Stillabothrium davidcynthiaorum Daigler et Reyda, 2016

Reyda, Florian B., Healy, Claire J., Haslach, Andrew R., Ruhnke, Timothy R., Aprill, Tara L., Bergman, Michael P., Daigler, Andrew L., Dedrick, Elsie A., Delgado, Illari, Forti, Kathryn S., Herzog, Kaylee S., Russell, Rebecca S. & Willsey, Danielle D., 2016, A new genus of rhinebothriidean cestodes from batoid elasmobranchs, with the description of five new species and two new combinations, Folia Parasitologica (038) 63 (38), pp. 1-28 : 8-11

Stillabothrium davidcynthiaorum Daigler et Reyda sp. n.

Figs. 1 , 4 , 5 , 16B

ZooBank number for species:

urn:lsid:zoobank.org:act:D36AE2D9-C4A6-4C4D-8F82-E9C0FAF1F92C

Description (based on whole mounts of 32 complete mature worms, cross sections of 1 strobila and longitudinal sections of 1 scolex and 3 scoleces prepared for SEM): Worms ( Fig. 4A ) euapolytic, acraspedote, 0.62–2.59 mm (1.29 ± 0.57; n = 30) long, greatest width 195–561 (332 ± 84.7; n = 32) at level of scolex; 4–10 (7 ± 2.1; n = 32) proglottids per worm. Cephalic peduncle lacking; darkly staining germinative zone 12–40 (22 ± 7; n = 29) long.

Scolex ( Fig. 4B ) consisting of scolex proper bearing 4 stalked bothridia. Stalks 25–100 (52 ± 20; n = 23) long by 27–83 (55 ± 17; n = 23) wide, attached slightly posterior to middle of bothridia. Bothridia ( Fig. 4B ) varying in shape with degree of contraction, from shallowly-deltoid ( Fig. 5A ) to deeply-deltoid ( Figs. 4B , 5B ), facially loculated, 72–175 (108 ± 26; n = 20) long by 140–325 (202 ± 42; n = 32) wide; bothridial margins with thin rim. Anterior region of bothridia ( Fig. 4B ) with 3 (n = 28) horizontally oriented loculi (i.e. loculi wider than long) with 2 complete transverse septa and one partial medial longitudinal septum. Anteriormost loculus 22–49 (31 ± 8; n = 18) long and 37– 78 (47 ± 9; n = 25) wide. Posterior region of bothridia with 10 (n = 30) nonmedial longitudinal septa dividing bothridia into 11 primary loculi longer than wide, outermost primary loculi on each side subdivided by 2, or occasionally 3 (2.04 ± 0.2; n = 24) relatively short marginal septa into 3–4 small subloculi; longitudinal septa of posterior region not overlapping transverse septa of anterior region.

Loculi and septa of distal bothridial surfaces ( Fig. 5C ) bearing capilliform filitriches and coniform spinitriches. Proximal bothridial rim ( Fig. 5D ) bearing capilliform filitriches greater in length than those on distal bothridial surfaces ( Fig. 5C ). Proximal bothridial surfaces ( Fig. 5D,E ) away from rim bearing acicular filitriches and coniform spinitriches. Isolated cilia observed on proximal bothridial surfaces. Bothridial stalks ( Fig. 5F ) bearing capilliform filitriches and coniform spinitriches; strobila ( Fig. 5G ) bearing capilliform filitriches only.

Strobila with 1–5 (2.6 ± 0.9; n = 32) proglottids wider than long followed by 2–8 (4.1 ± 1.8; n = 32) proglottids longer than wide. Strobila widest at terminal proglottid; terminal proglottid 255–790 (438 ± 124; n = 31) long by 60–144 (108 ± 18; n = 32) wide; genital pore located 42–54% (48 ± 3.5; n = 21) of proglottid length from proglottid posterior margin. Immature proglottids 3–9 (5.5 ± 1.9; n = 32) in number. Mature proglottids 1–3 (1.2 ± 0.5; n = 32) in number, including 0–2 (0.2 ± 0.5; n = 32) vas deferens-mature proglottids.

Testes in mature proglottids 11–21 (16 ± 3; n = 32) in total number, 1 layer deep in cross section, arranged in 2 columns ( Fig. 4C ); columns extending from anterior margin of proglottid to anterior margin of cirrus sac, 13–49 (25 ± 8; n = 32) long by 24–50 (35 ± 6; n = 32) wide. Vas deferens coiled, entering anterior margin of cirrus sac, extending from level of ovarian isthmus to overlap posteriormost testes. Cirrus sac thin-walled, oval, extending medially to near midline of proglottid; cirrus sac in terminal mature proglottid 18–35 (26 ± 5; n = 26) long by 24–38 (31 ± 4; n = 24) wide; cirrus sac in vas deferens-mature proglottids 32–45 (39 ± 5; n = 5) long by 33–46 (40 ± 5; n = 5) wide. Cirrus spinitriches present.

Vagina ( Fig. 4C ) thick-walled, weakly sinuous, somewhat overlapping anterior margin of cirrus sac ( Fig. 16B ), 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 asymmetrical; poral and aporal ovarian lobes in terminal mature proglottids 75–254 (144 ± 40; n = 24) and 75–272 (152 ± 42; n = 24) long, respectively. Poral and aporal ovarian lobes in vas deferens-mature proglottids 145–269 (198 ± 48; n = 5) and 152–270 (206 ± 46; n = 5) long, respectively. Maximum width of ovary 39–139 (65 ± 21; n = 32). Ovarian isthmus near midpoint of ovary; poral lobe of ovary stopping 19–85 (31 ± 16; n = 28) short of genital pore. Mehlis’ gland well posterior to ovarian isthmus, 12–43 (27 ± 8; n = 29) long by 10–35 (20 ±; n = 29) 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 genital genitalia, and mostly interrupted by ovary ( Fig. 4C ). Uterus ventral, sacciform, extending from near isthmus of ovary to near anterior margin of proglottid.

I n f o r m a l s y n o n y m s: Rhinebothriinae New genus 3 sp. n. 6 of Healy et al. (2009), Caira et al. (2014), Ruhnke et al. (2015), Marques and Caira (2016).

T y p e h o s t: Himantura heterura (Bleeker) , dwarf whipray ( Myliobatiformes : Dasyatidae ).

A d d i t i o n a l h o s t s: Himantura macrura , Himantura gerrardi , Himantura uarnak 3.

Ty p e l o c a l i t y: South China Sea off Sematan (01°48’15''N; 109°46'47''E), Sarawak, Malaysian Borneo (hosts BO-19, BO-141, BO-170) .

A d d i t i o n a l l o c a l i t i e s: South China Sea off Mukah (02°53'52''N; 112°05'44''E), Sarawak, Malaysian Borneo (BO-47, BO-66, BO-67, BO-237, BO-238). Java Sea off Kalapseban (03°14'30''S; 112°54'52''E), Central Kalimantan , Indonesian Borneo (KA-99, KA-111). Java Sea off Singkawang (00°55'06''N; 108°58'60''E), West Kalimantan, Indonesian Borneo (KA-145) .

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 MZUM (P) No. 2016.9 (H). Paratypes: IPCAS No. C-739; LRP Nos. 8986–8991; 9038–9062 (including molecular vouchers, cross sections and SEM specimens); MZB Nos. Ca200–Ca201; MZUM (P) No. 2016.10 (P); SBC No. P-00070; USNM Nos. 1420461–1420466.

E t y m o l o g y: This species is named in honour of David and Cynthia Daigler, parents of A.L. Daigler, for their support of his education and his interests.

Remarks. Stillabothrium davidcynthiaorum sp. n. can be distinguished from S. ashleyae in its possession of 10, rather than eight, longitudinal septa on the central posterior region of the bothridium. While S. davidcynthiaorum and S. ashleyae are similar in possessing a range of 2–3 marginal septa on both of the lateral sides on the posterior region of the bothridium, the former differs from the latter in mean number (2.04 [n = 24] vs 2.94 [n = 16]).

In the present study we report specimens of S. davidcynthiaorum from potentially four species of Himantura , H. heterura , H. macrura , H. gerrardi and H. uarnak 3. Although S. davidcynthiaorum was encountered in four potential species of Himantura , we point out having encountered specimens morphologically similar to S. davidcynthiaorum in four additional species of Himantura that were examined during the survey work in Borneo, including Himantura cf. pastinacoides (BO-61, BO-168), H. undulata (BO-24), U. lobistomus (BO-247) and H. oxyrhyncha (KA-252). Further examination of the Stillabothrium specimens from those additional four species of Himantura is needed, in combination with DNA sequence data, to establish whether those cestodes are conspecific with S. davidcynthiaorum or represent an undescribed species of the genus.

Seven specimens of S. davidcynthiaorum were included in the phylogenetic analysis ( Fig. 1 , Table 1 ). One of the seven specimens ( LRP 3926 ) was previously included in the analysis provided by Healy et al. (2009) as ‘Rhinebothriinae New genus 3 sp. n. 6’.

Figures

Fig. 1. Phylogram based on Bayesian analysis of 1084 bp region of D1–D3 28S rDNA. Numbers above branches indicate Bayesian posterior probabilities, numbers below indicate Bootstrap percentage values, based on 1000 replicates. Scale indicates expected num- ber of substitutions per site. Diagrammatic line drawings of fully opened bothridia of the seven described species mapped onto the clades representing those respective species. Host species information in Table 1.

Fig. 4. Line drawings of Stillabothrium davidcynthiaorum sp. n. from Himantura heterura (Bleeker). A – whole worm (LRP 9046); B – scolex (holotype, MZUM [P] 2016.9 [H]); C – terminal proglottid (LRP 9046).

Fig. 5. Scanning electron micrographs of Stillabothrium davidcynthiaorum sp. n. from Himantura uarnak 3 (A, C, F) and Himantura heterura (Bleeker) (B, D, E, G). A, B – scoleces, letters indicate locations of other SEMs; C – distal bothridial surface in center of loc- ulus; D – proximal bothridial surface with rim; E – proximal bothridial surface near rim; F – proximal bothridial surface; G – strobila.

Fig. 16. Light micrographs of terminal genitalia of Stillabothrium species, each with genital pore oriented left. A – Stillabothrium ashleyae sp. n. from Dasyatis biasa (Last, White et Naylor); B – Stillabothrium davidcynthiaorum sp. n. from Himantura gerrardi (Gray); C – Stillabothrium campbelli sp. n. from Himantura cf. pastinacoides; D – Stillabothrium hyphantoseptum sp. n. from Pastinachus solocirostris Last, Manjaji et Yearsley; E – Stillabothrium jeanfortiae sp. n. from Himantura australis Last, White et Naylor; F – Stillabothrium cadenati comb. n. from Zanobatus schoenleinii (Müller et Henle).