Phoreiobothrium jahki, 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 : 337

Phoreiobothrium jahki n. sp.

( Figs. 1 , 2 )

Type host. Rhizoprionodon cf. acutus 3 (sensu Naylor et al. 2012b) ( Carcharhiniformes , Carcharhinidae ).

Type locality. South China Sea off Sarawak, Malaysia, Borneo (02°49'01.20"N, 110°52'47.16"E).

Date of collection. 20 April 2004.

Type material. Holotype ( MZUM [P] No. 2015.1[H]; whole mount of immature worm) and 1 paratype ( MZUM [P] No. 2015.2[P]; whole mount of immature worm); 1 paratype (SBC No. P-00067; whole mount of immature worm); 4 paratypes ( USNM Nos. 1283353–1283356; whole mounts of 4 immature worms); 7 paratypes (LRP Nos. 8743–8749; whole mounts of 4 incomplete worms and 3 whole-mounted SEM strobilar vouchers). Scoleces examined with SEM retained at the University of Connecticut and the University of Kansas.

Site of infection. Spiral intestine.

Etymology. This species honors Joseph (Jahk) Baer who, through the generosity of his mother Jennifer, now has a tapeworm to call his very own.

Description. (Based on 11 whole mounts of immature worms, and 3 immature worms prepared for SEM with their strobilar vouchers). Worms 4.4–7.8 (5.5 ± 1.1; 7) mm long, euapolytic or possibly hyperapolytic, greatest width 174–311 (215 ± 56; 5) generally at level of posterior proglottid; 29–41 (35 ± 4; 7) proglottids per worm. Scolex consisting of scolex proper bearing 4 essentially rectangular bothridia and cephalic peduncle, 152–173 (164 ± 8; 10) wide at level of hooks. Bothridia 164–196 (179 ± 10; 20; 10) long by 97–125 (110 ± 9; 20; 11) wide; each bearing anterior muscular pad in form of loculus, 1 pair of hooks, and post-hook region divided into subequal anterior and posterior loculi. Muscular pad 24–48 (33 ± 6; 16; 9) long, anterior margin without papillae. Anterior loculus conspicuously longer than posterior loculus, 111–152 (128 ± 10; 19; 10) long, posterior margin bearing numerous papillae-like projections; posterior loculus shallowly obovoid in form, 36–63 (50 ± 7; 22; 11) long, subdivided into 10–15 (12 ± 2; 20; 10) subloculi; subloculi 8–15 (11 ± 2; 33; 11) wide, medial subloculi substantially longer than lateral subloculi; boundary between anterior and posterior loculi with double septum ( Figure 2 B). Hooks tri-pronged, each with blunt talon embedded in musculature of scolex; prongs unequal in length, hollow, covered with thin layer of tissue; accessory piece between bases of hooks in a pair absent. Lateral hook measurements: A 32–39 (36 ± 3; 7), B 30–41 (36 ± 4; 7), C 22–29 (27 ± 2; 7), D 35–48 (41 ± 5; 7), E 18–23 (21 ± 2; 7), F 14–19 (17 ± 2; 7); medial hook measurements: A' 32–46 (38 ± 4; 14; 11), B' 32–45 (40 ± 5; 14; 11), C' 24–37 (31 ± 3; 14; 11), D' 40–58 (50 ± 6; 14; 11), E' 18–31 (23 ± 3; 14; 11), F' 14–19 (17 ± 2; 14; 11); lateral and medial hooks approximately equal in length. Cephalic peduncle 659–1,164 (919 ± 138.5; 11) long, with inconspicuous posterior margin.

Apex of scolex proper, muscular pad, and proximal ( Figure 2 E) and distal bothridial ( Figure 2 F) surfaces covered with papilliform filitriches only. Cephalic peduncle covered with acicular filitriches and large gladiate spinitriches ( Figure 2 D). Strobila covered with capilliform filitriches and sparsely arranged large gladiate spinitriches decreasing in density posteriorly.

Proglottids acraspedote. Immature proglottids 29–41 (35 ± 4; 7) in number, initially wider than long, becoming longer than wide with maturity; posterior-most immature proglottid 271–1,146 (639 ± 274; 8) long by 168–311 (211 ± 54; 7) wide. Mature and gravid proglottids not observed. Testes 72–163 (110 ± 33; 8; 4) in number, of these 8–18 (12 ± 4; 7; 4) in postvaginal poral field, elongate oval to round, 13–23 (18 ± 4; 9; 3) long by 12-42 (30 ± 8; 9; 3) wide, 1 layer deep in cross section, extending from anterior of proglottid to anterior margin of ovary, in 4–6 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, 77–107 (87 ± 14; 4) long by 23– 30 (27 ± 3; 5) wide, containing coiled cirrus; cirrus armed with spinitriches. Genital pores marginal, irregular alternating, 39–57 (47 ± 7; 6) % 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, Hshaped in frontal view, bilobed in cross section, lobulated, essentially symmetrical, 89–305 (185 ± 84; 5) long by 105–171 (131 ± 35; 3) 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 Remarks. Phoreiobothrium jahki n. sp. is easily distinguished from the 11 valid members of the genus based on the unique presence of a shallowly obovoid posterior loculus in which the medial subloculi are conspicuously longer than the lateral subloculi. Furthermore, it possesses tri-pronged, rather than bi-pronged, hooks as seen in P. manieri Caira, Healy & Swanson, 1996 , and basal prongs that are well developed, rather than extremely reduced, as in P. exceptum Linton, 1924 , P. lewinense Caira, Richmond & Swanson, 2005 and P. puriensis Srivastav & Capoor, 1982 . Unlike those of P. anticaporum Caira, Richmond & Swanson, 2005 , the genital pores are positioned in the middle, rather than at the extreme anterior margin of the proglottids (39–57 vs. 85–95% of proglottid length from posterior end). The anterior margin of its muscular pad (pre-hook region of Caira et al. 2005) lacks, rather than possesses, 4–5 small, muscular papillae as seen in P. perilocrocodilus Caira, Richmond & Swanson, 2005 . The number of subloculi distinguishes P. j a hk i n. sp. from an additional four species: it has a greater number of subloculi than P. pectinatum Linton, 1924 (10–15 vs. 6–7) but fewer than P. blissorum Caira, Richmond & Swanson, 2005 , P. lasium Linton, 1889 (as redescribed by Caira et al. 2005) and P. robertsoni Caira, Richmond & Swanson, 2005 (10–15 vs. 23–31, 25–30 and 25–29, respectively). Phoreiobothrium jahki n. sp. further differs from P. tiburonis Cheung, Nigrelli & Ruggieri, 1982 (as redescribed by Caira et al. 2005) in its possession of smaller hooks (e.g., B 30–41 vs. 40–60, C 22–20 vs. 35–53); these species also differ in that whereas fully mature proglottids were never seen on the strobila of the new species, P. tiburonis bears 1–3 on the strobila. In their original description of this species Cheung et al. (1982) even reported seeing eggs.

Figures

FIGURE 1. Line drawings of Phoreiobothrium jahki n. sp. A. Scolex (LRP No. 8743). B. Hooks (USNM No. 1283353). C. Whole worm (MZUM [P] No. 2015.1 [H]). D. Terminal, immature proglottid (MZUM [P] No. 2015.1 [H]).

FIGURE 2. Scanning electron micrographs of Phoreiobothrium jahki n. sp. A. Scolex, small letters indicate locations of Figures 2 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.