Acanthobothrium hypanus, Zaragoza-Tapia & Pulido-Flores & Monks, 2020

Zaragoza-Tapia, Francisco, Pulido-Flores, Griselda & Monks, Scott, 2020, Three new species of Acanthobothrium Blanchard, 1848 (Cestoda: Onchoproteocephalidea) in Stingrays (Dasyatidae) from the Pacific coast in Mexico, Zootaxa 4766 (1), pp. 139-172 : 162-163

Acanthobothrium hypanus n. sp.

( Figs. 2 , 13–21 )

urn:lsid:zoobank.org:act:318691F1-20CD-4EC5-9F2B-A19C5E680927

Type host: Hypanus longus ( Myliobatiformes : Dasyatidae ).

Type locality: La Puntilla, Mazatlán, Sinaloa, Mexico.

Site of infection: Spiral intestine.

Deposited material: Holotype ( CNHE–11255 ) , 3 paratypes (CNHE–11256), and 3 paratypes (HWML– 216261).

ZooBank registration: The Life Science Identifier (LSID) urn:lsid:zoobank.org:act:318691F1-20CD-4EC5-9F2B-A19C5E680927

Etymology: The species is named for the genus of the type host, Hypanus.

Description. Based on whole mounts of 5 mature worms and 3 incomplete specimens. Entire worms 3–6.5 mm (4.46 ± 1.41; 5; 5) long ( Fig. 2 ), greatest width at level of mature proglottids, euapolytic; 18–22 (20 ± 2; 5; 5) proglottids per worm ( Fig. 2 ). Scolex consisting of scolex proper and cephalic peduncle, scolex proper with four bothridia, 300–350 (331 ± 16; 8; 8) long by 250–300 (264 ± 22; 6; 6) wide. Maximum width of scolex at level of posterior margin of anterior loculus ( Figs. 13 and 18 ); surfaces of scolex covered with microtriches ( Fig. 19 ). Bothridia free posteriorly, 238–270 (253 ± 11; 8; 14) long by 113–150 (128 ± 14; 6; 14) wide, each with 3 loculi separated by two transverse septa, and specialized anterior region in form of muscular pad ( Figs. 13 and 18 ). Muscular pad 54–66 (63 ± 4; 6; 12) long by 100–113 (106 ± 5; 6; 12) wide, with apical sucker 24–30 (27 ± 2; 7; 13) long by 43–55 (48 ± 4; 7; 13) wide, each with one pair of bipronged hooks at posterior margin ( Figs. 13 and 18 ). Anterior loculus of bothridia 125–150 (134 ± 8; 7; 14) long; middle loculus 50–70 (60 ± 14; 7; 6) long; posterior loculus 43–75 (60 ± 10; 7; 14) long ( Figs. 13 and 18 ); loculus length ratio (anterior:middle:posterior) 1:0.45:0.45. Velum present between medial margins of bothridia at posterior margin of posterior loculus ( Figs. 13 and 18 ).

Hooks bipronged, hollow, with tubercle on proximal surface of axial prong; internal channels of axial and abaxial prongs continuous, smooth, the base and anterior part of each hook embedded in muscular pad, axial prongs slightly longer than abaxial prongs ( Figs. 13–14 and 18 ). Bases (handles) of medial and lateral hooks touching each other ( Fig. 14 ). Lateral hook measurements: A 40–43 (41 ± 1; 6; 12), B 75–85 (79 ± 3; 6; 12), C 75–80 (77 ± 2; 6; 11), D 113–118 (114 ± 2; 6; 12). Medial hook measurements: A’ 38–43 (40 ± 1; 6; 12), B’ 80–85 (81 ± 2; 6; 12), C’ 75–75 (75 ±0; 6; 12), D’ 110–118 (114 ± 2; 6; 11).

Cephalic peduncle 450–1,900 (728 ± 481; 8; 8) long by 90–150 (128 ± 21; 8; 8) wide, covered with microtriches ( Fig. 20 ). Proglottids craspedote. Immature proglottids 11–16 (14 ± 2; 5; 5) in number, 50–150 (88 ± 29; 8; 22) long by 175–315 (228 ± 38; 8; 22) wide; mature proglottids 4–7 (5 ± 1; 5; 5) in number, 275–813 (485 ± 167; 8; 14) long by 230–313 (268 ± 20; 8; 14) wide ( Figs. 2 and 15 ), terminal mature proglottids 750–1,075 (910 ± 133; 5; 5) long by 285–385 (322 ± 38; 5; 5) wide ( Figs. 2 and 16 ). Gravid proglottids not observed. Genital pores marginal, irregularly alternating, 34–64% (55 ± 7; 8; 14) of proglottid length from anterior end in mature proglottids. Testes oval in frontal view, arranged irregularly anterior to ovarian lobes, two layer deep, 28–38 (30 ± 2; 7; 20) long by 38–68 (53 ± 8; 7; 20) wide ( Fig. 15 ); testes 36–47 (42 ± 3; 8; 16) in total number,19–24 (22 ± 2; 8; 16) aporal,12–17 (15 ± 2; 8; 16) preporal, 4–6 (6 ± 1; 8; 16) postporal, no testes posterior to ovarian isthmus. Cirrus sac pyriform ( Figs. 15–17 and 21 ), 100–138 (119 ± 12; 8; 12) long by 28–70 (45 ± 13; 8; 12) wide in mature proglottids. Cirrus expanded at base, armed with spinitriches. Vagina thick walled covered with gland cells, extending along medial line of pro- glottid from oӧ type, reaching to anterior margin of cirrus sac to common genital atrium; vaginal sphincter absent; seminal receptacle not seen. Ovary asymmetrical; poral lobe 150–285 (192 ± 40; 8; 9) long in mature proglottids, reaching to cirrus sac; aporal lobe 225–388 (263 ± 52; 8; 9) long, reaching to anterior margin of cirrus sac ( Figs. 15 and 16 ), inverted A-shaped in frontal view ( Figs. 2 , 15–16 ), lobulated, ovarian isthmus posterior to mid-point of ovary. Mehlis’ gland posterior to ovarian isthmus. Vitellarium follicular, comprised of two lateral band, 1–2 small follicules wide on each lateral band, extending from near anterior margin of proglottid to near posterior margin of proglottid, interrupted by vagina and cirrus sac ( Figs. 15 and 16 ); follicles 5–10 (7 ± 1; 8; 24) long by 15–30 (22 ± 5; 8; 24) wide. Uterus thin-walled, sacciform, extends from near anterior part of proglottid to near oӧ type. Excretory ducts lateral. Eggs not seen.

Remarks: Acanthobothrium hypanus n. sp. is a Category 2 species (sensus Ghoshroy & Caira 2001): Species have a total length ≤ 15 mm (3–6.5 mm); number of proglottids ≤ 50 proglottids (18–22 proglottids); the number of testes per proglottids ≤ 80 (36–47 testes per proglottid); and with an asymmetrical ovary. The new species is the seventh species of Acanthobothrium reported from H. longus in the world being preceded by A. cimari ; A. costarricense ; A. puntarenasense and A. vargasi that have been reported as Category 2 species (see Table 1 ); A. cleofanus Monks, Brooks & Lonce de Leon, 1996 , that has been reported as Category 3 species, and A. obuncus Marques, Brooks & Barriga, 1997 that has been reported as Category 6 species. There are currently 42 described Category 2 species (including A. ppdeleoni n. sp.). Acanthobothrium hypanus n. sp. differs from all but A. bullardi ; A. cimari and A. olseni . The new species can be distinguished from A. bullardi by the length of the scolex proper (250–300 vs. 633–943), the new species has abaxial prong lengths longer than that of A. bullardi (75–85 vs. 40–68), and the width of cirrus sacs in mature proglottids is shorter than that of A. bullardi (28–70 vs. 100–153). Acanthobothrium hypanus n. sp. has the length of bothridia shorter than that of A. cimari (238–270 vs. 321–438), the length of the cirrus sacs in mature proglottids is shorter than that of A. cimari (100–138 vs. 145–180), and width of the testes is smaller than that of A. cimari (28–38 vs. 44–72). The new species differs from A. olseni by the diameter of the accessory sucker (43–55 vs. 24–34), and by the width of the cirrus sacs in mature proglottids (28–70 vs. 84–168). Acanthobothrium hypanus n. sp. can be distinguished from A. ppdeleoni n. sp. by the number of proglottids (16–22 vs. 6–14), presents proglottids craspedote vs. proglottids acraspedote respectively, the width of the scolex proper is greater than that of A. ppdeleoni n. sp. (300–350 vs. 160–250) and the width of the accessory sucker is greater than that of A. ppdeleoni n. sp. (43–55 vs. 25–38).

Figures

FIGURES 1–3. Light microscope photographs of entire worms of the three new species (Holotypes). 1. Acanthobothrium ppdeleoni n. sp. (CNHE–11253); 2. Acanthobothrium hypanus n. sp. (CNHE–11255); 3. Acanthobothrium sinaloaensis n. sp. (CNHE–11257). Scale bars: 1, 2 and 3 = 500 μm.

FIGURES 13–17. Holotype of Acanthobothrium hypanus n. sp. (CNHE–11255): 13. Scolex. Note: the black arrow tip show the presence of velum; 14. Hooks; 15. Mature proglottid; 16. Terminal mature proglottid; 17. Genitalia. Scale bars: 13, 15, 16 and 17 = 100 μm; 14. = 50 μm.

FIGURES 18–21. Light microscope photographs of holotype of Acanthobothrium hypanus n. sp. (CNHE–11255): 18. Scolex; 19. Details of bothridium; 20. Details of peduncle cephalic; 21. Genitalia. Scale bars: 18 = 100 μm; 19 and 20 = 10 μm; 21 = 50 μm. Abbreviations: vl, velum; mt, microtriches; vg, vagina; cs, cirrus sac; gp, genital pore.