SEM micrographs of metacestodes (type XV) of different sizes from Chimaera monstrosa. (A) Overview of a worm 3.5 mm long; note rounded bothridia. (B) Overview of a worm 13 mm long; note longitudinal furrow along its body. (C) View from above scolex of 14 mm long worm; note 4-lobed dome with apical organ at the apex of the scolex proper and 4 foliose bothridia with concave and folded margins. (D) Overview of a worm 2 mm long; note rounded, smooth bothridia. (E) Ventral bothridia of a worm 3.5 mm long; note slight marginal waves. (F) Concave inner margin of contracted bothridium; note muscular elevations. (G) Body near posterior end of 15 mm long worm. (H) Body posterior segment of 15 mm long worm. (I) Side view of scolex of 15 mm long worm; note foliose bothridia and domed lobes of the scolex proper. (J) Apical organ of scolex proper. (K) View from above scolex of 9 mm long worm. (L) Accessory sucker of bothridium. Abbreviations: ao, apical organ; as, accessory sucker of bothridium; bm, bothridial margin; bt, bothridium; dl, domed lobe of the scolex proper; lf, longitudinal furrow; me, muscular elevations; mf, marginal fold; mw, marginal waves; pbe, posterior body end; pp, posterior proglottid; sp, scolex proper.

Surface microtriches of metacestodes (type XV) of different sizes from Chimaera monstrosa, under SEM (A–E, J, K) and TEM (F–I, L, M). (A) Scolex spinithrix of 2 mm long worm. (B) Ridges of posteriorly directed spinitriches of the scolex proper of 13 mm long worm; note filitriches between ridges. (C) Gladiate posteriorly directed spinitriches of the scolex proper of 13 mm long worm. (D) Body filitriches of 2 mm long worm. (E, K) Upright bothridial spinitriches; note thin filitriches between them. (F) Ultrastructure of gladiate spinithrix. (G) Ultrastructure of 2 filithrix types on the body of 13 mm long worm. (H) Ultrastructure of bothridial spinithrix. (I) Formation of filitriches within distal tegumental cytoplasm. (J, L, M) Emerging filitriches along surface outgrowths of the body. Abbreviations: b, microthrix baseplate; bs, base of microtriches; c, microthrix cap; dm, developing microtriches; dtc, distal tegumental cytoplasm; fl, fll, fl2, filitriches of different kinds; gs, gladiate spinitriches; pr, parallel ridges; so, surface outgrowth; tn, tunic surrounding microthrix base.

Tegumental ultrastructure of the scolex proper, bothridia, and scolex unicellular glands of metacestodes (type XV) from Chimaera monstrosa. (A) Section through bothridial muscle complex and scolex proper; note large excretory duct. (B) Bothridial muscle complex surrounded by distal tegumental cytoplasm and tunica propria in 3.5 mm long worm. (C) Tegumental vesicles of heterogeneous content. (D) Basal matrix underlying the distal tegumental cytoplasm of the scolex proper. (E) Basal matrix underlying the distal tegumental cytoplasm of the bothridial muscle complex. (F) Distal tegumental cytoplasm of the scolex proper; note glandular duct. (G) Bothridial distal tegumental cytoplasm; note muscle complex, with well-developed radial muscles and their attachment site, hemidesmosomes. (H) Tegumental cell; note numerous heterogeneous vesicles filling its cytoplasm. (I) Glycogen-containing muscle cell of bothridial muscle complex of 13 mm long worm. (J) Cisternal muscle cell of bothridial muscle complex; note dilated cisternae in its sarcoplasm. (K) Unicellular gland cell of the scolex proper; note numerous secretory granules in its cytoplasm. (L) Inner border of bothridial muscle complex; note tunica propria, to which radial muscles are attached via hemidesmosomes. (M) Two secretory ducts passing through the distal tegumental cytoplasm. (N) Neuronal perikarya of the scolex proper; inset: neuronal vesicles. Abbreviations: bmc, bothridial muscle complex; cm, circular muscles; dc, dilated cisternae of cisternal muscle cells; dtc, distal tegumental cytoplasm; exd, excretory duct; gd, glandular duct; gsp, glycogen-containing sarcoplasmic process; h, hemidesmosomes; ld, lamina densa; lm, longitudinal muscles; lr, lamina reticularis; m, mitochondria; n, nucleus; nv, neuronal vesicles; rm, radial muscles; sg, secretory granules; sp, scolex proper; tp, tunica propria; tv, tegumental vesicles.

Structural components of the scolex and body of metacestodes (type XV) from Chimaera monstrosa. (A) Protonephridial terminal complex of excretory system in 9 mm long worm. (B) Cerebral ganglion section; note mixed muscle cell and ganglion neuropile. (C–E) Cisternal muscle cells with sarcoplasm filled with dilated cisternae; note exocytosis of cisternal content into extracellular space (E). (F) Undifferentiated cells of the neck region. (G) Ciliated nerve ending in apical scolex region. (H, I) Calcareous corpuscles in bothridial muscle complex; note disrupted cytoplasm in lumen. (J) Calcareous corpuscles in the scolex proper; note a thin layer of peripheral cytoplasm with nucleus, dense lamella above it, and central, loose, flocculent material. (K) View of body tegument of 15 mm long worm. (L) Distal tegumental cytoplasm of the middle body of 13 mm long worm. (M) Different stages of the development of undifferentiated cells of the body tegument. Abbreviations: c, cilium; cc, calcareous corpuscle; cf, ciliated flame; cm, circular muscles; dc, dilated cisternae; dl, dense lamella; dtc, distal tegumental cytoplasm; ec, exocytosis; exd, excretory duct; fm, flocculent material; gn, ganglion neuropile; lm, longitudinal muscles; m, mitochondria; mc, muscle cell; mf, muscle fibers; n, nucleus; rdc, rest disrupted cytoplasm; se, sensory ending; sj, septate junction; tc, tegumental cell; uc, undifferentiated cell.

SEM micrographs of intestinal (A–E) and gall bladder (F–I) metacestodes (type XV) from Oncorhynchus spp. (A) Apical view of the scolex; note 4-lobed dome with apical organ of the scolex proper; note 4 accessory suckers of bothridia. (B) View of the scolex showing 2 bothridia with folded margins and large accessory sucker; note lobes of the scolex proper dome. (C) Bothridial microtriches. (D) View of intestinal metacestode. (E) Scolex proper microtriches. (F) View of gall bladder metacestode. (G) Scolex showing 4 bothridia with 2 loculi and unfolded margins; note small apical organ of the scolex proper and bifurcated dome’s lobe. (H) Coniform flask-shaped spinitriches of the scolex proper. (I) Bothridial microtriches. Abbreviations: al, anterior loculus of bothridium; ao, apical organ of the scolex proper; as, accessory sucker of bothridia; bl, bifurcated lobe; bs, base of microtriches; bt, bothridium; c, microthrix cap; cs, coniform spinitriches; dl, domed lobe of the scolex proper; fl, filitriches; gs, gladiate spinitriches; lf, longitudinal furrow; mf, marginal folds; pbe, posterior body end; pl, posterior loculus of bothridium.