Ultrastructure of the digestive system of the cercaria of Sanguinicola inermis Plehn, 1905 (Digenea: Sanguinicolidae)

Abstract

The digenean blood fluke Sanguinicola inermis and the family Sanguinicolidae have previously been described as apharyngeate and sucker-less. Examination of the digestive tract of the cercaria of S. inermis with transmission electron microscopy (TEM), however, has confirmed the presence of a well-developed and complex muscular region immediately adjacent to the sub-terminal mouth. The presence of this muscular region, which may be an oral sucker, emphasises the need for further ultrastructural studies on other members of the family. The adjacent oesophagus, composed of modified tegument, has distinct anterior and posterior regions. TEM shows that the surface of the posterior oesophagus is deeply folded and the apical cytoplasm and sunken cytons become filled with secretory granules, eventually forming a "secretory region" adjacent to the intestine. The dorsal, sac-like intestine is composed of a single layer of epithelial cells, the apical surface of which is drawn into shallow folds. Each cell contains numerous secretory granules, rough ER, and a single basal nucleus. The intestinal lumen, which contains electrondense striated bodies, is filled with fibrous material. Only two sensory oral papillae are associated with the digestive tract, positioned either side of the mouth opening and possibly acting as tango-, stretch-or pressure receptors. The papillae comprise several microtubules lying beneath the apical cytoplasm of the tegument within a nerve process, but there is no connection with the external body surface. The morphology of the alimentary canal of the S. inermis cercaria is discussed in relation to the functioning of the digestiv e system in preparation for establishment in the final host.

An ultrastructural study of alimentary tract development in the cercariae of Prosorhynchoides borealis (Digenea, Bucephalidae)

“…The apical projections of the caecal cells become more numerous and acquire a lamellar shape. On the whole, the gut ultrastructure of the fully formed P. borealis cercariae is similar to that of the other digenean larvae studied (Ebrahimzadeh and Kraft 1969;Køie 1971Køie , 1973McMichael-Phillips et al 1994a;Fujino 1997).…”

Ultrastructural observations on the cellular response of carp, Cyprinus carpio L., to eggs of the blood fluke Sanguinicola inermis Plehn, 1905 (Trematoda: Sanguinicolidae)

“…The precise way in which the encapsulation response around S. inermis eggs is initiated and operates is not known, although there appears to be a series of stages involved in the response. The egg shell of S. inermis is pale and thin, lacks pores and microspines and is unlikely to be quinone-tanned (McMichael-Phillips et al 1992b). The surface of the egg has shallow reticulations which may aid the passage of immature eggs through the uterus of the adult.…”

Sanguinicola platyrhynchi n. sp. (Digenea: Sanguinicolidae) parasite of visceral cavity of Hemisorubim platyrhynchos (Valenciennes, 1840) (Pisces: Pimelodidae) from the floodplain of the upper Paraná River, Brazil

“…However, the author calles this organ a pharynx. McMichael-Phillips et al (1994) showed the presence of this muscular complex well-developed in cercariae of S. inermis. These authors agreed with Kirk & Lewis (1993) who stated that this muscular element can be an oral sucker, but emphasized the need for further ultrastructural studies on other species of the family.…”