Phoreiobothrium nadiae, Caira, J. N. & Jensen, K., 2015

Caira, J. N. & Jensen, K., 2015, Insights on the identities of sharks of the Rhizoprionodon acutus (Elasmobranchii: Carcharhiniformes) species complex based on three new species of Phoreiobothrium (Cestoda: Onchoproteocephalidea), Zootaxa 4059 (2), pp. 335-350 : 339-341

Phoreiobothrium nadiae n. sp.

( Figs. 3 , 4 )

Type host. Rhizoprionodon cf. acutus 1 (sensu Naylor et al. 2012b) ( Carcharhiniformes , Carcharhinidae ). Type locality. Eastern Atlantic Ocean off Ouakam, Senegal (14°42'54"N, 17°29'28"W).

Additional localities. Eastern Atlantic Ocean off Soumbédioune, Senegal (14°40'42"N, 17°27'42"W). Date of collection (holotype). 11 January 2003.

Type material. Holotype ( MNHN No. HEL 547; whole mount of mature worm) and 1 paratype ( MNHN No.

HEL 548; whole mount of 1 mature worm); 3 paratypes ( USNM Nos. 1283350–1283352; whole mounts of 1 mature and 2 immature worms); 4 paratypes (LRP Nos. 8750–8753; whole mounts of 1 mature, 1 immature, 1 incomplete worm, and whole-mounted SEM strobilar voucher). Scolex examined with SEM retained at the University of Kansas.

Site of infection. Spiral intestine.

Etymology. This species honors the senior author’s sister Nadia in recognition of her excellence in the field and able assistance with some of our very first discoveries of tapeworm novelty.

Description. (Based on 8 whole mounts [4 mature and 4 immature or incomplete worms], and 1 mature worm prepared for SEM with its strobilar voucher). Worms 4.7–7.9 (6.2 ± 1.4; 4) mm long, euapolytic, greatest width 226–335 (283 ± 38; 6) at level of posterior proglottid; 20–36 (28 ± 6; 7) proglottids per worm. Scolex consisting of scolex proper bearing 4 rectangular bothridia and cephalic peduncle, 222–330 (257 ± 34; 8) wide at level of hooks. Bothridia 237–277 (250 ± 11; 16; 8) long by 163–193 (180 ± 12; 7; 5); each bearing anterior muscular pad in form of loculus, 1 pair of hooks, and post-hook region divided by horizontal septum into subequal anterior and posterior loculi. Muscular pad 48–60 (52 ± 5; 11; 6) long, anterior margin without papillae. Anterior loculus conspicuously longer than posterior loculus, 194–232 (212 ±13; 16; 8) long, posterior margin with few papillae-like projections; posterior loculus depressed obovoid in form, 27–39 (32 ± 4; 16; 8) long, subdivided into 18–28 (23 ± 3; 9; 6) subloculi; subloculi 5–9 (8 ± 1; 24; 8) wide, gradually decreasing in length towards medial and lateral edges of posterior loculus; boundary between anterior and posterior loculus with double septum ( Figure 4 B). Hooks tripronged, each with blunt talon embedded in musculature of scolex; prongs unequal in length, hollow, covered with thin layer of tissue; accessory piece between hook bases absent. Lateral hook measurements: A 47–53 (49 ± 3; 5), B 37–53 (45 ± 7; 4), C 41–51 (45 ± 4; 6), D 63–97 (74 ± 14; 5), E 22–33 (28 ± 4; 6), F 24–33 (27 ± 3; 7); medial hook measurements: A’ 47–58 (53 ± 4; 8; 7), B’ 46–61 (52 ± 5; 9; 7), C’ 34–50 (46 ± 6; 8; 7), D’ 43–85 (65 ± 15; 8; 7), E’ 26–31 (28 ± 2; 9; 7), F’ 29–32 (31 ± 1; 7; 6); lateral and medial hooks approximately equal in length. Cephalic peduncle 375–579 (515 ± 71; 8) long, with inconspicuous posterior margin.

Apex of scolex proper, muscular pad and distal bothridial surfaces ( Figure 4 F) covered with papilliform filitriches only. Proximal bothridial surfaces covered with papilliform filitriches and sparsely arranged, small gladiate spinitriches ( Figure 4 E). Cephalic peduncle covered with acicular filitriches and large gladiate spinitriches ( Figure 4 D). Strobila covered with capilliform filitriches and sparsely arranged large gladiate spinitriches decreasing in density posteriorly.

Proglottids acraspedote. Immature proglottids 20–34 (28 ± 6; 4) in number, initially wider than long, becoming longer than wide with maturity; posterior-most immature proglottid 439–699 (586 ± 96; 8) long by 267–314 (293 ± 22; 6) wide. Mature proglottids 1–3 (2 ± 1; 5) in number, 702–1,399 (1,032 ± 294; 5) long by 292–341 (317 ± 23; 4) wide, ratio of length to width 2.1–4.7:1 (3.4 ± 1.3; 4). Gravid proglottids not observed. Testes 54–64 (60 ± 2; 7) in number, of these 7–11 (9 ± 1; 7) in postvaginal poral field, elongate oval to round, 20–49 (35 ± 9; 15; 5) long by 46–66 (58 ± 9; 9; 3) wide, 1 layer deep in cross section, extending from anterior of proglottid to anterior margin of ovary, in 4–5 irregular columns anterior to cirrus sac. Vas deferens minimal, coiling at antero-medial margin of cirrus sac, entering cirrus sac at its antero-medial margin. Cirrus sac bent anteriorly, oblong, 129–146 (139 ± 3.5; 3) long by 39–66 (50 ± 31; 4) wide, containing coiled cirrus; cirrus armed with spinitriches. Genital pores marginal, irregular alternating, 43–48 (46 ± 2; 5) % of proglottid length from posterior end. Vagina weakly sinuous, extending along midline of proglottid from ootype region to anterior margin of cirrus sac, then laterally along anterior margin of cirrus sac, opening into common genital atrium anterior to cirrus sac. Ovary near posterior margin of proglottid, H-shaped in frontal view, bilobed in cross section, lobulated, essentially symmetrical, 170– 303 (247 ± 54; 5) long by 150–282 (202 ± 25; 4) wide. Mehlis’ gland posterior to ovarian isthmus. Vitellarium follicular, in 2 lateral bands; each band consisting of 1 dorsal and 1 ventral column of follicles, extending from near anterior margin of proglottid to posterior margin, interrupted by cirrus sac on dorsal side, uninterrupted by ovary. Uterus ventral, medial, extending from ootype to stop 2 testis-lengths short of anterior margin of testicular field. Excretory ducts in 2 lateral pairs. Eggs not observed.

Remarks. Phoreiobothrium nadiae n. sp. is easily distinguished from P. manirei in possessing tri-pronged rather than bi-pronged hooks. It conspicuously differs from P. anticaporum in possessing genital pores positioned near the middle, rather than at the extreme anterior end, of the proglottids (43–48 vs. 85–95% of proglottid length from posterior end). Unlike P. perilocrocodilus , it lacks, rather than possesses, 4–5 small, muscular papillae on the anterior margin of muscular pad. It is easily distinguished from P. exceptum , P. lewinensis and P. purinsensis in possessing basal prongs that are well developed, rather than extremely reduced. Phoreiobothrium nadiae n. sp. has many fewer testes than P. blissorum , P. l a s i u m and P. robertsoni (54–64 vs. 103–127, 95–139 and 74–132, respectively). Its greater number of subloculi readily distinguishes it from P. pectinatum and P. tiburonis (18–28 vs. 6–7, 8–13, respectively). With respect to P. j ah k i, not only does it possess fewer testes (54–64 vs. 72–143), but its posterior loculus, although obovoid, is much shorter and bears a greater number of subloculi (18–28 vs. 10–15) than that of the former species.

Figures

FIGURE 3. Line drawings of Phoreiobothrium nadiae n. sp. A. Scolex (LRP No. 8751). B. Hooks (USNM No. 1283351). C. Whole worm (MNHN No. HEL 547). D. Terminal, mature proglottid (MNHN No. HEL 547). E. Terminal genitalia (MNHN No. HEL 547).

FIGURE 4. Scanning electron micrographs of Phoreiobothrium nadiae n. sp. A. Scolex, small letters indicate locations of Figures 4 D – F. B. Subloculi. C. Pre-hook region and hooks. D. Microtriches on cephalic peduncle. E. Microtriches on proximal bothridal surface. F. Microtriches on distal bothridal surface.