Acanthobothrium schalli
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Ordo: Tetraphyllidea
Familia: Onchobothriidae
Genus: Acanthobothrium
Name
Acanthobothrium schalli Vardo-Zalik, Anne M., 2011 – Wikispecies link – Pensoft Profile
- Acanthobothrium schalli Vardo-Zalik, Anne M., 2011, Zootaxa 2838: 51-54.
Materials Examined
Type Host:Mustelus canis canis Mitchill; Dusky smooth-hound; Charcharhiniformes: Triakidae. Type locality: Gulf of Mexico, 26 24.20 ’N, 96 23.80 ’W at 45 fathoms 14. X. 94, coll. R. A. Campbell. Other hosts and localities: from Mustelus norrisi Springer; Narrowfin smooth-hound; Charcharhiniformes: Triakidae. Gulf of Mexico stations: 28 07.44’N, 92 46.50 ’W at 45 fathoms, 28 17.86 ’N94 10.94 W at 27 fathoms, 28.15.20’N, 94 10.94 ’W at 27 fathoms, 28 15.20 ’N at 94 10.94 ’W at 29 fathoms, 28 56.70 ’N, 93 56.11 W at 12 fathoms, 28 24.39 ’N, 92.20.29’W at 31.5 fathoms; coll. R. A. Campbell (vouchers USNPC103827–103829). Site of infection: spiral intestine. Prevalence:Mustelus canis: 7 / 7 individuals examined; M. norrisi: 4 / 4 individuals examined.
Etymology
Etymology: the species is named after Dr. Joseph J. Schall, parasitologist, University of Vermont, mentor of A. Vardo-Zalik.
Description
Description: Based on measurements of 17 whole mounted specimens and 2 worms examined by SEM. Small worms, 3–7 mm (4.4, n= 14) long, consisting of 10–23 (14, n= 13) segments. Strobila acraspedote, euapolytic. Scolex 396–520 (433, n= 17) long, maximum width 240–328 (284, n= 15), composed of 4 triloculate bothridia free at posterior ends; each bothridium with apical sucker and pad, armed with pair of bifid hooks. Bothridia 388–496 (427, n= 12) long by 100–170 (129, n= 17) wide, rounded posteriorly, mean (BL: BW) 2.9: 1. Bothridia covered with spinitriches over proximal surfaces and divided into three loculi by thin muscular septa. Anterior loculus 200– 250 (221, n= 19) long, middle loculus 50–70 (55, n= 19) long, posterior loculus 70–100 (83, n= 19) long; mean locular ratio (A: M: P) 1: 0.25: 0.38. Apical pad 100–130 (113, n= 14) long by 95–110 (102, n= 14) wide; accessory sucker 30–40 (36, n= 15) long by 20–40 (27, n= 15) wide, rims surmounted apically by bilobed lappets (Fig. 16).
Cephalic peduncle covered with spinitriches, 280 long when contracted to 1300 long extended (524, n= 15), maximum width 72–104 (93, n= 15) at junction with scolex; (BL: CPL) 1: 1.1 to 1: 3. Hook dimensions: Medial and lateral hook handles and prongs almost equal in length. Lateral hook (n= 22): A= 45–50 (50) B= 80–120 (95); C= 70–100 (87); D= 120–170 (142); E= 120–165 (138); W= 50–70 (57, n= 12). Medial hook (n= 22): A’= 45–55 (50, n= 16); B’= 90–125 (100, n= 22); C’= 60–120 (83, n= 20); D’= 130–175 (146); E’= 110–180 (136); W’= 50–80 (59, n= 12). Distinct knoblike tubercle 13.3–15.2 long on underside of axial prong of each hook; ratio (THL: BL) 1: 2 – 1: 2.6. Strobila: Rows of microtriches over segment strobila create striated appearance. Immature segments, 8–18 (11, n= 13) in number, initially wider than long, becoming longer than wide with maturity; all male and female genitalia apparent by segment number 10. Successive segments mature rapidly, sperm present in vas deferens by segments number 14–15. Mature segments 1–5 (3, n= 14) in number, longer than wide, terminal segment rounded posteriorly, 410–1040 (700, n= 18) long by 110–270 (199, n= 18) wide. Genital pores alternating irregularly, 34–51 % (42, n= 18) of segment length from posterior end; each with shallow genital atrium. Cirrus sac in posterior half of segment, 70– 120 (94, n= 14) long by 40–80 (50, n= 14) wide, containing armed cirrus. Testes 25–29 (27, n= 19) in number; preporal 9–11 (10, n= 19), aporal 12–15 (14, n= 19), and postporal 3–4 (3, n= 19); sub—spherical, 40–60 (49, n= 33) long by 20–50 (33, n= 36) wide; arranged in two single layered columns extending from ovarian isthmus to near anterior extremity of segment. Vagina anterior to cirrus sac, thick walled, parallels anterior margin of cirrus sac from genital atrium then descends in midline to join oviduct posterior to ovarian isthmus. Vaginal sphincter absent. Seminal receptacle not observed. Mehlis’ gland posterior to ovarian isthmus, oval, c. 48 long by 28 wide. Ovary posterior, inverted-A shaped, bilobed in cross section with numerous pendulous lobules (Fig. 19); total length 176– 344 (295, n= 9) by 120–192 (144, n= 9) wide at isthmus, anterior arms symmetrical throughout most of strobila (Figs.18, 19) not reaching cirrus sac, poral lobe 150–350 (234), aporal lobe 150–350 (241). Ovary larger in terminal segments, lobes slightly asymmetrical, differing by c. 5 % of total length; poral lobe terminating near level of cirrus sac, aporal lobe extending to or anterior to posterior margin of cirrus sac (Fig. 17); lobes united posteriorly, encircling Mehlis’ gland (Fig. 18). Uterus thick walled, tubular, extends from the level of the ovarian isthmus to level of the third most anterior testes. Vitellarium follicular, consisting of 2 lateral columns, each 1–2 follicles deep, extending from level of penultimate testis anteriorly to ovarian isthmus posteriorly, interrupted by vagina and cirrus sac. Excretory ducts lateral. Eggs not observed.
Discussion
Remarks:Acanthobothrium schalli is the first species described from sharks in the western Atlantic, occurring in all specimens examined of both M. c. canis (7) and M. norrisi (4) in the Gulf of Mexico. Acanthobothrium schalli can be differentiated from most category 1 species in possessing an ovary that has an inverted-A shape in dorsoventral view but is bilobed in cross-section, i.e. the posterior arms of the ovary are united posterior to the ovarian isthmus. The symmetrical anterior ovarian lobes in the majority of the segments of Acanthobothrium schalli is indicative of a category 1 species (SFFS) according to the parameters set by Ghoshroy & Caira (2001). The subtle elongation of the anterior aporal lobes by 5 % of their length in the oldest segments is similar to the category 1 species A. foulki and Acanthobothrium peruviense Reyda, 2008 with ovaries that Reyda & Caira (2006) described as “essentially symmetrical”. Five species of Acanthobothrium have been reported from sharks of the genus Mustelus: A. coronatum from M. mustelus in the Northeastern Atlantic and Mediterranean Sea (Baer 1948; Rees & Williams 1965); Acanthobothrium karachiense Bilqees, 1980; Acanthobothrium mujibi Bilqees, 1980 and Acanthobothrium rubrum Bilqees, 1980 in Mustelus (=Myrillo) manazo Bleeker from the Arabian Sea, Karachi coast of Pakistan (Bilqees 1980); and A. mathiasi in M. mustelus and M. canis from the Mediterranean Sea (Euzet 1959). Acanthobothrium schalli can be distinguished from A. coronatum, A. karachiense, A. mujibi, and A. rubrum by lesser number of testes (25–29 vs. 81 –115, 74–98, 36– 41, and 60–87 respectively). Acanthobothrium schalli differs from A. mathiasi in being smaller (3–7mm vs. 10–20 mm) with shorter total hook length (70–100 vs. 155–200) and different ovarian form (inverted- A vs. H-shaped). Compared to all species described from the western North Atlantic, A. schalli is most similar to A. lintoni (USNPC62938) from the electric ray Narcine brasiliensis Olfers in the Gulf of Mexico in scolex dimensions, hook form and accessory sucker diameter. Unfortunately, the holotype of A. lintoni (USNPC62938) is incomplete; it is 6mm long with 27 immature segments, all with underdeveloped reproductive organs. Segments of A. schalli mature more rapidly. The holotype of A. schalli is 7mm long with 18 fully discernable segments (Fig. 36) in which all reproductive organs can be recognized by segment number 10 and mature segments appear by number 14. Furthermore, A. schalli differs from A. lintoni in having larger anterior loculi (200–250 vs. 171–175 in USNPC62938), greater locular ratio (A:M:P 4: 1: 1.5 vs. 3: 1: 1), striated strobila vs. “smooth” in A. lintoni, larger cirrus sac (70–120x 40 –80 vs. 35– 84 x 13–74), larger ovary (176–344 vs. 19–51) and ovarian shape (inverted-A vs. Hshaped). Ghoshroy & Caira (2001) designated A. lintoni a possible mix of species fitting categories 1 (8, 9, 5).
Taxon Treatment
- 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: 51-54. doi
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