Functional ultrastructure of the hexacanth larvae in the bothriocephalidean cestode Eubothrium salvelini (Schrank, 1790) and its phylogenetic implications

Advanced stages of embryonic development and cotylocidial morphogenesis in the intrauterine eggs of Aspidogaster limacoides Diesing, 1835 (Aspidogastrea), with comments on their phylogenetic implications

“…Among them, in A. limacoides we distinguished two evidently different types of secretory regions: (1) neurosecretory-like cells connected with the larval nervous system and (2) gland cells, most probably of the merocrine type, with large electron-dense secretory granules which are comparable to the secretory granules described in the apical and/or lateral glands of digenean miracidia (Pan 1980;Eklu-Natey 1986) and to secretory granules reported in the penetration glands of cestodarian lycophores (Xylander 1986(Xylander , 1990) and eucestode hexacanth larvae (Świderski 1972;Świderski and Tkach 2002;Świderski and Mackiewicz 2004;Młocicki et al 2006Młocicki et al , 2010a.…”

“…The most probable function of the larval neurosecretory cells of parasitic platyhelminths is stimulating and controlling coordinated body movements during hatching and host penetration (Świderski 1997;Młocicki et al 2006). The second, and evidently different, type of glandular cells in larval A. limacoides is similar, to some extent, to those of the merocrine type previously reported in: [a] the apical and lateral glands of digenean miracidia (Pan 1980;Świder-ski 1984, 1985 and also in digenean cercariae (Stirewalt 1973(Stirewalt , 1974; [b] cestodarian lycophores, where about 12 gland cells of three or four different types have been described (Rohde 1986(Rohde , 1987Xylander 1986Xylander , 1990 the penetration glands of eucestode hexacanths which are directly involved in the mechanism of host invasion (Świderski and Tkach 2002;Świderski and Mackiewicz 2004;Młocicki et al 2006Młocicki et al , 2010a. Nevertheless, at present, there is not enough available information on these glandular structures for any ultrastructural or functional comparison.…”

“…In the Neodermata, neurosecretory granules associated with larval nerve cells have been reported as dense-cored vesicles, resembling the so-called 'elementary granules of neurosecretion (EG Ns)' found in other organisms, in numerous taxa, including the oncospheres of Hymenolepis nana (see Fairweather and Threadgold 1981), Inermicapsifer madagascariensis (see Świderski and Tkach 2002), Echinococcus granulosus and E. multilocularis (see Świderski 1994d, 1997), Mosgovoyia ctenoides (see Młocicki et al 2006) and Eubothrium salvelini (see Młocicki et al 2010a), and also in the larval stages of digeneans, such as Schistosoma mansoni and S. haematobium (see Pan 1980;Eklu-Natey 1986;Cousin and Dorsey 1991;Halton and Gustaffson 1996). The most probable function of the larval neurosecretory cells of parasitic platyhelminths is stimulating and controlling coordinated body movements during hatching and host penetration (Świderski 1997;Młocicki et al 2006).…”

Egg ultrastructure of the amabiliid cestode Tatria biremis Kowalewski, 1904 (Cyclophyllidea, Amabiliidae), with an emphasis on the oncospheral envelopes

“…However, the exact origin and nature of membranous vesicles and granules frequently observed in this species between the oncospheral membrane and the oncosphere surface remains unclear. They may potentially represent the remnants of a degenerating hookregion membrane as previously described in N. dispar (see Świderski and Tkach 1997b), penetration gland secretion (Swiderski and Tkach 2002;Młocicki et al 2006Młocicki et al , 2010b or a by-product of the oncospheral tegument formation (Fairweather and Threadgold 1981).…”

Ultrastructure and cytochemistry of vitellogenesis and the vitellocytes of the bothriocephalidean cestode Clestobothrium crassiceps (Rudolphi, 1819), a parasite of the teleost fish Merluccius merluccius (L., 1758) (Gadiformes, Merlucciidae)

“…Two types of egg have so far been described for bothriocephalidean cestodes: (a) those which are operculate and unembryonated in utero, as occur in Bothriocephalus clavibothrium (see Świderski 1994), and (b) those which are anoperculate and embryonated in utero, as occur in Eubothrium salvelini (see Świderski et al 2005Świderski et al , Młocicki et al 2010. It is likely, however, that future studies will show that there is a greater variety of egg types in this order.…”