Gigantorhynchus echinodiscus ( Diesing, 1851 )

Gomes, Ana Paula Nascimento, Cesário, Clarice Silva, Olifiers, Natalie, Bianchi, Rita de Cassia, Jr., Arnaldo Maldonado & Vilela, Roberto do Val, 2019, New morphological and genetic data of Gigantorhynchus echinodiscus (Diesing, 1851) (Acanthocephala: Archiacanthocephala) in the giant anteater Myrmecophaga tridactyla Linnaeus, 1758 (Pilosa: Myrmecophagidae), International Journal for Parasitology: Parasites and Wildlife 10, pp. 281-288 : 283-284

3.2. Redescription of Gigantorhynchus echinodiscus ( Diesing, 1851)

( Figs. 1–17 )

General: Body of medium size, narrow, and pseudo segmented ( Fig. 8 ). Sexual dimorphism present, females larger than males. Proboscis cylindrical ( Figs. 1 , 7 and 12 ), similar in both sexes, armed with 18 hooks ( Figs. 12 and 14 ), arranged in two rows of hooks that present a root that bifurcated anterior and posteriorly ( Figs. 1 , 7 and 14 ). First row with six robust hooks; second row with 12 hooks in pairs, smaller than first row ( Figs. 2 and 14 ). Measurement of the hooks and root: from the tip of the hook to the root, total length of the hook; and total length of the root: six hooks of the first row measuring 0.16–0.23 (0.20); 0.12–0.18 (0.15); 0.11–0.16 (0.14). The 12 hooks of the second row measured 0.18–0.19 (0.18); 0.11–0.13 (0.12); 0.11–0.12 (0.11). The crown is separated from numerous small-rootless spines by a slight space without hooks ( Fig. 12 ). Twenty-one to 23 small-rootless spines arranged in longitudinal rows 0.05–0.08 (0.07) ( Figs. 1, 2 , 12 and 13 ). One lateral papilla located in the base of the neck on each side with a slightly elevated border and a central pore ( Figs. 1 , 13 and 15 ). After the proboscis, there is a small region without pseudo segmentation in both sexes. Lemnisci long and filiform ( Fig. 3 ).

Male (nine specimens): Body 45.29–14.80 (31.53) long and 0.99–0.53 (0.78) wide. Proboscis and neck 0.65–0.45 (0.55) long, 0.30–0.55 (0.45) wide, with 18 apical hooks followed by 21–23 small rootless spines arranged on longitudinal rows. After the proboscis, a region without segmentation, 2.24–3.21 (2.72) long ( Fig. 8 ). Proboscis receptacle 0.48–0.64 (0.57) long, 0.21–0.32 (0.26) wide ( Fig. 1 ). Lemnisci 8.02–20.30 (14.87) (n = 3) long, reaching the middle of the trunk and sometimes bent on themselves ( Fig. 8 ). Two ellipsoid testes, narrow, and in tandem; anterior testis 1.63–2.71(2.25) long, 0.26–0.32 (0.29) wide; posterior testis 1.61–2.66 (2.13) long, 0.26–0.39 (0.29) wide ( Fig. 4 ). Eight cement glands in pairs, the group measuring 0.98–2.13(1.61) long and 0.45–0.76 (0.60) wide ( Figs. 4 and 9 ), followed by ejaculatory duct, 0.82–1.42 (0.97) long. Posterior end after the anterior testes without a segmentation region and measuring 5.45–8.53 (6.83), with smooth surface and a copulatory bursa at the end ( Figs. 4 , 9 , 16 and 17 ).

Female (six specimens): Body 102.79–52.92 (75.45) long, 0.79–1.13 (0.85) wide. Proboscis and neck 0.49–0.71 (0.55) long, 0.46–0.53 (0.48) wide. Proboscis receptacle 0.63–0.74 (0.70) long, 0.23–0.31 (0.27) wide ( Fig. 1 ). Lemnisci long, 13.23 mm long (n = 1) ( Fig. 8 ). Gonopore subterminal and vagina has sinuous lateral region in “guitar” format ( Figs. 5 and 10 ). Uterine bell to genital pore including the vagina, uterus, and uterine bell 0.69–0.97 (0.86) long (n = 5) ( Fig. 5 ). Eggs ellipsoid, with three membranes 0.059 –0.069 (0.064) long, 0.04–0.03 (0.036) wide (n = 26; Figs. 6 and 11 ).

Figures

Figs.1–6. Line drawing of Gigantorhynchus echinodiscus from Mymercophaga tridactyla. 1. Praesoma with the proboscis presenting a crown with robust hooks followed by small hooks, a receptacle proboscis, and papillae in the base of the neck; 2. Three different robust hooks in the crown and a one small type in the proboscis; 3. Unsegmented anterior part of the trunk, and lemnisci filiform reaching the middle region of the trunk; 4. Posterior region of adult male showing reproductive organs; 5. Posterior region of adult female showing the uterus, vagina and gonopore subterminal; 6. Egg.

Figs. 7–11. Light microscopy of adult Gigantorhynchus echinodiscus from Mymercophaga tridactyla. 7. Proboscis with a crown of large hooks in the apex and small hooks, and a proboscis receptacle (Re); 8. Trunk with pseudo segmentation (arrows) and the end of the lemnisci (Le); 9. Male reproduction organs, testis (Te), cement glands in pair (Cgl), ejaculatory duct (Ed); 10. Detail of the posterior end of adult female showing the uterus (Ut), vagina (Va, arrow) and gonopore subterminal (Gp); 11. Egg ellipsoid showing the outer membrane thick (Om), inner membrane (Im) thin, embryo (Em).

Fig. 12–17. Scanning electron micrographs of adult Gigantorhynchus echinodiscus from Mymercophaga tridactyla. 12 and 13. Cylindrical proboscis armed with hooks (Ho) showing a space (Sp) between the two circles of large hooks and small rootless spines, neck (Ne), trunk (Tr), lateral papillae (Pa, arrowhead); 14. Detail of the crown with two circles of large hooks (arrow – 1st row and asterisk – 2nd row); 15. Detail of the lateral papillae; 16 and 17. Posterior end of adult male showing the region without pseudo-segmentation (cross) and a copulatory bursa protruding from the body (CB).