Stillabothrium jeanfortiae Forti, Aprill et Reyda sp. n.

Figs. 1, 10, 11, 16E

ZooBank number for species:

urn:lsid:zoobank.org:act: D2B25027-058D-4E3D-B880-F1FA5AB763DB

Description (based on whole mounts of 20 complete mature worms, cross sections of 1 strobila and longitudinal sections of 1 scolex and 2 scoleces prepared for SEM): Worms (Fig. 10A) euapolytic, acraspedote, 1.7–3.9 mm (2.5 ± 0.6; n = 20) long, greatest width 428–822 (588 ± 121; n = 20) at level of scolex; 5–10 (7.1 ± 1.2; n = 20) proglottids per worm. Cephalic peduncle lacking, small darkly staining germinative zone present.

Scolex (Fig. 10B) consisting of scolex proper bearing four stalked bothridia. Stalks 30–125 (77 ± 25; n = 16) long by 65–140 (94 ± 18; n = 16) wide, attached slightly posterior to middle of bothridia. Bothridia (Figs. 10A,B, 11A) always constricted but varying in shape with degree of contraction, broadly (Fig. 10B), shallowly (Fig. 10A), very shallowly (Fig. 11A), or depressed deltoid, facially loculated, 218–305 (259 ± 21; n = 20) long by 255–460 (339 ± 58; n = 20) wide. Anterior region of bothridia (Figs. 10A,B, 11A) with 3 horizontally oriented loculi (i.e. loculi wider than long) with 3 complete complete transverse septa (n = 20). Anteriormost loculus 35–60 (46 ± 7; n = 18) long by 64–115 (81 ± 16; n = 18) wide. Posterior region of bothridia (Figs. 10A,B, 11A) with 6 (n = 20) nonmedial longitudinal septa dividing bothridia into 7 loculi longer than wide; longitudinal septa not overlapping transverse septa in anterior region of bothridia.

Loculi and septa of distal bothridial surfaces (Fig. 11B) bearing coniform spinitriches and, less conspicuously, capilliform filitriches. Proximal bothridial rim (Fig. 11C) bearing capilliform filitriches greater in length than those on distal bothridial surfaces (Fig. 11B). Proximal bothridial surfaces away from rim bearing densely arranged capilliform filitriches throughout bothridium (Fig. 11E). Proximal bothridial surfaces near bothridial rim bearing coniform spinitriches (Fig. 11D) that do not extend to stalks. Bothridial stalks and strobila (Fig. 11F) bearing capilliform filitriches only.

Strobila with 2–5 (3.2 ± 0.8; n = 20) proglottids wider than long followed by 3–7 (3.9 ± 1.0; n = 20) proglottids longer than wide. Strobila widest at terminal proglottid; terminal proglottid 724–1 260 (1 013 ± 185; n = 20) long by 92–192 (132 ± 24; n = 20) wide; genital pore located 42–56% (48 ± 4; n = 20) of proglottid length from proglottid posterior margin. Immature proglottids 4–8 (5.8 ± 1.0; n = 20) in number. Mature proglottids 1–2 (1.4 ± 0.5; n = 20) in number, including 0–1 (0.3 ± 0.5; n = 20) vas deferens-mature proglottid.

Testes in mature proglottids 20–29 (23 ± 2; n = 20) in total number, in 1 layer deep in section, arranged in 2 columns (Fig. 10C), columns extending from anterior margin of proglottid to anterior margin of cirrus sac, 26–52 (38 ± 8; n = 16) long by 29–55 (42 ± 7; n = 16) wide. Vas deferens coiled, entering anterior margin of cirrus sac, extending from level of ovarian isthmus anteriorly to overlap posteriormost testes. Cirrus sac thin-walled, oval, extending medially past midline of proglottid. Cirrus sac in terminal mature proglottid 55–81 (72 ± 8; n = 15) long by 47–73 (59 ± 8; n = 15) wide; cirrus sac in vas deferens-mature proglottids 80–87 (84 ± 3; n = 5) long by 62–80 (72 ± 7; n = 5) wide. Cirrus spinitriches present.

Vagina (Fig. 10C) thick-walled, non-sinuous, somewhat overlapping medial portion of cirrus sac (Fig. 10C), extending along midline of proglottid from ootype region to anterior margin of cirrus sac, then laterally to open into genital atrium anterior to cirrus sac; vaginal sphincter absent. Seminal receptacle present. Ovary near posterior end of proglottid, H-shaped in frontal view, tetralobed in cross section; ovarian lobes somewhat asymmetrical; poral and aporal ovarian lobes in terminal mature proglottids 238–396 (304 ± 47; n = 12) and 265–394 (318 ± 45; n = 12) long, respectively. Poral and aporal ovarian lobes in vas deferens-mature proglottids 355–486 (412 ± 58; n = 6) and 370–488 (434 ± 48; n = 6) long, respectively. Maximum width of ovary 60–122 (91 ± 19; n = 17). Ovarian isthmus at or posterior to midpoint of ovary; poral lobe of ovary stopping 18–70 (51 ± 14; n = 17) short of genital pore. Mehlis’ gland well posterior to ovarian isthmus, 32–72 (47 ± 13; n = 16) long by 22–35 (28 ± 4; n = 16) wide. Vitellarium follicular; vitelline follicles arranged in 1 dorsal and 1 ventral column on each side of proglottid; columns extending from anterior to posterior margin of proglottid, interrupted by terminal genitalia and mostly interrupted by ovary (Fig. 10A,C). Uterus ventral, sacciform extending from near ovarian isthmus to near anterior margin of proglottid.

T y p e a n d o n l y k n o w n h o s t: Himantura australis Last, White et Naylor, Reticulate whipray ( Dasyatidae: Myliobatiformes).

T y p e a n d o n l y k n o w n l o c a l i t y: Gulf of Carpentaria (Indian Ocean) off Weipa (12°35'11''S; 141°42'34''E), Queensland, Australia (CM03-3, CM03-25, CM03-65) .

S i t e o f i n f e c t i o n: Spiral intestine.

Ty p e m a t e r i a l: Holotype QM No. G 235198. Paratypes: LRP Nos. 8999; 9118–9133 (including molecular vouchers, sections, and SEM specimens); QM Nos. G 235199– G235200; USNM Nos. 1420478–1420483; IPCAS No. C-740 .

E t y m o l o g y: This species is named in loving memory of Jean Forti, mother of K.S. Forti, for her support of her daughter’s education.

Remarks. Stillabothrium jeanfortiae sp. n. is the fifth new Stillabothrium species described in this study. Its configuration of bothridial septa is unique relative to its four described congeners. Stillabothrium jeanfortiae is distinguished from S. ashleyae and S. davicynthiae in that it lacks, rather than possesses, marginal septa in the posterior region of bothridia. It also differs from S. ashleyae and S. davicynthiae in that the three loculi in its anterior region of bothridia are oriented in tandem, instead of occurring as a row of one and then two loculi. Stillabothrium jeanfortiae can be distinguished from S. campbelli and S. hyphantoseptum in that it lacks, rather than posseses, septa that overlap one another.

Stillabothrium jeanfortiae is described from the stingray Himantura australis from the Gulf of Carpentaria in northern Australia. Specimens similar in morphology to S. jeanfortiae were encountered in H. leoparda (NT-117), also from the Gulf of Carpentaria, but confirmation of the identity of this material awaits further study. Specimens with a similar bothridial morphology to that of S. jeanfortiae were also encountered in a diversity of species of Himantura during survey work in Borneo. Those specimens can be readily distinguished from S. jeanfortiae based on proglottid morphology, but their taxonomic treatment also awaits further study.

One specimen of S. jeanfortiae was included in the phylogenetic analysis (Fig. 1, Table 1). It grouped with two undescribed species of Stillabothrium from Senegal.