Ultrastructure of the vitellarium in the digeneans Phyllodistomum angulatum (Plagiorchiida, Gorgoderidae) and Azygia lucii (Strigeida, Azygiidae)

Abstract

Fine structural features of the vitellarium of two digeneans, Phyllodistomum angulatum and Azygia lucii, are documented and compared with those of other digenean species. The cytodifferentiation of immature vitelline cells (vitellocytes) assumes the production and subsequent accumulation in their cytoplasm of several inclusions. Mature vitelline cells of P. angulatum are characterized by the presence of vitelline clusters (~2.7 μm in diameter, with ~100 vitelline globules of ~0.35 μm in diameter) and osmiophobic, saturated lipid droplets (~2-3 μm in diameter), and in A. lucii vitelline clusters of the same diameter include much fewer vitelline globules (~50 globules of ~0.5 μm in diameter), osmiophilic lipid droplets and α-glycogen. In both P. angulatum and A. lucii, interstitial cells are also present within the vitellarium. Two types of contact sites (septate and tight junctions) between adjoining interstitial cells also occur in both digenean species. Judging from the present and previous ultrastructural studies, it is suggested that there are three potential discriminatory characters of the digenean vitellarium (the number of different types of cell components within the vitellarium, the presence and type of junctional complexes between these cells, and the isolation of the vitellarium from the surrounding tissue) which may prove useful for a better understanding of the biology and evolutionary history of the different digenean groups.

Ultrastructural characteristics of the vitellarium of Brandesia turgida (Brandes, 1888) (Digenea: Pleurogenidae) and an examination of the potential usefulness of such vitelline traits in digenean systematics

“…4 B). The same vitelline cytoarchitecture as occurs in the gorgoderids has also been found in the azygiid Azygia lucii by Poddubnaya et al (2012), in the fasciolid Fasciola hepatica by Irwin and Threadgold (1970) and Hanna (1976), in the paramphistomid Orthocoelium scoliocoelium by Sharma and Swarnakar (1992) and in the haploporid Haploporus lateralis by Sampour (2008). Finally, despite the small number of digenean species studied in relation to their vitelline cytoarchitecture, specific structural patterns of the vitellarium can be observed in certain digenean families or even superfamilies.…”

“…In the gorgoderids Gorgoderina vitelliloba (see Irwin & Maguire, 1979) and Phyllodistomum angulatum (see Poddubnaya et al, 2012) a different type of basic structure of the vitellarium is found. This includes the presence of: (1) two types of cells within the vitelline masses (vitellocytes and interstitial cells, the latter with the same cytomorphology); (2) intercellular septate junctions between the interstitial cells; and (3) a fibrous sheath surrounding the vitelline masses (Fig.…”

“…In relation to this, two different levels of the organization of the vitellarium within the Digenea have been shown. In one group, a single type of cell (vitelline cells at different stages of development) is present (Grant et al, 1977;Holy & Wittrock, 1986;Podvyaznaya, 1990;Świd-erski et al, 2011), whereas in another group there are cells of two types (vitelline cells at different stages of development and interstitial cells) within the vitellarium (Irwin & Threadgold, 1970;Hanna, 1976;Irwin & Maguire, 1979;Poddubnaya et al, 2012). In relation to this, no members of the family Pleurogenidae have been studied in terms of their vitelline ultrastructure, but, within the superfamily Microphalloidea, species of three other families, i.e.…”

“…Ultrastructural investigations of vitellogenesis in the Digenea have previously been undertaken by Tulloch and Shapiro (1957), Björkman and Thorsell (1963), Burton (1963), Koulish (1969), Irwin and Thread-.... gold (1970), Hanna (1976), Grant et al (1977), Irwin and Maguire (1979), Erasmus et al (1982), Fukuda et al (1983), Holy and Wittrock (1986), Hendow and James (1989), Podvyaznaya (1990Podvyaznaya ( , 2003, Sharma and Swarnakar (1992), Chaymardanov and Tanyüksel (1995), Sampour (2008), Świderski et al (2011Świderski et al ( ), Poddubnaya et al (2012 and Greani et al (2012a, b). Although little attention has been paid to the study of the ultrastructural architecture of the digenean vitellarium itself, three aspects of vitelline cytoarchitecture have been suggested as possibly useful phylogenetic indicators for digeneans (Poddubnaya et al, 2012) and for parasitic platyhelminths in general (Poddubnaya et al, 2013). These are: the number of different types of cells within the vitellarium; the presence and type of junctional complexes occurring between these cells; and the isolation of the vitellarium from the surrounding tissues.…”

Reinvestigation of vitellogenesis in Caryophyllaeus laticeps (Pallas, 1781) (Cestoda, Caryophyllidea, Caryophyllaeidae), monozoic tapeworm of Abramis brama (Pisces, Teleostei)

“…Ultrastructural characters of the vitellarium might be useful .... for a better understanding of the relationships between different taxa within the neoophoran Platyhelminthes (Gremini & Falleni, 1998) including Cestoda (Świderski & Mackiewicz, 1976;Świderski & Xylander, 2000;Bruňanská et al, 2005;Poddubnaya et al, 2006Poddubnaya et al, , 2012Levron et al, 2007). The structure and composition of eggshell-forming globules in vitellocytes have been considered to be especially phylogenetically informative (Gremigni & Falleni, 1991;Falleni et al, 2001).…”