Stillabothrium Healy and Reyda, 2016

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 : 177

Stillabothrium Healy and Reyda, 2016

Emended diagnosis: Rhinebothriidea . Worms euapolytic, small. Scolex consisting of scolex proper and 4 bothridia; cephalic peduncle absent; short germinative zone present; apical organ absent. Bothridia stalked, consisting of anterior and posterior regions with distinctly different arrangement of loculi and septa; bothridial margins with thin rim. Anterior region of bothridia with multiple loculi that are horizontally oriented rows (i.e., loculi wider than long) or somewhat round in shape, with two or more complete transverse septa. Marginal loculi on bothridium present or absent. Posterior region of bothridium either divided into odd number of vertically oriented column-like loculi (loculi that are longer than wide) by even number of nonmedial longitudinal septa, or laced with muscle fibers that do not constitute septa. When present, nonmedial longitudinal septa all incomplete, or a combination of incomplete and complete; incomplete nonmedial longitudinal septa either abut posterior-most transverse septum of anterior region of bothridia, or overlap one or more posteriormost transverse septa. Longitudinal septa of posterior region, when present, appear as ridges in section with proximal and distal portions that are different; proximal portion of septa formed by underlying bothridial wall, consisting of radial muscles oriented with proximal ends of fibers adjacent to each other; distal portion of septa formed by separate muscle bundle; proximal and distal portions of septa separated by a triangular gap.

Testes numerous, arranged in 2 columns, 1 layer deep in cross section, restricted to pre-poral region of proglottid. Cirrus sac extending medially to or past midline of proglottid. Cirrus spinitriches present. Vas deferens extending posteriorly to ovarian isthmus, entering cirrus sac at anterior margin. Vagina opening anterior to cirrus sac; vaginal sphincter absent. Ovary H-shaped in frontal view, tetralobed in cross section. Vitellarium follicular; follicles in 2 lateral bands; bands interrupted by terminal genitalia and usually also by ovary. Uterus saccate, medial, extending from posterior margin of proglottid or ovarian isthmus anteriorly to near anterior margin of proglottid. Parasites of batoids ( Rhinobatidae , Zanobatidae , and Dasyatidae ); Indo-Pacific and coastal Afrotropics.

Type species: Stillabothrium ashleyae Willsey and Reyda, 2016 .

Additional species: Stillabothrium allisonae Dedrick and Reyda, 2018 , Stillabothrium amuletum (Butler, 1987) Healy and Reyda, 2016 ; Stillabothrium biacetabulatum n. comb.; Stillabothrium borneoense Herzog, Meininger, and Reyda, 2021 ; Stillabothrium cadenati (Euzet, 1954) Healy and Reyda, 2016 ; Stillabothrium campbelli Delgado, Dedrick, and Reyda, 2016 ; Stillabothrium charlotteae Iwanyckyj, Dedrick and Reyda, 2018 ; Stillabothrium davidcynthiaorum Daigler and Reyda, 2016 ; Stillabothrium hyphantoseptum Herzog, Bergman and Reyda, 2016 ; Stillabothrium jeanfortiae Forti, Aprill and Reyda, 2016 ; Stillabothrium lunae n. sp.; Stillabothrium mariae n. sp.

Remarks

The generic diagnosis of Stillabothrium is emended to receive S. mariae and S. biacetabulatum n. comb. In both species, the portion of the bothridium posterior to the anterior transverse loculi is undivided but associated with muscle fibers that do not contribute to the formation of septa and is therefore not facially loculated. We have described this condition in both species as marginally loculate. The diagnosis is also modified to accommodate the morphology of S. charlottae because it possesses a row of round loculi in the anterior portion of its bothridium (see Dedrick et al., 2018).