The Ultrastructure of the Gastrodermis and the Nutrition of the Gill Parasitic Atriaster heterodus Lebedev and Paruchin, 1969 (Platyhelminthes: Monogenea)

Abstract

The gastrodermis of Atriaster heterodus Lebedev & Paruchin, 1969 (Polyopisthocotylea), a gill parasite from Diplodus argenteus (Valenciennes, 1830) The functional morphology of the digestive system has been studied for different Monogenea (Smyth & Halton 1983, Bogitsh 1993 and the feeding in polyopisthocotyleans and monopisthocotyleans is generally distinct with the former ingesting blood (Llewelyn 1954, Halton 1982 and the latter, mucus and epithelial cells. However, blood pigments were observed in a few monopisthocotyleans (Uspenskaya 1962, Kearn 1963, Fournier 1978, Buchmann et al. 1987) while Allen and Tinsley (1989) demonstrated blood and epithelial cells at the same time in the gut lumen of a polyopisthocotylean species.Atriaster heterodus Lebedev & Paruchin, 1969 (Polyopisthocotylea) was recently reported from Rio de Janeiro coast (Santos et al. 1996). Surface topography and ultrastructural aspects of the spermatogenesis of this species have been described by Santos et al. (1997). The ultrastructure of the gastrodermis and the nutrition of this species are described herein. This paper represents the first ultrastructural study of gut caeca and nutrition of a marine monogenean from Brazil. MATERIALS AND METHODSParasites -Sixty five specimens of A. heterodus were obtained from the gills of 25 Diplodus argenteus (Valenciennes, 1830) Sparidae, collected in Copacabana beach, Rio de Janeiro, Brazil.Histochemistry -Monogeneans and gill filaments were fixed in 5% buffered formalin or 70% ethanol. Samples were embedded in paraffin and cut in 5 mM sections which were deparaffinized with xylene and prior to staining, hydrated in decreasing concentrations of ethanol to water. Histochemical reactions are indicated with the references and color of positive reactions as follows. Lilly and Fullmer (1976) were tested Perls (+=blue-green), Okajima (+=or-ange-red) and Dunn-Thompson (+= emerald green). The picric alcohol solubility test (Llewelyn 1954) was tested for hematin (+=solve).Ultrastructure -For ultrastructural studies, parasites were fixed for 2 hr at 4°C in a solution containing 4% paraformaldehyde, 2.5% glutaraldehyde and 0.3M sucrose in 0.1M cacodylate buffer in sea water, pH 7.2. After being washed in the same solution, they were post-fixed for 1 hr in dark conditions in a solution containing 1% OsO 4 , 0.8% potassium ferricyanide, and 5mM CaCl 2 in

Ultrastructure and cytochemistry of the tegument of Atriaster heterodus (Platyhelminthes: Monogenea)

“…The morphology and topography of Atriaster heterodus Lebedev & Parukhin, 1969 have been previously studied by Euzet and Maillard (1973), Mamaev (1984) and Santos et al (1996), and the ultrastructure of gastrodermis by Santos et al (1998). The ultrastructure of the outer layer of the tegument of Atriaster sp.…”

Gastrodermis ultrastructure of the different life stages of the polyopisthocotylean monogenean gill parasite Discocotyle sagittata

“…Variations in the ultrastructural organization of the gastrodermis are reported among different families of the Polyopisthocotyla (Halton et al 1968 ; Brennan and Ramasamy 1996 ; Santos et al 1998 ; Poddubnaya et al 2015 ). As in the present study, and in the diclidophorid Diclidophora merlangi (Kuhn, in Nordmann, 1832) and the chimaericolid C. leptogaster , the digestive cells alternate with the connecting syncytium within the cecal wall (Halton et al 1968 ; Poddubnaya et al 2015 ), whereas in the thoracotylid Pricea multae Chauhan 1945 and hexabothriids Rajanchocotyle emarginata (Olsson 1876) Sproston 1946 and Callorhynchocotyle callorhynchi (Manter 1955) Boeger, Kritsky and Pereira 1989, the digestive cells occur in groups and may project deep into the lumen (Brennan and Ramasamy 1996 ; Poddubnaya et al 2015 ).…”

“…The digestive cells and connecting syncytium in both the oncomiracidium and adult D. sagittata are connected at the luminal surface, by septate junctions. Similar junctions were reported in other polyopisthocotylean monogeneans, e.g., D. merlangi (see Halton et al 1968 ), Polystomoides , Neopolystoma , and Concinnocotyla (see Rohde 1973 ; Watson and Whittington 1996 ) and in the chimaericolid C. leptogaster and hexabothriids R. emarginata and C. callorhynchi (see Poddubnaya et al 2015 ), but neither in the thoracocotylid P. multae (see Brennan and Ramasamy 1996 ) nor in the microcotylid Atriaster heterodus Lebedev & Parukhin 1969 (see Santos et al 1998 ). The mechanism of digestion in the oncomiracidium gastrodermis resembles that reported in other tissue feeding monopisthocotyleans (see for example, Arafa et al 2013 ).…”