Zyxibothrium duffyi, Bueno & Caira, 2023

Bueno, Veronica M. & Caira, Janine N., 2023, Phylogenetic relationships, host associations, and three new species of a poorly known group of “ tetraphyllidean ” tapeworms from elasmobranchs, Zootaxa 5254 (1), pp. 30-50 : 40-41

Zyxibothrium duffyi n. sp.

( Figs. 7A– D , 8A–G )

ZooBank No. A0050BAE-FA9B-439D-B546-66F6BBFB2883

Type and only known host: Brochiraja asperula (Garrick and Paul) , smooth deep-sea skate; ( Rajiformes : Arhynchobatidae Fowler ).

Type locality: Chatham Rise , New Zealand (44°0’S, 174°05’E). Site of infection: Spiral intestine. Type specimens: Holotype ( NMNZ No. W.003925 ) and three paratypes ( NMNZ Nos. W.003926 – W.003928 ); three paratypes ( LRP Nos. 9785 , 9990 , 1045 ) and two SEM vouchers (LRP Nos. 9796 , 10946 ); two paratypes ( USNM Nos. 1678894 – 1678895 ). Scoleces prepared for SEM retained with JNC at the University of Connecticut.

Sequence data: OQ186460 and OQ186461 (hologenophores LRP No. 9797 [CR-88-1, VB213] and LRP No. 9798 [CR-88-2, VB214]).

Etymology: This name honors elasmobranch biologist Clinton Duffy from the Department of Conservation, Wellington, New Zealand for his enthusiasm for elasmobranch parasites and for providing us with elasmobranch samples and their cestodes from New Zealand.

Description. Based on eight complete mature worms, and one scolex observed with SEM.

Worms euapolytic, 2.9–5.2 (4.2 ± 0.9; 6) mm long greatest width at level of scolex; 8–18 (14.4 ± 3.5; 8) proglottids per worm. Scolex consisting of four muscular bothridia and short cephalic peduncle. Scolex proper 374–805 (640.1 ± 147.4; 7) long by 556–737 (648.9 ± 63.6; 7) wide. Bothridia broadly ovoid, 342–629 (480.3 ± 90.5; 14; 7) long by 187–365 (290.5 ± 59.7; 6; 12) wide; each divided into five facial loculi arranged as one single anterior loculus followed by two consecutive pairs of loculi; septum dividing anterior pair of loculi slightly offset laterally from septum dividing posterior pair of loculi ( Figs. 7A , 8A ). Cephalic peduncle 65–248 (149.7 ± 73.8; 6) long by 218–274 (253.1 ± 20.5; 6) wide.

Apex of scolex ( Fig. 8B ) densely covered with capilliform filitriches; distal bothridial surfaces ( Fig. 8F ) densely covered with gladiate spinitriches interspersed with long slender aristate gladiate spinitriches and capilliform filitriches; proximal surfaces of anteriormost loculus ( Fig. 8C ) and anterior pair of loculi ( Fig. 8D ) densely covered with long slender aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches; proximal surfaces of posterior pair of loculi ( Fig. 8E ) densely covered with long slender aristate gladiate spinitriches interspersed with gladiate spinitriches, filitriches not observed; cephalic peduncle ( Fig. 8G ) densely covered with long slender gladiate spinitriches interspersed with long slender aristate gladiate spinitriches, filitriches not observed.

Proglottids slightly craspedote. Immature proglottids 7–16 (13.1 ± 3.4; 8) in number, wider than long, becoming longer than wide with maturity ( Fig. 7C ). Mature proglottids 1– 2 (1.3 ± 0.5; 8) in number, longer than wide ( Fig. 7D ), 1031–1597 (1247.3 ± 182.7; 8) long by 310–564 (413.4 ± 77.1; 8) wide, length:width ratio 2.5–3.9 (3.1 ± 0.6; 8):1; gravid proglottids not observed. Genital pores marginal, irregularly alternating, 94–97% (96 ± 1; 8) of proglottid length from posterior margin in terminal mature proglottid. Testes 32–51 (39.6 ± 7.6; 6; 7) in number, two layers deep, arranged in single dorsal field extending from mid-level of proglottid to anterior margin of proglottid, oval in frontal view, 30–53 long (41.5 ± 6.8; 23; 8) by 45–82 (64.1 ± 11; 8; 23) wide. Vas deferens highly coiled posterior to cirrus sac, extending posteriorly to level of ovarian bridge and then anteriorly to enter cirrus sac at medial margin. Cirrus sac ( Fig. 7B ) thin-walled, pyriform, tilted posteriorly, containing coiled cirrus, 276–355 (318.1 ± 26.1; 7) long by 134–182 (157.7 ± 16.3; 7) wide; cirrus armed with small spinitriches. Vagina thick-walled, weakly sinuous, extending from ootype along medial line of proglottid to level of cirrus sac, crossing cirrus sac ventrally and extending along anterior margin of cirrus sac to open into genital atrium anterior to cirrus; vaginal sphincter lacking; seminal receptacle lacking. Ovary near posterior end of proglottid, with smooth margins, H-shaped in frontal view, bilobed in cross-section, symmetrical; 168–266 (207.3 ± 30.2; 8) at widest point, 243– 488 (328.4 ± 62.1; 8; 16) long. Mehlis’ gland posterior to ovarian isthmus. Vitellarium follicular; follicles in two lateral bands; each band consisting of multiple columns of follicles, extending anteriorly to midlevel of cirrus sac, converging posterior to ovary; vitelline follicles oval, 17–33 (24.7 ± 64.4; 8; 24) long by 16–36 (24.3 ± 5.8; 8; 24) wide. Uterus medial, saccate, ventral to vagina, extending anteriorly from ovarian isthmus to posterior margin of cirrus sac. Excretory vessels four, arranged in one dorsal and one ventral pair on each lateral margin of proglottid. Oncospheres not observed.

Remarks. Zyxibothrium duffyi n. sp. differs from Z. kamienae most conspicuously in having five, rather than four, loculi on each bothridium. It can be further distinguished from Z. kamienae in that it is euapolyic rather than apolytic, possesses a greater number of testes (32–51 vs 19–24), and has a greater number of proglottids (8–18 vs 5–8).

Figures

FIGURE 7. Line drawings of Zyxibothrium duffyi n. sp. (A) Scolex (paratype, CR-65-5, LRP No. 9990). (B) Detail of terminal genitalia (paratype, CR-28-1, LRP No. 9785). (C) Whole worm (holotype, CR-65-1, NMNZ No. W.003925). (D) Mature proglottid (holotype, CR-65-1, NMNZ No. W.003925).

FIGURE 8. Scanning electron micrographs of Zyxibothrium duffyi n. sp. (A) Scolex, small letters indicate location of details in micrographs B–G. (B) Apex of scolex densely covered with capilliform filitriches. (C) Proximal surface of anteriormost loculus densely covered with long slender aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (D) Proximal surfaces of anterior pair of loculi densely covered with long slender aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (E) Proximal surfaces of posterior pair of loculi densely covered with long slender aristate gladiate spinitriches interspersed with gladiate spinitriches, filitriches not observed. (F) Distal bothridial surface densely covered with long slender aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (G) Cephalic peduncle densely covered with long slender gladiate spinitriches interspersed with long slender aristate gladiate spinitriches, filitriches not observed.