Acanthobothrium ulmeri, Vardo-Zalik, Anne M. & Campbell, Ronald A., 2011

Vardo-Zalik, Anne M. & Campbell, Ronald A., 2011, Five new species of Acanthobothrium van Beneden, 1849 (Cestoda: Tetraphyllidea) in elasmobranchs from the northwest Atlantic and Gulf of Mexico with first records from smooth-hound sharks and guitarfish, Zootaxa 2838, pp. 41-64 : 55-57

Acanthobothrium ulmeri sp. nov.

( Figs. 20–24 , 31, 34 )

Specimens deposited: holotype (USNPC 103830); paratypes (USNPC 103831–103837, 103839, 103842, 103846).

Host: Raja texana Chandler, 1921 ; Roundelskate; Rajiformes : Rajidae .

Type locality: Gulf of Mexico 29º20.29’N, 93º43.76’W at 8 fathoms 28. x. 94, coll. R. A. Campbell.

Other localities: 28º 5.53’ N, 94º 54.91’W at 30 fathoms; 28º 40.04’N, 94º 21.19’W at 17 fathoms; 27º 58.57’N, 95º 21.61’W at 35 fathoms; 28º 13.40’N, 94º 43.15’W at 27.5 fathoms; 28º 20.71’N, 94º 12.99’W at 26.7 fathoms; 28º 9.31’ N, 94º 18.25’W at 30 fathoms; 27º 59.27’N, 93º 58.04’W at 45 fathoms.

Site of infection: spiral intestine.

Prevalence: 10/11 individuals examined.

Etymology: The species is named in honor of the late Dr. Martin J. Ulmer, Iowa State University, former president of the American Society of Parasitologists, mentor and friend of RAC.

Description: Based on measurements of 15 whole mounted specimens and SEM of 2 specimens. Small cestodes 720–3380 (1622, n=10) long. Strobila consisting of 3–11 (6, n= 13) acraspedote segments, euapolytic. Scolex 357–464 (350, n=10) long by 224–280 (240, n=10) wide, composed of 4 triloculate bothridia free at posterior ends; each with apical sucker and pad, armed with pair of bifid hooks. Bothridia 281–432 (385, n=21) long by 87–128 (113, n=21) wide, acuminate or rounded posteriorly, covered with spinitriches over proximal surfaces and divided into three loculi by thin muscular septa. Anterior loculus 156–205 (180, n=12) long, middle loculus 57–87 (72, n=12) long, posterior loculus 65–106 (89, n=12) long. Apical pad 58–84 wide, bearing a single accessory sucker 23–29 (25, n=7) in diameter. Ratios of (A: M: P) 1: 0.40: 0.48; (BL: BW) 3.37: 1; (BL: CPL) 1: 0.15–1: 0.4 (1: 0.32). Cephalic peduncle short, 48–176 (112, n=15) long by 48–64 (55, n=13) wide, overlapped by bothridia, covered with spinitriches and long filitriches.

Hook dimensions: Hooks of dissimilar form and dimensions. Lateral hook: prongs widely divergent, forming distinct Y-shape: (n=7): A =21–30 (28); B= 61–78 (66); C = 59–72 (63); D= 80–103 (91); E= 77–103 (90); W= 38– 48 (44). Medial hook: prongs form narrow U-shape (n=7): A’ = 25–29 (27); B’ = 61–76 (69); C’ = 53–72 (63); D’= 82–103 (91); E’= 80–100 (87); W’= 19–38 (36). (THL: BL) 1: 4.2 to 1: 4.3.

Strobila: Immature segments 4–9 (6, n=8) in number, initially wider than long, rapidly elongating with maturity. Mature segments longer than wide, 280–1010 (597, n=13) long by 150–270 (219, n=13) wide, 1–3 (2, n=8) per worm. Genital pores 47–69% (56%, n=10) of segment length from posterior extremity, irregularly alternating, each with shallow genital atrium. Cirrus sac near middle of segment, pyriform, 70–120 (91, n=10) long by 50–100 (75, n=10) wide, extending almost to midline. Cirrus armed, basal region covered with gland cells ( Fig. 23 ). Testes arranged in two, single layered columns lateral to uterus, beginning anterior to the ovary and extending to anterior extremity of segment, never between the ovarian lobes. Testes 18–26 (23, n=22) in number, 5–9 (7, n=22) preporal, 9–15 (12, n=22) aporal, 3–5 (3.6, n=22) postporal; subspherical, 20–60 (34, n=36) long by 35–80 (51, n=36) wide. Ovary posterior, 160 long by 80 wide in immature segments, 160–360 (248) long by 88–168 (130) wide in mature segments, H-shaped, tetralobed, posterior arms converge and overlap posteriorly. Ovarian arms nearly symmetrical, distinctly lobulated, aporal arms 90–370 (233, n=10) long, poral arms 115–350 (224, n=10) long, 45–140 (92, n=10) wide, anterior arms barely reach level of testes and about half the distance to cirrus sac. Vagina anterior to cirrus sac, thick walled, densely covered by gland cells near junction with genital atrium, muscle fibers apparent, with internal constriction ( Fig. 23 ), opens into a shallow genital atrium, parallels anterior border of cirrus sac to midline, turns posteriorly and descends to ootype. Vaginal sphincter absent. Mehlis’ gland elliptical, 12–30 long by 10–23 wide, located immediately posterior to ovarian isthmus. Uterus median, tubular, thick walled, extending in median line from Mehlis’ gland to level of most anterior testes. Vitellarium follicular, in 2 lateral columns, each composed of 2 columns of follicles, extending from ovary to posterior margin of the most anterior testes; follicles irregular, oblong, 23–30 long by 15–27 wide.

Remarks: Acanthobothrium ulmeri is a category 1 species whose bothridia longer than the cephalic peduncle is rare among all congeners. This character in combination with its small size (<3.5 mm), preovarian distribution of 18–26 testes, ovarian lobes reaching c. 50% of the distance to the cirrus sac from the posterior end of the segment differentiate it from all but a few other known category 1 species worldwide. In the Atlantic Ocean coastal waters of North and South America and the Mediterranean Sea only A. dujardinii , common to skates ( Raja spp .) in the eastern North Atlantic and A. mathiasi from Mustelus in the Mediterranean Sea, are noted for having short cephalic peduncles overlapped by their bothridia. Acanthobothrium ulmeri differs from A. dujardinii in the lack of lappets on the bothridial margins, absence of testes between the ovarian lobes (present in A. dujardinii ) and shorter total hook length (80–103 vs. 180–210). It can be distinguished from A. mathiasi by a number of characters, the more obvious being a much smaller size (<3.5 mm vs. 10–20 mm), shorter total hook length (80–103 vs. 155–200), fewer postporal testes (3–5 vs. 7) and absence of testes between the ovarian lobes (present in A. mathiasi ). Acanthobothrium ulmeri occurred in mixed infections with A. westi sp. nov., described below. Acanthobothrium ulmeri is differentiated from A. lentiginosum by its’ smaller scolex (357–464 vs. 550–780), shorter total hook lengths (82– 103 vs. 100–140 medial), a smaller (THL: BL) ratio (1: 4.2– 4.3 vs. 1: 2.7–2.8), shorter interprong width of medial hooks (19–38 vs. 40–60), and absence of testes between the ovarian lobes (compare Figs. 11 and 22 ); it can be distinguished from A. schalli by the extent of the ovarian lobes (1/2 distance to the cirrus vs. just below cirrus sac in A. schalli ) and testes distribution (preovarian vs. between the ovarian lobes).

Of the 27 category 1 species lacking postovarian testes discussed by Fyler et al. (2009) five species from Australia and the Indo-Pacific region have a short cephalic peduncle not extending beyond the bothridia: A. bartonae , A. gnomus , A. moorae , A. stevensi , and A. thomasae . Acanthobothrium ulmeri can be differentiated from each of these species as follows: from A. bartonae in its absence of hook tubercles, smaller hook handles (21–30 vs. 51– 60), and hook lengths, i.e. shorter medial and lateral axial prongs (61–76 and 61–78 vs. 81–82 and 76–94); it differs from A. gnomus by more testes (18–26 vs. 8–13) and presence of postporal testes (absent in A. gnomus ); A. ulmeri lacks a vaginal sphincter and testes between the ovarian lobes, both present in A. stevensi ; and it differs from A. thomasae by possessing fewer preporal testes (3–5 vs. 5–9).

Figures

FIGURES 20 – 24. Acanthobothrium ulmeri sp. nov. from the roundel skate, Raja texana. 20. Scolex. Note acuminate bothridia and short cephalic peduncle 21. Hooks showing two variations in form of lateral hook. 22. Terminal segment. 23. Terminal genitalia. Note vaginal constriction. 24. Entire worm. Scale bars: Fig. 20 = 100 µm. Fig. 21 = 25 µm. Figs. 22, 23 = 50 µm. Fig. 24 = 250 µm.

FIGURES 31 – 36. New Acanthobothrium species from Gulf of Mexico. 31. A. ulmeri sp. nov., holotype. 32. A. westi sp. nov., holotype. 33. A. westi sp. nov., scolex from specimen 2.24 mm long. 34. A. ulmeri sp. nov., scolex from specimen 1.2 mm long. 35. A. schalli sp. nov. detail of hooks showing elongated tubercles. 36. A. schalli sp. nov., holotype, entire worm with 18 segments. Scale bars: Figs. 31, 32 = 250 µm, Figs. 33, 34, 35 = 50 µm, Fig. 36. = 500 µm.

FIGURES 9 – 13. Acanthobothrium lentiginosum sp. nov. from the Atlantic guitarfish. 9. Scolex. 10. Hooks. 11. Mature segment. Note posterior extent of testes. 12. Detail of bilobed ovary, inverted A-shaped. 13. Entire worm. Scale bars: Figs. 9, 11, 13 = 100 µm. Figs. 10, 12 = 50 µm.