Stillabothrium mariae, Ruhnke & Pommelle & Aguilar & Hudson & Reyda Key Words Abstract, 2022

Ruhnke, Timothy R., Pommelle, Cheyenne P., Aguilar, Daniela, Hudson, Hannah & Reyda Key Words Abstract, Florian B., 2022, Two New Species Of Stillabothrium (Cestoda: Rhinebothriidea) From Stingrays From Northern Australia And One New Combination, Journal of Parasitology 108 (2), pp. 166-179 : 174-176

Stillabothrium mariae n. sp. Ruhnke, Pommelle and Reyda

(Informal synonym: Rhinebothriinae New genus 3 n. sp. 4 of Healy et al. (2009), Caira et al. (2014), Ruhnke et al. (2015), Marques and Caira (2016).)

( Figs. 6–7 )

Description (based on whole mounts of 26 complete mature worms, cross sections from 2 scoleces and 2 strobilae, and 5 scoleces prepared for SEM): Worms ( Fig. 6A ) euapolytic, acraspedote, 1.43–2.74 mm (2.03 ± 1.43; n ¼ 26) long, greatest width 194–318 (255 ± 36; n ¼ 26) at level of scolex; 6–13 (9 ± 1.8; n ¼ 26) proglottids per worm. Cephalic peduncle absent; darkly staining germinative zone present.

Scolex ( Figs. 6B , 7A ) consisting of scolex proper bearing four stalked bothridia. Stalks 103–175 (137 ± 19; n ¼ 14) long by 41– 130 (74 ± 25; n ¼ 14) wide, attached posterior to middle of bothridia. Bothridia varying in shape due to degree of contraction, from cup-like to nearly flat, facially loculated, 245–319 (283 ± 21; n ¼ 26) long by 108–223 (162 ±33; n ¼ 26) wide; bothridial margins with thin rim of tissue ( Fig. 7A ). Anterior region of bothridia ( Figs. 6B , 7A ) with 10–12 horizontally oriented loculi that are wider than long, posterior loculus of relative equal length and width. Anterior loculus 20–33 (27 ± 4; n ¼ 21) long by 27–48 (36 ± 5; n ¼ 21) wide. Posterior-most loculus of bothridium laced with horizontal and longitudinal muscle fibers (see Fig. 6B ) and lacking conspicuous septa. Marginal loculi present posterior to horizontal loculi, 11 or 13 in number (n ¼ 6).

Loculi and septa ( Fig. 7B ) of distal bothridial surfaces bearing capilliform filitriches and coniform spinitriches. Bothridial rim bearing capilliform filitriches ( Fig. 7C ). Proximal bothridial surfaces away from rim ( Fig. 7C ) bearing acicular filitriches. Posterior portion of proximal bothridial surface ( Figs. 7D, 7E ) bearing patch of coniform spinitriches near, but not extending to, bothridial rim. Isolated cilia observed on distal bothridial surfaces ( Fig. 7B ). Strobila bearing capilliform filitriches only.

Strobila ( Fig. 6A ) with 2–6 (4 ± 1.3; n ¼ 26) proglottids wider than long followed by 4–8 (5 ± 0.9; n ¼ 26) proglottids longer than wide. Strobila widest at terminal proglottid; terminal proglottid 446–748 (625 ± 79; n ¼ 26) long by 87–167 (113 ± 20; n ¼ 26) wide; genital pore located 46–64% (55 ± 4; n ¼ 26) of proglottid length from proglottid posterior margin. Immature proglottids 5–10 (8 ± 1.6; n ¼ 26) in number. Mature proglottids 1–3 (2 ± 1; n ¼ 26) in number. Testes in mature proglottid 12–19 (16 ± 1.9; n ¼ 26) in total number, 1 layer deep, arranged in 2 columns ( Fig. 6C ); columns extending from anterior margin of proglottid to level of genital pore, 16–46 (29 ± 6; n ¼ 26) long by 26–53 (35 ± 7; n ¼ 26) wide. Vas deferens coiled, entering anterior margin of cirrus sac, extending from anterior portion of ovary to overlap posterior-most testes ( Fig. 6C ). Cirrus sac thin walled, round to oval, extending medially past midline of proglottid. Cirrus sac in terminal mature proglottid 53–100 (67 ± 11; n ¼ 25) long by 43–87 (61 ± 12; n ¼ 24) wide. Cirrus spinitriches present.

Vagina ( Fig. 6C ) thick-walled, strongly sinuous, overlapping medial and anterior margin of cirrus sac, somewhat recurved, extending past midline of proglottid from ootype then laterally to open to genital atrium anterior to cirrus sac; vaginal sphincter absent. Seminal receptacle not observed. Ovary near posterior end of proglottid, H-shaped in frontal view, tetralobed in section; ovarian lobes symmetrical, 124–248 (203 ± 35; n ¼ 18) long in terminal mature proglottids. Maximum width of ovary 38–67 (49 ± 10; n ¼ 15). Ovarian isthmus at or anterior to midpoint of ovary; poral lobe of ovary stopping 42–92 (69 ± 16; n ¼ 17) short of genital pore and stopping 12–32 (21 ± 7; n ¼ 12) short of cirrus sac. Mehlis’ gland posterior to ovarian isthmus, 23–39 (29 ± 5; n ¼ 8) long by 18–29 (22 ± 5; n ¼ 8) wide. Vitellarium follicular; vitelline follicles arranged in 1–2 dorsal and 1–2 ventral columns on each side of proglottid; columns extending from near anterior to posterior margin of proglottid, interrupted by terminal genitalia, and interrupted to varying degrees by ovary ( Fig. 6C ). Uterus ventral, sacciform, extending from near isthmus of ovary to near anterior margin of testicular field.

Taxonomic summary

Type host: Maculabatis astra (Last, Manjaji-Matsumoto & Pogonoski) , the Blackspotted whipray ( Myliobatiformes : Dasyatidae ).

Type locality: Arafura Sea east of Wessel Islands (11°17 ′ 44 ′′ S, 136°59 ′ 48 ′′ E), Northern Territory, Australia (hosts NT-24 and NT-26) .

Site of infection: Spiral intestine.

Type material: Holotype QM No. G 239547 . Paratypes: LRP Nos. 10810-10812, 10814-10817 (including whole mounts, sections, and SEM specimens) ; QM Nos. G239548–G239550; USNM 1661764–1661767 ; Hologenophores LRP Nos. 10809, 10813.

Etymology: This species is named for parasitologist Dr. Maria Pickering.

ZooBank registration: urn:lsid:zoobank.org:act:90B6BBD5-D777-43F7-AD3F-E37B8A1B9284 .

Remarks

Stillabothrium mariae n. sp. can be distinguished from the 12 previously described species of Stillabothrium by the unique configuration of loculi on its bothridia. The presence of 10–11 wider than long horizontally oriented loculi of S. mariae in the anterior portion of its bothridia sets it apart from 11 of its 12 congeners: S. allisonae (4), S. amuletum (4), S. ashleyae (3), S. biacetabulatum (3), S. borneoense (4), S. cadenati (3), S. charlottae (0), S. davidcynthiaorum (3), S. hyphantoseptum (6–8), S. jeanfortiae (3), and S. lunae (7–8). Stillabothrium mariae is distinguished from the only other congener that also possesses a relatively large number of horizontally oriented loculi, S. campbelli (10–12), and from all other members of the genus except S. biacetabulatum in that it lacks, rather than possesses, conspicuous septa and loculi that are longer than wide in the posterior portion of its bothridia. Stillabothrium mariae is further distinguished from S. campbelli in that its bothridia are longer (245–319 vs. 166–240), and from S. campbelli and S. biacetabulatum in that the vagina of S. campbelli and S. biacetabulatum is not recurved, whereas it is in S. mariae . The tapeworm specimen included in the phylogenetic analyses of Healy et al. (2009), Ruhnke et al. (2015), and Marques and Caira (2016) as Rhinebothriinae New genus 3 n. sp. 4 (GenBank FJ177114) is here identified as Stillabothrium mariae n. sp.

Figures

Figure 6. Line drawings of Stillabothrium mariae n. sp. (A) Whole worm of holotype (QM G239547). (B) Scolex of paratype (LRP 10814). (C) Terminal proglottid of paratype (QM G239547).

Figure 7. Scanning electron micrographs of Stillabothrium mariae n. sp. (A) Scolex; small letters indicate location of details shown in B–E. (B) Distal bothridial surface. (C) Proximal bothridial surface at bothridial rim. (D, E) Proximal bothridial surface at posterior bothridium.