Acanthobothrium westi, 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 : 57-61

Acanthobothrium westi sp. nov.

( Figs. 25–30 , 32, 33 )

Specimens deposited: holotype (USNPC 103841) and paratypes (USNPC 103838, 103840, 103843–103845, 103847).

Host: Raja texana Chandler, 1921 ; Roundel skate; Rajiformes : Rajidae .

Type Locality: western Gulf of Mexico, 28º 13.40’ N, 94º 43.15’ W at depth of 27.5 fathoms. 23. x. 94, coll. R. A. Campbell.

Other localities: 27º 58.57’N, 95º 21.61’ W at 35 fathoms, 20. x. 94; coll. R.A. Campbell.

Site of infection: spiral intestine.

Prevalence: 2 of 11 individuals examined.

Etymology: the species is named after Dr. Warwick R. West, mentor to RAC and former chairman of the Department of Biology, University of Richmond for his guidance and support.

Description: Based on measurements of 8 whole mounted specimens. Small cestodes 1520 – 2340 (1950, n= 7) long, strobila consisting of 5–11 (10, n= 7) acraspedote segments, euapolytic. Scolex 215–277 (241, n= 7) long by 200–240 (224, n= 7) wide composed of 4 triloculate bothridia free at posterior ends; each bothridia with pad and apical sucker, and armed with one pair of bifid hooks. Bothridia 182–232 (216, n=12) long by 82–128 (102, n=12) wide, rounded posteriorly, joined by a velum ( Fig. 25 ), covered with filitriches and spinitriches over proximal surfaces and bothridial margins, divided into three loculi by thin muscular septa. (BL: BW) 1.75: 1 to 2.3: 1. Anterior loculus 72–123 (99, n=12) long, middle loculus 35–49 (41, n=12) long, posterior loculus 27–42 (32, n=12) long. Ratio of locular lengths (A: M: P) 1: 0.29: 0.26 to 1: 0.35: 0.26. Apical pad 80–99 (91, n=14) wide, bearing a single accessory sucker 23–36 (31, n= 14) in diameter. Cephalic peduncle 216–480 (265, n=7) by 76–85 (82, n=7) wide, covered with spinitriches. Ratio of bothridial length to cephalic peduncle length (BL: CPL) 1: 1.14 to 1: 2.4.

Hook dimensions: Hooks delicate, dissimilar in form. Lateral hook (n=8): A= 25–28 (26); B= 42–53 (48); C= 38–48 (44); D= 63–72 (68); E= 63–73 (66); W= 34–48 (42). Medial hook (n= 8): A’ = 23–25 (24); B’= 49–57 (53); C’= 38–48 (43); D’= 69–76 (73); E’= 63–72 (67); W’= 32–49 (41). (THL: BL) 1: 2.5 to 1: 2.6.

Strobila: Immature segments wider than long, 4–9 (6, n=8) in number, elongating with maturity. Mature segments 500–624 (570, n=13) long by 160–224 (195, n=13) wide, 1–3 (2, n=8) per worm. Genital pores 45–56% (50%, n=10) of segment length from posterior extremity, irregularly alternating. Genital atrium indistinct. Cirrus sac postequatorial, 72–84 long by 72 to 80 wide, pyriform in early segments, subspherical in oldest segments, tilted slightly posteriorly. Cirrus armed. Testes preovarian, 20–24 (22, n=22) per segment, subspherical, 30–48 long by 19–38 wide, in two, single-layered columns, extending from anterior margin of ovary to near anterior extremity of segment. Testis distribution 7–10 (7.7, n=22) preporal, 2–3 (2.8, n=22) postporal, 10–13 (10.7, n=22) aporal. Vagina anterior to cirrus sac, thick walled, arches from genital pore along anterior margin of cirrus sac to midline, turns posteriorly descending to join oviduct posterior to ovarian isthmus. Vaginal sphincter absent. Seminal receptacle not observed. Ovary posterior, 152–176 long by 57–88 wide, H-shaped, bilobed in cross section with 4–6 distinct pendulous lobules. Ovarian lobes nearly symmetrical, poral lobe often slightly (7%) longer (154–179 by 27– 30) than aporal lobe ( Fig. 29 ), lobes may overlap posteriorly but not united. Mehlis’ gland posterior to ovarian isthmus, 17–23 long by 20–21 wide. Uterus median, tubular, thick walled, extending anteriorly about 79–85% of segment length. Vitellarium follicular, in 2 lateral columns, each column 1–2 follicles wide, extending from anterior ovarian lobes to level of second testes anteriorly, interrupted by genital terminalia on poral side; follicles irregular in shape, c. 10–17 long by 7–13 wide. Excretory ducts lateral.

Remarks: Acanthobothrium westi is a new category 1 species based on the criteria of Ghoshroy& Caira (2001). Distinguishing characters include the combination of small size, cephalic peduncle length, preovarian disposition of the testes, testis number, short extent of the ovarian lobes, and hook dimensions in contrast to other category 1 species. Compared to category 1 species in Atlantic coastal waters of the United States the presence of postporal testes and fewer testes (20–24 vs. 36–54) differentiates A. westi from A. fogeli ; it has fewer postporal testes (2–3 vs. 5–10) than A. lineatum ; A. westi has fewer testes (20–24 vs. 30–46), and fewer segments (5–11 vs. 5– 60) than A. lintoni ; and it differs from A. paulum by fewer segments per strobila (5–11 vs. 22–50), fewer antiporal testes (10–13 vs. 17–34) and shorter ovarian lobes (108–154 vs. 620–676); A. westi has fewer segments (5–11 vs. 17–26) and fewer testes (20–24 vs. 38–57) than A. himanturi ; it is smaller than A. marplatense (<2.5 mm vs. 4.79– 8.44 mm) with fewer segments (5–11 vs. 18–30); and it is shorter than A. mathiasi (2.5mm vs. 10–20 mm) which has bothridia longer than the cephalic peduncle. Acanthobothrium westi differs from Category 1 species described herein by the following: A. westi differs from A. lentiginosum by possessing shorter total hook lengths (69–76 vs. 100–140) and the absence of testes between the ovarian lobes (compare Figs. 11 and 29 ); it differs from A. schalli in the absence of testes between ovarian lobes; it differs from A. ulmeri by numerous scolex features including total hook length (63–76 vs. 80–103), and bothridia consistently shorter than the longer cephalic peduncle (216–480 vs. 48–176) resulting in (BL: CPL) ratio of (1: 1.14–2.4 vs. 1: 0.15–0.4) and locular length ratio (A:M:P) of 1: 0.29– 0.35: 0.26 vs. 1: 0.4: 0.48.

Only a few species of Acanthobothrium from the eastern Atlantic and Mediterranean Sea that closely resemble A. westi are known well enough for critical comparison. In his review of the genus Williams (1969) pointed out the need for redescription of several species from the eastern North Atlantic similar to species described from elasmobranchs in the western North Atlantic. Among those descriptions are A. benedeni and the large and small forms of A. filicolle which may be a mix of species and remain unresolved. Of the recognizable species that are comparable, A. westi lacks lappets on the bothridial margins seen in A. dujardinii and A. edwardsi . It also differs from A. minus in lacking a vaginal sphincter and testes between the ovarian lobes; and it is distinguished from A. quadripartitum and A. tripartitum by possessing symmetrical ovarian lobes that do not reach the cirrus sac.

Acanthobothrium westi can be distinguished from other category 1 species from the eastern Pacific as follows: from A. monksi by smaller size (up to 2.3 mm vs. up to 7.6 mm) and fewer segments than A. monksi and A. royi (5– 11 vs. 24–48, 19–26 respectively); it differs from A. nicoyaense by the lack of a vaginal sphincter and protruding genital pore; it has smaller bothridia (182–232 vs. 422–435) and smaller medial total hook length (69–76 vs. 163– 166) than A. atahualpai ; and it differs from A. minusculum and A. dollyae in number of testes (20–24 vs. 6–10, 42– 45 respectively).

Of the category 1 species from the Indo-Pacific region A. westi differs from A. foulki and A. larsoni , A. marymichaelorum , A. saliki and A. southwelli in the absence of postovarian testes and from A. guptai by testis number (20–24 vs. 44–45). It lacks the horizontal band of musculature across the posterior loculi possessed by A. asnihae and absence of postporal testes of A. gnomus . Acanthobothrium westi has a broader, rounder posterior loculus compared to the abruptly acuminate posterior loculus of Acanthobothrium lepidum Reyda & Caira, 2006 and it differs from A. oceanharvestae , A. rowmanowi and A. zimmeri as follows: from A. zimmeri in lacking postovarian testes; it is differentiated from A. rowmanowi by testis number (20–24 vs. 34–53), posterior position of the genital pore, fewer segments (5–11 vs. 16–23) and smaller size (<2.5 mm vs. 4– 7.1 mm); and it differs from A. oceanharvestae in number of postporal testes (2–3 vs. 6–11), testes between the longer ovarian lobes (176–182 vs. 380–711) which reach near the cirrus sac. Acanthobothrium westi has fewer segments than A. zainali (5-11 vs. 15–21).

Category 1 Australian species to be compared with A. westi are: A. bartonae , A. clarkae , A. laurenbrownae , A. martini , A. odonoghuei , A. rohdei , A. pearsoni and A. urolophi . Acanthobothrium westi differs as follows: it has shorter medial/lateral axial prongs (49–57 and 42–53 vs. 81–82 and 76–94) and lacks the hook tubercles present in A. bartonae ; possesses fewer testes than A. clarkae , A. laurenbrownae , A. pearsoni , and A. urolophi (20–24 vs. 45– 52, 31–46, 56–60, 34–41 respectively) but more testes than A. martini (20–24 vs. 8–11); it differs from A. mooreae in the absence of a vaginal sphincter and smaller anterior loculus (72–123 vs. 147–175); A. odonoghuei has testes distributed between the ovarian lobes and has a cephalic peduncle with very long hairlike microtriches, not observed in A. westi ; it differs from A. rohdei by in lacking a vaginal sphincter (present in A. rohdei ) and the cirrus sac does not extend beyond the midline; and from A. stevensi and A. thomasae which have testes between the ovarian lobes.

Figures

FIGURES 25 – 30. Acanthobothrium westi sp. nov. from Raja texana. 25. Scolex, note rounded bothridia joined by velum and length of cephalic peduncle. 26. Hooks, note form of lateral hook (left). 27. Hooks, note form of lateral hook (right). 28. Bothridium, note bothridial form and position of septa. 29. Terminal (mature) segment. 30. Detail of ovary. Note overlap of left lobe over right lobe posteriorly. Scale bars: Figs. 25, 29 = 100 um. Figs. 26, 27 = 35 um. Figs. 28, 30 = 50 um.

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.