is lined by a syncytium with nucleated cytons located in the surrounding parenchyma. The atrium lining is not continuous with the body tegument and possesses specific secretory inclusions and a thick glycocalyx. Septate junctions connect the atrium syncytium to the excretory bladder epithelium at its anterior end and to the syncytial excretory epithelium lining the caudal vesicle and the lateral caudal ducts at its posterior. In the excretory pores the caudal duct syncytium is joined to the tegument by septate desmosomes.

Morpho-functional specialization of the branching sporocyst of Prosorhynchoides borealis Bartoli, Gibson & Bray, 2006 (Digenea, Bucephalidae)

“…3c and d). They are similar to those of the cercariae of P. borealis described in detail under the name Bucephaloides gracilescens by Podvyaznaya & Galaktionov (2004). The structure of the flame cells, capillaries and excretory tubules is typical for digeneans (fig.…”

Comparative analysis of the cytoarchitecture of the excretory bladder of adult Digenea (Platyhelminthes) with consideration of the presence of mineralized excretory corpuscles in marine and freshwater adult worms

“…The presence of undifferentiated cells below the distal bladder epithelium may support such occurrence. However, bulging nucleated portions are also present in the bladder epithelium of A. lucii (present study), A. amphoraeiormes (Podvyaznaya 1989) and in the cercarial excretory bladder of Bucephaloides gracilescens (Podvyaznaya and Galaktionov 2004), but in these species an elimination of nucleated portion into the bladder lumen was not observed.…”

An ultrastructural study of excretory system development in the cercariae of Prosorhynchoides gracilescens (Rudolphi, 1819) and Prosorhynchus squamatus Odhner, 1905 (Digenea, Bucephalidae)

“…The aim of the present study is to describe the ultrastructural aspects of excretory system development in the cercariae of Prosorhynchoides gracilescens (syn. Bucephaloides gracilescens) and Prosorhynchus squamatus as the continuation of earlier studies of Podvyaznaya & Galaktionov (2004) on the fine structure of the excretory system of mature cercariae of the same species.…”

“…The excretory atrium of mature P. gracilescens (syn. Bucephaloides gracilescens) and P. squamatus cercariae was described by Podvyaznaya & Galaktionov (2004) as a short, broad median duct positioned in close proximity to the body-tail junction and lined by a syncytial epithelium which was structurally similar to that of the tegument. In the region of the body-tail junction this epithelium abutted with the outer tegument and this led the authors to conclude that the excretory atrium of P. gracilescens and P. squamatus larvae was a primordial definitive excretory pore (which would open to the exterior after the loss of the tail).…”

“…During the fifth stage, development of the excretory bladder, the excretory atrium and lateral caudal ducts was completed ( Figs 1F, 2G, 8B) and the lining of each acquired all the features seen in mature cercariae and described by Podvyaznaya & Galaktionov (2004). The median caudal duct increased in width to become the caudal vesicle ( Figs 1F, 2G).…”