Donax variabilis, Say, 1822

Warren, Micah B. & Bullard, Stephen A., 2019, First elucidation of a blood fluke (Electrovermis zappum n. gen., n. sp.) life cycle including a chondrichthyan or bivalve, International Journal for Parasitology: Parasites and Wildlife 10, pp. 170-183 : 181

3.5. Histopathology of infected Donax variabilis

We sectioned four tissue blocks that generated a total of 580 paraffin sections on 116 slides. Sporocysts and cercariae of the new species infected gonad but also occupied the spaces between the digestive diverticulum, intestinal arms, stomach, and crystalline sac ( Figs. 13–15 ). Developing cercariae were within sporocysts ( Fig. 15 ). Fewer than 10 oocytes that bordered sporocysts were observed in all of the examined sections; some were surrounded by an aggregate of basophilic, granular cells (possibly infiltrating immune response hemocytes or nutritive cells [ Cheng, 1996]) ( Fig. 14 ). Uninfected variable coquina clams (control tissue) had normal gonad and no demonstrable pathological change.

Figures

Figs. 9–15. Scanning electron microscopy and histopathology of cercaria of Electrovermis zappum Warren and Bullard n. gen., n. sp. (Digenea: Aporocotylidae) infecting variable coquina clam, Donax variabilis Say, 1822 (Bivalvia: Cardiida: Donacidae). (9) Whole body, arrow = dorsal fin fold. (10) Body, white arrows = possible secretion masses from penetration glands; white bar = anterior-most end including concentric spines; white arrows = lateral body spine rows, lateral view (11) Higher magnification of lateral body margin, arrows = tegumental papillae. (12) Higher magnification of anterior body end, showing space between spines of anterior sucker and those of the lateral body margin. (13) Histological section of infected gonad adjacent to intestinal arms (ia) and digestive diverticulum (dd). (14) Histological section showing infiltration of hemocytes (*) surrounding intestinal arm (ia), spororcysts (sp), and ooctyes (arrow). (15) Higher magnification of sporocyst containing developed cercaria (arrow) adjacent to digestive diverticulum (dd).