Yamaguticestus metini, Caira & Bueno & Jensen, 2021

Caira, Janine N., Bueno, Veronica & Jensen, Kirsten, 2021, Emerging global novelty in phyllobothriidean tapeworms (Cestoda: Phyllobothriidea) from sharks and skates (Elasmobranchii), Zoological Journal of the Linnean Society 193, pp. 1336-1363 : 1351-1353

YAMAGUTICESTUS METINI SP. NOV.

( FIGS 5F–J , 6 )

ZooBank registration: 54904E20-1BBD-4F54-AE02- EA093DE8E5DE.

Description: (Based on one whole mature worm, one partial mature worm, one immature worm, two detached mature proglottids, two detached gravid proglottids, four detached dehisced proglottids, and one scolex examined with SEM.) Worms euapolytic, acraspedote, 80 mm long; proglottids 400 in total number; maximum width at level of mature proglottids. Scolex consisting of four bothridia, 472–596 long, 529–704 wide. Bothridia oval, with apical sucker and single, undivided loculus ( Figs 5F , 6A ), 409–435 (478 ± 60; 2; 4) long, 280–315 (302 ± 15; 2; 4) wide, sessile anteriorly, free posteriorly; apical sucker 201– 281 (231 ± 28; 3; 8) long, 176–253 (224 ± 27; 3; 6) wide; apical sucker length as percentage of bothridial length 46–57% (50 ± 4; 3; 6). Cephalic peduncle lacking. Neck 1016 long. Distal surface of apical sucker ( Fig. 5G ) and anterior-most regions of loculus densely covered with acicular filitriches; distal surface of remainder of loculus densely covered with gongylate columnar spinitriches and capiliform filithriches ( Fig. 5H ). Proximal bothridial surface densely covered with acicular filitriches ( Fig. 5I ). Neck and strobila with capilliform filitriches arranged in wide scutes ( Fig. 5J ). Immature proglottids wider than long, becoming longer than wide with maturity ( Fig. 6B ), 397 in number. Mature proglottids three in number. Terminal proglottid 2138 long, 1567 wide; length-to-width ratio 1.4:1 ( Fig. 6C ). Testes 158–184 in total number, 13–20 in number in post-poral field, 30–42 (34 ± 4; 2; 8) long, 33–50 (42 ± 6; 2; 8) wide. Vas deferens minimal, coiled medial to cirrus sac. Cirrus sac narrowly oblong (sensu Clopton, 2004), 451 long, 79 wide, thin walled, containing weakly coiled cirrus ( Fig. 6E ); cirrus armed with spinitriches. Genital pores irregularly alternating, 73% of proglottid length from posterior end; genital atrium shallow. Vagina surrounded by glandular cells, weakly sinuous, extending from ootype along midline of proglottid to anterior margin of cirrus sac, then laterally along anterior margin of cirrus sac to open into common genital atrium anterior to cirrus sac. Ovary subterminal in position, H-shaped in frontal view, 577 long, 554 wide, tetralobed in cross-section; ovarian margins strongly digitiform ( Fig. 6D ). Vitellarium follicular; follicles irregular in shape, arranged in two lateral bands; each band consisting of multiple columns of follicles, extending throughout length of proglottid, interrupted ventrally by terminal genitalia, not interrupted by ovary. Uterus medial, ventral, sacciform, extending from ovarian isthmus to cirrus sac; uterine duct entering uterus at mid-level. Excretory vessels 4, arranged in one dorsal and one ventral pair on each lateral margin of proglottid. Detached mature proglottids (two, each from different host) 1977–2814 long, 1521–2019 wide, length-to-width ratio 1.3–1.4:1; genital pore 67–68% of proglottid length from posterior end; testes 169–186 in total number, 17 in post-poral field, 29–43 (36 ± 4; 2; 8) long, 37–60 (49 ± 8; 2; 8) wide; cirrus sac 389–417 long, 68–84 wide; ovary 435–591 long, 578–606 wide. Detached gravid proglottids (two from same host) 4065–5318 long, 1781–3097 wide, length-to-width ratio 1.7–2.3:1; genital pore 57–58% of proglottid length from posterior end; testes 187–203 in total number, 22–24 in post-poral field, 45–57 (50 ± 5; 2; 8) long, 61–72 (67 ± 4; 2; 8) wide; cirrus sac 422–429 long, 87–92 wide; ovary 652–938 long, 615–711 wide; oncospheres spherical, 23–26 (24 ± 1; 2; 8) long, 20–25 (23 ± 2; 2; 8) wide, too densely packed to assess whether packaged in cocoons. Detached dehisced proglottids (four from same host) 6145–8028 (6971 ± 882; 4) long, 1974–2552 (2269 ± 236; 4) wide, length-to-width ratio 1.8–2.2 (2 ± 0.2; 4):1; genital pore 45–56% (50 ± 5; 4) of proglottid length from posterior end; testes 159–172 (167 ± 7; 3) in total number, seven to 14 in post-poral field, 54–104 (81 ± 14; 4; 16) long, 70–104 (82 ± 9; 4; 16) wide; cirrus sac 499–586 (540 ± 37; 4) long, 85–129 (109 ± 18; 4) wide; ovary 827–1323 (1045 ± 218; 4) long, 749–1092 (866 ± 154; 4) wide.

Type host: Tiger catshark, Halaelurus natalensis (Regan, 1904) ( Carcharhiniformes: Pentanchidae ).

Ty p e l o c a l i t y: I n d i a n O c e a n o f f S o u t h A f r i c a (33°47′40.2″S, 26°05′7.2″E).

Additional localities: Indian Ocean off South Africa (33°59′24″S, 25°12′1.2″E; 34°10′7.2″S, 24°54′55.2″E) .

mm

5

Site of infection: Spiral intestine.

Type material: Holotype [mature worm (on three slides), NMB P no. 734], two paratype detached proglottids (both dehisced, NMB P nos 735 and 736); one paratype (mature worm, USNM no. 1638648), three paratype detached proglottids (one mature, USNM no. 1638649; one gravid, USNM no. 1638650; one dehisced, USNM no. 1638651); one paratype (immature worm, LRP no. 10288), five paratype detached proglottids (one mature, LRP no. 10289; one gravid, LRP no. 10290; three dehisced, LRP nos 10291, 10331, and 10332), one paratype (immature worm SEM voucher, LRP no. 10292).

Sequence data: GenBank accession MW 419963 , hologenophore (AF-179; JW423) LRP no. 10326.

Etymology: This species is named for Dr Metin Coşgel, Professor of Economics at the University of Connecticut, in recognition of his dedication, advocacy and enthusiasm for ecology and evolutionary biology as interim Head of the Department of Ecology & Evolutionary Biology.

Remarks: Yamaguticestus differs from both Y. squali and Y. longicollis in the remarkably large size of its apical sucker, which, rather than being restricted to the anterior margin of the bothridium as in Y. longicollis and Y. squali as redescribed by Euzet (1959) and Vasileva et al. (2002), occupies nearly half of the length of the bothridium. Furthermore, unlike both previously described species, the ovary of Y. metini is subterminal, rather than terminal, in position in the proglottid.

Figures

Figure 5. Scanning electron micrographs of Yamaguticestus. A, scolex of Yamaguticestus squali. B, surface of bothridium of Y. squali anterior to apical sucker. C, distal surface of bothridium of Y. squali. D, proximal surface of bothridium of Y. squali. E, scutes on surface of neck of Y. squali. F, scolex of Yamaguticestus metini. G, surface of apical sucker of Y. metini. H, distal surface of bothridium of Y. metini. I, proximal surface of bothridium of Y. metini. J, scutes on surface of neck of Y. metini.

Figure 6. Line drawings of adult of Yamaguticestus metini (specimen accession numbers in parentheses). A, scolex (NMB P no. 734). B, whole worm (USNM no. 1638648). C, mature proglottid (USNM no. 1638648). D, detail of ovary (USNM no. 1638648). E, detail of terminal genitalia (USNM no. 1638648).