Pentaloculum grahami, 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 : 35-38

Pentaloculum grahami n. sp.

( Figs. 3A–E , 4A–H , 5 )

ZooBank No. B8C37A6D-016A-4D85-A132-C6E7E1063BC3

Type and only known host: Parascyllium collare Ramsay and Ogilby , collared carpetshark; ( Orectolobiformes : Parascylliidae Gill ).

Type locality: Crowdy Head , New South Wales, Australia (31°50’S, 152°45’E). Site of infection: Spiral intestine. Type specimens: Holotype ( QM No. G240343 ) and two paratypes (QM Nos. G240344 – G240345 ); two paratypes and one SEM voucher (LRP Nos. 10947 – 10949 ); two paratypes ( USNM Nos. 1678892 – 1678893 ) . Scoleces prepared for SEM retained with JNC at the University of Connecticut.

Sequence data: KF685749 and MK321595 (hologenophores, LRP No. 8344 [KJG-17, TE-166] and LRP No. 9956 [KJG-17, JW-147]).

Etymology: This name honors fish biologist Ken Graham from the New South Wales State Fisheries and the Australian Museum who collected all specimens of Parascyillium collare examined in this study.

Provisional names: New genus 1 n. sp. of Caira et al. 2001; New genus 7 n. sp. 1 of Caira et al. 2014 and Ruhnke et al. 2015; Pentaloculum n. sp. 2 of Eudy et al. 2019.

Description. Based on one incomplete mature and six complete mature worms, and two scoleces observed with SEM.

Worms apolytic, 12.1–51.6 (28.9 ± 15.7; 6) mm long, greatest width at level of terminal proglottid; 105–174 (131 ± 29; 6) proglottids per worm. Scolex 358–460 (406 ± 38.6; 7) long by 433–593 (516.9 ± 68.9; 7) wide, consisting of four muscular sessile bothridia. Bothridia broadly ovoid, 276–405 (348.5 ± 41.3; 6; 10) long by 230– 311 (254.2 ± 23.4; 5; 9) 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 diving posterior pair of loculi ( Figs. 3A , 4A ). Cephalic peduncle lacking.

Apex of scolex ( Fig. 4C ) covered with gladiate spinitriches and densely packed capilliform filitriches; distal bothridial surfaces ( Fig. 4B ) and proximal surfaces of margins of bothridia ( Fig. 4E – G ) densely covered with long-tipped aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches; proximal surfaces away from bothridial margins ( Fig. 4H ) densely covered with short-tipped wide aristate gladiate spinitriches, filitriches not observed; scolex proper ( Fig. 4D ) densely covered with gladiate spinitriches interspersed with capilliform filitriches.

Proglottids craspedote. Immature proglottids 98–151 (127 ± 23.4; 6) in number, wider than long. Mature proglottids 2–11 (5.8 ± 3.8; 6) in number, wider than long ( Fig. 3B ), 330–830 (606.1 ± 220.6; 6; 10) long by 962– 1402 (1229 ± 150.9; 6; 10) wide, length:width ratio 0.3–0.9 (0.5 ± 0.2; 6; 10):1. Gravid proglottids 1–12 (5.2 ± 3.9; 6) in number, wider than long, becoming longer than wide with maturity ( Fig. 3D ), 954–4881 (3056.6 ± 1554.1; 6) long by 988–2512 (1407.8 ± 581; 6) wide. Genital pores marginal, irregularly alternating, 42–57% (52 ± 6; 5) of proglottid length from posterior margin in terminal-most mature proglottid.Testes30–58 (44.3± 10.5;5;6)in number, two layers deep, arranged in single field anterior to cirrus sac, oval in frontal view, 28–57 long (42.3 ± 9.7; 4; 12) by 74–123 (98 ± 15.6; 4; 12) wide. Vas deferens narrow, highly coiled, extending posteriorly to near level of ovary then anteriorly to enter cirrus sac at median margin. Cirrus sac ( Fig. 3C ) thin-walled, narrowly obovoid, containing coiled cirrus, 149–218 (181.1 ± 21.9; 5; 9) long by 333–629 (434.2 ± 86.8; 5; 9) wide; cirrus highly expanded at base, armed with small spinitriches. Vagina thick-walled, weakly sinuous, extending from ootype along medial line of proglottid to level of cirrus sac, then 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 slightly lobulated margins, H-shaped in frontal view, bilobed in cross-section, 446–537 (501.9 ± 29.8; 5; 9) at widest point by 78–237 (155.5 ± 52.4; 5; 18) long. Mehlis’ gland posterior to ovarian isthmus. Vitellarium follicular; follicles in two lateral bands; each band consisting of multiple columns of follicles, extending throughout length of proglottid, not interrupted by cirrus sac or ovary, converging posterior to ovary; vitelline follicles oval, 22–38 (29.6 ± 5.7; 5; 15) long by 28–52 (38.7 ± 8.1; 5; 15) wide. Uterus medial, saccate, ventral to vagina, extending anteriorly from ovarian isthmus to mid-level of testicular field. Excretory vessels four, arranged in one dorsal and one ventral pair on each lateral margin of proglottid. Oncospheres organized in cocoons ( Fig. 5A–B ). Cocoons spherical, containing 5–7 (6.1 ± 0.6; 1; 10) oncospheres, polar filaments lacking; oncospheres spherical, 50–81 (69.7 ± 5; 1; 10) long by 63–79 (71.6 ± 4.1; 1; 57) wide.

Remarks. Pentaloculum grahami n. sp. differs from P. macrocephalum and P. hoi in total worm length (12.08 – 51.62 vs. 8 and 1.7–3.5 mm, respectively) and total number of proglottids (105–174 vs. 23 and 16–26, respectively). It can be further distinguished from P. macrocephalum and P. hoi in that its mature proglottids are wider than long, as opposed to longer than wide, and in that the ovary is H-shaped rather than inverted A-shaped. It further differs from P. hoi in that its cocoons lack, rather than possess, bipolar filaments. It is of note that Hayden and Campbell (1981) described Zyxibothrium kamienae as possessing eggs that were contained in a membranous intrauterine tube, rather than arranged in cocoons.

Figures

FIGURE 3. Line drawings of Pentaloculum grahami n. sp. (A) Scolex (paratype, SA-2-1, LRP No. 10947). (B) Mature subterminal proglottid (paratype, SA-16-1, USNM No. 1678892). (C) Detail of terminal genitalia (holotype, SA-16-3, QM No. G240343). (D) Gravid terminal proglottid (holotype, SA-16-3, QM No. G240343). (E) Whole worm (holotype, SA-16-3, QM No. G240343).

FIGURE 4. Scanning electron micrographs of Pentaloculum grahami n. sp. (A) Scolex, small letters indicate location of details in micrographs B–H. (B) Distal bothridial surface densely covered with long-tipped aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (C) Apex of scolex covered with gladiate spinitriches and densely packed capilliform filitriches. (D) Scolex proper densely covered with gladiate spinitriches interspersed with capilliform filitriches. (E) Proximal surface of margin of anteriormost loculus densely covered with long-tipped aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (F) Proximal surfaces of margins of anterior pair of loculi densely covered with long-tipped aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (G) Proximal surfaces of margins of posterior pair of loculi densely covered with long-tipped aristate gladiate spinitriches interspersed with gladiate spinitriches and capilliform filitriches. (H) Proximal surfaces away from margins of posterior pair of loculi densely covered with short-tipped wide aristate gladiate spinitriches, filitriches not observed.

FIGURE 5. Photomicrographs of cocoons of Pentaloculum grahami n. sp. showing variation in number of oncospheres. (A) Cocoon containing five oncospheres. (B) Cocoon containing six oncospheres.