Fig. 3

Representative electron micrographs of fourth-stage Anisakis pegreffii larva gut. a Detailed view of a pharynx with uniformly dense cuticle (C) lining the pharyngeal lumen. Numerous mitochondria (arrows) can be seen interspersed between muscle fibres. Insert: higher magnification showing densely packed muscle fibres (arrowheads), mitochondria, and rough endoplasmic reticulum (RER) (thin arrow). b Cross section through a collapsed intestine, showing the intestinal lumen (L) filled with finely granulated electron-lucent content. Microvilli (Mv) are directed in multiple directions, with prominent rootlets forming the terminal web (thin arrows) extending from their basal end. Numerous mitochondria (arrows) are seen subapically, surrounded by patches of granulated cytoplasm (glycogen). Note the same electron-dense tubular structures as those in L3 (asterisks). c Overview of spindle-shaped enterocytes with laterally located organelles (curved arrows), while the central part of the cytoplasm is empty. Insert: close-up of two large multi-cristate mitochondria. d Large nucleus of intestinal cell with a prominent nucleolus (Nu). Insert: detailed view of nuclear envelope with numerous nuclear pores (arrow heads). In the perinuclear space, well developed RER (long arrow) and Golgi apparatus (Ga) can be seen. e Complex junction between two intestinal cells. Note the long rootlets (long arrows) extending from basal ends of microvilli (Mv). f Deep invaginations of the basal enterocyte membrane with three small vesicles surrounded by a double membrane (curved arrows) adjacent to the invaginations. Scale-bars: a, b, d, 2 µm; c, 10 µm; insert in c, 500 nm; insert in d, 200 nm; e, 1 µm, f, 200 nm